Patent Description:
The silverleaf whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae), is an important insect pest of melon and other cucurbit species. Infestation can cause severe yield loss, both directly through feeding damage cause by the whiteflies and larvae, as well as indirectly through sugary excretions serving as substrate for sooty mold and/or transmission of pathogenic viruses, such as CYSDV (Cucurbit Yellow Stunting Disorder), CVYV (Cucurbit Vein Yellowing Virus) or MYaV (Melon Yellowing Associated Virus), and bacteria.

To control B. tabaci insecticides, such as imadacloprid, are frequently applied and breeding for resistance is required to reduce insecticide use.

<NPL>) identified three accessions with potential antibiosis resistance to B. tabaci biotype B, PI161375, PI414723 and PI532841.

<NPL>) identified low levels of field resistance in three Indian Accessions (PI414723, PI164723 and <NUM>) and one Korean accession (PI161375).

<NPL>) mapped QTLs (Quantitative Trait Loci) for B. tabaci biotype B resistance, affecting the number of progenies produced by one female of biotype B (antibiosis resistance), to linkage group VII, for one whitefly clonal population, and to linkage group IX, for a different whitefly clonal population. The QTLs were only minor (LOD value <NUM> and <NUM>) and the resistance allele for both of these minor QTLs originated from the Korean accession PI161375.

The genetics of whitefly resistance are still largely unknown, most likely to the difficulties to manage whiteflies in the laboratory and difficulties in establishing reliable assays for whitefly resistance.

Tests that are used to identify resistance are either free-choice tests or non-choice tests or field tests.

In free choice assays the insects can choose among different plant genotypes for feeding and reproduction. Such free choice-tests are used to identify antixenosis (non-preference) resistance, i.e. resistance caused by factors that make a plant genotype less attractive. See e.g. <NPL>) who used a free-choice leaf disc assay to show that PI414723 is rejected quickly by whiteflies and that therefore a antixenosis mechanism may exist in this accession in addition to the antibiosis mechanism detected by Sauvion et al. (<NUM>, supra).

In non-choice tests for resistance the insects cannot choose among different plant genotypes for feeding and reproduction, but are only allowed to feed and reproduce on one genotype. This type of resistance affects the insects biotic potential, e.g. they die, produce fewer offspring or grow more slowly (antibiosis or antibiotic resistance).

It is an object of the invention to provide whitefly resistance sources and a genetic region comprising the resistance locus, or a part thereof, which confer resistance, especially antixenosis (non-preference) resistance and field resistance, against whiteflies, B. tabaci biotype B. It is a further object of the invention, as set out in the appended claims, to provide cultivated melon plants (Cucumis melo L. ) and cells, tissues, fruits and other parts of such plants comprising in their genome a whitefly resistance-conferring locus (or a resistance-conferring part thereof), either in homozygous or heterozygous form, whereby the melon plants are resistant against whitefly. Also seeds from which whitefly resistant melon plants can be grown are an embodiment of the invention, as set out in the appended claims.

In a further aspect molecular markers are provided, which can be used to detect the presence of the B. tabaci resistance-conferring locus, or a resistance-conferring part thereof, in plants or plant cells of Cucumis melo L. as set out in the appended claims. One or more of the markers can, thus, for example be used to transfer the resistance locus, or a resistance-conferring part thereof, into cultivated melon plants which are susceptible to B. tabaci as described herein. In one embodiment the resistance locus, or resistance-conferring part thereof, is the locus on chromosome <NUM> as found in seeds deposited under accession number NCIMB <NUM> or NCIMB <NUM> as set out in the appended claims. In a different embodiment the resistance locus, or resistance conferring part thereof, is the locus on chromosome <NUM> as found in seeds deposited under accession number NCIMB <NUM> or NCIMB <NUM> as set out in the appended claims.

One or more of the markers linked to, or genetically and physically associated with, the B. tabaci resistance locus, or resistance conferring part thereof, can also be used to identify new B. tabaci -resistance sources on chromosome <NUM>, such as other wild accessions of Cucumis melo or wild relatives of melon comprising a B. tabaci -resistance locus on chromosome <NUM> and for transferring (introgressing) the resistance locus, or a B. tabaci-resistance conferring part thereof, from such accessions into cultivated melon plants. tabaci resistance conferring quantitative trait locus (QTL) on chromosome <NUM> (equivalent to ICuGI Linkage Group XI, or LG XI) was named Wf_11. <NUM> (for whitefly chromosome <NUM>, QTL <NUM>).

<CIT> describes a QTL for ZYMV/WMV resistance introgressed onto chromosome <NUM>, but this QTL maps to a different region of chromosome <NUM>, especially to the other half of chromosome <NUM> than the QTL of the instant invention.

The indefinite article "a" or "an" does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements. The indefinite article "a" or "an" thus usually means "at least one".

As used herein, the term "plant" includes the whole plant or any parts or derivatives thereof, such as plant organs (e.g., harvested or non-harvested storage organs, tubers, fruits, leaves, seeds, etc.), plant cells, plant protoplasts, plant cell or tissue cultures from which whole plants can be regenerated, plant calli, plant cell clumps, and plant cells that are intact in plants, or parts of plants, such as embryos, pollen, ovules, ovaries, fruits (e.g., harvested tissues or organs, such as harvested melon fruits or parts thereof), flowers, leaves, seeds, tubers, bulbs, clonally propagated plants, roots, root-stocks, stems, root tips and the like. Also any developmental stage is included, such as seedlings, immature and mature, etc. When "seeds of a plant" are referred to, these either refer to seeds from which the plant can be grown or to seeds produced on the plant, after self-fertilization or cross-fertilization.

"Plant variety" is a group of plants within the same botanical taxon of the lowest grade known, which (irrespective of whether the conditions for the recognition of plant breeder's rights are fulfilled or not) can be defined on the basis of the expression of characteristics that result from a certain genotype or a combination of genotypes, can be distinguished from any other group of plants by the expression of at least one of those characteristics, and can be regarded as an entity, because it can be multiplied without any change. Therefore, the term "plant variety" cannot be used to denote a group of plants, even if they are of the same kind, if they are all characterized by the presence of one or two loci or genes (or phenotypic characteristics due to these specific loci or genes), but which can otherwise differ from one another enormously as regards the other loci or genes.

"F1, F2, F3, etc." refers to the consecutive related generations following a cross between two parent plants or parent lines. The plants grown from the seeds produced by crossing two plants or lines is called the F1 generation. Selfing the F1 plants results in the F2 generation, etc..

"F1 hybrid" plant (or F1 hybrid seed) is the generation obtained from crossing two inbred parent lines. Thus, F1 hybrid seeds are seeds from which F1 hybrid plants grow. F1 hybrids are more vigorous and higher yielding, due to heterosis.

The term "allele(s)" means any of one or more alternative forms of a gene at a particular locus, all of which alleles relate to one trait or characteristic at a specific locus. In a diploid cell of an organism, alleles of a given gene are located at a specific location, or locus (loci plural) on a chromosome. One allele is present on each chromosome of the pair of homologous chromosomes. A diploid plant species may comprise a large number of different alleles at a particular locus. These may be identical alleles of the gene (homozygous) or two different alleles (heterozygous). Thus, for example reference may herein be made to a Wf-allele of the B. tabaci resistance locus Wf_11.

The term "gene" means a (genomic) DNA sequence comprising a region (transcribed region), which is transcribed into a messenger RNA molecule (mRNA) in a cell, and an operably linked regulatory region (e.g. a promoter). Different alleles of a gene are thus different alternatives form of the gene, which may be in the form of e.g. differences in one or more nucleotides of the genomic DNA sequence (e.g. in the promoter sequence, the exon sequences, intron sequences, etc.), mRNA and/or amino acid sequence of the encoded protein.

The term "locus" (loci plural) means a specific place or places or a site on a chromosome where for example a gene or genetic marker is found. tabaci resistance locus or Wf-resistance locus (or B. tabaci resistance-conferring locus) is, thus, the location in the genome of melon, where the Wf-resistance gene is found. In cultivated melon the B. tabaci resistance locus is found on chromosome <NUM> (using the ICuGI nomenclature for chromosome or Linkage Groups, i.e. LG XI) and is preferably introgressed into the cultivated melon genome (i.e. onto chromosome <NUM>, or LG XI) from wild melon accessions, such as (but not limited to) the two wild melon accessions deposited under accession numbers NCIMB <NUM> and NCIMB41966, or from other wild melons or wild relatives of melon which are crossable with C. melo and from which crosses fertile offspring can be produced.

A "quantitative trait locus", or "QTL" is a chromosomal locus that encodes for one or more alleles that affect the expressivity of a continuously distributed (quantitative) phenotype. tabaci resistance conferring quantitative trait locus is named herein Wf_11.

"ICuGI" refers to the International Cucurbit Genomics Initiative, which publishes genetic maps of e.g. Cucumis melo (world wide web of icugi. org under cgi-bin/cmap/map_set_info?species_acc=CM). The current version of the C. melo genome map is of March <NUM>th, <NUM> and the map of chromosome <NUM> is referred to as ICuGI_XI (or LG XI, or Linkage Group XI) and contains <NUM> markers (<NUM> AFLP, <NUM> ISSR, <NUM> RAPD, <NUM> RFLP, <NUM> SNP, <NUM> SSR markers) on a linkage group spanning <NUM> to <NUM>. Herein melon chromosome <NUM> and LG XI are used interchangeably.

"Genetic distance" between loci (e.g. between molecular markers and/or between phenotypic markers) on the same chromosome is measured by frequency of crossing-over, or recombination frequency (RF) and is indicated in centimorgans (cM). One cM corresponds to a recombination frequency of <NUM>%. If no recombinants can be found, the RF is zero and the loci are either extremely close together physically or they are identical. The further apart two loci are, the higher the RF.

"Physical distance" between loci (e.g. between molecular markers and/or between phenotypic markers) on the same chromosome is the actually physical distance expressed in base pairs (bp), kilo base pairs (kb) or megabase pairs (Mb). melo has a total haploid genome size of about <NUM> Mb, divided into <NUM> chromosome pairs, see <NPL> and <NPL>.

