Unraveling the genetic architecture of rice yield potential by investigating the impacts of heterosis and inbreeding depression

Understanding the inheritance pattern, heterotic groups, and inbreeding depression is a prerequisite for hybrid rice seed production. Therefore, this study employed a full diallel mating system involving two tall varieties and three medium-statured mutants. The results revealed the significant differences in plant height, panicle length, tillers per plant, fertility percentage and grain yield. Heterosis was more pronounced for grain yield (24.2%), followed by tillers per plant (19.8%), and panicle length (19.2%). Conversely, inbreeding depression was lowest for tillers per plant (–11.5%) and grain yield (–6.8%). The additive–dominance model provided a good fit for tillers per plant and plant height, indicating the importance of both additive (D) and dominance components (H1 and H2). However, for panicle length, fertility percentage, and grain yield, the model only partially fit, suggesting a more intricate genetic architecture involving both additive and nonadditive genetic effects. Plant height and tillers per plant appear to be predominantly exhibited by additive genes, making them well- suited for improvement through pedigree selection strategies. Conversely, fertility percentage and grain yield seem to be more influenced by overdominant gene effects, indicating the potential for exploiting hybrid vigor to enhance these traits in breeding programs. Additionally, the high narrow-sense heritability of plant height (84%) and tillers per plant (93%), coupled with additive effects, indicates promising prospects for genetic improvement of these traits in rice breeding programs.