ENHANCED WINTER-BUD FROST RESISTANCE AND IMPROVED PRODUCTION IN SELECTED CLONES OF SOUR CHERRY

Predictable yield of high quality fruit is the main goal for sour cherry producers. However, throughout the last twenty years, harvested yields have been fluctuating, even in the most widely grown clones such as ‘Birgitte’ and ‘Viki’. Since 2002, a number of selected individuals with apparently improved yield have been derived from these clones. The present study aims to investigate and evaluate both phenotypic and genotypic characteristics of these selected trees, to better understand the mechanisms underlying the improved performance they seem to provide. A first season of data has been gathered to illustrate the freezing behaviour of overwintering buds, using simple thermal analysis (STA) to detect intra-bud freezing, supported by micropropagation to measure post-thaw viability. When subjected to simulated frost treatments, the buds typically exhibited two exotherms before reaching -9°C, with those from the improved lines having lower nucleation temperatures for the second, commonly damaging, exotherm and higher post-thaw viability than the parent material. These improved lines also had the largest first exotherms, providing the greatest amount of latent heat that will afford protection to the primordial tissue by limiting subsequent cooling.