Evaluation of faba bean genotypes in normal and drought stress conditions by tolerance and susceptibility indices

In the 2017-2018 growing season, two separate experiments were conducted in Iran in a randomized block experiment with three replicates and under two irrigation conditions. Genotypes G2, G8, G5 and G7 with the highest seed yield under both conditions were classified in group A. Genotypes G7, G8 and G2 were the drought tolerant and superior genotypes based on the indices MP, GM, STI, YI, YSI, HM, RDI, DI, SNPI, MRP, REI, MSTIK1 and MSTIK2. Genotypes G2, G8, and G7 with the lowest average sum of ranks (ASR) were tolerant genotypes. Yp had a positive significant correlation with TOL, MP, GMP, STI, HM, ATI, SSPI, MRP, REI, MSTIK1, MSTIK2, Ynorm, and Z. Cluster analysis also identified genotypes G2, G8, G5, and G7 with the highest tolerance to drought stress. The stress tolerance index (STI), modified stress tolerance index K1 (MSTIK1), and average sum of ranks (ASR) were more useful to select favorable field bean genotypes under dryland and irrigated conditions. Using these three indices, genotype G7 was found to be the most tolerant genotype to drought stress. Moreover, this study proposed a new idea for evaluating the stress tolerance and susceptibility of genotypes by using standardized and normalized yield data under stress and normal conditions based on the range of variation and standard deviation, and verified these values in current data and other data of 18 rice genotypes. Moreover, the present study recommended the application of this idea to other data sets and verified its advantages.