bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Crop Load on Budbreak Influences Return Bloom in Alternate Bearing ‘Pixie’ Mandarin
Authors: Verreynne Johannes S. , Lovatt Carol J.
Published: January 2019

Alternate bearing trees produce a heavy (on) crop followed by a light (off) crop. Whereas it is well documented for citrus that fruit number in the current crop inversely affects flower number in the return bloom, when in the phenology of the tree and how fruit exert an effect on floral intensity the following spring remained unresolved. ‘Pixie’ mandarin (Citrus reticulata) was used as the model system to investigate when and how fruit perpetuate cyclic differences in floral intensity. Parent shoots (current spring flush shoots) were tagged on on-crop trees and fruit were removed from individual shoots or whole trees. The number of summer and fall (summer/fall) vegetative shoots that developed on parent shoots with and without fruit and the contribution of spring shoots (floral and vegetative) made by parent shoots alone (now 1 year old) and by their summer/fall shoots to return spring bloom was quantified. Removal of fruit from individual shoots on on-crop trees in June or July had no effect on the number of flowers contributed by parent (current spring) shoots to return bloom, but increased total flower number 4-fold because summer/fall shoot number increased more than 8-fold. Removal of fruit from individual shoots of on-crop trees after July had no effect on flower number. In the whole tree experiment, parent + summer/fall shoots of off-crop trees produced more flowers the following spring than on-crop trees due to greater flower production by both parent shoots and their greater number of summer/fall shoots. Removal of all fruit in July from on-crop trees resulted in 2-fold more flowers in spring compared with off-crop trees due to the increased number of flowers contributed by both parent shoots (75% of the total) and the increased number of summer/fall shoots. The importance of summer/fall shoots to return bloom was confirmed by removing all summer/fall shoots from off-crop trees. This reduced floral intensity to that of on-crop trees. Removing all fruit from on-crop trees in December increased the percentage of budbreak in spring and flower number on parent shoots to that of off-crop trees, whereas the number of summer/fall shoots and the number of flowers the parent shoots contributed to bloom were both less than that of off-crop trees. For the branch and whole tree experiments, flower number was significantly correlated with the percentage of spring budbreak on parent + summer/fall shoots (r
2 = 0.88, P ≤ 0.0001 and r
2 = 0.71, P ≤ 0.0001; respectively). Taken together, the results of this research provide evidence that fruit of the ‘Pixie’ mandarin reduce floral intensity of the return bloom by inhibiting budbreak, which reduces summer/fall shoot growth and thus the number of nodes that can bear inflorescences and development of spring shoots, which are predominantly floral.
Accumulation of Chiro-inositol and Other Non-structural Carbohydrates in Limonium Species in Response to Saline Irrigation Waters
Authors: Liu Xuan , Grieve Catherine
Published: January 2019

Two statice cultivars, Limonium perezii cv. Blue Seas and L. sinuatum cv. American Beauty, were grown in greenhouse sand tanks to determine the effect of salt stress on carbohydrate accumulation and partitioning. For the first experiment, irrigation waters were prepared to simulate typical saline-sodic drainage effluent in the San Joaquin Valley of California with electrical conductivities of 2.5, 7, 11, 15, 20, 25, and 30 dS·m−1. A second experiment compared responses to two types of irrigation waters with salinity levels of 2.5, 6, 8, 10, 12, 16, and 20 dS·m−1: 1) San Joaquin Valley drainage waters, and 2) solutions mimicking concentrations of Colorado River water, a major irrigation water source for southern California. In addition to the presence of myo-inositol and three common sugars (fructose, glucose, and sucrose), chiro-inositol was for the first time isolated and identified in leaf and root tissues of both Limonium species. As salinity increased from 2.5 to 30 dS·m−1, leaf chiro-inositol concentration increased from 6.4 to 52.8 and from 2.6 to 72.9 μmol·g−1 dry weight for L. perezii and L. sinuatum, respectively, suggesting that chiro-inositol contributes substantially to osmotic adjustment in the stressed plants. Meanwhile, leaf myo-inositol concentration remained low in both species and showed little response to salinity. Before salt stress, the seedlings contained little chiro-inositol, indicating that salt enhanced chiro-inositol synthesis per unit of biomass formation. Significant (P ≤ 0.05) increasing trends for fructose and glucose and a decreasing trend for sucrose with increasing salinity were observed in the leaves of L. perezii but not L. sinuatum. As a result, the leaves of L. perezii had higher glucose and fructose but lower sucrose levels than that of L. sinuatum. However, no significant (P > 0.05) salt effect was found on the sum of the three common sugar concentrations in either species. Therefore, the accumulation of chiro-inositol resulted in a change in carbon partitioning among the soluble carbohydrates (i.e., the ratio of leaf chiro-inositol over a sum of the three common sugars rose from 0.034 to 0.29 dS·m−1 and from 0.012 to 0.32 dS·m−1 for L. perezii and L. sinuatum, respectively, as salinity increased from 2.5 to 30 dS·m−1). Salt stress did not affect starch accumulation and caused no carbon reserve deficiency. Furthermore, it was observed that salinity increased chiro-inositol phloem transport. The chiro-inositol response might be a physiological process for Limonium salt adaptation. The types of saline irrigation waters (i.e., sodium sulfate-dominated waters vs. a sodium chloride system) appear to have little effect on carbohydrate accumulation and partitioning in L. perezii.
Photosynthetic Light Response and Epidermal Characteristics of Sun and Shade Pecan Leaves
Authors: Lombardini Leonardo , Restrepo-Diaz Hermann , Volder Astrid
Published: January 2019

