Physiological and Biochemical Seasonal Changes in Vitis Genotypes with Contrasting Freezing Tolerance

Abstract

In this study we characterized the influence of genotype and bud position on seasonal changes in freezing tolerance (FT, LT50) and soluble sugars especially raffinose, in buds of field-grown cold-sensitive Cabernet franc (CF, Vitis vinifera) and cold-tolerant Couderc 3309 (C-3309, V. riparia x V. rupestris) and Concord (CD, V. labruscana) over two years and the influence of artificial deacclimation. Generally basal buds were more FT and the cold-hardy cultivars CD and C-3309 had the lowest LT50 compared to the cold-sensitive CF. Among all sugars, fructose, glucose, sucrose, raffinose, and stachyose had strong correlation with LT50 but there were distinctive responses associated with bud position and cultivar that were related to raffinose. Basal buds accumulated the most raffinose, and raffinose concentrations were 2- to 3- fold higher in the cold-hardy than those in the cold sensitive cultivar. Furthermore, cold hardy cultivars CD and C-3309 started accumulating raffinose with decreasing photoperiod and prior to exposure to cold temperature resulting in an early increase of FT. These results suggest that affinose accumulation might be an early step in the process of cold acclimation that coincides with early development of FT. It is concluded that bud raffinose concentration might be a useful detection tool and a metabolic marker during the early stages of cold acclimation to distinguish various Vitis genotypes with contrasting FT.