bluuebunny/crossref_metadata_2025 huggingface dataset:
The Content and In Vivo Metabolism of Gibberellin in Apple Vegetative Tissues
Authors: Yang Xiaohua , Brown Susan K. , Davies Peter J.
Published: January 2019

Despite the demonstrated importance of gibberellins (GAs) as regulators of fruit tree stature, information on their in vivo metabolism in apple vegetative tissues is still lacking. To determine whether the GA content and metabolism differs between dwarf and standard phenotypes and the influence of rootstocks, [14C]GA12, a common precursor of all GAs in higher plants, was applied to vigorously growing apple (Malus ×domestica) shoots collected from the scion cultivar Redcort on MM.106, a growth-promoting rootstock, and dwarf and standard seedlings on their own roots from progeny 806 (a cross between a breeding selection with reduced stature and an advanced breeding selection with a standard tree form). Twenty-one metabolites were identified by high-performance liquid chromatography (HPLC) and used as tracers for the purification of endogenous GAs. The existence of endogenous and [2H]-labeled GA12, GA15, GA53, GA44, GA19, GA20, and GA3 was demonstrated by gas chromatography–mass spectrometry (GC-MS); GA20 was the major GA present, with slightly less GA19 and GA44, and with GA3 present at approximately one-third the level of GA20. Despite specific searching, neither GA4, GA7, GA1, nor GA29 was found, showing that [14C]GA12 is metabolized mainly through the 13-hydroxylation pathway and that GA3 is a bioactive GA in apple vegetative tissues. The invigorating rootstock led to a slow GA metabolic rate in ‘Redcort’. For self-rooted plants, the same GAs were identified in dwarf and standard seedlings from progeny 806, although standard plants metabolized at twice the speed of dwarf plants. Young branches of dwarf 806 plants treated with GA3 were one-third longer with more nodes but similar in internode length. We conclude that the dwarf phenotype in progeny 806 is not caused by a lack of certain GAs in the GA biosynthesis pathway downstream of GA12.
Changes in CsFT Transcript Abundance at the Onset of Low-temperature Floral Induction in Sweet Orange
Authors: Chica Eduardo J. , Albrigo L. Gene
Published: January 2019

As in arabidopsis (Arabidopsis thaliana), putative citrus (Citrus) Flowering locus T (FT) homologs are strong promoters of flowering and apparently are key components of the molecular mechanism controlling floral induction in these species. An abundance of citrus FT gene transcripts during floral induction is consistent with the role of their products as floral-promoting signals. However, specific details about how the floral induction process is initiated and sustained remain largely unknown. We report changes in transcript abundance of a FT gene (CsFT) from sweet orange (Citrus sinensis) at the onset of floral induction by low temperatures and at different times of the day. Using a combination of field and growth room experiments, we determined that the abundance of CsFT transcripts increased within 1 day after initial exposure to cool floral-inductive temperatures, and that CsFT transcript abundance was higher in the afternoon than in the morning and evening. The presence of photoperiod cycles seemed to be required to sustain the increasing CsFT transcript abundance, because exposure to floral inductive conditions under continuous light or darkness did not increase the abundance of CsFT transcripts after 3 days. Our results suggest that the regulation of CsFT expression responds rapidly (overnight) to the onset of floral-inductive cool temperatures, is sensitive to changes in temperature, and requires alternation of light and dark cycles to sustain transcript accumulation during induction.
Consequences of Injury Caused by Cameraria caryaefoliella (Lepidoptera: Gracillariidae) on Pecan Gas Exchange and Chlorophyll Fluorescence
Authors: Lombardini Leonardo , Volder Astrid , Nesbitt Monte L. , Cartmill Donita L.
Published: January 2019

After an outbreak of blotch leafminer (Cameraria caryaefoliella) on field-grown pecan (Carya illinoinensis) trees in 2010, an experiment was conducted to evaluate the consequences of the injury on carbon assimilation and photosynthetic efficiency, and, in particular, to assess if low-to-moderate injury induces a compensatory increase in photosynthesis. Gas exchange and light-adapted fluorescence were measured on non-injured portions of the leaflet lamina adjacent to the injured area as well as on portions of leaflets that included leafminer injury. Results indicate that damage of the photosynthetic apparatus did not extend beyond the injured areas by leafminers. Furthermore, although a strong relationship between the proportion of leafminer injury and area-based net CO2 assimilation rate of injured leaflet tissue was found, there was no evidence that pecan leaves were able to compensate for leafminer injury by upregulating CO2 assimilation in leaflet tissue that was unaffected.
Production of Intersectional Hybrids between Colchicine-induced Tetraploid Shashanbo (Vaccinium bracteatum) and Highbush Blueberry ‘Spartan’
Authors: Tsuda Hirotoshi , Kunitake Hisato , Yamasaki Mai , Komatsu Haruki , Yoshioka Katsunori
Published: January 2019