An experiment was conducted to investigate the morphologic characteristics and photosynthetic response of sun and shade leaves of mature pecan [Carya illinoinensis (Wangenh.) K. Koch] trees. Treatments were established according to leaf type (sun or shade leaves) and cultivar (Pawnee and Stuart). Sun leaves were chosen from those growing on exterior portions of the tree canopy and exposed to full sunlight for most of the day [≥1500 μmol·m−2·s−1 photosynthetic photon flux (PPF)]. Shade leaves were those growing in interior parts of the tree canopy (≤100 μmol·m−2·s−1 PPF). Epidermis characteristics, leaf area, and chlorophyll (Chl) content were also measured. Results indicated that stomatal density (stomata/mm2), leaf area, and leaflet area were greater in sun leaves than in shade leaves in both cultivars investigated. Specific leaf area was greater in shade leaves than sun leaves. Chlorophyll fluorescence, total Chl content, Chl a, Chl b, and Chl a/b were unaffected by leaf type or cultivar. In both cultivars, photosynthetic light response curves showed that area-based maximum assimilation rate (Amax) in shade leaves was about half of that measured in sun leaves in June through August. However, in October, Amax of sun leaves dropped to values similar to those measured in shade leaves. Light compensation point of photosynthesis and dark respiration rate were always lower in shade leaves than in sun leaves. Overall, there were only minor differences between the cultivars. Pecan trees require careful canopy management to avoid self shading and to maintain productivity. These results could help determine optimal levels of canopy light interception and could be used to develop canopy and crop management practices.
The Role of Chitinase Gene Expression in the Defense of Harvested Banana Against Anthracnose Disease
Authors: Ma Bao-Cheng , Tang Wan-Li , Ma Li-Yan , Li Ling-Ling , Zhang Lu-Bin , Zhu Shi-Jiang , Zhuang Chuxiong , Irving Donald
Published: January 2019

The pathogenic fungus Colletotrichum musae infects developing green bananas (Musa spp. AAA group), but remains latent until the fruit ripens. The aim of this research was to determine whether the appearance of disease symptoms is regulated by chitinase gene expression following treatment of fruit with benzothiadiazole (BTH) and methyl jasmonate (MeJA), and with physical (heat) and chemical (H2O2 and Ca2+-related) treatments. In bananas inoculated with C. musae, BTH and MeJA lowered disease severity and stimulated higher gene expression compared with the untreated controls during ripening. However, in naturally infected bananas, BTH and MeJA treatments slightly reduced transcription of the chitinase gene in green bananas, but they prolonged gene expression in ripe bananas and significantly reduced disease severity. The combination of H2O2 and the NADPH oxidase inhibitor, diphenylene iodonium, down-regulated chitinase gene expression and compromised disease resistance compared with H2O2 alone. Heat treatment (HT) or the combination of HT followed by CaCl2 reduced disease, but only the latter significantly upregulated chitinase gene expression. The combination of HT and a calcium ionophore (A23187) resulted in different disease indicies and different levels of gene expression depending upon the order of application: HT followed by A23187 induced higher gene expression and lower disease. The results suggest that disease resistance of green bananas could be related to high and prolonged levels of chitinase gene expression, and chitinase could be involved in harvested banana's anthracnose resistance activated by different defense pathway signals, such as BTH, MeJA, H2O2, and Ca2+.
Priming Soilless Growing Medium with Disaccharides Stimulated Microbial Biofilm Formation, and Increased Particle Aggregation and Moisture Retention during Muskmelon Transplant Production
Authors: Welbaum Gregory E. , Shen Zhen-Xing , Watkinson Jonathan I. , Wang Chun-Li , Nowak Jerzy
Published: January 2019

Priming commercial growing media and soils with dilute sugar solutions was investigated as a means of stimulating beneficial microflora to improve transplant productivity. Muskmelon (Cucumis melo) seedlings were grown in soilless growing medium primed with equal volumes of 50 mm sucrose or trehalose. After priming, the time when 50% of plants showed wilting symptoms was delayed 45 hours and the mean time that seedling xylem tension reached –1.0 MPa was delayed 70 hours compared with watered controls. Sucrose or trehalose priming improved water retention in the presence and absence of plants grown in sphagnum-based medium after an incubation period of ≈24 h, but no improvement occurred when autoclaved medium or acid-washed sand were primed. Light micrographs of primed medium revealed positive staining of opaque material between organic-matter particles with alcian blue, a polysaccharide-specific stain. Sixteen bacterial colonies were cultured in liquid medium from leachate of positive-stained, primed, growing-medium samples and identified via 16S rRNA gene sequencing. Identified colonies were Curtobacterium pussillum, Paenibacillus lautus, Brevundimonas, and 13 Bacillus spp., including well-characterized biofilm producers. Increased soil-moisture retention was the result of a complex, glucose-based, hydrophilic, polysaccharide polymer of bacterial origin that was produced in liquid culture from extracts of primed medium.
Differential Responses of Warm-season and Cool-season Turfgrass Species to Heat Stress Associated with Antioxidant Enzyme Activity
Authors: Du Hongmei , Wang Zhaolong , Huang Bingru
Published: January 2019