"Introgression fragment" or "introgression segment" or "introgression region" refers to a chromosome fragment (or chromosome part or region) which has been introduced into another plant of the same or related species by crossing or traditional breeding techniques, such as backcrossing, i.e. the introgressed fragment is the result of breeding methods referred to by the verb "to introgress" (such as backcrossing). In melon, wild melon accessions or wild relatives of melon are often used to introgress fragments of the wild genome into the genome of cultivated melon, Cucumis melo. Such a cultivated melon plant thus has a "genome of cultivated C. melo", but comprises in the genome a fragment of a wild melon or of a wild relative of melon, e.g. an introgression fragment of a related wild Cucumis genome, such as Cucumis melo ssp. agrestis, C. acidulous, C. callosus, C. trigonus, C. picrocarpus, or another wild melon or wild relative of melon. It is understood that the term "introgression fragment" never includes a whole chromosome, but only a part of a chromosome. The introgression fragment can be large, e.g. even half of a chromosome, but is preferably smaller, such as about <NUM> Mb, <NUM> Mb, <NUM> Mb, <NUM> Mb, <NUM> Mb, <NUM> Mb or less, such as about <NUM> Mb or less, about <NUM> Mb or less, about <NUM> Mb or less, about <NUM> Mb or less, about <NUM> Mb or less, about <NUM> Mb or less, about <NUM> Mb or less, about <NUM> Mb or less, about <NUM> Mb or less, about <NUM> Mb (equals <NUM>,<NUM>,<NUM> base pairs) or less, or about <NUM> Mb (equals <NUM>,<NUM> base pairs) or less, such as about <NUM>,<NUM> bp (equals <NUM> kilo base pairs) or less, about <NUM>,<NUM> bp (<NUM> kb) or less, about <NUM>,<NUM> bp (<NUM> kb) or less, about <NUM>,<NUM> bp (<NUM> kb) or less.

A genetic element, an introgression fragment or a gene or allele conferring a trait (such as resistance against whitefly) is said to be "obtainable from" or can be "obtained from" or "derivable from" or can be "derived from" or "as present in" or "as found in" a plant or seed or tissue or cell if it can be transferred from the plant or seed in which it is present into another plant or seed in which it is not present (such as a line or variety) using traditional breeding techniques without resulting in a phenotypic change of the recipient plant apart from the addition of the trait conferred by the genetic element, locus, introgression fragment, gene or allele. The terms are used interchangeably and the genetic element, locus, introgression fragment, gene or allele can thus be transferred into any other genetic background lacking the trait. Not only seeds deposited and comprising the genetic element, locus, introgression fragment, gene or allele can be used, but also progeny/descendants from such seeds which have been selected to retain the genetic element, locus, introgression fragment, gene or allele, can be used and are encompassed herein, such as commercial varieties developed from the deposited seeds or from descendants thereof. Whether a plant (or genomic DNA, cell or tissue of a plant) comprises the same genetic element, locus, introgression fragment, gene or allele as obtainable from the deposited seeds can be determined by the skilled person using one or more techniques known in the art, such as phenotypic assays, whole genome sequencing, molecular marker analysis, trait mapping, chromosome painting, allelism tests and the like.

The "Wf_<NUM>-allele" or "Wf-allele" or "whitefly resistance allele" refers to a B. tabaci biotype B resistance-conferring allele found at the B. tabaci resistance-conferring locus Wf_11. <NUM>, or at the resistance-conferring part of the locus, introgressed into cultivated melon (onto cultivated C. melo chromosome <NUM>) from a wild melon or wild relative of melon, e.g. from plants of which a representative sample of seeds were deposited under accession number NCIMB <NUM> or NCIMB <NUM>. The term "Wf-allele", thus, also encompasses Wf-alleles obtainable from other B. tabaci biotype B resistant Cucumis accessions, such as Wf_11. <NUM> orthologous alleles (see below). When one or two Wf-alleles are present at the Wf_11. <NUM> resistance-conferring locus in the genome (i.e. in heterozygous or homozygous form), the plant is resistant against B. tabaci biotype B, i.e. has a B. tabaci resistance phenotype. In cultivated melon plant lacking the introgression fragment, the C. melo allele found at the same locus on chromosome <NUM> is herein referred to as "wf" allele (or whitefly-susceptible allele). As the resistance is dominant, wf/wf plants show a B. tabaci-susceptible phenotype, whereas Wf/wf plants and Wf/Wf plants are plants which possess the B. tabaci resistant phenotype conferred by the Wf-allele (i.e. are resistant to B. tabaci biotype B).

"Wf orthologous alleles" or "Wf orthologs" or "orthologs of Wf" are alleles of Wf_11. <NUM> resistance gene present in other wild relatives of melon, on the orthologous chromosomes <NUM>. Such orthologous alleles may, thus, be found on orthologous chromosome <NUM> of wild relatives of C. melo, such as C. callosus, C. trigonus, C. picrocarpus and others and are transferrable, by introgression, onto cultivated C. melo chromosome <NUM>.

tabaci resistance phenotype" or "B. tabaci biotype B resistance phenotype" or "Wf resistance" or "whitefly resistance" or "whitefly resistant plants" or "B. tabaci biotype B resistant plants" refers to resistance against B. tabaci biotype B conferred by the Wf allele (or by the Wf orthologous allele) when present in the C. melo genome in one or two copies (i.e. in heterozygous or homozygous from). The Wf resistance phenotype and the presence of the Wfallele and/or orthologs of Wf can be tested using the "Wf resistance assay" and/or the Wfmarker assays.

A "Wf - resistance assay" or "Wf assay" can be carried out in different ways, either by controlled environment tests and/or as a field test, as described herein below and in the Examples. The assay is preferably a free-choice assay, preferably in a field with natural whitefly infestation. Sufficient plants per replicate and sufficient replicates should be used, as well as appropriate control plants (especially whitefly susceptible controls, such as varieties Medellin F1 (Nunhems) or Caribbean Gold F1 (Rijk Zwaan), and preferably also resistant controls, such as plants grown from seeds of NCIMB <NUM> and NCIMB <NUM>). Average numbers of adult whiteflies and/or third instar nymphs can be counted on leaf discs and/or on whole leaves in order to determine whether a plant line has whitefly resistance, i.e. statistically the average number of adult whiteflies and/or third instar nymphs is significantly reduced in a whitefly resistant plant line compared to the susceptible control plant.

The "Wf - marker assay" is a molecular marker assay which can be used to test whether on C. melo chromosome <NUM> an introgression from a wild melon, or wild relative of melon, comprising the Wf-resistance allele is present in the genome (or whether in wild melon or wild relatives of melon comprise the Wf_11. <NUM> QTL-comprising region in their genome), by determining the genotype of one or more (e.g. of any <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>,<NUM>, <NUM>, <NUM>, or more) SNP (Single Nucleotide Polymorphism) markers of the group consisting of: mME20364 and/or mME17490 and/or mME15248 and/or mME17306 and/or mME26059 and/or mME38084 and/or mME21974 and/or mME12777 and/or mME15151 and/or mME26139 and/or mME48762 and/or mME25039 and/or mME40109 and/or of any wild melon or wild-relative of melon genome-specific marker in-between SNP markers mME20364 and mME40109, such as in between any two of the aforementioned markers as described elsewhere herein and as can be seen on <FIG>. The molecular markers are genetically and physically linked to Wf_11.

"Melon" or "muskmelon" refers herein to plants of the species Cucumis melo. Melons or 'muskmelons', Cucumis melo, can be classified into: C. melo cantalupensis, C. melo inodorous and C. melo reticulatus. melo cantalupensis are also referred to as Cantaloupes and are primarily round in shape with prominent ribs and almost no netting. Most have orange, sweet flesh and they are usually very fragrant. In contrast to the European cantaloupe, the North American 'Cantaloupe' is not of this type, but belongs to the true muskmelons. melo inodorous (or winter melons) can be subdivided into different types, such as Honeydew melon, Piel de Sapo, Sugar melon, Japanese melon, etc. C. melo reticulatus is the true muskmelon, with reticulated skin (netted) and includes Galia melons, Sharlyn melons and the North American cantaloupe.

"Cultivated melon" refers to plants of Cucumis melo i.e. varieties, breeding lines or cultivars of the species C. melo, cultivated by humans and having good agronomic characteristics, especially producing edible and marketable fruits of good size and quality and uniformity; preferably such plants are not "wild plants", i.e. plants which generally have much poorer yields and poorer agronomic characteristics than cultivated plants and e.g. grow naturally in wild populations. "Wild plants" include for example ecotypes, PI (Plant Introduction) lines, landraces or wild accessions or wild relatives of a species.

Melon and the wild relatives of melon is/are diploid and has/have <NUM> pairs of homologous chromosomes, numbered <NUM> to <NUM>. "Melon chromosome <NUM>" refers to the C. melo chromosome <NUM>, as known in the art and as referred to by the ICuGI nomenclature. "Orthologous chromosome <NUM>" refers to the chromosome <NUM> of wild relatives of melon, parts of which can be introgressed into cultivated melon chromosome <NUM>.

"Wild melon" includes wild plants of the species Cucumis melo, e.g. C. melo ssp agrestis, C. texanus, C. acidulous, seeds deposited under NCIMB <NUM>, NCIMB <NUM>, and other wild C. melo accessions, as e.g. landraces or PI accessions found on http://www. gov or other seed collections. Seeds deposited under NCIMB <NUM> were obtained from the ARS-GRIN collection and have as designated origin 'India'. Seeds deposited under NCIMB <NUM> were obtained from the ARS-GRIN collection and have an unknown origin.

"Wild relatives of melon" include wild plants of other Cucumis species, but which can be crossed with Cucumis melo to produce fertile offspring (optionally with the aid of embryo rescue, temperature-dependent enhancement of pollen-tube growth, or similar techniques to overcome reproductive barriers) and from which chromosome fragments can be obtained and transferred into Cucumis melo (either by interspecific crosses with C. melo or via crosses with a bridge species). Examples of wild relatives of melon are C. anguria, C. metuliferus, Cucumis callosus, Cucumis trigonus, Cucumis ficifolius, C. picocarpus, C. zeyheri, C. africanus, C. meeusei, C. prophetarum, C. hystrix, C. queenslandicus, and other Cucumis species (see e.g. <NPL>).

"Average" or "mean" refers herein to the arithmetic mean and both terms are used interchangeably. The term "average" or "mean" thus refers to the arithmetic mean of several measurements. The skilled person understands that the phenotype of a plant line or variety depends to some extent on growing conditions and that, therefore, arithmetic means of at least <NUM>, <NUM>, <NUM>, <NUM> or more plants (or plant parts) are measured, preferably in randomized experimental designs with several replicates and suitable control plants grown under the same conditions in the same experiment. "Statistically significant" or "statistically significantly different" refers to a characteristic of a plant line or variety (e.g. a cultivated melon plant comprising the Wf_11. <NUM> QTL of the invention) that, when compared to a suitable control (e.g. a Wf susceptible plant line or variety) show a statistically significant difference in that characteristic (e.g. p < <NUM> using ANOVA) from the (mean of the) control, e.g. a "statistically significantly reduced" average number of adult whiteflies and/or third instar nymphs in plants comprising the Wf_11. <NUM> QTL compared to susceptible controls.

