Evaluation of Drought Tolerance in Rice Varieties using Yield-based Indices at Vegetative and Reproductive Stage

To evaluate drought tolerance of rice genotypes in vegetative and reproductive stages, an experiment was conducted in split plot design based on RCBD with two replications on research field of Rice Research Institute in 2008. Three levels of drought stress including normal irrigation (control), drought stress in vegetative and reproductive stages as main factor and 26 rice genotypes as sub-factor were applied. In this study, on the basis of yield performance in stressed and non-stressed environments, indices of mean productivity (MP), stress tolerance (TOL), geometric mean productivity (GMP), harmonic mean (HM), stress susceptibility index (SSI), tolerance index (STI) and drought response index (DRI) were calculated. Analysis of variance for all indices showed significant difference among the genotypes at 0.01 probability level, which implies to exist genetic variation among genotypes. The index that select the genotypes which led to yield elevation under both normal and stress conditions, was considered as the best index. Accordingly, indices of STI and GMP were found to be the best indices for drought resistance selection. Regarding these criteria, the entries of Kadous, Sahel, Nemat, Danial and Line 8 were considered as the most tolerant genotypes. Results of principle component analysis displayed that varieties of Danial, Nemat and Sahel were tolerant and Line 30 and Domsiah were sensitive at both growth stage of rice.