Heat stress may limit the growth of turfgrasses through the induction of oxidative stress, causing cellular and physiological damage. The objective of the study was to examine the association of heat and oxidative stresses between warm-season (C4) and cool-season (C3) turfgrasses. Plants of zoysiagrass (Zoysia matrella L. Merr. cv. Manila) (C4) and tall fescue (Festuca arundinacea Shreber cv. Barlexus) (C3) were exposed to optimal temperature conditions (24 °C for tall fescue and 34 °C for zoysiagrass) or heat stress (10 °C above the respective optimal temperature for each species) in growth chambers. Zoysiagrass exhibited less severe decline in turf quality and photochemical efficiency and less severe oxidative damage in cellular membranes as demonstrated by lower membrane electrolyte leakage and lipid peroxidation compared with tall fescue when both were exposed to heat stress. The activities of superoxide dismutase (SOD) and peroxidase (POD) declined with heat stress for both species, but to a lesser extent in zoysiagrass than in tall fescue, whereas catalase activity did not change significantly under heat stress and did not exhibit species variation. Our results demonstrate that the superior heat tolerance in zoysiagrass in comparison with tall fescue was associated with greater oxidative scavenging capacity as a result of the maintenance of higher SOD and POD activities.
Structure and Histochemistry of the Micropylar and Chalazal Regions of the Perisperm–endosperm Envelope of Cucumber Seeds Associated with Solute Permeability and Germination
Authors: Salanenka Yuliya A. , Goffinet Martin C. , Taylor Alan G.
Published: January 2019

The perisperm–endosperm (PE) envelope surrounding the embryo of cucumber (Cucumis sativus) acts as a barrier to apoplastic permeability and radicle emergence. The envelope consists of a single cell layer of endosperm whose outer surface is covered by noncellular lipid and callose-rich layers. We compared the structure and histochemistry of the radicle tip and chalazal regions of the envelope, because these regions differ in permeability. Seeds were treated with coumarin 151, a nonionic, fluorescent tracer with systemic activity. Treated seeds were imbibed and on seedcoat removal, the root tip area of the membrane-covered embryo accumulated the fluorescent tracer, but the tracer could not penetrate the envelope that bordered the cotyledons and chalazal region. The cone-shaped remnant of tissue opposite the micropylar region of the envelope was identified as nucellar tissue, the “nucellar beak.” The cuticular membrane and callose layer of the PE envelope were interrupted in the nucellar beak as well as in the chalazal region. Their role in permeability is apparently substituted by the presence of thick-walled suberized cells in the beak and chalaza. A canal was observed in the center of the nucellar beak that likely provided a conduit for the tracer to diffuse from the environment to the embryo. This canal was the remnant of pollen tube entry through the nucellus and was plugged with several cells, presumably residue of the suspensor. These cells degenerated just before cucumber seed germination. This remnant of the pollen tube canal presumably offers less mechanical resistance in the nucellar beak that might help facilitate radicle protrusion during germination. Cells of the outermost and basal regions of the nucellar beak as well as the walls of endosperm cells contained pectic material. Significant pectin methylesterase activity was found in the lateral and cap regions of the PE envelope long before seed germination. Lack of callose in the envelope at the radicle tip suggests that callose does not act as a barrier to radicle emergence during cucumber seed germination.
An Oryzalin-induced Autoallooctoploid of Hibiscus acetosella ‘Panama Red’
Authors: Contreras Ryan N. , Ruter John M. , Hanna Wayne W.
Published: January 2019

Hibiscus acetosella Welw. ex Hiern. ‘Panama Red’ PP20,121 (Malvaceae) has generated public and grower interest due to its attractive red foliage and vigorous growth, however, a horticultural goal is to develop more compact forms. Even though organs of induced polyploids are often larger than the wild type, whole plants are often shorter in stature. Three studies were conducted to induce polyploidy and to evaluate the growth and reproductive potential of the resulting polyploids. In study 1, seeds were soaked for 24 hours in aqueous solutions of 0%, 0.2%, 0.4%, or 0.5% colchicine (w/v) plus 0.5% dimethyl sulfoxide. In studies 2 and 3, apical meristems of seedlings at the cotyledon stage were treated for 1 or 3 days with 0, 50, 100, or 150 μm oryzalin solidified with 0.8% agar. Visual observations and measurement of guard cells were used to identify plants that potentially had their chromosome number doubled. Flow cytometry of nuclei stained with DAPI was used for confirmation of polyploidy. No induced polyploidy was observed following seed treatment with colchicine at the rates and duration used in this study. One-time application of 50 μm oryzalin resulted in a single mixoploid (4x + 8x) in which the ploidy of the L-I, L-II, and L-III histogenic layers were identified as a 4–4-4 + 8, respectively. Three-day applications with 100 and 150 μm oryzalin resulted in an octoploid (8x) and a mixoploid (4x + 8x), respectively. The mixoploid from the 3-day treatment stabilized at the 8x level before flowering, but was identified as a 4 + 8-x-4 cytochimera. Plant height was reduced, leaves were smaller, internodes were shorter, and canopy volume was reduced in the octoploid (8x) form compared with the tetraploid (4x) form. Furthermore, in contrast to the tetraploid, the octoploid produced no self-pollinated seed and performed poorly as a staminate and pistillate parent in controlled crosses. This represents the first time oryzalin has been reported to induce polyploidy in Hibiscus L. section Furcaria DC. H. acetosella is an allotetraploid species with the genome composition AABB. The resulting autoallooctoploid (AAAABBBB) form of ‘Panama Red’ exhibits a more compact habit and reduced production of seed.
Occurrence of Unreduced Female Gametes Leads to Sexual Polyploidization in Lantana
Authors: Czarnecki David M. , Deng Zhanao
Published: January 2019

