Evaluation of Black Cumin (Nigella sativa L.) Ecotypes under Drought Stress Conditions at Flowering Stage

Water deficiency causes crop yield loss, especially in flowering and pollination stage. This investigation was conducted out as a field experiment in Agriculture Faculty of University of Mohaghegh Ardabili in 2018, to evaluate drought tolerance of ecotypes at flowering stage. All plots were arranged in split plots based on a randomized complete block design with three replications. The main factor of experiment included two irrigation levels (full irrigation and irrigation until flowering stage) and sub-factor consisted of 10 different ecotypes of black cumin. Analysis of variance showed that the effect of drought stress on all studied traits except flowering date was significant. Drought stress significantly reduced the mean of all traits except flowering date and oil percentage. Comparison of mean data showed that the highest grain yield and oil content were observed in Semirom and Kazemain ecotypes, respectively. Also, the highest 1000-grain weight was obtained and in Ardestan and Khomeini Shahr ecotypes at full irrigation. Based on the results of cluster analysis under drought stress condition, the studied ecotypes were divided into three groups. Ecotypes of third group including Khomeini Shahr, Semirom, Isfahan, Ardestan and Shahreza had higher yield and yield components than ecotypes in other groups. Therefore, these ecotypes were identified as high yielding and drought tolerant. Also, three-dimensional plots based on stress tolerance index (STI), yield stability index (YSI), yield under full irrigation (Yp) and end-season drought stress (Ys) showed that the ecotypes of Khomeini Shahr, Semirom, Isfahan, Shahreza and Ardestan are considered as superior ecotypes in both conditions.