Evaluation of Tolerance to Terminal Drought Stress in Sunflower Genotypes (Hellianthus annuus L.)

Water stress is one of the most important challenges that the plant faces. Regarding the importance of drought stress and its effect on plant yield, 12 oilseed sunflower genotypes under normal and drought stress conditions were evaluated in the year 2016. In conditions of normal and drought stress, genotypes of Progress and Sor had the highest grain yield potential respectively. 11 tolerance and stress susceptibility indices were calculated based on grain yield in non-stress and drought stress conditions. The MP, GMP, STI, Harm, YI and DI indices were used due to positive and significant correlation with grain yield under both normal and stress conditions for identification and selection of tolerant and sensitive drought stress genotypes. The first two components of the analysis of the main components of the studied indices and grain yield in both conditions justifies more than 99% of the variation. The coefficients of the analysis of the main components of the indices, the first component was named as the component of grain yield potential and drought stress tolerance and the second component as a component of drought stress susceptibility. Cluster analysis based on the values of first and second components derived from drought stress indices, classified genotypes into five independent groups. The genotypes used in this study showed high genetic diversity in drought stress. Finally, the Progress and Sor genotypes were the most tolerant and the Lakomka genotype was the most sensitive genotype for the end of season drought stress.