Effective selection criteria for assessing drought tolerance indices in barley (Hordeum vulgare L.) accessions

Aridity is a wide-spread problem seriously influencing barley (Hordeum vulare L.) production. Drought indices were used for screening tolerant genotypes. Hence, in order to evaluate forty two barley accessions for drought stress tolerance, two experiments were conducted under field conditions at Satloo station of agricultural research center of west Azerbaijan province, Urmia, Iran in 2010-11 seasons. Two separate simple lattice experiments were carried out under different moisture regimes including well-watered and interrupted water at grain filling period stage. Analysis of variance showed that grain yield was significantly difference (p≤0.05). Accessions of 15, 20, 37, 39 and 41 were more than 7ton/h in well-watered conditions. In addition, under drought stress conditions accessions of 24, 28, 37, 38 and 39 had higher grain yield than 6ton/h. At both conditions numbers of 37 and 39 had the highest grain yield. All drought tolerance indices with grain yield under well-watered conditions had positive significant correlation coefficients and within them GMP and MP had the highest values (r=0.86 ** and r=0.83 ** ), respectively. Therefore, it is an indirect criterion for selecting superior genotypes. In contrast, under drought stress conditions indices of MP, GMP, STI and HAR were positive significant correlations with grain yield and with in them MP and STI had the highest values (r=0.88 ** ). Hence these indices were the best indirect selection criterion for selecting the best genotypes. Comparison of indices at both conditions showed that MP had the highest positive significant correlations, therefore it was the best criterion for selecting genotypes with high grain yield at both well-watered and drought stress conditions. Based on drought tolerance indices accessions of 37 and 39 were tolerant and 6, 8, 10 and were susceptible. Principal component analysis showed that two first components explained more than 95% of variations. MP, GMP and STI indices with 63.97% variations had the highest coefficients at first components and identified tolerant genotypes. TOL and SSI with 29.87% variations had the highest coefficients at the second components and identified susceptible genotypes. Cluster analysis characterized accessions in two different tolerant and susceptible groups. At regression analysis with stepwise method MP remained at the final model and had 0.61 determination coefficient.