Lantana camara, a member of the verbena family, is a popular ornamental yet highly invasive plant. It can escape from cultivation through seed dispersal and can contaminate native lantana species (Lantana depressa) through cross-pollination. Ploidy manipulation is being used as a genetic approach to produce sterile, noninvasive lantana cultivars. Polyploids have been observed in lantana (Lantana), but little information is available about the mechanisms for lantana polyploidization and the possible effects of natural polyploidization on the sterility (or fertility) of lantana triploids. In this study, we analyzed the ploidy level of more than 1500 lantana progeny from self, open, and/or controlled pollinations of 10 commercial cultivars and seven breeding lines. Our results confirmed the occurrence of unreduced gametes, specifically, unreduced female gametes (UFGs), in lantana. The frequency of UFG formation varied among commercial cultivars, and cultivars/breeding lines could be categorized into two groups: UFG producers and nonproducers. Tetraploid cultivars Gold, Pink Caprice, and Radiation fall into the UFG-producing group, while diploid cultivars Cream, Denholm White and Lola and tetraploid cultivars Carlos, Dallas Red and Irene belong to the nonproducer group. The frequency of UFG formation observed in nine UFG producers was 5.5% to 100%, varying with cultivar, growing condition, and/or pollination scheme. Progeny of the cross between ‘Carlos’ (seed parent) and ‘Gold’ (pollen parent) also showed the ability to produce UFGs, indicating that the trait (UFG formation) could be transmitted from ‘Gold’ to its progeny and is likely to be controlled by nuclear gene(s). Lantana triploids with or without the UFG-forming ability in its genetic background showed a significant difference in seed set: the former produced abundant seed when pollinated, while the latter produced little or no seed. The results stress the need to avoid using lantana with UFG-forming ability as parents in crosses designed to produce sterile triploids for invasiveness control. Additionally, the results from this study suggest multiple pathways for emergence and evolution of polyploids in cultivated and naturalized lantana populations.
Variations in Ribosomal RNA Gene Loci in Spider Lily (Lycoris spp.)
Authors: Chang Yu-Chu , Shii Chou-Tou , Chung Mei-Chu
Published: January 2019

Lycoris species of the Amaryllidaceae are important ornamental and medicinal plants in Asia. Karyotypes of Lycoris species have been studied extensively since the time when their chromosome numbers were first counted over 80 years ago. Based on karyotype, Lycoris taxa can be classified into the monomorphic A group, dimorphic MT group, and the sterile dikaryotype MT-A group. Numerous reports dealing with karyotype analysis and phylogenetic relationship in the genus Lycoris have been published. However, there are disputes and controversies regarding karyotype evolution resulting from lacking efficient and reliable markers for chromosome identification in the genus Lycoris. In this study, we applied fluorescent in situ hybridization (FISH) to visualize the 5S and 45S rDNA loci on chromosomes as landmarks for chromosome identification in Lycoris taxa. In total, 12 accessions of three karyotype groups, including nine species and three artificial dikaryotype hybrids, were investigated. A high degree of variation in the number and position of 5S and 45S rDNA loci was detected among Lycoris taxa. There were four to 14 FISH signals of 5S rDNAs and two to 12 FISH signals of 45S rDNAs observed in each investigated Lycoris accession. Lycoris accessions with the same karyotype 2n = 22A may have different numbers of rDNA loci, which distributed at different chromosomal positions. In an interspecific hybrid, the number and chromosomal position of both 5S and 45S rDNA loci were either the combinations of those in their parental species or considerably modified. Overlapping FISH signals of 5S and 45S rDNAs were colocalized with a 4′, 6-diamidino-2-phenylindole-positive band at the end of the p-arm on almost every T-type chromosome (but not the A-type chromosomes). Based on the features of T-type chromosomes, the possibility of centromeric fission in karyotypic evolution of Lycoris is discussed.
Water Relations and Abscisic Acid in Pot-grown Strawberry Plants under Limited Irrigation
Authors: Jensen Nauja Lisa , Jensen Christian R. , Liu Fulai , Petersen Karen K.
Published: January 2019

We investigated the effect of full irrigation (FI), deficit irrigation (DI), partial root zone drying (PRD), and nonirrigation (NI) on soil and plant–water relations, leaf stomatal conductance (gs), and abscisic acid (ABA) concentration in the xylem sap ([ABA]xylem) of pot-grown strawberry plants (Fragaria ×ananassa cv. Honeoye) in a greenhouse experiment. The DI and PRD treatments, irrigated with 70% of the volume of FI, reduced soil water content (θ), whereas crown water potential (ψcrown), leaf water potential (ψleaf), and gs were only significantly reduced from 11 to 15 days after initiation of irrigation treatments. Although [ABA]xylem was not significantly affected by the DI and PRD treatments, the NI plants increased [ABA]xylem, which coincided with decreased ψcrown, ψleaf, and gs 3 to 4 days after withholding irrigation. When ψcrown dropped below a critical value of −0.4 MPa, [ABA]xylem was linearly correlated with ψcrown. The gs tended to decrease as a function of [ABA]xylem, but gs was also affected by the water vapor pressure deficit (VPD) of the air. It is concluded that we did not observe a significant difference between strawberry plants grown in PRD and DI because ψcrown had to be below −0.4 MPa and soil water potential (ψsoil) had to be below −0.25 MPa before [ABA]xylem increased, these values were only reached toward the end of the experimental period (11–15 days after initiation of irrigation treatments).
Suppression of Shade- or Heat-induced Leaf Senescence in Creeping Bentgrass through Transformation with the ipt Gene for Cytokinin Synthesis
Authors: Xing Jinpeng , Xu Yan , Tian Jiang , Gianfagna Thomas , Huang Bingru
Published: January 2019