A "recombinant chromosome" refers to a chromosome having a new genetic makeup arising through crossing over between homologous chromosomes, e.g. a "recombinant chromosome <NUM>", i.e. a chromosome <NUM> which is not present in either of the parent plants and arose through a rare crossing-over event between homologous chromosomes of a chromosome <NUM> pair. Herein, for example, a recombinant melon chromosome <NUM> comprising a Wf-resistance conferring locus, or resistance-conferring part thereof (comprising a Wf-resistance allele), is provided. The recombinant chromosome <NUM> comprises an introgression fragment from a wild or wild relative of melon, which fragment comprises a Wf-resistance conferring allele (as can be determined through the Wf resistance phenotype and/or by the presence of one or more of the molecular markers).

The term "traditional breeding techniques" encompasses herein crossing, backcrossing, selfing, selection, double haploid production, embryo rescue, protoplast fusion, marker assisted selection (MAS), mutation breeding etc. as known to the breeder (i.e. methods other than genetic modification/transformation/transgenic methods), by which, for example, a recombinant chromosome <NUM> can be obtained, identified and/or transferred.

"Backcrossing" refers to a breeding method by which a (single) trait, such as Wf resistance, can be transferred from an inferior genetic background (e.g. a wild melon or wild relative of melon; also referred to as "donor") into a superior genetic background (also referred to as "recurrent parent"), e.g. cultivated melon. An offspring of a cross (e.g. an F1 plant obtained by crossing a wild, Wf -resistant melon with a cultivated, Wf -susceptible melon; or an F2 plant or F3 plant, etc., obtained from selfing the F1) is "backcrossed" to the parent with the superior genetic background, e.g. to the cultivated, Wf -susceptible, parent. After repeated backcrossing (BC1, BC2, etc.) and optionally selfings (BC1S1, BC2S1, etc.), the trait of the inferior genetic background is incorporated into the superior genetic background.

"Marker assisted selection" or "MAS" is a process of using the presence of molecular markers, which are genetically linked to a particular locus or to a particular chromosome region (e.g. introgression fragment), to select plants for the presence of the specific locus or region (introgression fragment). For example, a molecular marker genetically and physically linked to an Wf-resistance locus, can be used to detect and/or select melon plants comprising the Wf-resistance locus. The closer the genetic linkage of the molecular marker to the locus (e.g. about <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or less), the less likely it is that the marker is dissociated from the locus through meiotic recombination.

"LOD-score" (logarithm (base <NUM>) of odds) refers to a statistical test often used for linkage analysis in animal and plant populations. The LOD score compares the likelihood of obtaining the test data if the two loci (molecular markers loci and/or a phenotypic trait locus) are indeed linked, to the likelihood of observing the same data purely by chance. Positive LOD scores favor the presence of linkage and a LOD score greater than <NUM> is considered evidence for linkage. A LOD score of +<NUM> indicates <NUM> to <NUM> odds that the linkage being observed did not occur by chance.

"Vegetative propagation", "vegetative reproduction" or "clonal propagation" are used interchangeably herein and mean the method of taking part of a plant and allowing that plant part to form at least roots where plant part is, e.g., defined as or derived from (e.g. by cutting of) leaf, pollen, embryo, cotyledon, hypocotyl, cells, protoplasts, meristematic cell, root, root tip, pistil, anther, flower, shoot tip, shoot, stem, fruit, petiole, etc. When a whole plant is regenerated by vegetative propagation, it is also referred to as a vegetative propagation or a vegetatively propagated plant.

"Cell culture" or "tissue culture" refers to the in vitro culture of cells or tissues of a plant.

"Regeneration" refers to the development of a plant from cell culture or tissue culture or vegetative propagation.

"Transgene" or "chimeric gene" refers to a genetic locus comprising a DNA sequence, such as a recombinant gene or a recombinant chromosome or part thereof, which has been introduced into the genome of a melon plant by transformation, such as Agrobacterium mediated transformation. A plant comprising a transgene stably integrated into its genome is referred to as "transgenic plant". A transgene or transgenic plant may also contain a complete recombinant chromosome or part of a recombinant chromosome, e.g. the part comprising the Wf-allele, introduced into the genome by transformation.

An "isolated nucleic acid sequence" or "isolated DNA" refers to a nucleic acid sequence which is no longer in the natural environment from which it was isolated, e.g. the nucleic acid sequence in a bacterial host cell or in the plant nuclear or plastid genome.

A "host cell" or a "recombinant host cell" or "transformed cell" are terms referring to a new individual cell (or organism) arising as a result of at least one nucleic acid molecule, having been introduced into said cell. The host cell is preferably a plant cell or a bacterial cell. The host cell may contain the nucleic acid as an extra-chromosomally (episomal) replicating molecule, or comprises the nucleic acid integrated in the nuclear or plastid genome of the host cell, or as introduced chromosome, e.g. minichromosome.

"Sequence identity" can be determined by alignment of two peptide or two nucleotide sequences using global or local alignment algorithms. Sequences may then be referred to as "substantially identical" or "essentially similar" when they are optimally aligned by for example the programs GAP or BESTFIT or the Emboss program "Needle" (using default parameters, see below) share at least a certain minimal percentage of sequence identity (as defined further below). These programs use the Needleman and Wunsch global alignment algorithm to align two sequences over their entire length, maximizing the number of matches and minimises the number of gaps. Generally, the default parameters are used, with a gap creation penalty = <NUM> and gap extension penalty = <NUM> (both for nucleotide and protein alignments). For nucleotides the default scoring matrix used is DNAFULL and for proteins the default scoring matrix is Blosum62 (<NPL>). Sequence alignments and scores for percentage sequence identity may for example be determined using computer programs, such as EMBOSS as available on the world wide web under ebi. uk/Tools/psa/emboss_needle/). Alternatively sequence similarity or identity may be determined by searching against databases such as FASTA, BLAST, etc., but hits should be retrieved and aligned pairwise to compare sequence identity. Two proteins or two protein domains, or two nucleic acid sequences have "substantial sequence identity" if the percentage sequence identity is at least <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>% or more (e.g. at least <NUM>, <NUM><NUM><NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or more (as determined by Emboss "needle" using default parameters, i.e. gap creation penalty = <NUM>, gap extension penalty = <NUM>, using scoring matrix DNAFULL for nucleic acids an Blosum62 for proteins).

The present invention relates to a cultivated Cucumis melo plant comprising resistance against Bemisia tabaci biotype B (referred to herein as Wfresistance) as set out in the appended claims. In particular, the resistance is conferred by an introgression fragment on cultivated melon chromosome <NUM>, wherein said introgression fragment is from a wild plant of the species Cucumis melo as set out in the appended claims.

The present inventors crossed two different wild C. melo accessions, representative seeds of which were deposited under NCIMB <NUM> and NCIMB <NUM>, to a Wf-susceptible melon breeding line of cantaloupe background and to a Wf-susceptible melon breeding line of canary background, respectively, and carried out QTL-mapping.

Surprisingly, in both mapping populations, a highly significant QTL for Wf - resistance was found on melon chromosome <NUM>, indicating that different wild Cucumis melo accessions comprise a Wf- resistance locus on chromosome <NUM>, which was transferred into cultivated C. melo and conferred Wf- resistance onto the cultivated melon plant. In the two mapping populations the QTL, which was named Wf_11. <NUM>, explained <NUM>% and <NUM>% of the observed phenotypic variation for Wf resistance and is, therefore, highly significant. Two cultivated melon plants which comprise different size introgressions of the Wf_11. <NUM> QTL in homozygous form (i.e. two recombinants; comprising a recombinant chromosome <NUM>) have been deposited under accession numbers NCIMB <NUM> and NCIMB <NUM>. NCIMB <NUM> comprises the Wf_11. <NUM> QTL from NCIMB41966 and NCIMB42221 comprises the Wf_11. <NUM> QTL from wild accession NCIMB41965. Both show high field resistance against B. tabaci Biotype B, as seen in the (statistically) significantly reduced average number of <NUM>rd instar nymphs and average number of adult whiteflies compared to the average numbers found on the susceptible parents lacking the introgression.

Reference herein to an introgression fragment on chromosome <NUM> having a QTL or an Wf-resistance conferring locus (or resistance-conferring part thereof) encompasses that the introgression fragment comprises all parts of the resistance-conferring locus needed to confer Wf-resistance. In cases of smaller introgression fragments, the introgression fragment is at least a large enough introgression region so that Wf-resistance is conferred by the introgression fragment when the introgression fragment is in heterozygous or homozygous form in the C. melo genome. So, when the introgression fragment is present in, or transferred into, a Wf susceptible melon line or variety, the otherwise susceptible line or variety becomes resistant against Wf as determinable by a Wf-resistance assay. The presence of the introgression fragment in the DNA of the cells, tissues or organs of the melon plant can be confirmed by detecting the presence of the resistant genotype of one or more SNP markers described herein, e.g. in the Wf marker assay. It is noted that the presence of the molecular markers as set out in the appended claims is a tool to confirm the presence of the introgression fragment on chromosome <NUM> in phenotypically resistant plants and/or to differentiate the instant plants from other phenotypically resistant plants (which e.g. have Wf resistance on other chromosomes). As different size introgression fragments are encompassed herein not all markers need to be present, and the presence of the markers as set out in the appended claims is sufficient. The introgression is found in the lower half of the chromosome <NUM> map, below the ICuGI SNP marker Ps_24-E03, as shown in <FIG>, especially starting from and/or below marker mME20364.

Thus, in one aspect a cultivated melon plant is provided which comprises Wf-resistance (as determinable in a Wf -resistance assay) and which comprises the resistant genotype of the markers as set out in the appended claims.

As described herein different size introgression fragments can equally confer resistance, so that the presence of the resistant genotype of one or more markers of the following groups and sub-groups is described herein:.

Markers "in between" the above mentioned markers are for example those which are positioned in between those markers as seen in <FIG>, or other markers that are not explicitly shown in <FIG>, but which are also flanked by the marker pairs mentioned. The skilled person can easily identify new markers in the genomic region or subgenomic region being flanked by any of the marker pairs listed above. Such markers need not to be SNP markers, but can be any type of genotypic or phenotypic marker mapped to that genomic or subgenomic region. Preferably such markers are genetically and physically linked to the Wf_11. <NUM> QTL as present in (and as derivable from) at least wild accessions NCIMB <NUM> and NCIMB41966, but preferably also as present in other wild melons or wild relatives of melon which comprise Wf resistance. In other words, the markers are preferably indicative of the presence of the QTL on chromosome <NUM> in a non-source specific manner.

