Evaluation of Genetic Variation for Drought Tolerance and Determination of the Best Selection Criteria in Safflower Genotypes (Carthamus tinctorius L.)

  Abstract In order to evaluate genetic variation and drought tolerance of safflower cultivars (Carthamus tinctorius L.), an experiment was conducted using fifteen cultivars in a randomized complete block design with three replications under drought and normal conditions during ۲۰۱۴-۲۰۱۵ farming season. Drought tolerance indices, such as tolerance (TOL), stress tolerance index (STI), stress susceptibility index (SSI), mean productivity (MP) and geometric mean productivity (GMP) were calculated to distinguish cultivars having the best seed yield as well as drought tolerance. The correlation coefficients illustrated that STI and GMP were the best and efficient selection criteria to distinguish drought tolerant and high-yielding cultivars. Significant and positive correlation was found between yield in both stress and normal conditions with GMP, MP and STI. Principal component analysis (PCA) showed that first and second PC accounted for ۹۷.۱% of the total variation. Biplot graphical display represented that lines ۲, ۱۱, ۱۴ and ۱۵ were highly adapted to the both normal, stress conditions, and classified them in high-yielding and drought tolerant groups, while genotypes numbered as ۱۰, ۱۲ and ۱۳ were potential and stable under normal. condition. Based on data analysis, cultivars numbered as ۱, ۵, ۶ and ۹ had lowest yield under both moisture regimes, lines ۳, ۴, ۷ and ۸ showed high-yielding under stress regimes. Cluster analysis ordered the genotypes into six groups with ۵, ۳, ۲, ۲, ۲ and ۱ genotypes, respectively. In conclusion, present investigation revealed that drought conditions induced reduction of yield of some cultivars, while others were tolerant to drought stress. Hence, breeders can select drought tolerant safflower lines based on the GMP and STI indices.