With crosses between colchicine-induced tetraploid shashanbo (Vaccinium bracteatum section Bracteata) and tetraploid highbush blueberry ‘Spartan’ (Vaccinium corymbosum section Cyanococcus), intersectional hybrids were produced. The hybridity of these plants was confirmed based on DNA markers and morphological characteristics. The morphological characteristics, blooming date, and ripening period of the hybrids were intermediate between those of the parents. Ploidy analyses by flow cytometry and chromosome counting revealed that these hybrids were tetraploid. Four hybrids set fruit in the field and these two hybrids showed high pollen stainability. It was noteworthy that fruit of two hybrids had high soluble solids concentration compared with ‘Spartan’ and the fruit pulp of the hybrids was tinged with red as shashanbo. These hybrids could be useful in breeding new cultivars with high sugar content, abundant phytochemicals, extensive environmental adaptability as well as late flowering and fruit maturity.
Identification of Proteins for Salt Tolerance Using a Comparative Proteomics Analysis of Tomato Accessions with Contrasting Salt Tolerance
Authors: Nveawiah-Yoho Peter , Zhou Jing , Palmer Marsha , Sauve Roger , Zhou Suping , Howe Kevin J. , Fish Tara , Thannhauser Theodore W.
Published: January 2019

Tomato (Solanum lycopersicum) has a wide variety of genotypes differing in their responses to salinity. This study was performed to identify salt-induced changes in proteomes that are distinguishable among tomatoes with contrasting salt tolerance. Tomato accessions [LA4133 (a salt-tolerant cherry tomato accession) and ‘Walter’ LA3465 (a salt-susceptible accession)] were subjected to salt treatment (200 mm NaCl) in hydroponic culture. Salt-induced changes in the root proteomes of each tomato accession were identified using the isobaric tags for relative and absolute quantitation (iTRAQ) method. In LA4133, 178 proteins showed significant differences between salt-treated and non-treated control root tissues (P ≤ 0.05); 169 proteins were induced (1.3- to 5.1-fold) and nine repressed (–1.7- to –1.3-fold). In LA3465, 115 proteins were induced (1.3- to 6.4-fold) and 23 repressed (–2.5- to –1.3-fold). Salt-responsive proteins from the two tomato accessions were involved in the following biological processes: root system development and structural integrity; carbohydrate metabolism; adenosine-5′-triphosphate regeneration and consumption; amino acid metabolism; fatty acid metabolism; signal transduction; cellular detoxification; protein turnover and intracellular trafficking; and molecular activities for regulating gene transcription, protein translation, and post-translational modification. Proteins affecting diverse cellular activities were identified, which include chaperonins and cochaperonins, heat-shock proteins, antioxidant enzymes, and stress proteins. Proteins exhibiting different salt-induced changes between the tolerant and susceptible tomato accessions were identified, and these proteins were divided into two groups: 1) proteins with quantitative differences because they were induced or repressed by salt stress in both accessions but at different fold levels; and 2) proteins showing qualitative differences, where proteins were induced in one vs. repressed or not changed in the other accession. Candidate proteins for tolerance to salt and secondary cellular stresses (such as hypo-osmotic stress and dehydration) were proposed based on findings from the current and previous studies on tomato and by the use of the Arabidopsis thaliana protein database. Information provided in this report will be very useful for evaluating and breeding for plant tolerance to salt and/or water deficit stresses.
The Architectural Complexity of Crown Bud Clusters in Gentian: Anatomy, Ontogeny, and Origin
Authors: Samarakoon Uttara C. , Funnell Keith A. , Woolley David J. , Ambrose Barbara A. , Morgan Ed R.
Published: January 2019

Shoot productivity and overwintering survival of gentians (Gentiana sp.) are determined by the initiation and subsequent development of crown bud clusters. Understanding of the anatomical features and origins of crown buds and bud clusters, and plant ontogeny, the morphological features of crown buds, and their associated development is required to achieve manipulation of bud initiation, emergence, and development. Anatomical features of the crown bud clusters were examined using both light and confocal microscopy using hybrids of Gentiana triflora × G. scabra. The initiation of bud clusters presented characteristics typical of adventitious buds in terms of their origin and presence of external vascular connection to the parental tissue. In contrast, crown buds forming subsequently within the cluster developed as axillary buds within that initial bud, collectively forming on a compact stem with minimal internode elongation. Stem elongation within the cluster after application of gibberellic acid enabled identification of a hierarchical arrangement of buds within the cluster with one bud at each node and arranged spirally at 90°. Arrangements of buds within the cluster were different from the opposite decussate phyllotaxis in floral shoots with two axillary buds at each node. Based on the current study, a crown bud cluster originated from a first bud initial, which was adventitious followed by development of subsequent crown buds within the cluster as axillary buds from this first bud initially with a single bud developing at each node.
Mature Sweet Cherries Have Low Turgor
Authors: Knoche Moritz , Grimm Eckhard , Schlegel Henrik Jürgen
Published: January 2019

