Evaluation of drought tolerance of twelve improved barley genotypes in dry and warm condition

Drought stress due to water deficit and terminal temperatures is a serious problem in agriculture, and it is one of the most important factors contributing to crop yield loss. To evaluate drought tolerance of barley, 12 advanced barley genotypes were studied in two rainfed and irrigated conditions (in a subtropical region, Gachsaran) in 2006-2007 in a RCB design with three replications. Results revealed that all genotypes showed some loss in all studied characteristics in water deficit stress. The most yield loss due to drought stress was observed for genotypes #5 and #8 (2.6 and 1.68 t ha^-1, respectively), while genotype #10 showed the least yield loss (0.77 t ha^-1). Correlation analysis showed that yield in irrigated environment was correlated with yield in water deficit condition (r=0.62), indicating that selection for yield in normal conditions (YP) will be desirable and will positively affect yield under drought stress (YS). The comparisons between different evaluation indeces of drought response to drught show that there was not colinearity between the results obtained by two group indeces (sensitivity evaluation indices vs. tolerance evaluation indices) in identification of tolerant genotypes, so that with TOL, LOS and SSI, lines #10, 9 and 4 had least sensitivity, while with MP, STI, GMP and HAR, lines #5, 6 and 11 had highest drought tolerance. To choose and introduce best criteria of drought tolerance, the correlation of above indices with yield under normal and drought stress was evaluated. Results showed that none of sensitivity evaluation indices (TOL, LOS and SSI) had significant correlations with yield under stress, while all tolerance evaluation indices (MP, STI, GMP and HAR) had significant correlations with yield under both conditions, indicating that using these later criteria for evaluation of drught tolearnce will be more desirable in breeding programes.