Evaluation of Drought Tolerance Indices for Selection of Superior Genotypes in Black Cumin (Nigella sativa L.)

Drought stress is considered as one of the most important constraints to the crop production, including medicinal plants in many arid and semi-arid regions. This study was carried out to determine the most effective indices for drought tolerance and identification of tolerance genotypes under drought conditions in N. sativa. For this purpose, 36 genotypes of N. sativa were tested as a split plot experiment based on a randomized complete block design with three replications at Agricultural Research Field of Shahrekord University, Shahrekord, Iran under two irrigation conditions (non- stress and drought stress) at 2017-2018. The results showed that there were significant differences among different genotypes in terms of all drought stress tolerance indices. A modest correlation was observed between grain yield under normal and stress conditions (R2 = 0.43). Grain yield showed a positive and significant correlation with all indices under normal conditions, except for yield stability index (YSI). The MP, GMP and STI had positive and significant correlations with grain yield under both normal and drought stress conditions. According to principal component analysis, the first component explained about 63% of the total variation, which was correlated positively with YP, MP, GMP, and STI indices. Therefore, MP, GMP and STI could be used to select drought-tolerant genotypes. Based on the high grain yield potential and high drought tolerance observed for Nige53, Nige59 and 38923 genotypes, these genotypes could be recommended for cultivation under drought stress conditions and further studies in breeding programs.