The pressure inside a mature sweet cherry (Prunus avium L.) fruit is thought to be an important factor in rain cracking. However, to our knowledge, this pressure has never been quantified directly. The objectives of this study are to quantify: 1) the cell turgor () in fruit using a cell pressure probe (CPP) and a vapor pressure osmometer (VPO); and 2) the tissue pressure in a fruit () using both a fruit pressure probe (FPP) and a compression-plate technique (CP). The value of in mesocarp cells of mature sweet cherry fruit averaged 28.1 kPa in ‘Samba’ and 17.5 kPa in ‘Sam’ at depths below the fruit surface between 200 and 400 μm. A (range 38 to 64 kPa for different cultivars) calculated from the tissue water potential ( = –2968 to –4035 kPa) and the osmotic potential () ( = –3020 to –4116 kPa) of excised mesocarp discs as determined by VPO was of the same order of magnitude as that by CPP. Similar low values were obtained by FPP (range 8.0 to 11.8 kPa across cultivars). The were consistently lower than the values measured by CPP or by VPO. The value in the mesocarp increased slightly with increasing depth below the surface. However, was always negligible (e.g., ‘Samba’ = 10 kPa) compared with either (‘Samba’ = –2395 kPa) or calculated water potential () (‘Samba’ = –2385 kPa). When subjecting intact fruit to CP, linear relationships were obtained between the forces applied and the resulting aplanation areas. The values obtained by CP (range in sweet cherry 18.4 to 36.1 kPa) were somewhat larger than the values obtained by FPP (range in sweet cherry 8.0 to 11.8 kPa). Incubating fruit for up to 7.5 h in deionized water or for up to 96 h in air enclosed above dry silica gel had no measurable effects on . The low and the low values are not unique to sweet cherry. Values of the same order of magnitude were obtained also in mature sour cherry (Prunus cerasus L.), european plum (Prunus domestica L.), grape (Vitis vinifera L.), gooseberry (Ribes uva-crispa L.), red currant (Ribes rubrum L.), black currant (Ribes nigrum L.), blueberry (Vaccinium corymbosum L.), and tomato (Solanum lycopersicum L.). Possible explanations for the very low values of and are discussed.
Highly Fertile Intersectional Blueberry Hybrids of Vaccinium padifolium Section Hemimyrtillus and V. corymbosum Section Cyanococcus
Authors: Ehlenfeldt Mark K. , Polashock James J.
Published: January 2019

The primary gene pool of Vaccinium species used by blueberry breeders has traditionally been the North American Vaccinium species of section Cyanococcus. Blueberries in commercial production represent three primary Vaccinium species and two ploidy levels. Significant use has been made of the secondary gene pool of Vaccinium, especially in the development of southern highbush blueberry (Vaccinium ×corymbosum) cultivars. Section Hemimyrtillus species are distantly related and are best considered part of the tertiary gene pool of Vaccinium. Vaccinium padifolium, a member of section Hemimyrtillus and native to the Madeira Islands, Portugal, has features of notable value to conventional blueberry development, among these: upright structure, strong growth, abundant flowering and fruiting, good self-fertility, inflorescence structure suited to mechanical harvesting, and indeterminate/repeat flowering. Our objective was to incorporate germplasm from this section into cultivated materials and transfer the desirable traits these species possess for commercial production. We used V. padifolium as a female in crosses with V. corymbosum and generated two highly fertile hybrids. These hybrids are intermediate in morphology, phonological, and their hybridity has been confirmed through DNA testing. These hybrids were used in further crosses to a variety of section Cyanococcus selections and have generated numerous second-generation hybrids. We have also determined by flow cytometry the ploidy levels of the hybrids and several previously unevaluated section Hemimyrtillus species.
Flowering Time in Watermelon Is Associated with a Major Quantitative Trait Locus on Chromosome 3
Authors: McGregor Cecilia E. , Waters Vickie , Vashisth Tripti , Abdel-Haleem Hussein
Published: January 2019

U.S. watermelon (Citrullus lanatus) production is worth ≈$0.5 billion annually to growers and nearly all of them are dependent on reliable synchronized flowering time of triploid cultivars and diploid pollenizers in their production fields. One aspect of this synchronization is time to flowering, the change from the vegetative to reproductive phase of a plant. Flowering time has emerged as one of the key traits in horticultural and agronomic crops to breed for escape from biotic and abiotic stresses. However, very little is known about the control of flowering time in watermelon. The number of genes involved, mode of inheritance, heritability, and the possible candidate genes are all unknown. In this study, quantitative trait loci (QTL) associated with days to first male flower (DMF), days to first female flower (DFF), and the female-male flower interval (FMI) were identified in a ‘Klondike Black Seeded’ × ‘New Hampshire Midget’ recombinant inbred line population over 2 years. Heritability for DMF, DFF, and FMI were 0.43, 0.23, and 0.10, respectively. Control of flowering time was oligogenic with a major, stable, colocalized QTL on chromosome 3 responsible for ≈50% of the phenotypic variation observed for DMF and DFF. This region of the draft genome sequence contains 172 genes, including homologs of the flowering locus T (Cla009504) and tempranillo 1 (Cla000855) genes associated with flowering time in other species. Cla009504 and Cla000855 represent excellent candidate genes toward the development of a functional marker for marker-assisted selection of flowering time in watermelon. In addition to the major QTL on chromosome 3, two other QTL were identified for DMF (chromosomes 2 and 3) and DFF (chromosomes 3 and 11) and one for FMI on chromosome 2. Understanding the genes involved in this trait and the ability to select efficiently for flowering time phenotypes is expected to accelerate the development of new watermelon cultivars in changing environmental conditions.
Transcript Abundance of Phytoene Synthase 1 and Phytoene Synthase 2 Is Associated with Natural Variation of Storage Root Carotenoid Pigmentation in Carrot
Authors: Bowman Megan J. , Willis David K. , Simon Philipp W.
Published: January 2019