As can be seen in <FIG>, three markers are population (source) specific, i.e. found only in one of the resistance sources. These are markers mME17011, which is linked to QTL Wf_11. <NUM> originating from resistance source NCIMB41965 and markers mME22724 and mME21134, which are linked to QTL Wf_11. <NUM> originating from resistance source NCIMB <NUM>. Such source specific markers can of course also be used to identify and/or transfer the Wf_11. <NUM> QTL derived from that source. Other source specific markers can be developed by the skilled person.

Thus, in one aspect a cultivated melon plant is provided which comprises Wfresistance (as determinable in a Wf - resistance assay) and which comprises the resistant genotype as set out in the appended claims.

The resistance genotype of each of the markers refers to the genotype present in the plant comprising the Wf_11. <NUM> QTL in homozygous or heterozygous form. The resistance genotype of the markers is shown herein below:.

As the resistance is dominant, also the heterozygous introgression confers resistance. Thus, the presence of the introgression fragment is determinable by the presence of the resistance genotype of one or more markers, whereby the resistance genotype may be the single nucleotide in homozygous form (e.g. CC for mME20364) or in heterozygous form (e.g. CT for mME20364). The susceptible genotype is homozygous for the other nucleotide (for mME20364 this is TT).

In one aspect a cultivated melon plant is provided herein, which is resistant against whitefly due to the presence of a recombinant chromosome <NUM>. The recombinant chromosome <NUM> comprises an introgression fragment which comprises a Wfresistance conferring QTL, as determinable by the presence of a resistance genotype of the markers as set out in the appended claims.

Exemplary are cultivated melon plants comprising a recombinant chromosome <NUM> and/or an introgression fragment on chromosome <NUM> as present in seeds deposited under accession number NCIMB <NUM> or NCIMB <NUM>, or progeny (descendants) thereof which retain the Wf resistance QTL. However, the skilled person can easily make other cultivated melon plants comprising the Wf resistance QTL of the invention.

Plants deposited under accession number NCIMB <NUM> (comprising an introgression fragment on chromosome <NUM> derivable from NCIMB <NUM>) comprise an introgression fragment of about <NUM>. The introgression fragment is in homozygous form and is detectable by (the resistance genotype of) one or more markers selected from the group: mME17490 and/or mME15248 and/or mME17306 and/or mME26059 and/or mME38084 and/or mME21974 and/or mME12777 and/or mME17011 and/or mME15151 and/or mME26139 and/or mME48762 and/or mME25039 and/or mME40109 and/or of any wild melon or wild-relative of melon genome-specific marker in-between SNP markers mME17490 and mME40109, such as in between any two of the aforementioned markers (see also <FIG>). This plant comprises field resistance against B. tabaci, as shown in the Examples.

Plants deposited under accession number NCIMB <NUM> (comprising an introgression fragment on chromosome <NUM> derivable from NCIMB <NUM>) comprise an introgression fragment of about <NUM>. The introgression fragment is in homozygous form and is detectable by (the resistance genotype of) one or more markers selected from the group: mME22724 and/or mME15248 and/or mME17306 and/or mME26059 and/or mME38084 and/or mME21974 and/or of any wild melon or wild-relative of melon genome-specific marker in-between SNP markers mME22724 and mME21974, such as in between any two of the aforementioned markers (see also <FIG>). This plant comprises field resistance against B. tabaci, as shown in the Examples.

Therefore, in one aspect a cultivated melon plant is provided comprising whitefly resistance due to a recombinant chromosome <NUM>, said recombinant chromosome <NUM> comprises a resistance genotype as set out in the appended claims.

Progeny (descendants obtained by selfing and/or crossing) of a plant comprising a recombinant chromosome <NUM> as described herein may either retain the same size introgression fragment as in the parent plant or may comprise smaller size introgression fragments, which however still confer the B. tabaci resistance phenotype. The smaller introgression fragment, therefore, retains the resistance conferring part of the introgression fragment and the markers on that fragment.

Thus, in one aspect, it was found that a Quantitative Trait Loci (QTL Wf_11. <NUM>) which confers B. tabaci-resistance is present on chromosome <NUM> of wild melons and that this QTL, when transferred (introgressed) into a cultivated, B. tabaci-susceptible melon variety or breeding line, and when present in heterozygous or homozygous form, confers B. tabaci-resistance onto the cultivated melon plant. The QTL, or the introgression fragment comprising the QTL (comprising the Wf-resistance allele), is thus dominant, i.e. it is sufficient to have the introgression fragment on one of the chromosomes <NUM> (one recombinant chromosome <NUM>), while the homologous chromosome <NUM> of the pair may be a (non-recombinant) chromosome <NUM> of cultivated C. melo lacking the introgression fragment.

Although the present sources of Wf-resistance allele introgressions are two wild sources (NCIMB <NUM> and NCIMB <NUM>, from unknown origin and from India), there are likely other wild Cucumis accessions which comprise Wf- resistance alleles or Wf orthologous alleles at the same locus on chromosome <NUM>. Such Wf- resistance alleles or Wf-resistance orthologous alleles can also be identified and introgressed into cultivated C. melo as described herein, to generate a cultivated C. melo plant comprising a genome of C. melo and a recombinant chromosome <NUM>, whereby the recombinant chromosome <NUM> comprises a wild Cucumis species introgression fragment, which confers an Wf - resistance phenotype onto the cultivated C. melo plant when present in homozygous or heterozygous form.

Accessions of wild melons and wild relatives of melon, such as accessions obtainable from the USDA National Plant Germplasm System collection or other germplasm collections, can be screened for B. tabaci biotype B resistance using phenotypic and/or Wf-marker assays, and resistant accessions can be crossed with a Cucumis melo plant lacking B. tabaci resistance. The F2 generation (or further generation, such as the F3, F4, etc. and/or a backcross generations) can then be screened for recombinant plants having the Wf - resistance phenotype and/or the introgression fragment or a resistance conferring part thereof, using the molecular marker assays (Wf marker assay) described herein.

Thus, in an embodiment a cultivated Cucumis melo plant comprising resistance against Bemisia tabaci biotype B (Wf) is provided.

The presence of a Wf- resistance phenotype can be determined using the Wf resistance assay (e.g. vide infra), whereby plants are screened for resistance in the field or controlled environment using known methods. Importantly, sufficient plants (e.g. at least <NUM>, <NUM>, <NUM> or more) of a line or variety are included in sufficient replicates (e.g. at least <NUM>, <NUM>, <NUM> or more). Also suitable controls should be included, such as susceptible varieties or susceptible lines. Examples of B. tabaci susceptible controls are the Piel de Sapo variety Medellin F1 (Nunhems) and the Western Shipper variety Caribbean Gold F1 (Rijk Zwaan).

In the Wf - resistance assay plants are grown under the same environmental conditions, exposed to B. tabaci (e.g. natural field infestation), either the average number of nymphs (<NUM>rd instar) and/or the average number of adult whiteflies for each line or variety are determined at one or more time-points. Average disease scores can then be calculated for a line or variety. When the average number of nymphs and/or adult whiteflies is (statistically) significantly lower on the line or variety comprising the recombinant chromosome <NUM> compared to the susceptible control(s), such as the variety Medellin F1, that line or variety comprises a Wf-resistance phenotype of the invention. In one aspect, the average number of <NUM>rd instar nymphs and/or of adult whiteflies is <NUM>% or less than that of the susceptible control, preferably, it is <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, <NUM>% or less, or <NUM>% or less of the average number found on the susceptible control variety when grown under the same conditions.

The resistance against Wf is conferred by an introgression fragment on chromosome <NUM>, wherein the introgression fragment is derived from a wild melon genome or from a wild relative of melon. The introgression fragment comprises the Quantitative Trait Locus (QTL) referred herein to as Wf_11. <NUM>, which locus in turn comprises a Wf-resistance allele, or a Wf-orthologous resistance allele, of the Wf - resistance gene.

The cultivated melon plants according to the invention, thus, have a recombinant chromosome <NUM>, which comprises an introgression fragment of a wild melon chromosome <NUM> as set out in the appended claims.

As the resistance is dominant, the resistance phenotype is seen when the resistance allele is in heterozygous or homozygous form, the cultivated melon plants according to the invention have the introgression fragment, or the resistance-conferring part thereof, on chromosome <NUM> in heterozygous or homozygous form.

The introgression fragment is derivable from (or derived from) or obtainable from (or obtained from) a wild plant of the species Cucumis melo, which comprises the Wf QTL (Wf_11. <NUM>) on chromosome <NUM> as set out in the appended claims.

In a specific embodiment, the introgression fragment comprising the B. tabaci resistance locus is derivable from (or derived from) or obtainable from (or obtained from) wild C. melo plants, a representative sample of seeds of which has been deposited under accession number NCIMB <NUM> or NCIMB41966. In one aspect the invention provides a cultivated C. melo plant which comprises resistance against B. tabaci biotype B, wherein the resistance is conferred by an introgression fragment on melon chromosome <NUM>, wherein said introgression fragment (conferring said Wf resistance) is obtained by (or obtainable by) crossing a plant of which seeds were deposited under Accession number NCIMB <NUM> or NCIMB41966 with a cultivated melon plant. Both these wild C. melo accessions have a Wf-resistance phenotype as shown in the Examples.

In one aspect described herein but not according to the invention the presence of the introgression fragment, or the chromosome <NUM> region (or orthologous chromosome <NUM> region), comprising the Wf-resistance locus, is detectable by a molecular marker assay which detects at least one, or at least <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or more of the following Single Nucleotide Polymorphism (SNP) markers:.

As mentioned, these SNP markers were found to be genetically linked to (or associated with) the introgression fragment on chromosome <NUM> comprising the QTL Wf <NUM> in both mapping populations, i.e. in plants comprising the resistance QTL from two different wild melon accessions.

