Repeatability of drought tolerance indices in bread wheat genotypes

ABSTRACT: In order to investigate the relationships and repeatability among several drought tolerance/resistance indices a randomized complete block design with four replications was conducted under rainfed and irrigated conditions for three years. The results of combined analysis of variance showed that the environment (E), genotype (G) and genotype × environment (GE) interaction effects were highly significant (P < 0.01). Differences in ranking of genotypes based on each index from year to year, exhibited that drought tolerance of genotypes is influenced by year effect. The E effect was the most important source of yield variation and accounted for 55.7% of total sum of squares (TSS) followed by GE interaction (14.6%) and genotypes effect (13.3% ). The mean yield of genotypes under stress condition varied from 2841.08kg for genotype B6 to 3906.67kg for genotype B9, while mean yield of genotypes under non-stress condition ranged from 4258.33kg attributed to genotype B16 to 6847.92kg related to genotype B9. The results showed that genotype B9 was superior than the other genotypes under stress and irrigated conditions. The indices STI , TOL , SDI , DI , RDY , ATI and SSPI were consistently correlated with each other over the years, indicating that they can be used as alternative for each other to select drought tolerant genotypes with high yield performance in both stress and non-stress conditions. The criteria HM , YI , K1STI , K2STI and SNPI revealed repeatable correlations over the years and can be used to screen drought resistant and stable genotypes.