Carotenoids are isoprenoid compounds synthesized in plants that serve as photoprotectants essential for photosynthesis and provide plant tissues with red, orange, and yellow pigmentation. These compounds are important in human health, because they serve as both vitamin A precursors as well as having antioxidant properties. Carrot (Daucus carota ssp. sativus) provides an important source of carotenoids in the human diet, providing up to 30% of provitamin A in the United States. Although essential to human health, very little is currently understood about the accumulation of carotenoids in carrot. To better understand the molecular mechanism for carotenoid accumulation in carrot, we used reverse-transcription quantitative polymerase chain reaction (PCR) to evaluate the expression of nine genes in the carotenoid biosynthetic pathway in storage root tissue. No significant difference was found among white, yellow, orange, and dark orange carrot roots in seven of the nine genes evaluated. However, increased phytoene synthase 1 (PSY1) and phytoene synthase 2 (PSY2) expression was observed in orange and dark orange carrot roots compared with yellow and white carrots. Increased PSY1 and PSY2 expression was not observed in the leaf tissue of these genotypes, indicating a different mechanism for carotenoid accumulation in the leaf tissue of carrot. This study is the first to demonstrate that naturally occurring mutations that dramatically increase carotenoid accumulation in orange carrot are associated with increased PSY1 and PSY2 expression and it provides insights into the mechanism underlying the biosynthesis of these important photoprotectants and nutrients.
Nitrogen Source for Inflorescence Development in Phalaenopsis: I. Relative Significance of Stored and Newly Absorbed Nitrogen
Authors: Susilo Hadi , Peng Ying-Chun , Alex Chang Yao-Chien
Published: January 2019

Phalaenopsis orchid is a slow-growing crop that responds slowly to fertilization. In this study, we used 15N-labeled Johnson’s solution to investigate the accumulation and use of fertilizer nitrogen (N) during the vegetative and reproductive growth stages of Phalaenopsis Sogo Yukidian ‘V3’ with a focus on the nitrogen source for inflorescence development. Labeling of fertilizer applied to mature plants 6 weeks before forcing or at 6 weeks into forcing showed that in the inflorescence, the ratio of N derived from fertilizer applied 6 weeks before forcing to the N derived from fertilizer applied 6 weeks into forcing was 31% to 69%, which shows the importance of newly absorbed fertilizer for supplying the N needed for inflorescence development. The fate of fertilizer N applied during the small, medium, or large plant stage of vegetative Phalaenopsis Sogo Yukidian ‘V3’ was traced separately with 15N-labeling. The capacity of the plant to accumulate N after fertilizer application was different during the various stages of vegetative growth, with large plants having more N storage capacity as a result of their greater biomass. However, the percentage of the accumulated N that was later allocated to the inflorescence was similar regardless of the stage of fertilizer application: of the fertilizer N absorbed during various stages of the vegetative period, 6% to 8% was allocated to the inflorescence at the visible bud stage. This result highlights the mobility of N stored early on within the plant. By calculation, of the total N in the inflorescence at the visible bud stage, the N absorbed during the small, medium, and large plant stages contributed 7%, 11%, and 25%, respectively, whereas N applied after spiking made up the other 57%. This result indicates that both N stored during the vegetative stage and N applied during the reproductive stage contribute significantly to inflorescence development.
Genetics and Mapping of the Cl Gene for Circumlineated Pattern in Common Bean Using AFLP-based Bulk Segregant Analysis and SNP-based Bidirectional Selective Genotyping
Authors: Aranda Luwbia , Porch Timothy G. , Bassett Mark J. , Lara Laura , Cregan Perry B.
Published: January 2019

Circumlineatus (cl) in common bean (Phaseolus vulgaris L.) is identified by a precipitation line in the seedcoat at the boundary of the white and colored zones. Cl is recessive and is expressed in partly colored seedcoats (t) with restricted patterns such as virgarcus. In this study, amplified fragment length polymorphism (AFLP) and single nucleotide polymorphism (SNP) markers, and the common bean genome sequence were used in combination with bulk segregant analysis and bidirectional selective genotyping to identify the genetic location of Cl. Markers were identified that cosegregated with Cl using Cl/Cl and cl/cl F3 and F5 progeny bulks from the cross t z cl G b v virgarcus BC3 5-593 × t zsel Cl G b v sellatus BC3 5-593. Two bands from an AFLP primer combination, which yielded unambiguous polymorphisms between the bulks, were cloned and sequenced. The two sequences were used to interrogate the common bean whole genome sequence identifying a region also found through cosegregation analysis using bidirectional selective genotyping with SNPs. Thus, the Cl gene was localized on Pv09 using cosegregating AFLP and SNP markers, and the physical location was confirmed with the whole genome sequence.
Dw2, a New Dwarfing Locus in Apple Rootstocks and Its Relationship to Induction of Early Bearing in Apple Scions
Authors: Fazio Gennaro , Wan Yizhen , Kviklys Dariusz , Romero Leticia , Adams Richard , Strickland David , Robinson Terence
Published: January 2019

