Governance of Gene Action and Combining Ability for Certain Grain Quality Traits in Three Diverse Rice (Oryza sativa L.) Growing Ecosystems

Traditional varieties or land races from diverse rice growing ecosystems serving as repository of desirable gene pools for rice improvement including rice hybrids have been marginalized or are at the verge of perhaps total genetic erosion. Biotechnology patent systems and intellectual property rights intrinsic with genetically engineered rices weigh in at odds, competing with these good grain qualified traditional rices. Genetic analyses have been made to uncover the supremacy of gene action and combining ability for certain grain quality related physicochemical traits in seven diverse ecogeographical genotypes of ‘indica’ rice using a 7 × 7 half-diallel cross following Griffing's Model-1, Method-2. Comparative results obtained from 7 parents + 21 F(1)s + 21 F(2)s revealed the involvement of both additive (polygenic) and non-additive (epistasis or interallelic) gene action(s) in the governance of grain quality traits. However, the ratio of σ(2) g/σ(2) (s) exhibited greater importance of non-additive genes for all the traits except kernel length in F(1). This suggests the plausibility of exploitation of heterosis in rice as a self-pollinated crop. Epistasis gene action (interallelic interaction) was found to be more pronounced for all the traits. The genotypes NS 19 (for grain weight), T 21 and IR 24 (for both kernel length and L/B ratio) and Jal Lahri (for protein content) emerged as good general combiners with high ‘gca’ values. The six specific crosses, viz., Mahsuri/IR 24, NDR 359/Jal Lahri, Sarjoo 52/Jal Lahri, Mahsuri/T 21, Sarjoo 52/NS 19 and Sarjoo 52/T 21, revealed significant ‘sca’ effects suggesting their role in improvising for certain physicochemical grain quality traits. These crosses were found to retain at least one parent with high ‘gca’ value and the other parent having either high, average or low ‘gca’ effects indicating for the occurrence of both additive as well as non-additive genetic interactions. These findings may be of greater relevance in shuffling and combining the genes/traits between traditional and modern rice varieties (e.g., semi-dwarf, good to moderate tillering, medium maturity and good grain quality with high protein content) in almost all rice growing ecosystems.