Deciphering Genetic control of grain quality, zinc, and iron content in rice using six-parameter generation mean analysis

Rice serves as a primary food source for half of the global population and its biofortification plays a vital role in addressing malnutrition and hunger. The present investigation aimed to elucidate the genetic control of eleven key rice grain micronutrient and quality traits using six-parameter generation mean analysis (GMA) across four diverse crosses. The experiment was conducted during Kharif-2018 at Agricultural Research Farm, Banaras Hindu University, Varanasi, UP, India (Loc-1) and during Rabi-2019 at NRRI, Cuttack, Odisha, India ((Loc-2) to generate the experimental materials (F 1 , F 2 , BC 1 and BC 2 ). The six generations (P 1 , P 2 , F 1 , F 2 , BC 1 and BC 2 ) of four different crosses [Cross 1 (HUR 105 × Sathi), Cross 2 (HUR 105 × Dudhkander), Cross 3 (HUR 3022 × Sathi) and Cross 4 (HUR 3022 × Dudhkander)] were evaluated independently during Kharif 2019 using randomized complete block design with three replications at Loc−1. The mean data collected for eleven studied traits were subjected to GMA. Significant variation among generations indicated substantial genetic diversity for all the studied traits, including grain Zn and Fe content. The analysis revealed that both additive and non-additive gene effects contributed to trait expression; however, non-additive gene action predominated for most traits. Among epistatic components, additive × additive (i) interactions were frequently significant, indicating the presence of fixable gene effects and suggesting more predictable and higher genetic gain under early selection. Dominance × dominance (l) epistasis was significant for several traits, whereas additive × dominance (j) effects were largely non-significant. Duplicate epistasis was observed for grain Zn, grain Fe, KL, KLAC, KBAC, LBBC, and ER indicating lower genetic gain under early-generation selection for these traits due to limited fixation of favorable alleles whereas, higher genetic gain can be realized through delayed selection in advanced generations or through heterosis breeding. In contrast, complementary epistasis, identified for grain Zn in cross 4, KL in cross 1, KLAC and KBAC in cross 1, and ADV in crosses 1 and 2, reflects reinforcing gene action that favors the accumulation of desirable alleles and higher genetic gain can be realized through early generation selection strategy. Overall, understanding the interplay of gene actions and interactions will contribute towards developing efficient breeding strategy to exploit Zn and Fe rich biofortified rice variety with good cooking quality traits.