The ability of certain apple rootstocks to dwarf their scions has been known for centuries and their use revolutionized apple (Malus ×domestica) production systems. In this investigation, several apple rootstock breeding populations, planted in multiple replicated field and pot experiments, were used to ascertain the degree of dwarfing when grafted with multiple scions. A previous genetic map of a breeding population derived from parents ‘Ottawa 3’ (O.3) and ‘Robusta 5’ (R5) was used for quantitative trait locus (QTL) analysis of traits related to scion vigor suppression, induction of early bearing, and other tree size measurements on own-rooted and grafted trees. The analysis confirmed a previously reported QTL that imparts vigor control [Dw1, log of odds (LOD) = 7.2] on linkage group (LG) 5 and a new QTL named Dw2 (LOD = 6.4) on LG11 that has a similar effect on vigor. The data from this population were used to study the interaction of these two loci. To validate these findings, a new genetic map comprised of 1841 single-nucleotide polymorphisms was constructed from a cross of the dwarfing, precocious rootstocks ‘Geneva 935’ (G.935) and ‘Budagovsky 9’ (B.9), resulting in the confirmation and modeling of the effect of Dw1 and Dw2 on vigor control of apple scions. Flower density and fruit yield data allowed the identification of genetic factors Eb1 (LOD = 7.1) and Eb2 (LOD = 7.6) that cause early bearing of scions, roughly colocated with the dwarfing factors. The major QTL for mean number of fruit produced per tree colocated with Dw2 (LOD = 7.0) and a minor QTL was located on LG16 (LOD = 3.5). These findings will aid the development of a marker-assisted breeding strategy, and the discovery of additional sources for dwarfing and predictive modeling of new apple rootstocks in the Geneva® apple rootstock breeding program.
Estimating an Aggregate Economic Genotype to Facilitate Breeding and Selection of Strawberry Genotypes in Southeast Queensland
Authors: Herrington Mark E. , Hardner Craig , Wegener Malcolm , Woolcock Louella , Dieters Mark J.
Published: January 2019

The Queensland strawberry (Fragaria ×ananassa) breeding program in subtropical Australia aims to improve sustainable profitability for the producer. Selection must account for the relative economic importance of each trait and the genetic architecture underlying these traits in the breeding population. Our study used estimates of the influence of a trait on production costs and profitability to develop a profitability index (PI) and an economic weight (i.e., change in PI for a unit change in level of trait) for each trait. The economic weights were then combined with the breeding values for 12 plant and fruit traits on over 3000 genotypes that were represented in either the current breeding population or as progenitors in the pedigree of these individuals. The resulting linear combination (i.e., sum of economic weight × breeding value for all 12 traits) estimated the overall economic worth of each genotype as H, the aggregate economic genotype. H values were validated by comparisons among commercial cultivars and were also compared with the estimated gross margins. When the H value of ‘Festival’ was set as zero, the H values of genotypes in the pedigree ranged from –0.36 to +0.28. H was highly correlated (R2 = 0.77) with the year of selection (1945–98). The gross margins were highly linearly related (R2 > 0.98) to H values when the genotype was planted on less than 50% of available area, but the relationship was non-linear [quadratic with a maximum (R2 > 0.96)] when the planted area exceeded 50%. Additionally, with H values above zero, the variation in gross margin increased with increasing H values as the percentage of area planted to a genotype increased. High correlations among some traits allowed the omission of any one of three of the 12 traits with little or no effect on ranking (Spearman’s rank correlation 0.98 or greater). Thus, these traits may be dropped from the aggregate economic genotype, leading to either cost reductions in the breeding program or increased selection intensities for the same resources. H was efficient in identifying economically superior genotypes for breeding and deployment, but because of the non-linear relationship with gross margin, calculation of a gross margin for genotypes with high H is also necessary when cultivars are deployed across more than 50% of the available area.
Leaf Photosynthesis in Nitrogen-starved ‘Western’ Pecan Is Lower on Fruiting Shoots than Non-fruiting Shoots during Kernel Fill
Authors: Heerema Richard J. , VanLeeuwen Dawn , St. Hilaire Rolston , Gutschick Vince P. , Cook Bethany
Published: January 2019

Photosynthetic function in nut trees is closely related to nitrogen (N) nutrition because much of tree N is held within the leaf photosynthetic apparatus, but growing fruit and seeds also represent strong N sinks. When soil N availability is low, nut trees remobilize and translocate N from leaves to help satisfy N demand of developing fruit. Our objective was to describe shoot-level impacts of pecan [Carya illinoinensis (Wangenh.) K. Koch.] fruiting on leaf N and photosynthesis (Pn) during kernel fill under a range of tree N statuses. Our study was conducted in a mature ‘Western’ pecan orchard near Las Cruces, NM. In 2009, 15 trees showing a range of N deficiency symptom severity were grouped according to leaf SPAD into low, medium, and high N status categories. Differential N fertilizer rates were applied to the soil around high and medium N trees to accentuate differences in N status among the three categories. Light-saturated leaf Pn was measured on fruiting and non-fruiting shoots during kernel fill in 2009 and 2010. After measurement of Pn, the leaflet and its leaflet pair partner were collected, dried, and analyzed for tissue N. Leaf N concentration was significantly lower on fruiting shoots than non-fruiting shoots on all three sampling dates. The tree N status main effect was also significant, whereas the two-way interaction of shoot fruiting status and tree N status was not. Photosynthesis of leaves on fruiting shoots was significantly lower than that of non-fruiting shoots on all sampling dates. These data suggest that N demand by the growing kernel reduced N in leaves on the same shoot. Consequently, Pn of those leaves was reduced. The effect of tree N status and shoot fruiting status was best summarized with an additive model where there is a larger relative reduction in leaf N and Pn for fruiting shoots on trees with low N status.
Combining Ability Analysis in 10 Strawberry Genotypes Used in Breeding Cultivars for Tolerance to Verticillium Wilt
Authors: Masny Agnieszka , Żurawicz Edward , Pruski Kris , Mądry Wiesław
Published: January 2019