Cytokinins have been associated with delaying or suppressing leaf senescence in plants. The objectives of this study were to determine whether the expression of the ipt gene that encodes adenine isopentenyltransferase would delay leaf senescence induced by shade or heat stress in a perennial grass species. Creeping bentgrass (Agrostis stolonifera cv. Penncross) was transformed with ipt isolated from agrobacterium (Agrobacterium tumefaciens) using two gene constructs (SAG12-ipt and HSP18-ipt) designed to activate cytokinin synthesis during shade or heat stress. Whole plants of nine SAG12-ipt transgenic lines and the nontransgenic control plants were incubated in darkness at 20 °C for 20 days. Chlorophyll content of all transgenic lines and the control line decreased after dark treatment, but the decline was less pronounced in transgenic lines. All transgenic lines had higher isopentenyladenine (iP/iPA) content than the control line after 20 days of treatment. In six of the transgenic lines, iP/iPA content remained the same or higher after dark treatment. Whole plants of nine HSP18-ipt transgenic lines and the control plants were incubated at 35 °C for 7 days. Chlorophyll and iP/iPA content declined in the control plants, but the nine transgenic lines had a significantly higher concentration of iP/iPA and were able to maintain chlorophyll content at the prestress level. Our results suggest that expression of SAG12-ipt or HSP18-ipt in creeping bentgrass resulted in increases in cytokinin production, which may have led to the delay and suppression of leaf senescence induced by shade or heat stress.
Microsatellite Markers as Reliable Tools for Fig Cultivar Identification
Authors: Achtak Hafid , Oukabli Ahmed , Ater Mohammed , Santoni Sylvain , Kjellberg Finn , Khadari Bouchaib
Published: January 2019

Accurate and reliable cultivar identification of crop species is essential to ensure plant material identity for registration and for cultivar protection. In this article, we proposed six simple sequence repeat (SSR) loci as a sufficient tool to characterize fig (Ficus carica L.) germplasm in Morocco maintained in an ex situ collection. A set of 17 microsatellite loci was used to characterize 75 accessions representing eight caprifigs, 51 local accessions, 11 foreign accessions, and five accessions of unknown origin. Eighty-five alleles with a mean number of six alleles per locus were observed in 62 distinct genotypes. Suspected synonyms and homonyms were confirmed, some of which maybe resulted from somatic mutation. Based on genetic criteria, including linkage disequilibrium, discrimination power, and molecular criteria as polymerase chain reaction conditions of loci multiplexing, we proposed a key identification set using six microsatellite markers to discriminate all genotypes present in the ex situ collection. Our selected SSR loci set can be used for larger genetic studies of fig germplasm, and a similar approach can be adopted for other fruit species.
Genetic Mapping of the Scab Resistance Gene in Cucumber
Authors: Zhang Shengping , Miao Han , Gu Xing-fang , Yang Yuhong , Xie Bingyan , Wang Xiaowu , Huang Sanwen , Du Yongchen , Sun Rifei , Wehner Todd C.
Published: January 2019

Scab, caused by Cladosporium cucumerinum Ell. et Arthur, is a prevalent disease of cucumber (Cucumis sativus L.) worldwide. Scab can cause serious losses for cucumber production, especially in protected culture such as high tunnel production. Resistance to cucumber scab is dominant and is controlled by a single gene, Ccu. Breeding for resistant cultivars is the most efficient way to control the disease. Selection for resistance might be made easier if the gene were mapped to linked markers. Thus far, there are no tightly linked (genetic distance less than 1 cM) simple sequence repeat (SSR) markers for the Ccu gene, and no studies on mapping of the Ccu gene in cucumber using SSR markers. The objective of this study was to identify SSR markers for use in molecular breeding of scab resistance. In this study, we used a population of recombinant inbred lines (RILs). The population included 148 individuals derived from the cucumber inbred line 9110 Gt (Ccu Ccu) crossed with line 9930 (ccu ccu). The Ccu gene was mapped to linkage group 2, corresponding to chromosome 2 of cucumber. The flanking markers SSR03084 and SSR17631 were linked to the Ccu gene with distances of 0.7 and 1.6 cM, respectively. The veracity of SSR03084 and SSR17631 was tested using 59 diverse inbred lines and hybrids, and the accuracy rate for the two markers was 98.3%. In conclusion, two SSRs closely linked to scab resistance gene Ccu have been identified and can be used in a cucumber breeding program.
Inheritance of Resistance to Bacterial Spot Race T4 from Three Tomato Breeding Lines with Differing Resistance Backgrounds
Authors: Hutton Samuel F. , Scott Jay W. , Jones Jeffrey B.
Published: January 2019

Resistance of tomato (Solanum lycopersicum) to bacterial spot race T4 (Xanthomonas perforans) was characterized by generation means analysis (GMA) in three advanced breeding lines: Fla. 8326, Fla. 8233, and Fla. 8517. GMA of Fla. 8326 for two of three seasons (Fall 2006 and Summer 2007) indicated that resistance is mostly dominant with significant additive and epistatic effects. GMA of Fla. 8233 in Spring 2007 and of Fla. 8517 in Summer 2007 also showed dominance to be the main effect in addition to additive and epistatic effects. Duplicate dominance or recessive suppressor type epistasis was indicated in each breeding line. Transgressive segregation was not clearly observed in F2 populations of crosses between resistant parents, suggesting that these lines have quantitative trait loci in common.
Transferability of Microsatellite Markers in the Betulaceae
Authors: Gürcan Kahraman , Mehlenbacher Shawn A.
Published: January 2019

