Variation in the chilling requirement and budburst rate of wild Vitis species

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.