General combining ability (GCA) and specific combining ability (SCA) effects of 10 strawberry (Fragaria ×ananassa) cultivars (Darselect, Selvik, Elianny, Figaro, Sonata, Susy, Salsa, Albion, Charlotte, and Filon) for severity of verticillium wilt (Verticillium dahliae) were estimated. Progeny consisting of 45 F1 full-sib families from the crosses made in a half diallel mating design according to the IV Griffing’s method was evaluated in two field experiments conducted in 2009 and 2010 on a soil heavily infested with V. dahliae inoculum. Each hybrid family was represented by 60 seedlings (four replicates of 15 plants each). The analysis of variance revealed significant (P < 0.01) GCA and SCA effects of the parental cultivars for the verticillium wilt severity in plants. This suggests that genetic additive and non-additive effects are involved in the inheritance of strawberry tolerance to verticillium wilt. In 2009, a significant negative GCA effect (P < 0.05) for the verticillium wilt severity in plants was found in ‘Selvik’, ‘Filon’, and ‘Sonata’, indicating genetic transmission of tolerance from parents to the offspring. On the other hand, a significant (P < 0.05) and positive for the verticillium wilt severity GCA effect was found for ‘Figaro’ in 2009, indicating the transmission from this parent to its offspring relatively high susceptibility to the wilt. Only in one hybrid family, ‘Albion’ × ‘Charlotte’, was the SCA effect significantly positive (P < 0.05) for verticillium wilt severity in plants, whereas two other hybrid families—‘Selvik’ × ‘Salsa’ and ‘Sonata’ × ‘Albion’—showed significantly negative SCA effects (P < 0.05). Three of 10 evaluated genotypes (i.e., ‘Selvik’, ‘Filon’, and ‘Sonata’) were found to be the most valuable parents to the strawberry breeding program for tolerance to verticillium wilt. The least suitable cultivar for this purpose was ‘Figaro’.
Association of the Fusarium Wilt Race 3 Resistance Gene, I-3, on Chromosome 7 with Increased Susceptibility to Bacterial Spot Race T4 in Tomato
Authors: Hutton Samuel F. , Scott John W. , Vallad Gary E.
Published: January 2019

Bacterial spot of tomato (Solanum lycopersicum), caused by several Xanthomonas species, is one of the most important diseases of the crop in humid production regions of the world. Conventional breeding approaches for resistance to bacterial spot previously identified race-specific resistances, but current efforts also seek to use quantitative trait loci (QTLs) effecting broad-spectrum resistance. Resistance QTLs and candidate QTLs have been reported on several chromosomes, including a major QTL on chromosome 11. Fusarium wilt (Fusarium oxysporum f. sp. lycopersici) race 3 resistance gene, I-3, is associated with smaller fruit size and has been implicated in other associations with negative characteristics. We evaluated four F2 populations involving the bacterial spot-tolerant breeding lines Fla. 8517, Fla. 8233, and Fla. 8326 across two field seasons to validate and quantify previously identified loci and to test for an effect of I-3 on bacterial spot sensitivity. The chromosome 11 QTL and the I-3 locus were each consistently positively and negatively associated with resistance, respectively, and together explained from 44% to 47% of the variation in each population. The chromosome 11 QTL displayed a dominant to incompletely dominant effect, reducing infection by 14% to 25%. This QTL is distinct from the X. perforans race T3 hypersensitivity loci, Rx-4 and Xv3. The I-3 locus contributed to as much as a 20% increase in infection in I-3/I-3 plants vs. i-3/i-3 plants, and heterozygosity for I-3 generally resulted in an intermediate susceptible response. Significant effects for QTLs on chromosomes 3, 5, and 12 were also observed, but these effects were not consistent in all populations or seasons in which they were segregating. Implications of these findings toward breeding strategies are discussed.
Additive Genetic Effects for Resistance to Foliar Powdery Mildew in Strawberry Revealed through Divergent Selection
Authors: Kennedy Colleen , Osorio Luis F. , Peres Natalia A. , Whitaker Vance M.
Published: January 2019

Powdery mildew (PM) of strawberry (Fragaria sp.) is a ubiquitous, wind-spread disease caused by the obligate parasite Podosphaera aphanis. To control PM, multiple fungicide applications are necessary each season, and none of the major cultivars in Florida have high levels of resistance. Therefore, the objectives of this study were to observe the response to selection and to estimate genetic parameters for PM and related traits in the University of Florida breeding population. In 2010, clonally replicated individuals from seven biparental crosses arising from 11 parents were included in a field trial in which clonally replicated seedlings were evaluated visually for percent coverage of PM mycelium using a modified Horsfall-Barratt scale of 0 to 6. Broad- (H2) and narrow-sense (h2) heritabilities for PM score were (mean ± se) 0.50 ± 0.08 and 0.40 ± 0.39, respectively, for the base population. After the second round of selection in the resistant population, no additive variance was detected, indicating that alleles for PM resistance had become fixed. In contrast, after two rounds of divergent selection in the susceptible population, there remained considerable additive variance (h2 = 0.42 ± 0.65). Moderate to high heritability estimates and a clear response to selection indicate that resistance to PM is genetically controlled through mostly additive effects. Selection of parents based on field trials with natural inoculum should result in good progress toward more resistant cultivars. The consistently moderate to strong genotypic and genetic correlations among PM and canopy density (CD) indicate that selection for PM resistance will result in reduced CD. Therefore, CD must be monitored over successive rounds of selection for low levels of PM to prevent CD falling below the commercially acceptable range.
Effect of Drought on Storage Root Development and Gene Expression Profile of Sweetpotato under Greenhouse and Field Conditions
Authors: Solis Julio , Villordon Arthur , Baisakh Niranjan , LaBonte Don , Firon Nurit
Published: January 2019