Microsatellite-containing sequences for the Betulaceae (Betula, Corylus, and Alnus) were retrieved from GenBank and used to develop twelve new microsatellite marker primer pairs that amplified and were polymorphic in european hazelnut (Corylus avellana). The primer pairs were characterized using 50 european hazelnut accessions. Nine of these microsatellites that segregated in a mapping population were assigned to linkage groups. The 12 new primer pairs will be useful in genetic studies in Corylus and Betula. To investigate transferability of microsatellite primer pairs in the family Betulaceae, we assessed the ability of 129 simple sequence repeat (SSR) primer pairs (75 from Corylus, 52 from Betula, and two from Alnus) to amplify DNA of 69 accessions representing diverse taxa. Microsatellite primer pairs from Betula amplified 92% of Betula, 51% of Alnus, 41% of Corylus, 37% of Carpinus, 35% of Ostryopsis, and 34% of Ostrya accessions. In the 69 accessions, microsatellite primer pairs from Corylus amplified 81% of Corylus, 55% of Carpinus, 53% of Ostrya, 51% of Ostryopsis, 41% of Alnus, and 39% of Betula accessions. An additional 147 SSR primer pairs developed from Corylus, used to amplify a subset of 32 accessions, gave similar values: 92% in Corylus, 33% in Carpinus, 33% in Ostrya, 44% in Ostryopsis, 35% in Alnus, and 54% in Betula. The high transferability (>39%) of microsatellite primer pairs between Betula and Corylus will allow comparative studies of the two genera with the greatest economic importance.
Effects of Simulated Dark Shipping on Photosynthetic Status and Post-shipping Performance in Phalaenopsis Sogo Yukidian ‘V3’
Authors: Hou Jiunn-Yan , Setter Tim L. , Alex Chang Yao-Chien
Published: January 2019

Phalaenopsis plants are routinely shipped long distances in total darkness. To determine how these long dark periods affect photosynthetic status in Phalaenopsis Sogo Yukidian ‘V3’, changes of net CO2 uptake, photosystem II (PS II) efficiency, and abscisic acid (ABA) concentration after a long-term simulated dark shipping were investigated. Net CO2 uptake rate, malate concentration, and titratable acidity in potted Phalaenopsis Sogo Yukidian ‘V3’ decreased after a 21-day simulated dark shipping at 20 °C, but recovered gradually with time after shipping. It took 6 to 9 days to recover to a normal photosynthetic status after shipping. The value of Fv/Fm was little affected by shipping. Therefore, net CO2 uptake rate would be a better indicator for estimating the recovery time after shipping. After shipping, fresh weight loss, leaf ABA concentration, and number of yellowed leaves of bare-root plants were higher than those of potted plants, and increased with longer durations (7, 14, and 21 days) of the simulated dark period. The spiking (the emergence of flowering stems) date was delayed when plants were stored in a bare-root condition. The concentration of ABA in leaves rose in the first 3 days after simulated shipping and then decreased within the next 3 to 8 days. Plants that received photosynthetic photon flux (PPF) at 399 μmol·m−2·s−1 after shipping had lower PS II efficiency and reduced net CO2 uptake rate than those given less PPF levels. We recommend a post-shipping acclimation for 6 to 9 days with gradual light increase (34–72–140–200 μmol·m−2·s−1 PPF) or maintaining a light level of 140 μmol·m−2·s−1 PPF for Phalaenopsis to achieve a better photosynthetic status after prolonged dark storage.
Color and Phenolic Content Changes during Flower Development in Groundcover Rose
Authors: Schmitzer Valentina , Veberic Robert , Osterc Gregor , Stampar Franci
Published: January 2019

In the present study, the chemical and morphological status of eight cultivars of groundcover rose (Rosa ×hybrida) with a range of flower colors was investigated. From the methanolic extracts of rose petals collected from flowers at four developmental stages, several phenolic compounds were identified via high-performance liquid chromatography/mass spectrometry, including five anthocyanins, which are especially important for the visual attributes of rose flowers. Colorimetric parameters were also measured and correlated with total anthocyanins and cell sap pH levels. During flower development from bud to senescent stage, a significant trend was detected; lightness (L*) increased, b* decreased in all analyzed roses, and a* decreased in pink and red cultivars. Cell sap pH level increased from bud to senescent petals; fresh weight, dry weight, and water content increased to fully open stage and were then reduced in senescent petals. Total anthocyanin and quercetin content increased from bud stage to fully open flowers, and was decreased in senescent ones. However, the highest content of total phenolics was measured in buds and partially opened flowers, respectively. Three distinct groups were formed according to the content of total anthocyanins and quercetins; white cultivars were most distant from the red ones, which were similar to the pink and light red cultivars.
Patterns of Root Production and Mortality during Transplant Establishment of Landscape-sized Sugar Maple
Authors: Richardson-Calfee Lisa E. , Harris J. Roger , Jones Robert H. , Fanelli Jody K.
Published: January 2019

Root system regeneration after transplanting of large trees is key to successful establishment, yet the influences of different production systems and transplant timing on root growth remain poorly understood. Patterns of new root production and mortality were therefore measured for 1 year after transplanting landscape-sized Acer saccharum Marsh. (sugar maple). Trees were transplanted into root observation chambers (rhizotrons) from two production systems, balled-and-burlapped (B&B) and pot-in-pot (PIP), in November, December, March, April, and July and compared with non-transplanted trees. Although root production stopped in midwinter in all transplants and non-transplanted field-grown trees, slight wintertime root production was observed in non-transplanted PIP trees. Root mortality occurred year-round in all treatments with highest mortality in winter in the transplanted trees and spring and summer in the non-transplanted trees. Non-transplanted PIP trees had significantly greater standing root length, annual production, and mortality than non-transplanted field and transplanted PIP trees. For B&B trees, greatest standing length, production, and mortality occurred in the April transplant treatment. Production and mortality were roughly equal for non-transplanted trees, but production dominated early dynamics of transplanted trees. Overall, increases in root length occurred in all treatments, but the magnitude and timing of root activity were influenced by both production system and timing of transplant.
High-frequency Oligonucleotides in Watermelon Expressed Sequenced Tag-unigenes Are Useful in Producing Polymorphic Polymerase Chain Reaction Markers among Watermelon Genotypes
Authors: Levi Amnon , Wechter William P. , Harris Karen R. , Davis Angela R. , Fei Zhangjun
Published: January 2019

