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Genève, Switzerland

Londo J.P.,Grape Genetics Research Unit | Johnson L.M.,Cornell University
Environmental and Experimental Botany | Year: 2014

Cultivated grapevine (Vitis vinifera) is one of the most important agricultural fruit crops in the world and grapevines are often grown in environments very different than the Mediterranean climate from where they were domesticated. To meet the environmental demands of varied climate, grapevine breeders often utilize wild grapevine species for adaptive traits, particularly in regard to abiotic stress resistance. In this study, we characterized both the chilling requirement and days to budburst phenotypes in wild grapevine species. Using survival analysis, we examined the effect of varied lengths of low temperature on budburst in 27 different genotypes of grapevine, including seven wild grapevine species, three cultivated grape varieties, and four hybrid varieties. Results of our two-year study demonstrate a wide range in both intraspecific and interspecific variation in these traits. Trends within the data allow us to categorize low and high chill species. Correlated with these categories are fast and slow maximal budburst phenotypes. When compared with geographic distribution of species and genotypes, patterns between northern and southern populations suggest that chilling requirement and budburst rate are adaptive traits. © 2013. Source


Cadle-Davidson L.,Grape Genetics Research Unit | Cadle-Davidson L.,Cornell University | Wakefield L.,Cornell University | Seem R.C.,Cornell University | Gadoury D.M.,Cornell University
Journal of Phytopathology | Year: 2010

RNA expression profiling of obligately parasitic plant microbes is hampered by the requisite interaction of host and parasite. This can be especially problematic in the case of powdery mildews, such as Erysiphe necator (syn. Uncinula necator), which grow superficially but tightly adhere to the plant epidermis. We developed and refined a simple and efficient technique in which nail polish was used to remove conidia, appressoria, hyphae, conidiophores, and developing ascocarps of E. necator from grapevine (Vitis vinifera) leaves and showed that RNA isolated after removal was not contaminated with V. vinifera RNA. This approach can be applied to expression analyses throughout fungal development and could be extended to other epiphytic pathogens and saprophytes. Source


Cousins P.,Grape Genetics Research Unit
Acta Horticulturae | Year: 2014

Grapevine seedlings initially display spiral phyllotaxy of true leaves, then undergo a shift to alternate phyllotaxy with the production of the first lateral meristems (typically tendrils). The node at which the shift from spiral to alternate phyllotaxy occurs varies from about the 4th to about the 12th node on the vine. To investigate the genetic control of the transition from spiral phyllotaxy to alternate phyllotaxy, a population segregating for this trait was developed and screened. The population derived from four female parents and six male parents crossed in a Design 2 mating array (all female parents crossed to all male parents). The female parents were the pistillate flowered rootstock varieties 1613 Couderc, 93-5 Couderc (California clone), Vitis rupestris 187G, and Fercal. The male parents were staminate flowered grape rootstock germplasm, species, and species hybrid selections with diverse backgrounds, including accessions from the USDA ARS National Clonal Germplasm Repository, Davis, California (denoted with DVIT accession numbers): IAC 572, Vitis labrusca Y137 DVIT 1392, Vitis hybrid Y93 DVIT 1519, Vitis hybrid Q126 DVIT 1456, Vitis hybrid Q130 DVIT 1466, and Vitis hybrid R127 DVIT 1490. The species background of the male parents includes V. labrusca, V. mustangensis, V. riparia, V. tiliifolia, and V. rupestris. Seedlings from controlled crosses were grown in individual pots in a greenhouse with artificial illumination to provide 24 h day length. The node number of the first observed lateral meristem was recorded; the goal was 50 seedlings per population for each of 24 populations, although some populations showed poor seed germination. Male and female parents differ from one another at P ≤0.01, with male parents falling into three groups and female parents into two groups based on the mean node of phyllotaxy shift in their seedlings. Narrow sense heritability of the first tendril bearing node is estimated at 0.23 based on breeding value of male parents and at 0.45 based on breeding value of female parents. Source


Wakefield L.,Cornell University | Gadoury D.M.,Cornell University | Seem R.C.,Cornell University | Milgroom M.G.,Cornell University | And 3 more authors.
Phytopathology | Year: 2011

Asexual sporulation (conidiation) is coordinately regulated in the grape powdery mildew pathogen Erysiphe necator but nothing is known about its genetic regulation. We hypothesized that genes required for conidiation in other fungi would be upregulated at conidiophore initiation or full conidiation (relative to preconidiation vegetative growth and development of mature ascocarps), and that the obligate biotrophic lifestyle of E. necator would necessitate some novel gene regulation. cDNA amplified fragment length polymorphism analysis with 45 selective primer combinations produced ≈1,600 transcript-derived fragments (TDFs), of which 620 (39%) showed differential expression. TDF sequences were annotated using BLAST analysis of GenBank and of a reference transcriptome for E. necator developed by 454-FLX pyrosequencing of a normalized cDNA library. One-fourth of the differentially expressed, annotated sequences had similarity to fungal genes of unknown function. The remaining genes had annotated function in metabolism, signaling, transcription, transport, and protein fate. As expected, a portion of orthologs known in other fungi to be involved in developmental regulation was upregulated immediately prior to or during conidiation; particularly noteworthy were several genes associated with the light-dependent VeA regulatory system, G-protein signaling (Pth11 and a kelch repeat), and nuclear transport (importin-β and Ran). This work represents the first investigation into differential gene expression during morphogenesis in E. necator and identifies candidate genes and hypotheses for characterization in powdery mildews. Our results indicate that, although control of conidiation in powdery mildews may share some basic elements with established systems, there are significant points of divergence as well, perhaps due, in part, to the obligate biotrophic lifestyle of powdery mildews. Source


Frenkel O.,Cornell University | Frenkel O.,Israel Agricultural Research Organization | Portillo I.,University of Bologna | Brewer M.T.,Cornell University | And 4 more authors.
Plant Pathology | Year: 2012

Transcriptome sequences of the grape powdery mildew fungus Erysiphe necator were used to develop microsatellite markers (EST-SSRs) to study its relatively unexplored population structure in its centre of diversity in eastern North America. Screening the transcriptome sequences revealed 116 contigs with candidate microsatellites, from which 11 polymorphic microsatellite markers were developed from 31 markers tested. Eight of these markers were used to genotype isolates from different regions and hosts in the eastern USA and compare them to samples from southern France and Italy. Genetic diversity in the eastern USA is much greater than in Europe. Bayesian cluster analyses showed that 10 isolates from North America have high affinities with, but differ from, European group A; these are referred to as A-like isolates. No isolates with close affinity to European group B were found in the eastern USA. Bayesian analyses also detected genetic differentiation between isolates from Vitis rotundifolia and isolates from other Vitis hosts. Genetic differentiation detected between the northeastern and southeastern USA was mostly attributable to the A-like isolates in the southeast, which are significantly more aggressive than the other populations. This research demonstrates that transcriptome sequencing of fungal pathogens is useful for developing genetic markers in protein-coding regions and highlights the role of these markers in population biology studies of E. necator. © 2011 The Authors. Plant Pathology © 2011 BSPP. Source

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