Evaluation of late season drought resistance in wheat cultivars using grain yield, its components and drought resistance indices

In a 2-year field experiment (2009-10 and 2010-11) 30 wheat cultivars were compared under with and without late season drought stress conditions. The experiments were conducted as a split plot based on randomized complete block design with four replicates at Research Farm of College of Agriculture, Shiraz University. Drought stress treatments (without stress, as control, and irrigation cutting off at anthesis stage) and wheat cultivars were assigned into main plots and sub plots, respectively. In this study mean productivity (MP), stress susceptibility index (SSI), stress tolerance index (STI), geometric mean productivity (GMP), tolerance (TOL), and yield stability index (YSI) were calculated based on grain yield under both with and without drought stress conditions. The results showed where irrigation cut off at anthesis, Kavir cultivar with 390.48 g/m2 had the greatest grain yield; while, under normal irrigation treatment the greatest grain yield was achieved from Shiroudi cultivar (873.83 g/m2). Comparison of means under normal irrigation conditions showed that Ghods cultivar (57.7 grains per spike) and Yavarous cultivar (20.72 grains per spike) had the highest and lowest grains per spike, respectively. Under drought stress conditions, the highest and lowest grains per spike were obtained by Zarin (39.4 grains per spike) and Souraplata (9.9 grains per spike), respectively. In the present study, 1000- grain weight was significantly different between irrigation treatments. Sistan cultivar had the greatest (45 g) 1000- grain weight under normal conditions, and Omid cultivar produced the greatest (35 g) 1000- grain weight under terminal drought stress conditions. Comparison of the mean of wheat cultivars showed that highest grain yield was achieved under stress and non-stress conditions in Kavir and Derakhshan cultivars, respectively. The lowest grain yield under both conditions was obtained from Veernak cultivar. The results of this investigation indicated that GMP, STI and MP, which had the highest significant correlation with the grain yield under both conditions, were assigned as the most appropriate indices for evaluating the drought tolerance of cultivars.