Greenhouse and field culture systems were used to study the effect of drought conditions on the storage root (SR) formation in ‘Beauregard’ sweetpotato (Ipomoea batatas). In the greenhouse culture system, drought was simulated by withholding water for 5 and 10 days after transplanting (DAT) cuttings in dry sand. Control plants received water at planting and every 3 days thereafter. In the field studies, natural drought conditions and selective irrigation were used to impose water deprivation during the critical SR formation period. Greenhouse drought for 5 and 10 DAT reduced the number of SRs by 42% and 66%, respectively, compared with the controls. Field drought resulted in a 49% reduction in U.S. #1 SR yield compared with the irrigated condition. Quantitative real-time polymerase chain reaction (PCR) analysis showed differential expression of a set of sweetpotato transcription factors and protein kinases among greenhouse-grown plants subjected to well-watered conditions and water deficit during 5 DAT. A significant enhancement of expression was observed for known drought stress-associated genes such as an abscisic acid-responsive elements-binding factor, dehydration-responsive element-binding factor, and homeo-domain-zip proteins. Members of calcium-binding proteins showed differential expression under drought stress. For the first time it is reported that knotted1-like homeobox and BEL1-like genes showed altered expression in response to drought stress under a greenhouse condition. In summary, the results suggest that water deprivation during the SR formation period influences root development and expression patterns of stress-responsive genes and those previously found associated with SR formation in sweetpotato.
Water Potential and Its Components in Developing Sweet Cherry
Authors: Schumann Christine , Schlegel Henrik Jürgen , Grimm Eckhard , Knoche Moritz , Lang Alexander
Published: January 2019

Susceptibility of sweet cherry (Prunus avium L.) fruit to rain cracking increases toward maturity and is thought to be related to increases in both tissue pressure () and cell pressure (). Furthermore, at a given water potential (), one might expect the increase in and the to balance the decrease in osmotic potential (). The objectives of our study were to quantify and in developing sweet cherry using vapor pressure osmometry (VPO), compression plate (CP), and the cell pressure probe (CPP). In addition, the tissue water potential was determined by quantifying the bending of strips of fruit skin and the change in projected area of discs excised from the flesh when incubated in a range of sucrose solutions of varying osmotic potentials (). Fruit growth followed a sigmoid pattern with time with the Stage II/Stage III transition occurring at ≈55 days after full bloom (DAFB). The and the were constant up to ≈55 DAFB but decreased to –2.8 MPa at maturity. The calculated by subtracting the from averaged ≈350 kPa up to 48 DAFB and then decreased at a decreasing rate to ≈21 kPa toward maturity. The determined from bending assays using excised skin strips or from water uptake of excised flesh discs was essentially constant up to ≈48 DAFB, then decreased until ≈75 DAFB and remained constant thereafter. These values were in good agreement with those determined by VPO. The as determined by CP passed through a transient peak at ≈41 DAFB, then decreased until ≈63 DAFB and remained constant and low until maturity. Similarly, by CPP increased from 27 to 48 DAFB, remained constant until ≈55 DAFB, and then decreased until maturity. Our data demonstrate a consistent decrease in and that coincides with a decrease in of sweet cherry during Stage III. Because and are low relative to , the change in parallels that in . The reason for the low turgor most likely lies in the accumulation of apoplastic solutes. These prevent a catastrophic increase in pressure that would otherwise lead to the bursting of individual cells and the cracking of entire fruit.
An Improved High-performance Liquid Chromatographic Method for the Determination of Soluble Sugars in Root Exudates of Greenhouse Cucumber Grown under CO2 Enrichment
Authors: Li Xun , Chu Wenying , Dong Jinlong , Duan Zengqiang
Published: January 2019

