Biplot Analysis of Three Carthamus Species and their F2 Hybrids Evaluated under Drought Stress in Seedling Stage

Drought stress is one of the most important environmental factors affecting growth, development and production of crop plants. Drought tolerance in germination and seedling growth stage is very important especially for crop production in dry regions. Sufficient genetic diversity in cultivated species of safflower is limited and seems to be of potential benefit in search of wild species. In this study drought tolerance of three Crathamus species and their respective F2 hybrids (direct and reciprocal from paired crosses) was evaluated under four levels of osmotic potential of polyethylene glycol (0, -5, -10 and -15 bars) using a factorial experiment based on the completely randomized design with three replications. Increasing water stress levels caused significantly more reductions in the germination, root length, shoot length, root dry weight, shoot dry weight and seedling dry weight of cultivated genotypes as compared with wild species C. palaestinus (Cp), C. oxyacanthus (Co) and their F2 progenies indicating that wild species sustained more moisture stress tolerance than cultivated species. Results of drought tolerance indices (such as TOL and STI) also confirmed that wild species and F2 progenies had more drought tolerance in germination stage. Biplot analysis, according to principle component analysis (PCA), indicated that C. tinctorius was the most sensitive and the hybrids of C. oxyacanthus × C. palestinus were the most drought tolerant genotypes which can be due to heterosis. Results also showed that the F2 hybrids from crosses between cultivated species (C. tinctorius) and wild species (C. oxyacanthus and C. palestinus) had high tolerance to drought stress and can be used for developing drought tolerant genotypes in inter-specific hybridization breeding programs.