Thus, in one aspect described herein, but not according to the invention, the Wf- resistant cultivated melon plants comprise at least one Cytosine (CC or CT genotype) instead of two Thymines (TT genotype) at nucleotide <NUM> of SEQ ID NO: <NUM> (referred to as SNP marker mME20364); and/or they comprise at least one Adenine (AA or AG genotype) instead of two Guanines (GG genotypes) at nucleotide <NUM> of SEQ ID NO: <NUM> (referred to as SNP marker mME17490); and/or they comprise at least one Cytosines (CC or CT genotype) instead of two Thymines (TT genotype) at nucleotide <NUM> of SEQ ID NO: <NUM> (referred to as SNP marker mME15248); and/or they comprise at least one Cytosine (CC or CT genotype) instead of two Thymines (TT genotype) at nucleotide <NUM> of SEQ ID NO: <NUM> (referred to as SNP marker mME17306); and/or they comprise at least one Adenine (AA or AT genotype) instead of two Thymines at nucleotide <NUM> of SEQ ID NO:<NUM> (referred to as SNP marker mME26059); and/or they comprise at least one Guanine (GG or GA genotype) instead of two Adenines (AA genotype) at nucleotide <NUM> of SEQ ID NO: <NUM> (referred to as SNP marker mME38084); and/or they comprise at least one Cytosine (e.g. CC or CA genotype) instead of two Adenines (AA genotype) at nucleotide <NUM> of SEQ ID NO: <NUM> (referred to as SNP marker mME21974); and/or they comprise at least one Cytosine (CC or CT genotype) instead of two Thymines (TT genotype) at nucleotide <NUM> of SEQ ID NO: <NUM> (refereed herein to as SNP marker mME12777); and/or they comprise at least one Guanine (GG or GA genotypes) instead of two Adenines (AA genotype) at nucleotide <NUM> of SEQ ID NO: <NUM> (referred to as SNP marker mME15151); and/or they comprise at least one Cytosine (CC or CA genotypes) instead of two Adenines (AA genotype) at nucleotide <NUM> of SEQ ID NO: <NUM> (referred to as SNP marker mME26139); and/or they comprise at least one Cytosines (CC or CA genotype) instead of two Adenines (AA genotype) at nucleotide <NUM> of SEQ ID NO: <NUM> (referred to as SNP marker mME48762); and/or they comprise at least one Cytosines (CC or CT genotype) instead of two Thymines (TT genotype) at nucleotide <NUM> of SEQ ID NO: <NUM> (referred to as SNP marker mME25039); and/or they comprise at least one Thymine (TT or TC genotype) instead of two Cytosines (CC genotype) at nucleotide <NUM> of SEQ ID NO: <NUM> (referred to as SNP marker mME40109), or any wild melon or wild-relative of melon genome-specific marker as listed in groups a) to zzz) above.

The SNP genotype refers to two nucleotides, and genomic sequences comprising one of these two nucleotides, one on each chromosome <NUM> of the chromosome pair. So a plant having a CC genotype for mME20364 has an identical nucleotide (C) on both chromosomes at nucleotide <NUM> of SEQ ID NO:<NUM>, while a plant having an AC genotype for mME21974 has one chromosome with an A at nucleotide <NUM> of SEQ ID NO: <NUM> and one chromosome with a C at nucleotide <NUM> of SEQ ID NO: <NUM>.

The skilled person can easily identify any wild melon or wild-relative of melon genome-specific marker as listed in a) to zzz) above. This can for example be done by sequencing genomic regions in-between any of the markers mentioned herein or by mapping new markers to a region in between any of the marker regions or sub-regions listed in groups a) to zzz). Preferably, but not necessarily, such markers are common markers, i.e. they are present on chromosome <NUM> of more than one QTL Wf_11. <NUM> resistance source, e.g. they are present in at least two or more Wf resistance sources, such as in NCIMB <NUM> and/ NCIMB <NUM> and/or any other wild melon or wild relative of melon which has Wf resistance due to a QTL on chromosome <NUM>.

Three markers were found in only one of the two populations, namely markers mME17011, mME22724 and mME21134 (see <FIG>). These markers are, therefore, not 'common' markers, but population specific markers. Obviously, such non-common markers can equally be used in identifying and/or selecting plants comprising an introgression fragment on chromosome <NUM> having QTL Wf_11. <NUM> and/or transferring an introgression fragment comprising QTL Wf_11. <NUM> from one melon plant into the genome of another melon plant (e.g. into a whitefly susceptible cultivated melon plant). Also, such herein 'non-common' markers may very well be/become common markers if they are also found in other Wf resistant plants comprising the Wf_11.

Marker mME17011 was found only in the population derived from NCIMB <NUM>, such as cultivated melon representative seeds of which were deposited under accession number NCIMB <NUM>. The marker is located in between makers mME12777 and mME15151 and falls therefore into the groups a)-e), m)-q), x)-bb), hh)-ll), qq)-uu), yy)-ccc), fff)-jjj) and lll)-ppp), as described above. The resistance genotype of mME17011 can be detected by at least one Thymine (TT or TC genotype) instead of two Cytosines (CC genotype) at nucleotide <NUM> of SEQ ID NO: <NUM>.

Markers mME22724 and mME21134 were only found in the population derived from NCIMB <NUM>, such as cultivated melon representative seeds of which were deposited under accession number NCIMB <NUM>. The marker mME22724 is located in between makers mME1749 and mME15248 and falls therefore into the groups a)-k) and m) - w). The marker mME21134 is located in between makers mME12777 and mME15151 and falls therefore into the groups a)-e), m)-q), x)-bb), hh)-ll), qq)-uu), yy)-ccc), fff)-jjj) and lll)-ppp), as described above. The resistance genotype can be detected by at least one Adenine (AA or AG genotype) instead of two Guanines (GG genotype) at nucleotide <NUM> of SEQ ID NO: <NUM> (for marker mME22724) or by at least one Thymine (TT or TC genotype) instead of two Cytosines (CC genotype) at nucleotide <NUM> of SEQ ID NO: <NUM>.

Thus in one aspect described herein, but not according to the invention, the presence of the introgression fragment, or the chromosome <NUM> region (or orthologous chromosome <NUM> region), comprising the Wf-resistance locus, is detectable by a molecular marker assay which detects at least one, or at least <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or more of the following Single Nucleotide Polymorphism (SNP) markers:.

Wf-resistant cultivated melon plants comprising at least one marker, preferably at least <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or more markers, selected from the markers mentioned in any group and sub-groups disclosed herein are described herein.

In a further aspect as described herein, but not according to the invention, the Wf - resistant cultivated melon plants comprise at least one Cytosine (CC or CT genotype) instead of two Thymines (TT genotype) at nucleotide <NUM> of SEQ ID NO: <NUM> (referred to as SNP marker mME20364); and/or they comprise at least one Adenine (AA or AG genotype) instead of two Guanines (GG genotypes) at nucleotide <NUM> of SEQ ID NO: <NUM> (referred to as SNP marker mME17490); and/or they comprise at least one Cytosines (CC or CT genotype) instead of two Thymines (TT genotype) at nucleotide <NUM> of SEQ ID NO: <NUM> (referred to as SNP marker mME15248); and/or they comprise at least one Cytosine (CC or CT genotype) instead of two Thymines (TT genotype) at nucleotide <NUM> of SEQ ID NO: <NUM> (referred to as SNP marker mME17306); and/or they comprise at least one Adenine (AA or AT genotype) instead of two Thymines at nucleotide <NUM> of SEQ ID NO:<NUM> (referred to as SNP marker mME26059); and/or they comprise at least one Guanine (GG or GA genotype) instead of two Adenines (AA genotype) at nucleotide <NUM> of SEQ ID NO: <NUM> (referred to as SNP marker mME38084); and/or they comprise at least one Cytosine (e.g. CC or CA genotype) instead of two Adenines (AA genotype) at nucleotide <NUM> of SEQ ID NO: <NUM> (referred to as SNP marker mME21974); and/or they comprise at least one Cytosine (CC or CT genotype) instead of two Thymines (TT genotype) at nucleotide <NUM> of SEQ ID NO: <NUM> (refereed herein to as SNP marker mME12777); and/or they comprise at least one Guanine (GG or GA genotypes) instead of two Adenines (AA genotype) at nucleotide <NUM> of SEQ ID NO: <NUM> (referred to as SNP marker mME15151); and/or they comprise at least one Cytosine (CC or CA genotypes) instead of two Adenines (AA genotype) at nucleotide <NUM> of SEQ ID NO: <NUM> (referred to as SNP marker mME26139); and/or they comprise at least one Cytosines (CC or CA genotype) instead of two Adenines (AA genotype) at nucleotide <NUM> of SEQ ID NO: <NUM> (referred to as SNP marker mME48762); and/or they comprise at least one Cytosines (CC or CT genotype) instead of two Thymines (TT genotype) at nucleotide <NUM> of SEQ ID NO: <NUM> (referred to as SNP marker mME25039); and/or they comprise at least one Thymine (TT or TC genotype) instead of two Cytosines (CC genotype) at nucleotide <NUM> of SEQ ID NO: <NUM> (referred to as SNP marker mME40109), and/or comprise any wild melon or wild-relative of melon genome-specific marker as listed in groups a) to zzz). In one aspect the wild melon or wild relative of melon genome-specific marker is selected from the group comprising the TT or TC genotype for SNP marker mME17011 at nucleotide <NUM> of SEQ ID NO: <NUM>; the AA or AG genotype for SNP marker mME22724 at nucleotide <NUM> in SEQ ID NO: <NUM>; and the TT or TC genotype for SNP marker mME21134 at nucleotide <NUM> in SEQ ID NO: <NUM>.

In one aspect as described herein, the introgression fragment, or the chromosome <NUM> region (or orthologous chromosome <NUM> region) comprising the Wf-resistance locus, which is detectable by the above markers is from a wild plant of the species Cucumis melo, and in one aspect, as set out in the appended claims, it is from a plant of which a representative sample of seeds has been deposited under accession number NCIMB <NUM> and NCIMB <NUM>, thus the QTL, and the chromosome <NUM> region comprising the QTL, is in one aspect the QTL as found in NCIMB <NUM> or in NCIMB <NUM>. In one aspect the introgression fragment, or the recombinant chromosome <NUM>, is obtained from crossing a plant grown from seeds deposited under accession number NCIMB <NUM> or NCIMB <NUM> with another melon plant, especially a cultivated melon plant of the species C. The cultivated melon plant is for example a plant which is susceptible against whitefly. The cultivated melon may be any line, variety or cultivar, such as cantaloupe, Canary, Western Shipper, Eastern Shipper, Charentais, Galia, Honey Dew, Piel de Sapo or other.

Thus, in one aspect as described herein, but not according to the invention, the Wf-resistant melon plant comprises an introgression fragment on chromosome <NUM>, which is obtainable from seeds of which a representative sample has been deposited under NCIMB <NUM> or NCIMB <NUM> and wherein the introgression fragment comprises, or is detectable by, at least <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or more SNP markers selected from the group consisting of.