This study described a simple and quick method to detect trace quantities of a non-reducing sugar (viz. sucrose) in the root exudates of cucumber (Cucumis sativus) under CO2 enrichment. Sucrose was determined by analyzing fructose and glucose before and after invertase digestion using high-performance liquid chromatography. Using this technique, the optimal hydrolysis condition was 5.00 μg·mL−1 invertase for 10 minutes. The detection limit of ultraviolet-visible detector by post-column derivatization with tetrazolium was 0.25, 0.43, 0.48, and 1.95 μg·mL−1 for fructose, glucose, sucrose, and maltose, respectively, and sensitive enough for determination of sugars in root exudates. The dry weight of cucumber at the seedling stage (19 days after transplant) increased by 58.4% when the CO2 level was elevated from 380 to 1200 μmol·mol−1, whereas the differences were not significant at the initial fruiting stage (63 days after transplant). The photosynthesis rate in 1200 μmol·mol−1 CO2 was 58.0% higher than that in 380 μmol·mol−1 CO2 at the seedling stage and 74.2% higher at the initial fruiting stage. Total amount of sugars in cucumber root exudates was significantly increased with increasing CO2 concentration. The total sugars in root exudates increased by 130.4% and 102.3% in 1200 μmol·mol−1 CO2 compared with that in 380 μmol·mol−1 CO2 at seedling and initial fruiting stages, respectively. Elevated CO2 altered sugar composition in root exudates. Sugars in root exudates released per plant were significantly higher at the initial fruiting stage than that at the seedling stage, whereas the differences in sugars released per gram of root tissue between these two growth stages were not significant. Our results suggest that sugars were increased only in as much as root mass increased. This study provides a simple and quick method to detect 1 to 500 μg·mL−1 sugars in root exudates, and the results illustrate the variation in the sugar composition in cucumber root exudates among the CO2 levels and growth stages.
Characterization of Eastern Filbert Blight-resistant Hazelnut Germplasm Using Microsatellite Markers
Authors: Muehlbauer Megan F. , Honig Josh A. , Capik John M. , Vaiciunas Jennifer N. , Molnar Thomas J.
Published: January 2019

The development of new cultivars resistant to the disease eastern filbert blight (EFB), caused by Anisogramma anomala, is of primary importance to hazelnut (Corylus sp.) breeders in North America. Recently, a large number of EFB-resistant cultivars, grower selections, and seedlings from foreign germplasm collections were identified. However, for a significant number of these, little is known of their origin, relationships, or genetic background. In this study, 17 microsatellite markers were used to investigate the genetic diversity and population structure of 323 unique accessions, including EFB-resistant and tolerant germplasm of uncertain origins, in comparison with a panel of known reference accessions representing a wide diversity of Corylus cultivars, breeding selections, and interspecific hybrids. The resulting allelic data were used to construct an unweighted pair group method using arithmetic averages (UPGMA) dendrogram and STRUCTURE diagram to elucidate relationships among the accessions. Results showed 11 consensus groups with EFB-resistant or tolerant accessions in all, providing strong evidence that EFB resistance is relatively widespread across the genus Corylus. Furthermore, open-pollinated seedlings tended to group together with reference accessions of similar geographic origins, providing insight into their genetic backgrounds. The results of this study add to the growing body of knowledge of hazelnut genetic resources and highlight recently introduced EFB-resistant seedling germplasm as new, unrelated genetic pools of resistance.
Autophagy and Apoptosis Associated with Abortive Pollen Development in the Cytoplasmic Male-sterile Line GP1BC1-12 of Platycodon grandiflorum
Authors: Shi Fenghua , Sui Chun , Jin Yue , Huang Hao , Wei Jianhe
Published: January 2019

Platycodon grandiflorum (balloon flower) is widely cultivated for medicinal, edible, and ornamental purposes. The cytoplasmic male-sterile line GP1BC1-12 of P. grandiflorum has been used to produce hybrids, but its mechanism of sterility has not been studied. In this work, the mechanism was evaluated by a combination of transmission electron microscopy (TEM) and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling assay. Observations showed that autophagy and apoptosis were simultaneously present in the abortive anthers. Autophagy was indicated by the autophagic vesicles, abnormal arrangement of endoplasmic reticulum, and the vacuole’s invagination. Apoptosis was characterized by chromatin aggregation and DNA cleavage. It was concluded that programmed cell death is one of the direct reasons for cytoplasmic male sterility in P. grandiflorum. This study first noted the simultaneous presence of the features of apoptosis, microautophagy, and macroautophagy in the abortive anthers of P. grandiflorum.
Development and Validation of High-glucoraphanin Broccoli F1 Hybrids and Parental Lines
Authors: Gu Honghui , Wang Jiansheng , Yu Huifang , Zhao Zhenqing , Sheng Xiaoguang , Chen Jisuan , Xu Yingjun
Published: January 2019

Sulforaphane is an anticarcinogenic isothiocyanate derived from 4-methylsulfinylbutyl glucosinolate (glucoraphanin), which is abundant in broccoli (Brassica oleracea var. italica) florets. However, some breakdown products from alkenyl glucosinolates present in many broccoli cultivars, particularly oxazolidine-2-thione hydrolyzed from 2-(R)-hydroxy-3-butenyl glucosinolate (progoitrin), have potentially harmful effects on human and animal health. The main objective of this study was to improve the glucoraphanin concentration in F1 hybrids by cross-breeding with inbred lines and doubled haploids. Glucoraphanin concentrations in 31 of the 61 F1 hybrids were significantly higher (P = 0.05) than that of the commercial cultivar (Youxiu) with the highest concentration of glucoraphanin (4.18 μmol·g−1 dry weight) among eight reference cultivars. Sixteen of the F1 hybrids had glucoraphanin concentrations 3-fold higher than that of ‘Youxiu’. Alkenyl glucosinolates were not detected in the new hybrids as a result of the parents having few of these compounds but were found in five reference cultivars. Most F1 hybrids showed moderate indole glucosinolate concentrations and acceptable commercial traits. IL609 and IL702.2 were determined to be promising parental lines as a result of the high glucoraphanin concentration that they and their offspring contained. The findings also indicated that some F1 hybrids do not show the high-glucoraphanin character of their parents; consequently, evaluation of these F1 hybrids for their glucosinolate content is required for breeding high-glucoraphanin broccoli.