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ISHS Acta Horticulturae 827: IX International Conference on Grape Genetics and Breeding

BREEDING WINE GRAPES FOR RESISTANCE TO DOWNY MILDEW

Authors:   R. Sestras, S.D. Moldovan, M. Ardelean, S. Oprea
Keywords:   grape, cross, seedlings, resistance, susceptibility, downy mildew
DOI:   10.17660/ActaHortic.2009.827.100
Abstract:
Some 2290 F1 hybrid individuals, belonging to eight cross combinations of wine grape, were tested for their response to natural infection of Plasmopara viticola. In each combination, ‘Gewürztraminer’ was used either as maternal or as paternal parent, while the other parent was an interspecific selection rated as highly resistant to downy mildew (derived from ‘Saint Emilion’ x ‘Rayon d’or’ and ‘Seyve-Villard 12-375’ x ‘Regina viilor’ combinations). Scoring of disease susceptibility was performed by visual observation and scored from “0” (no infection on leaves) to “5” (very strong infection). None of the observed hybrids was rated as “0”, the mean of experiment being 3.66. Differences were noted both among the studied combinations and within the same combination, depending on whether ‘Gewürztraminer’ was a maternal or paternal parent. These results suggest possible maternal effects. Variability indices were high in all combinations (s%=22.1-39.4) offering a good background for an efficient selection for resistance to Plasmopara viticola. However, the most efficient selection is expected in those combinations in which interspecific selections have participated as maternal genitors, where a higher proportion of resistant (tolerant) seedlings was found. Resistance to downy mildew seems to be polygenically inherited, with high heritability indices in broad sense (0.839 when ‘Gewürztraminer’ has been used as maternal genitor and 0.956 when ‘Gewürztraminer’ was used as maternal genitor). The small values found for heritability in narrow sense (0.055 and 0.316) suggested that additive effects are probably not the most important ones in the phenotypic expression of vine resistance/susceptibility to downy mildew.

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