To obtain the introgression fragment from the deposited seeds, a plant is grown from the seed and the plant is crossed with a susceptible C. melo plant to obtain F1 seeds. The F1 hybrid seed and plants grown therefrom, contain one chromosome <NUM> from the susceptible parent (without QTL Wf_11. <NUM>) and one chromosome <NUM> from the wild Wf-resistant parent. To generate recombination events between these two homologous chromosomes <NUM>, meiosis needs to take place and plants comprising the recombinant chromosomes <NUM> need to be identified. For example, the F1 can be selfed to produce F2 plants, and/or resistant F2 plants or F3 plants, etc., can be backcrossed to the susceptible parent. Plants which are resistant to whitefly can be screened for, and selected for, the presence of one or more of the above SNP markers in order to identify plants comprising a recombinant chromosome <NUM>, comprising a Wf-resistance conferring introgression fragment from the deposited seeds.

Similarly, cultivated melon plants comprising resistance against whitefly, whereby the resistance is conferred by an introgression fragment on chromosome <NUM>, can be generated and/or identified using different methods. For example, to obtain a cultivated melon plant comprising a Wf-resistance conferring introgression fragment from a wild melon or wild relative of melon, first a wild melon or wild relative of melon is identified which has an whitefly resistance phenotype and/or which comprises one or more of the SNP markers associated with Wf-resistance disclosed herein, e.g. any one, or more, or all of the markers above. The identified plant is crossed with a susceptible C. melo plant to obtain F1 seeds. The F1 hybrid seed and plants grown therefrom, contain one chromosome <NUM> from the susceptible parent (without QTL Wf_11. <NUM>) and one chromosome <NUM> from the wild Wf-resistant parent. To generate recombination events between these two homologous chromosomes <NUM>, meiosis needs to take place and plants comprising the recombinant chromosomes <NUM> need to be identified. For example, the F1 can be selfed to produce F2 plants, and/or resistant F2 plants or F3 plants, etc., can be backcrossed to the susceptible parent. Plants which are resistant to whitefly can be screened for, and/or selected for, the presence of one or more of the above SNP markers and/or screened for, and/or selected for, the presence of the Wf-resistance phenotype, in order to identify plants comprising a recombinant chromosome <NUM>, comprising a whitefly resistance conferring introgression fragment from the wild melon or wild relative of melon. Alternatively or in addition, QTL mapping can be carried out in order to identify further molecular markers linked to the QTL Wf_11. <NUM> and/or to generate cultivated C. melo plants comprising an introgression fragment on chromosome <NUM> which confers whitefly-resistance.

In one aspect described herein, but not according to the invention, the presence of the introgression fragment, or the chromosome <NUM> region (or orthologous chromosome <NUM> region), comprising the whitefly resistance locus, is detectable by a molecular marker assay which detects at least one (or <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or more) of the following markers:.

In one aspect described herein, but not according to the invention, at least one, two, at least three, at least four or more markers are detected from the markers of a) to n) above. In a specific embodiment at least one, two or three markers are detected selected from the group consisting of c) (mME15248), d) (mME17306), e) (mME26059), or any wild melon or wild-relative of melon genome specific marker in between marker b) (mME17490) and h) (mME12777) ), e.g. c) and d); c) and e); c) and a marker between b) and h); d) and e); d) and a marker between b) and h); or e) and a marker between b) and h).

Any wild melon or wild-relative of melon genome-specific marker in-between two markers (or flanked by two markers, which can be referred to as flanking markers) refers to (the resistance genotype of) any molecular marker which maps genetically to the chromosome <NUM> region in-between the markers (see <FIG>) and/or which lies physically in-between the markers, and which is indicative of the wild melon chromosome <NUM> region or of the wild-relative of melon chromosome <NUM> region. This means that the marker is polymorphic between the cultivated melon genome and the wild melon or wild-relative of melon genome. In one aspect, the marker is a Single Nucleotide Polymorphism, but other molecular markers such as RFLP, AFLP, RAPD, DNA sequencing, etc. may equally be used.

As two specific recombinants have been found which comprise two different introgression fragments conferring good resistance against whitefly, as shown in <FIG>, the presence of at least <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or more of the markers present in both recombinants is an aspect described herein. Thus (the resistance genotype of) any marker in-between marker mME17490 and mME12777 are preferably present and indicative of the QTL Wf_11. Examples of such markers are marker mME15248, mME17306, mME26059, mME38048, mME21974 and/or mME12777, and/or others in between the two flanking markers mME17490 and mME12777. Thus, in one aspect described herein at least <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM> markers are present selected from the group consisting of marker mME15248, mME17306, mME26059, mME38048, mME21974 and/or mME12777. In one aspect as set out in the appended claims at least <NUM> markers are present of the group consisting of marker mME15248, mME17306, mME26059, mME38048, mME21974 and mME12777.

In one embodiment, as set out in the appended claims, the presence of the introgression fragment, or the chromosome <NUM> region (or orthologous chromosome <NUM> region), comprising the Wf_11. <NUM> resistance locus, is detectable by a molecular marker assay which detects all of the following markers:.

Thus, in one aspect all of markers i) to vi) are detected.

The molecular markers described herein may be detected according to standard method. For example SNP markers can easily be detected using a KASP-assay (see www. kpbioscience. uk) or other assays. For developing the KASP-assay <NUM> base pairs upstream and <NUM> basepairs downstream of the SNP are selected and two allele-specific forward primers and one allele specific reverse primer is designed. See e.g. <NPL>, especially p1097-<NUM> for KASP assay method.

Thus, in one aspect, the SNP markers and the presence/absence of the marker associated with the Wf_11. <NUM>-resistance allele is determined using a KASP assay (e.g. as described in the Examples), but equally other assays can be used. For example, optionally DNA sequencing may also be used.

Physical mapping using BACs (Bacterial Artificial Chromosomes) and development of markers for the BACs can be carried out to map the physical location of Wf_11. <NUM> on chromosome <NUM> and to develop markers which lie physically between any of the markers mentioned and to determine physical distances between markers and/or determine introgression size.

The size of an introgression fragment can for example also be determined by visualization of the introgression using Fluorescent in situ hybridization (FISH) images (<NPL>).

In one embodiment of the invention, the Wf-resistance conferring introgression fragment is equal to or less than <NUM> Mb in size, equal to or less than <NUM> Mb in size, preferably equal to or less than <NUM> Mb in size, equal to or less than <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM> Mb in size, more preferably even less, such as equal to or less than 500kb, 400kb, 300kb, 200kb, 100kb, 50kb, 25kb, 20kb, 15kb, or less, but still comprises the Wf-resistance allele and still confers whitefly resistance to an otherwise susceptible C. melo plant. Resistance is conferred by the recombinant chromosome <NUM>, and the introgression fragment comprising the Wf resistance allele when the introgression fragment is in heterozygous or homozygous form. Plants with smaller introgression fragments on chromosome <NUM> can be generated by generating new recombinant plants from a population of plants derived from a cross between a cultivated whitefly susceptible plant and a wild whitefly resistant melon or relative of melon. Alternatively, when a cultivated C. melo plant having a whitefly-resistance conferring introgression fragment is identified, the introgression size can be reduced by e.g. selfing that plant and selecting recombinant progeny having smaller introgression sizes.

In tomato, for example the large S. chilense introgression fragment on chromosome <NUM> (about <NUM>) which comprises the Ty-<NUM> allele has been reduced by selecting a recombinant progeny line (LA1931-AL-F2), which comprises a much smaller S. chilense introgression fragment (about <NUM>) comprising Ty-<NUM> (see <NPL>).

The cultivated melon plant according to the invention may be an inbred or an F1 hybrid. In one aspect the F1 hybrid comprises the introgression fragment in heterozygous form, i.e. produced by crossing two inbred parent lines, one of which possesses the introgression fragment (preferably in homozygous form, although not necessarily) and collecting the F1 hybrid seeds from said cross. The F1 hybrid may also comprise the introgression fragment in homozygous form, i.e. produced by crossing two inbred parent lines, each comprising the introgression fragment in homozygous or heterozygous form.

The cultivated melon plant may be of any type. Preferably it has good agronomic and good fruit quality characteristics, such as large average fruit weight (at least <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or more), high average brix of the fruits (e.g. an average refractometer % total soluble solids of at least <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>% or more), many fruits being produced per plant, firm fruit flesh, etc. The cultivated melon may be a C. melo cantalupensis, C. melo inodorous and C. melo reticulatus. melo cantalupensis are also referred to as Canteloupes and are primarily round in shape with prominent ribs and almost no netting. Most have orange, sweet flesh and they are usually very fragrant. In contrast to the European cantaloupe, the North American 'Cantaloupe' is not of this type, but belongs to the true muskmelons. melo inodorous (or winter melons) can be subdivided into different types, such as Honeydew melon, Piel de Sapo, Sugar melon, Japanese melon, etc. C. melo reticulatus is the true muskmelon, with reticulated skin (netted) and includes Galia melons, Sharlyn melons and the North American cantaloupe. Melons come in many sizes and shapes including round, oval, and cylindrical. The flesh is generally orange and quite sweet, but some varieties of melon and specifically, the Persian melons, can have green or white flesh. Some green-fleshed melons are quite sweet, but most of the green- and white-fleshed melons have a less sweet, but very refreshing flavor. Melons according to the invention may be any type, e.g. any of the here mentioned types. in one aspect the Wf resistant melon is a Yellow Canary; in another aspect a cantaloupe.

Also other resistances may be introduced into the melon plants of the invention, such as resistance to one or more of the following diseases: MYaV resistance (Melon Yellowing Associated Virus); Bacterial Wilt, Root Rot, Crown Blight, Melon Rust, Powdery Mildew, Verticillum Wilt, Sulphur Burn, Scab, Watermelon Mosaic, Downy Mildew, Fusarium oxysporum f. melonis (Fom) race <NUM>, Fusarium oxysporum f. melonis (Fom) race <NUM>, Fusarium oxysporum f. melonis (Fom) race <NUM>, Fusarium oxysporum f. melonis (Fom) race <NUM>, Fusarium Wilt R2, Root Knot (Nematode), Anthracnose, Cucumber Mosiac, and Squash Mosaic, and/or resistance to one or more of the following pests: Aphid resistance, Pickle Worm, Darkling Ground Beetle, Banded Cucumber Beetle, Mite, Western Spotted Cucumber Beetle, Melon Leafhopper, Melon Worm, Western Striped Cucumber Beetle or Melon Leafminer. Other resistance genes, against pathogenic viruses, fungi, bacteria or pests may also be introduced. In one aspect also ZYMV and/or WMV (Zuccini Yellow Mozaic Virus / Watermelon Mosaic Virus) resistance may be introduced into plants comprising the Wf_11. <NUM> QTL, e.g. such as the QTL described in <CIT>, which QTL is at a different locus of chromosome <NUM> than the Wf <NUM> locus.

In one aspect seeds from which plants of the invention can be grown are provided. In one aspect the seeds are F1 hybrid seeds, which comprise the recombinant chromosome <NUM> in homozygous or heterozygous form and which have a whitefly-resistance phenotype when grown in the field.

