Possibility of using interspecific hybridization to increase genetic diversity of drought tolerance in safflower (Carthamus tinctorius L.) and effectiveness of different selection methods is poorly understood. The main objectives of this study were to evaluate the effectiveness of (a) interspecific hybridization to expand genetic diversity in safflower for agronomic traits and drought tolerance in advance generations and (b) different selection methods (direct vs. indirect) for improving seed yield. Interspecific hybridizations were performed between species of C. tinctorius × C. palaestinus (TP), C. palaestinus × C. oxyacantha (PO) and C. tinctorius × C. oxyacantha (TO). Based on the field screening of genotypes in F3 generation, four groups of selected genotypes (derived from combination of direct and indirect selection under both drought and normal environments along with selection based on drought tolerance index (STI)) were evaluated in F4 and F5 generations. Indirect selection for seed yield was significantly more efficient than direct selection. Selection in stress environment resulted to more efficiency than selection in normal environment. No significant difference was observed between direct selection and selection based on STI. The result showed that TP was the best population to combine high seed yield and drought tolerance in safflower.

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The use of appropriate selection methods are important to increase yield in breeding programs. Utilization of selection indices is one of the most effective method for selection of superior genotypes to improve the complex traits such as seed yield. In order to evaluate the efficiency of different selection methods, families of two F populations derived from interspecific hybridization of Carthamus tinctorius × Carthamus oxyacanthus (IO) and Carthamus palaestinus × Carthamus tinctorius (IP) were evaluated under two moisture environments (normal and drought-stress) at the research farm of Isfahan University of Technology during. The Smith-Hazel , Smith-Hazel and Pesek-Baker indices were measured based on the traits entered in step-wise regression model. The results indicated that under normal conditions, Pesek-Baker index was more effective than the Smith-Hazel and Smith-Hazel and was also more efficient for the selection of superior genotypes in IP population. Also, the Smith-Hazel and Smith-Hazel indices were more effective than Pesek-Baker index under drought-stress conditions in this population. Smith-Hazel and Smith-Hazel indices were more effective than Pesek-Baker index in IO population at two moisture environments. Efficiency of selection in IP population was more than IO population, thereby it can be used to develop superior genotypes in breeding programs. Since the C. palaestinus have less undesirable characters compared to other wild parents, it may be suitable source for transferring desirable genes to the cultivated species.

In the light of current global climate change, gene introgression from wild relatives is a key strategy for increasing adaptation of crops that lost their variation during evolutionary bottleneck. Fall‐sown safflower leads to earlier spring growth and potentially higher productivity than the spring‐sown safflower, because of escaping from the terminal stresses of drought, heat, disease, and pests as well as efficient use of winter precipitation. During the last decade, we developed advanced generations of three sets of recombinant inbred lines (RILs) derived from three crosses of Carthamus tinctorius × Carthamus palaestinus (TP), C. tinctorius × Carthamus oxyacanthus (TO) and C. palaestinus × C. oxyacanthus (PO). The objectives of this study were to assess the efficiency of gene introgression from two wild relatives of safflower and genetic variation of derived RILs in terms of adaptation to autumn sowing and cold tolerance in the field. The results showed a continuous variation for seed yield and oil content in RILs, indicating the existence of transgressive segregation in lines. Comparison of three interspecific populations indicated that lines derived from TP crosses showed high potential for autumn planting, winter hardness, and productivity of seed and oil yield. However, the RILs derived from PO and TO had higher chlorophyll fluorescence (Fv/Fm) than TP population. Our results indicated that restoring lost genes in safflower is possible by introgression from its close relatives (especially C. palaestinus species). Identified superior RILs can be checked for other biotic and abiotic tolerance to develop new varieties in this valuable oil seed crop.

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