2017 ASHS Annual Conference

Grapes are the most valuable horticultural crop in the U.S., and its acreage has been expanding rapidly in the cold regions of eastern and Midwestern states. However, the economic sustainability of the grape industry is limited by climatic constraints, in particular freezing temperatures. In order to mitigate freezing damage, various protection methods have been developed, with the purpose of either changing the environmental conditions in the vineyard or improving the freezing tolerance (FT) of grapevines. To address this issue, Dami and his group has developed a novel method consisting of foliar application of abscisic acid (ABA) that increased FT in various grape cultivars. However, it is currently unclear how exogenous application of ABA mediates the acquisition of FT in grapevines. It is the purpose of this study to understand the role of ABA on early plant responses by evaluating the effect of exogenous ABA application on the temporal (24 hours to four weeks) changes of FT, water content, and sugars in buds of two grape cultivars, Vitis vinifera ‘Cabernet franc’ (cold sensitive) and Vitis spp. ‘Chambourcin’ (moderately cold sensitive). Greenhouse-grown grapevines were used in multiple experiments conducted in 2013 and 2014. Treated vines were sprayed with a foliar application of ABA (400 mg. L^-1) and compared to untreated (control) vines, which were sprayed with deionized water. Bud FT consistently increased over time and was higher in treated than control vines as early as one week post-ABA application. Bud water content generally decreased over time and was lower in treated than control vines, but these changes were not consistent. Total and most individual sugars increased over time and were higher in treated than in control vines in ‘Chambourcin’ but not in ‘Cabernet franc’. Only raffinose was higher in treated than control vines in both cultivars. In ‘Cabernet franc’, its concentration peaked then decreased one week post ABA application. In ‘Chambourcin’, maximum raffinose levels were reached two weeks post ABA application. It is concluded that vine early responses to ABA is genotype –dependent and generally occurred one to two weeks post ABA application and led to increased FT, decreased water content, and increased sugar levels in buds. The new knowledge of understanding how ABA mediates early cold acclimation responses would help develop new strategies to mitigate freezing damage. Ultimately, the findings from this research will enhance the economic and environmental sustainability of grape production in cold regions.