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D. J. Gray, Z. T. Li, D. L. Hopkins, M. Dutt, S. A. Dhekney, M. M. Van Aman, J. Tattersall, and K. T. Kelley

Pierce's disease (PD), caused by the xylem-limited bacterium Xylella fastidiosa, is endemic to the coastal plain of the southeastern United States. Although native southern grapevines are tolerant to X. fastidiosa, all varieties of Vitisvinifera grown in the region will succumb to PD. Genetic transformation to add disease resistance genes, while not disturbing desirable phenotypic characters, holds promise for expanding the southeastern U.S. grape industry by allowing use of established fruit and wine varieties. We utilize embryogenic cell cultures and Agrobacterium strain EHA105 to refine transformation systems for Vitis species and hybrids. V. vinifera`Thompson Seedless' is employed as a model variety to test various transgenes for disease resistance, since as many as 150 independent transgenic plant lines routinely are produced from 1 g of embryogenic culture material. Transgenic plants are stringently screened for PD resistance in greenhouses by mechanical inoculation with X. fastidiosa. Transgenic plants are compared with both susceptible and resistant control plants by assessing typical PD symptom development and by assaying bacterial populations in xylem sap over time. Using these procedures, nine putative PD resistance genes have been inserted into grapevine and over 900 unique transgenic lines have been evaluated. A range of susceptible-to-resistant responses has been catalogued. Thus far, the best construct for PD resistance contains a grape codon-optimized hybrid lytic peptide gene in a high-performance bi-directional 35S promoter complex. Certain transgenic plant lines containing this construct exhibit better resistance than that of resistant control vines.

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Danielle Lo Giudice, Tony K. Wolf, and Richard P. Marini

Prohexadione-calcium (prohexadione-Ca) was evaluated for its ability to suppress vegetative growth of grapevines (Vitis vinifera L.) under field conditions. Two or three applications of 250 mg·L-1 prohexadione-Ca reduced primary shoot growth of `Cabernet Sauvignon', but had little effect on other canopy characteristics or cane pruning weights. The reduction of shoot growth was not persistent and shoot hedging was ultimately needed to avoid canopy shading. Similarly, three applications of either 125, 250, or 375 mg·L-1 prohexadione-Ca reduced `Cabernet franc' shoot growth, but again did not eliminate the need for shoot hedging. Cane pruning weights of `Cabernet franc' were unaffected by treatment, and canopy characteristics were generally not improved. Two prebloom and one postbloom application of 250 mg·L-1 prohexadione-Ca were evaluated on `Cabernet franc' and `Chardonnay' in separate field experiments. The prebloom treatments retarded shoot growth of `Chardonnay', but had no effects on `Cabernet franc' shoot characteristics. To retard shoot growth, prohexadione-Ca had to be applied prior to bloom; however, prebloom applications had the potential for severe reductions in crop yield.

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Julie M. Tarara and Jorge E. Perez Peña

-vine transpiration, g c , and whole-vine WUE in field-grown, mature grapevines in a semiarid climate. The additional deficits were each imposed independently during one of two main periods of fruit development that have been implicated in affecting fruit quality: 1

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Seon-Kyu Kim and Dong-Yong Choi

All possible grafting combinations of seven roostock s and six scion cultivars were made to evaluate the rootstock/scion compatibility in grapevine nursery production. Percentage of takes was variable from 20.5%(Uni Blanc/161-49 C.) to 87.3%(K 188-2/161-49 C). Among scion cultivars, mean percentage of takes varied from 82.5%(K 188-2) to 37.5%(Ugni Blanc) while roostocks with all scion cultivars varied from 69.9%(R 110) to 52.8%(101-14 Mgt.), indicating the greater effects of scion on percentage of takes. Variation in rooting index(0: none to 4:profuse rooting scale) was from 3.48(SV 5276/Rip. Gloire). 3.49(Neo Muscat/101-14 Mgt.) to 1.63(SV 5276/161-49 C). Mean rooting index of rootstocks with all scion cultivars varied from 3.10(101-14 Mgt.) to 1.95(161-49 C.) while that of scion cultivars varied from 3.07(SV 5276) to 2.44(Ugni Blanc). In rooted grafting, rootstock had a greater effect than scion cultivars.

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Jean Carlos Bettoni, Aike Anneliese Kretzschmar, Remi Bonnart, Ashley Shepherd, and Gayle M. Volk

did the other species. Fig. 1. Grapevine plants recovered after 90 min of plant vitrification solution 2 (PVS2) treatment with liquid nitrogen (+LN) or without liquid nitrogen (−LN) exposure. V. aestivalis shoot tips exposed to LN and recovered for

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Manuel Di Vecchi Staraz, Roberto Bandinelli, Maurizio Boselli, Patrice This, Jean-Michel Boursiquot, Valérie Laucou, Thierry Lacombe, and Didier Varès

, ‘Sangiovese’ is the cultivar with the highest number of clones registered in the Italian National Catalogue of Grapevine Cultivars (74 clones). The use of DNA profiling based on microsatellite markers has revolutionized grape diversity analysis in less than

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Seth DeBolt, Renata Ristic, Patrick G. Iland, and Christopher M. Ford

Environmental conditions play a significant role in regulating both primary and secondary metabolism during fruit ripening. In grapevines, the effect of light exposure on grape quality is of particular importance because it can be modulated using

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Michael J. Costello

growth is primarily in the off-season, and their water source is primarily rainfall, direct competition with the grapevines for water is minimized. However, after senescence in spring, weeds will take the place of the cover crop and must be managed to

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R. Paul Schreiner and Carolyn F. Scagel

The use of tissue nutrient tests to understand and diagnose the nutritional status of grapevines dates back to the 1920s work of Lagatu and Maume in France who developed the first recommendations for adequate N, P, and K levels in whole leaves

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James K. Mitchell, W. Keith Patterson, and Robert H. Ford

European Vitis vinifera L. (four cultivars); interspecific hybrid (seven cultivars); and American V. aestivalis Michx. (one cultivar), V. labrusca L. (three cultivars), and V. rotundifolia Michx. (two cultivars) grapevines were tested for susceptibility to septoria leaf spot disease. V. rotundifolia cultivars Cowart and Fry exhibited hypersensitive-type resistance. All other American, European, and hybrid cultivars tested were susceptible with varying levels of disease severity. Cultivars with little (e.g., interspecific hybrid) or no (e.g., European) V. labrusca L. heritage were more susceptible to septoria leaf spot than American V. labrusca cultivars.