Evaluation of Drought Tolerance Indices in Sesame Lines

To investigate genetic variation, and identification of tolerant genotypes according to quantitative indices of drought tolerance, 8 sesame genotypes were tested in a randomized complete block design with three replications under optimum and limited irrigation at the Research Station of College of Agriculture, Shiraz University. Based on the potential yield and yield under stress, quantitative indices of drought tolerance such as mean productivity (MP), geometric mean productivity (GMP), harmonic mean (HM), stress tolerance index (STI), stress susceptibility index (SSI) and tolerance index (TOL) were determined. The result of analysis of variance exhibited highly significant differences among the genotypes for all the indices measured, and yield under optimum and limited irrigation, indicating the existence of genetic variation among genotypes, and thus the possibility of selecting drought tolerant genotypes. Mean comparison displayed that the highest potential yield, stress yield, MP, GMP, HM and STI were related to the genotype number 5. Correlation analysis between indices, mean potential and stress yields indicated that every four indices are suitable for screening the genotypes. Based on these indices and higher yields under optimum and limited irrigation the best drought tolerant genotypes were identified to be genotypes number 4 and 5. Multivariate biplot indicated that the genotypes number 4 and 5 were located next to the vectors of drought tolerance indices, including MP, GMP, HM and STI. Cluster analysis showed genetic distance among genotypes. As a result, genotypes number 4 and 5 were identified as drought tolerant and genotypes number 1, 2 and 3 as susceptible to drought.