Heterosis has been a key strategy in breeding sunflowers to improve sunflower yield and develop superior cultivars. Inbreeding depression, which is the loss of fitness and performance induced by increased homozygosity, is a major problem in the sunflower hybrids program. This research aimed to evaluate seven diversified genotypes (FMC-0046, Thatta, SH-3, A-2, Turkish, Mehran, and ST-2) and their 12 F₁ hybrids and F₂ populations for heterotic effects and inbreeding depression in earliness, yield, and oil content under normal and water-deficit conditions. The study used a split-plot design with three replications, carried out in 2023 at the Sindh Agriculture University, Tandojam, Pakistan. The analysis of variance revealed significant (P ≤ 0.01) differences among F₁ and F₂ populations and genotype-by-environment interactions. Among the genotypes, FMC-0046, Turkish, and Mehran expressed the highest values for 1000 seed weight, head diameter, oil content, and seed yield plant-1. Among the F₁ hybrids and F₂ populations, FMC-0046 х Mehran, Thatta х Turkish, A-2 х Mehran, SH-3 х ST-2, and A-2 х ST-2 performed better with desirable heterosis and desirable inbreeding depression for yield and oil traits. Hence, these populations received recommendations for inclusion in future breeding programs for the development of water stress-tolerant cultivars.
Heterosis, inbreeding depression, yield and oil traits, water stress, sunflower (Helianthus annuus L.) genotypes
Under water-stressed conditions, FMC-0046 х Turkish, FMC-0046 х Mehran, and Thatta х ST-2 performed well for traits of the number of seeds head-1 and head diameter, respectively. A-2 х Mehran produced desired results for 1000 seed weight in a stressed environment.