In this study, we report a simple procedure for developing and using new types of polymerase chain reaction (PCR) primers, named “high-frequency oligonucleotides–targeting active genes” (HFO-TAG). The HFO-TAG primers were constructed by first using a “practical extraction and report language” script to identify oligonucleotides (8, 9, and 10 bases) that exist in high frequency in 4700 expressed sequence tag (EST)-unigenes of watermelon (Citrullus lanatus) fruit. This computer-based screening yielded 3162 oligonucleotides that exist 32 to 335 times in the 4700 EST-unigenes. Of these, 192 HFO-TAG primers (found 51 to 269 times in the 4700 EST-unigenes) were used to amplify genomic DNA of four closely related watermelon cultivars (Allsweet, Crimson Sweet, Charleston Gray, and Dixielee). The average number of DNA fragments produced by a single HFO-TAG primer among these four watermelon cultivars was considerably higher (an average of 5.74 bands per primer) than the number of fragments produced by intersimple sequence repeat (ISSR) or randomly amplified polymorphic DNA (RAPD) primers (an average of 2.32 or 4.15 bands per primer, respectively). The HFO-TAG primers produced a higher number of polymorphic fragments (an average of 1.77 polymorphic fragments per primer) compared with the ISSR and RAPD primers (an average of 0.89 and 0.47 polymorphic fragments per primer, respectively). Amplification of genomic DNA from 12 watermelon cultivars and two U.S. Plant Introductions with the HFO-TAG primers produced a significantly higher number of fragments than RAPD primers. Also, in PCR experiments examining the ability of primers to amplify fragments from a watermelon cDNA library, the HFO-TAG primers produced considerably more fragments (an average of 6.44 fragments per primer) compared with ISSR and RAPD primers (an average of 3.59 and 2.49 fragments per primer, respectively). These results indicate that the HFO-TAG primers should be more effective than ISSR or RAPD primers in targeting active gene loci. The extensive EST database available for a large number of plant and animal species should be a useful source for developing HFO-TAG primers that can be used in genetic mapping and phylogenic studies of important crop plants and animal species.
Genetic Diversity and Structure in a Collection of Ancient Spanish Pear Cultivars Assessed by Microsatellite Markers
Authors: Miranda Carlos , Urrestarazu Jorge , Santesteban Luis G. , Royo José B. , Urbina Valero
Published: January 2019

A collection of 141 old and local Spanish accessions of pear (Pyrus communis) from the Escuela Técnica Superior de Ingeniería Agraria-Universidad de Lleida (ETSIA-UdL) Pear Germplasm Bank in Lleida, Spain, were studied using a set of eight microsatellite markers to estimate the genetic diversity of the collection, to identify the genetic structure and relationships among its accessions, and to establish a representative core collection. An additional set of 13 well-known pear cultivars, currently grown in Spain and which represent a wide genetic diversity, were added as reference. The eight simple sequence repeat (SSR) loci amplified 97 alleles, with nine to 15 alleles per locus, and with the expected heterozygosity ranging from 0.65 to 0.89. All of the accessions except for 16 had at least one of the 48 rare alleles (frequency < 0.05) identified, and seven unique alleles were found in six accessions. Fifteen accessions were identified as synonyms and were excluded from the analysis. Genetic analyses performed by hierarchical clustering, Bayesian model-based clustering, and factorial correspondence analysis supported the existence of three groups among the accessions with moderate [fixation index (FST) = 0.074], but significant, differentiation. As a whole, most of the germplasm (about 75%) curated at the collection showed its genetic distinctness with respect to the main pear cultivars used in European orchards. In fact, most reference cultivars were included in one single cluster that, moreover, had the lowest genetic diversity and allelic richness, in spite of having been chosen as heterogeneous material from different origins. The obtained results were also used to create a core collection with 35 accessions constituting an efficient and accessible entry point in the ETSIA-UdL pear collection for breeding and research communities.
Identification of Resistance to the Large Raspberry Aphid in Black Raspberry
Authors: Dossett Michael , Finn Chad E.
Published: January 2019

The large raspberry aphid (Amphorophora agathonica Hottes) is an important vector of viruses in Rubus L. across North America. Although breeding for aphid resistance has long been recognized as an important tool for protecting red raspberries (Rubus idaeus L.) from viral infection, this is the first report of resistance to A. agathonica in black raspberry (Rubus occidentalis L.). Seedlings from 132 wild populations of black raspberries, representing the species' native range, were screened for resistance to A. agathonica. Strong resistance was found in three of these populations, one from Ontario (ORUS 3778), one from Maine (ORUS 3817), and one from Michigan (ORUS 4109). Resistance to the large raspberry aphid in ORUS 3778 and ORUS 3817 is dominant and appears to be conferred by different genes. We propose that the genes for resistance in ORUS 3778 and ORUS 3817 be designated Ag4 and Ag5, respectively. Resistance to A. agathonica in ORUS 4109 also appears to be controlled by a dominant allele at a single locus, but cannot be differentiated from Ag4 at this time.
Floral Morphology and Development in Georgia Plume, Elliottia racemosa (Ericaceae), a Rare Coastal Plain Endemic
Authors: Radcliffe Carrie A. , Affolter James M. , Wetzstein Hazel Y.
Published: January 2019

