Evaluation of hybrid seed production possibilities in safflower (carthamus tinctorius L.) via chemical male sterility and morphological marker-assisted selection

Safflower (Carthamus tinctorius L.) is a highly valuable oil and bioenergy crop belonging to the Compositae (Asteraceae) family. The majority of safflower cultivars grown worldwide are standard (open-pollinated) varieties, while hybrid varieties have not yet become widespread. In this study, the feasibility of gibberellic acid (GA₃)-assisted hybrid seed production was investigated using the monogenic spiny trait as a morphological marker. In 2022, the spineless cultivar 'Dinçer 5-18-1' as the female parent and the spiny cultivar 'Olas' as the male parent, sown in different ratios (1♀:1♂, 2♀:2♂, 4♀:2♂, 6♀:2♂, and 50%♀ + 50%♂ mixed planting). To induce chemical male sterility, 100 ppm GA₃ was applied twice to the flower buds of the female parent at weekly intervals. Treated plants were then exposed to open pollination. Seeds from the spineless female rows were harvested and grown in 2023 under a randomized complete block design with three replications. Outcrossing rates were determined based on the presence of spiny offspring in the rosette stage. While natural outcrossing rates ranged from 9.29% to 19.30%, the 2♀:2♂ planting pattern combined with GA₃ treatment achieved an outcrossing rate of 86.82%. F₁ hybrids exhibited 53.19% heterosis and 42.86% heterobeltiosis for seed yield. Positive heterosis and heterobeltiosis responses were also observed for yield-related traits such as head size, seed number, and 1000-seed weight. These results demonstrate that GA₃-assisted hybrid seed production is feasible in safflower without the need for manual emasculation and pollination.