USE OF SOME STRESS TOLERANCE INDICES FOR LATE DROUGHT IN SPRING WHEAT

In Mediterranean climate, unforeseen late drought stress is one of the factors causing important yield losses in wheat production. In this study, in order to determine drought-tolerant wheat (Triticum aestivum L.) genotypes and appropriate stress tolerance index under drought stress condition, two separate experiments were conducted with twenty four spring wheat cultivars/line in Bornova (rainfed) and Aydin (irrigated) during 2004-2005 growing season. Using grain yield of each genotype grown in irrigated and non-irrigated (drought) condition, drought tolerance (TOL), relative yield loss in drought environmental (RDY), geometric mean of yield (GM), stress susceptibilities index (SSI) and stress tolerant index (STI) were calculated, which are considered as drought stress predicting indices. It was observed that genotypes with high yield in irrigated condition had generally lower stress tolerances in drought condition, due to yield loss. A high positive correlation was determined between geometric yield mean and yields in drought and irrigated conditions. Also, a high positive correlation was observed between yields in both irrigated and non-irrigated conditions and STI value. It was concluded that the genotypes selected based on these two indices could be used as genetic resources in future drought-tolerance breeding programs. The selection firstly based on the geometric mean and by following that, taking into account the grain yield in drought conditions would be suggested for efficient selection for resistance to drought in wheat.