Also containers and packages containing or comprising seeds from which plants of the invention can be grown are provided herein. These may be labelled as containing cultivated melon seeds having whitefly resistance.

Also progeny seeds and progeny plants of plants of the invention are provided, which retain the whitefly resistance conferring introgression on chromosome <NUM>, or a smaller introgression, i.e. a resistance conferring part of the introgression fragment. Progeny may be any generation obtained by selfing a melon plant according to the invention and/or crossing a melon plant according to the invention with another melon plant one or more times. Progeny are, therefore, either the generation (seeds) produced from the first cross (F1) or selfing (S1), or any further generation produced by crossing and/or selfing (F2, F3, etc.) and/or backcrossing (BC1, BC2, BC1S1, etc.) one or more selected plants of the F1 and/or S1 and/or BC1 generation (or plants of any further generation, e.g. the F2) with another melon plant (and/or with a wild relative of melon). Progeny are preferably selected to retain the recombinant chromosome <NUM> comprising the introgression fragment from wild melon or from a wild relative of melon. Thus progeny also have the whitefly-resistance phenotype, preferably the same level of whitefly resistance as the plant used in the initial cross or selfing. The presence of (or retention of) the introgression fragment comprising the QTL Wf_11. <NUM> can be determined in the whitefly-resistance assay, phenotypically, and/or the molecular marker assay(s) described herein. Regarding phenotypic assessment, of course consideration needs to be given to the dominant nature of the Wf-resistance allele.

In a further aspect parts of the melon plants according to the invention are provided. Parts include for example cells and cell-cultures, tissue cultures, vegetative plant tissues (leaves, roots, etc.), flowers, pollen, embryos, fruits, parts of fruits, etc. The plant parts comprise the introgression fragment on chromosome <NUM>, as described, and as can be detected using one or more of the marker assays described. Also, when whole plants are regenerated from such melon parts, such as cells, cell- or tissue cultures, the regenerated plants comprise the recombinant chromosome <NUM>, and the whitefly resistance phenotype.

Thus, also provided is a plant cell, tissue or plant part of a plant or of a seed according the invention comprising at least one recombinant chromosome <NUM>, wherein said recombinant chromosome <NUM> comprises an introgression fragment from a wild C. melo plant and wherein said introgression fragment comprises an allele conferring whitefly resistance.

Also in vitro cell cultures and in vitro tissue cultures are encompassed herein, of cells or tissues comprising a recombinant chromosome <NUM> described. Preferably the cells or tissues can be regenerated into a whole melon plant, i.e. the cells are regenerable cells and the tissues comprise regenerable cells. Thus, also vegetative propagations of the plants according to the invention are an embodiment herein. Thus, a vegetatively propagated cultivated melon plant is provided which comprises the whitefly resistance phenotype and a recombinant chromosome <NUM> as described herein.

In a specific aspect a melon fruit harvested from a plant according to the invention is provided. Marketable melon fruits are generally sorted by size and quality after harvest. Also containers or packages comprising or consisting of harvested melon fruits are provided. Again, the cells of the fruits (such as cells of the fruit, e.g. exocarp, endocarp, fruit flesh, columnella) are distinguishable from other melons by the presence of the recombinant chromosome <NUM> (as determinable in one or more of the molecular marker assays and/or in a whitefly resistance assay by e.g. growing the seeds present in the fruits, or progeny obtained by selfing the plants grown from the seeds).

The invention also provides for a food or feed product comprising or consisting of a plant part described herein, the plant part comprising at least one recombinant chromosome <NUM>, wherein said recombinant chromosome <NUM> comprises an introgression fragment from a wild C. melo plant and wherein said introgression fragment comprises an allele conferring whitefly resistance. Preferably the plant part is a melon fruit or part thereof and/or an extract from a plant part described herein. The food or feed product may be fresh or processed, e.g., canned, steamed, boiled, fried, blanched and/or frozen, etc. For example, containers such as cans, boxes, crates, bags, cartons, Modified Atmosphere Packagings, films (e.g. biodegradable films), etc. comprising plant parts such as fruits or fruit parts (fresh and/or processed) described herein are also provided herein.

A further aspect described herein, but not according to the invention, is a method of producing a new cultivated melon plant which comprises an introgression fragment which confers whitefly-resistance when in homozygous or heterozygous form, as described. The method comprises crossing a plant of the invention, or a progeny plant thereof, either as male or as female parent, with a second melon plant (or a wild relative of melon) one or more times, and/or selfing a melon plant according to the invention, or a progeny plant thereof, one or more times, and selecting progeny from said crossing and/or selfing. The first and/or the second melon plant may for example be a line or variety of the species C. melo cantalupensis, C. melo inodorous or C. melo reticulatus.

Thus, a method for transferring the recombinant chromosome <NUM>, comprising the whitefly-resistance conferring locus (Wf_11. <NUM>), from one (cultivated) melon plant into another (cultivated) melon plant is described herein (but is not according to the invention), especially into whitefly-susceptible melon varieties or breeding lines.

The described method comprises the steps of:.

The presence or absence of the recombinant chromosome <NUM>, and of the introgression fragment, may be determined by one or more of the molecular marker assays described herein and/or by (a) whitefly-resistance assay(s). Further breeding in step f) may comprise selfing, crossing, double haploid production, backcrossing, etc. Plants and seeds obtainable by the above method are encompassed herein.

Thus the presence of the resistance genotype of one or more markers of the groups and/or subgroups described in a) to zzz) above is indicative of the presence of the introgression fragment. In particular the presence of the resistance genotype of one or more markers selected from the group: mME20364, mME17490, mME15248, mME17306 mME26059, mME38084, mME21974, mME12777, mME15151, mME26139, mME48762 mME2503, mME40109, any wild melon or wild-relative of melon genome-specific marker as listed in the groups and/or subgroups of a) to zzz) above, and any wild melon or wild relative of melon genome specific marker in-between the marker mME20364 and the marker mME40109. Any of these single markers, groups or subgroups of markers are referred to when reference is made herein to the "markers described elsewhere herein" or "molecular marker assays described herein".

Also described herein, but not according to the invention, is a method of producing C. melo F1 hybrid plants comprising a whitefly resistance phenotype comprising:.

The inbred melon plant of a) and b) may be homozygous and/or heterozygous for the introgression fragment, and they may contain introgression fragments of different sizes and/or of different origin, i.e. from different wild melons or wild relatives of melon.

The F1 hybrid seeds preferably comprise at least one recombinant chromosome <NUM> and the F1 plants grown from the seeds are therefore whitefly resistant in their phenotype.

The presence or absence of the recombinant chromosome <NUM>, and of the introgression fragment, may be determined by one or more of the molecular marker assays described herein and/or by (a) whitefly-resistance assay(s). Plants and seeds obtainable by the above method are encompassed herein.

In a different aspect a method for producing a cultivated C. melo plant comprising an introgression fragment on chromosome <NUM>, wherein said introgression fragment comprises a whitefly-resistance allele, is described herein (but is not according to the invention), said method comprising the steps:.

When referring to backcross populations in the method, the backcross populations may also be selfed, i.e. BC1S1, BC1S2, BC2S1, BC2S2, or others.

In one or more of steps b) to f) the presence of the whitefly-resistance allele (or the introgression fragment or wild chromosome <NUM> region comprising the allele) may be tested (and plants may be selected) by carrying out a molecular marker assay as described elsewhere herein, e.g. by determining whether the plant comprises the resistance genotype of one or more of the markers linked to the QTL, as described.

Using this method, one can generate and/or select new cultivated melon plants comprising an introgression with QTL Wf_11. <NUM> from a wild source, such as a wild melon or wild relative of melon (such as from NCIMB <NUM> or NCIMB <NUM>, or other wild melons or wild relatives of melon).

In one aspect the method for producing a cultivated C. melo plant comprising an introgression fragment on chromosome <NUM>, wherein said introgression fragment comprises a whitefly-resistance allele, is described herein but is not according to the invention, said described method comprises the steps:.

Also described herein, but not according to the invention, is a method for identifying a wild melon plant comprising whitefly resistance on chromosome <NUM>, said method comprising:.

In step c) also other molecular marker tests described elsewhere herein can be used. With this method one can, thus, screen wild melon accessions or wild relatives of melon for the presence of one or more of the markers and, thus, the presence of QTL Wf_11. <NUM> and introgress the resistance-conferring part of these new resistance sources into cultivated, whitefly-susceptible, melon plants.

Thus, for example, a method for identifying a wild melon plant comprising whitefly resistance on chromosome <NUM> is described herein but is not according to the invention, comprising the steps:.

Alternatively, a method for identifying a wild melon plant comprising whitefly resistance on chromosome <NUM> is described herein but is not according to the invention, comprises the following steps:.

In one aspect a method for identifying a cultivated C. melo plant comprising an introgression fragment on chromosome <NUM> is provided as set out in the appended claims, wherein said introgression fragment comprises a whitefly resistance allele, comprising:.

In this method also other molecular marker tests described elsewhere herein can be used. Thus, using this method one can detect the presence of an introgression fragment on chromosome <NUM> comprising QTL Wf_11. <NUM> in cultivated melon plants or plant parts.

In yet another aspect, as set out in the appended claims, a method for detecting whether a cultivated C. melo plant comprises an introgression fragment on chromosome <NUM>, wherein said introgression fragment comprises a whitefly-resistance allele, is provided, said method comprising:.

Molecular marker screening obviously involves obtaining plant material and analyzing the genomic DNA of the material for the marker genotype.

In this method also other molecular marker tests described elsewhere herein can be used. Thus, using this method one can detect the presence of an introgression fragment on chromosome <NUM> comprising QTL Wf_11. <NUM> in cultivated melon plants or plant parts. If one or more of the markers which are linked to the QTL are present, one can conclude that the plant comprises a whitefly-resistance conferring introgression fragment on chromosome <NUM>.

One can also use the methods and the markers described herein to reduce the size of the wild introgression fragment comprising the QTL Wf_11. <NUM>, i.e. to generate and select recombinants having a smaller introgression fragment on chromosome <NUM>, but which retain the whitefly resistance conferring part of the introgression fragment. One can equally develop alternative molecular markers linked to Wf_11. <NUM> for use in any of the aforementioned methods.

In one aspect the use of a recombinant chromosome <NUM> comprising an introgression fragment from a wild C. melo plant, said introgression fragment comprising an allele conferring whitefly-resistance, for breeding melon varieties having whitefly resistance is described herein but is not according to the invention.

