Combining Ability, Heritability, and Heterosis for Seed Weight and Oil Content Traits of Castor Bean (Ricinus communis L.)

Hybridization is an important evolutionary force, and heterosis describes the phenomenon where hybrids exhibit superior traits compared to their parents. This study aimed to evaluate the one-hundred-seed weight and fatty acid content in F1 generations, investigating the effects of different parental crosses using a 9 × 3 incomplete diallel design (NCII). One of the challenges faced in this study was the complexity of accurately determining the influence of both genetic and environmental factors on trait inheritance. A total of 36 F1 crosses were analyzed for general combining ability (GCA), specific combining ability (SCA), and heritability. The results showed that the level of each index in F1 is closely related to its parents. Significant differences in GCA and SCA were observed among parental traits in most crosses. The ratio of GCA to SCA ranged from 0 to 3, indicating the pivotal role of SCA over GCA in castor breeding efforts. High narrow-sense heritability was recorded in palmitic acid (30.98%), oleic acid (28.68%), and arachidonic acid (21.34%), suggesting that these traits are predominantly under the control of additive gene action, and hence these characters can be improved by selection. Additionally, heterosis exhibited diverse patterns across traits. Based on the evaluated combining ability, heritability, and heterosis, the inbred lines CSR181 and 20111149 were recommended for castor crossbreeding due to their potential to yield progeny with optimal oil-related traits. This research contributes valuable knowledge to the field of castor breeding, providing a foundation for developing superior castor cultivars.