Evaluation of Drought Tolerance in Safflower Genotypes using Tolerance Indices

Safflower (Carthamus tinctorius L.) contains considerable oil and so it is an important oil crop. This plant has been grown for its colorful petals to use them as a food coloring and flavoring agent, medicine and nutrition of livestock and birds. Moreover drought as one of the most important environmental stresses causes decrease in amount and efficiency of this crop production. The pupose of this research was evaluating the drought tolerance of safflower genotypes using some drought tolerance indices

This experiment was carried out as split plot in complete randomize block design with three replications in Abarkouh in 2016-2017. Irrigation treatment as the main factor was including three levels, includes non-stress, cut off irrigation from 50% of flowering stage to maturity (flowering stress) and cut off irrigation from the onset of seeding stage to maturity (seeding stress). Ten genotypes of safflower including Faraman, Sina, Goldasht, Parnian, Soffeh, local Arak 2811, local Isfahan, Kashan, Shiraz and Kerman were as sub factor. In this research, drought tolerance indices such as tolerance index (TOL), stress susceptibility index (SSI), mean productivity (MP), geometric mean productivity (GMP), harmonic mean (HM), stress tolerance index (STI), yield index (YI) and yield stability index (YSI) were calculated using seed yield under non-stress (Yp) and drought stress (Ys) conditions.

The results of combined analysis of variance revealed that genotype, stress and stress × genotype were significant for seed yield. Analysis of variance indicated that there were significant differences between the genotypes for Yp, Ys, and MP, GMP, HM, STI and YI indices at both stress conditions. Correlation coefficients between drought tolerance indices and seed yield showed that MP, GMP, HM, STI and YI indices had a positive and significant correlation with seed yield under non-stress and both stress conditions. Therefore these indices can be suitable for selecting better genotypes. Comparison of different safflower genotypes using multivariate biplot graph indicated that Sina, Kerman and Faraman genotypes were considered as superior genotypes in non-stress and both stress conditions because of locating of these genotypes next to the vectors of suitable drought tolerance indices. Biplot results were also confirmed by the results from three- dimensional graph of Yp, Ys and STI.

Biplot and three- dimensional graph results for studied genotypes showed that Sina, Kerman and Faraman genotypes could be suggested as drought tolerant genotypes under flowering and seeding stress conditions.