Georgia plume (Elliottia racemosa) is a threatened woody plant endemic to the Coastal Plain region of Georgia in the southeastern United States. Seed set is low in most populations, and sexual recruitment has not been observed in recent times. The objective of this study was to describe the floral biology of georgia plume. which is fundamental information needed to develop an understanding of the causes for lack of sexual reproduction in natural populations. Floral development was characterized and morphological characteristics at key developmental stages ranging from small, unopened buds to open flowers with receptive stigmas were examined using light and scanning electron microscopy. Flowering is protandrous, and anthers dehisce releasing pollen within closed buds before stigmas are receptive. Pollen tetrads, aggregated by viscin strands, are presented on unreceptive stigmas when petals reflex. Receptive stigmas developed a raised and lobed central region with a clefted opening leading to a stylar canal containing exudate produced in secretory regions. Receptivity of the non-papillate stigma is indicated by the formation of an exudate droplet, which is formed within 1 day after flower opening. Pollen viability was low to moderate; tetrad germination ranged from 20% to 40% using in vitro germination assays indicating poor pollen quality and may contribute to lack of seed development in some populations. No developmental abnormalities in stigmas or styles were observed indicating other factors are responsible for lack of sexual recruitment in the wild.
Variation in Concentration of Phenolic Acid Derivatives and Quercetin Glycosides in Foliage of Cranberry that May Play a Role in Pest Deterrence
Authors: Neto Catherine C. , Dao Christine A. , Salvas Michelle R. , Autio Wesley R. , Vanden Heuvel Justine E.
Published: January 2019

Several insect herbivores have been anecdotally reported to prefer ‘Howes’ cranberry leaves (Vaccinium macrocarpon) over those of ‘Early Black’. A series of studies were undertaken to determine whether these anecdotal reports are accurate and to compare phenolic profiles in the foliage of ‘Early Black’ and ‘Howes’ for compounds that differ in concentration and could be further investigated as possible feeding deterrents. Gypsy moth larvae (Lymantria dispar) demonstrated a significant feeding preference for ‘Howes’ over ‘Early Black’. Red-headed flea beetle adults (Systena frontalis) demonstrated a similar but not statistically significant trend, whereas cranberry weevil (Anthonomus musculus) did not prefer either cultivar. Compounds giving rise to six peaks in the phenolic profile were significantly greater in concentration in ‘Early Black’ than ‘Howes’ on at least one of three sampling dates during the growing season. Five of these compounds were isolated from leaves harvested at the June time point coinciding with gypsy moth infestation and identified as: 5-O-caffeoylquinic acid, 3-O-p-coumaroylquinic acid, 5-O-p-coumaroylquinic acid, quercetin-3-O-galactoside, and quercetin-3-O-rhamnoside.
Development, Linkage Mapping, and Use of Microsatellites in Bermudagrass
Authors: Harris-Shultz Karen R. , Schwartz Brian M. , Hanna Wayne W. , Brady Jeff A.
Published: January 2019

Genetic linkage maps of bermudagrass (Cynodon spp.) species using 118 triploid individuals derived from a cross of T89 [C. dactylon (2n = 4x = 36)] and T574 [C. transvaalensis (2n = 2x = 18)] were enriched with expressed sequence tags-derived simple sequence repeat (EST-SSR) markers. Primers were developed from 53 ESTs containing SSRs producing 75 segregating markers from which 28 could be mapped to the T89 and T574 genetic maps. With the addition of previously generated marker data, 26 T89 linkage groups and eight T574 linkage groups were formed using a log-of-odds (LOD) value of 4.0. The T89 and T574 linkage maps spanned 1055 cM and 311.1 cM and include 125 and 36 single-dose amplified fragments (SDAFs), respectively. Many of the SDAFs displayed disomic segregation and thus T89 may be a segmental allotetraploid or an allotetraploid. The additional EST-SSR markers add value to the maps by increasing marker density and provide markers that can be easily transferred to other bermudagrass populations. Furthermore, EST-SSRs can be immediately used to assess genetic diversity, identify non-mutated cultivars of bermudagrass, confirm pedigrees, and differentiate contaminants from cultivars derived from ‘Tifgreen’.
Flower Emasculation as the Cause for Lack of Fruit Set in Japanese Plum Crosses
Authors: Guerra María Engracia , Wünsch Ana , López-Corrales Margarita , Rodrigo Javier
Published: January 2019

Flower emasculation is widely used in breeding programs for hybridization of fruit trees. In japanese plum (Prunus salicina), some genetic crosses made by emasculation have resulted in very low or lack of fruit set, but the causes leading to this situation are not clear. In this work, the influence of flower emasculation on fruit set was evaluated in four japanese plum-type cultivars by comparing cross-pollinations performed with and without emasculation. Fruit set and fruit drop in the crosses were characterized until harvest. To ascertain which factors in the reproductive process could be related to the lack of fruit set, compatibility was determined for each cross by the observation of pollen tube growth under the microscope and by polymerase chain reaction. Likewise, the stage of ovule development was observed under the microscope in emasculated and non-emasculated flowers. An analysis of the different pollination treatments and the study of the compatibility relationships helped to dismiss factors that intervene in the reproductive process and to identify flower emasculation as the cause of premature degeneration of ovules and its implication in determining subsequent fruit set.