In one aspect the use of a recombinant chromosome <NUM> comprising an introgression fragment from a wild C. melo plant, said introgression fragment comprising an allele conferring whitefly-resistance, for breeding melon varieties having whitefly resistance is described herein but is not according to the invention, wherein said recombinant chromosomes <NUM> is the recombinant chromosome <NUM> as found in seeds deposited under accession number NCIMB <NUM> or NCIMB42220, or is derived from said recombinant chromosome <NUM>. Thus, in one aspect a cultivated melon plant according to the invention and as set out in the appended claims comprising a recombinant chromosome <NUM> obtained by (obtainable by) crossing a plant grown from seeds deposited under accession number NCIMB <NUM>,or NCIMB <NUM>, or from progeny thereof which retain the recombinant chromosome <NUM>, with another melon plant.

A representative sample of seeds of wild melon accessions comprising the QTL (designated Wf_11. <NUM>) for whitefly resistance on chromosome <NUM> were deposited by Nunhems B. on <NUM> May <NUM> at the NCIMB Ltd. (Ferguson Building, Craibstone Estate, Bucksburn Aberdeen, Scotland AB21 9YA, UK) according to the Budapest Treaty, under the Expert Solution (EPC <NUM>, Rule <NUM>(<NUM>)). Seeds were given the following deposit numbers: NCIMB <NUM> and NCIMB <NUM>.

Representative sample of seeds of cultivated melon plants comprising the QTL for whitefly resistance on chromosome <NUM> in homozygous form (designated Wf_11. <NUM>) was deposited by Nunhems B. on <NUM> February <NUM> at the NCIMB Ltd. (Ferguson Building, Craibstone Estate, Bucksburn Aberdeen, Scotland AB21 9YA, UK) according to the Budapest Treaty, under the Expert Solution (EPC <NUM>, Rule <NUM>(<NUM>)). Seeds were given the following deposit number: NCIMB <NUM> and NCIMB <NUM>.

The Applicant requests that samples of the biological material and any material derived therefrom be only released to a designated Expert in accordance with Rule <NUM>(<NUM>) EPC or related legislation of countries or treaties having similar rules and regulation, until the mention of the grant of the patent, or for <NUM> years from the date of filing if the application is refused, withdrawn or deemed to be withdrawn.

Access to the deposit will be available during the pendency of this application to persons determined by the Director of the U. Patent Office to be entitled thereto upon request. Subject to <NUM> C. § <NUM>(b), all restrictions imposed by the depositor on the availability to the public of the deposited material will be irrevocably removed upon the granting of the patent. The deposit will be maintained for a period of <NUM> years, or <NUM> years after the most recent request, or for the enforceable life of the patent whichever is longer, and will be replaced if it ever becomes nonviable during that period. Applicant does not waive any rights granted under this patent on this application or under the Plant Variety Protection Act (<NUM> USC <NUM> et seq.

The following non-limiting Examples describe how one can obtain plants according to the invention, comprising a recombinant chromosome <NUM>. Unless stated otherwise in the Examples, all recombinant DNA techniques are carried out according to standard protocols as described in <NPL>, and <NPL>; and in <NPL>. Standard materials and methods for plant molecular work are described in <NPL>. Standard breeding methods are described in <NPL>).

Several melon accessions were screened in Spain for white fly resistance under natural insect infestation. Two accessions were identified as being resistant, seeds of which were deposited under accession numbers NCIMB <NUM> and NCIMB <NUM>.

Two bi-parental mapping populations were developed from these two resistant sources. The first population was a cross between a white fly susceptible cantaloupe breeding line ((MA17115)-Q-<NUM>-<NUM>) and the resistant accession NCIMB <NUM> and the second was a cross between a canary breeding line ((<NUM>-<NUM>)-Q-<NUM>-K and the resistant accession NCIMB41966. F<NUM> populations were used for linkage mapping, and phenotyping for white fly resistance was done on F<NUM> families.

F<NUM> families were phenotyped in an insect-proof net house in <NUM> with appropriate susceptible controls (susceptible parent lines, and Medellin F1 and Caribbean Gold F1). Plants were maintained in pots, free of other insects and without insecticide. Each F<NUM> family was planted in four replicates with three plants/replicate/F<NUM> family in a randomized complete block design (RCBD). Fifteen days old plants were transferred to white fly chamber and exposed to whitefly infestation for <NUM> days after which they were transferred back to insect-free net house. Seven days (±<NUM> days, depending on temperature) after withdrawal from whitefly chamber, the third or fourth leaf was selected from each test plant. Five leaf discs (<NUM> diameter) were taken randomly from each leaf, and third instar whitefly nymphs (pink colored eye) were counted under stereomicroscope. Over the period of the experiment, temperature fluctuation was <NUM> - <NUM>.

Another round of phenotyping was conducted in <NUM> on F<NUM> recombinants. These F<NUM> recombinants were progeny of selection from large F<NUM> populations of both crosses (<NUM>,<NUM> F<NUM> individuals per cross) based on SNP markers spanning the QTL region. The same experimental design (RCBD) and scoring scale were applied as in <NUM>. Some F<NUM> individuals were selected based on resistance scores, tissue sampled and genotyped with QTL markers to fine-map the resistance QTL.

From the <NUM> screening, resistant F<NUM> recombinants carrying the QTL interval were selfed and their F<NUM> families were planted in Spain in <NUM> for field evaluation (free choice). The resistant and susceptible parents of both crosses were included in the field evaluation. Experimental lay out was RCBD with three replicates and three plants per replicate. Plants were transplanted to the field <NUM> days after sowing. Observations were made <NUM>, <NUM>, <NUM>, <NUM> and <NUM> days after transplanting (DAT). Adults white flies were counted <NUM>, <NUM> and <NUM> DAT while third and fourth instar nymphs were counted <NUM>, <NUM>, <NUM> and <NUM> DAT. Counting of instar was done on <NUM> leaf discs per plant. Analysis of variance (ANOVA) was conducted for test of significance among the genotypes. Seed deposits were made for F<NUM> recombinants (H11_5008-<NUM> and H11_5007-<NUM>), which have been given Accession numbers NCIMB <NUM> and NCIMB <NUM>, respectively.

Genotyping of the F<NUM> populations was conducted on a proprietary single nucleotide polymorphism (SNP) platform containing <NUM>,<NUM> SNPs. For each population, <NUM> individuals were analyzed. Linkage mapping was conducted with JoinMap <NUM>. Several ICuGI SSR (Single Sequence Repeat) and SNP markers from <NPL>) map were used as anchor markers for the assignment of chromosome number and map orientation of linkage groups. Genotyping of subsequent populations (large F<NUM> population and F<NUM> recombinants) was done using KASPar assays designed for polymorphic SNPs. QTL analyses were conducted with MapQTL <NUM>. Significant LOD threshold was determined by genome wide permutation with <NUM> iterations.

For both mapping populations linkage mapping analyses showed twelve linkage groups, corresponding to the haploid chromosome number of melon.

QTL analyses using phenotype data from replicated F<NUM> families showed a QTL for resistance to whitefly (Wf_11. <NUM>) on Chr11 from both mapping populations.

The peak LODs were <NUM> and <NUM>, and variation explained were <NUM>% and <NUM>% for population (<NUM>-<NUM>)-Q-<NUM>-K x NCIMB <NUM> and population (MA17115)-Q-<NUM>-<NUM> x NCIMB <NUM>, respectively (<FIG>).

Thirteen SNP markers were found to be common for the Wf_11. <NUM> QTL in both mapping populations, as listed herein below in Table <NUM> and shown in <FIG>:.

Three markers were population specific, as shown in Table <NUM>-B:.

From the analysis of markers spanning Wf_11. <NUM> QTL interval on large (<NUM>,<NUM> individuals each) F<NUM> populations of both crosses recombinants were selected. Phenotype data from replicated trial of F<NUM> families of these recombinants were matched with marker data of their respective F<NUM> progenitors.

Field evaluation conducted in Spain of the two F<NUM> families obtained from two F<NUM> recombinants carrying Wf_11. <NUM> QTL showed that the two F<NUM> families displayed significant higher resistance levels compared to their susceptible parents (Table <NUM> and <FIG>) as determined by ANOVA (P <<NUM>) both in the average number of adult white fly and average number of nymphs per <NUM> diameter leaf disc.

The above results show that the wild accessions NCIMB <NUM> and NCIMB <NUM> comprise a QTL for whitefly resistance on chromosome <NUM> and that an introgression fragment comprising this QTL was transferred into two recombinant cultivated melon lines. These cultivated melon lines show very good field resistance against whitefly.

In order to screen plants for the presence of one or more of the above molecular markers, linked to the introgression fragment conferring whitefly resistance, a KASP-assay (a SNP genotyping assay or KBioscience Allele-Specific PCR genotyping - assay) was developed for thirteen (<NUM>) SNP markers as detailed in Table <NUM> and <NUM> below.

Based on the genomic sequences comprising the SNP (see Table <NUM> below and Sequence listing), for each SNP marker two allele-specific forward primers (i.e. detecting either the nucleotide of the susceptible or resistant parent at the SNP locus) and one common reverse primer (underlined and in italics) were developed, indicated in Table <NUM> and <NUM> (all sequences are given in <NUM>'to <NUM>'direction).

Using the above primers, KASP-assays can be carried out according to standard protocols developed by KBioscience. uk (see www. kbioscience. uk), in order to detect the presence of either the resistant or susceptible SNP-genotype in homozygous or heterozygous form in plant DNA derived from melon cells or tissues. If the genotype at a given SNP is homozygous, only one fluorescent signal will be detected. If the genotype of the plant at a given SNP is heterozygous, a mixed fluorescent signal will be detected.

Claim 1:
A cultivated Cucumis melo plant comprising resistance against whitefly, wherein said resistance is conferred by an introgression fragment on chromosome <NUM> in homozygous or heterozygous form and wherein said introgression fragment is from a wild plant of the species Cucumis melo of which a representative sample of seeds has been deposited under accession number NCIMB <NUM> and NCIMB <NUM>, wherein said introgression fragment is detectable by all markers of the group:
i) the CC genotype or CT genotype for the SNP marker mME15248 in SEQ ID NO: <NUM>;
ii) the CC genotype or CT genotype for SNP marker mME17306 in SEQ ID NO: <NUM>;
iii) the AA genotype or AT genotype for SNP marker mME26059 in SEQ ID NO: <NUM>;
iv) the GG genotype or GA genotype for SNP marker mME38084 in SEQ ID NO: <NUM>;
v) the CC or AC genotype for SNP marker mME21974 in SEQ ID NO: <NUM>;
vi) the CC genotype or CT genotype for SNP marker mME12777 in SEQ ID NO: <NUM>.