Dissecting genetic architecture of quantitative traits using higher order statistics, variability studies and association analysis in rice MAGIC population

Rice is cultivated across diverse agro-climatic regions worldwide and its productivity is affected by many biotic and abiotic stresses. With the ever-increasing global population and changing climatic factors, the need to produce 25 % more rice by 2030 is becoming paramount. Improving the yielding ability of rice varieties vis-a-vis reducing the crop loss due to abiotic and biotic stresses is a promising approach. Breeding of varieties was mostly concentrated on developing single-, three-way-, or double-cross hybrids involving two, three or four parents to increase the genetic variation in breeding population. Multi- parental advanced inter-cross (MAGIC) populations provide a useful resource with diverse allelic combinations to be exploited by the rice community. The MAGIC population also presents opportunities for studying interactions of genome introgression and chromosomal recombination. Hence the present investigation was undertaken at Rice Research Station, Tirur during Samba (Aug–Dec), 2024 with two 8-parent MAGIC F3 rice populations to study the nature of trait distribution, genetic variability, heritability (h²), genetic advance as per cent of mean (GAM), genotypic correlation and path coefficient analysis for 15 agro-morphological, grain quality and physiological drought response (DR) traits. Phenotypic frequency distributions of traits indicated substantial phenotypic variation predominantly of quantitative nature as witnessed from the continuous normal curve in both the populations. Variability and h2 studies indicated high genotypic coefficient of variation (GCV), high h² and high GAM were concurrently recorded for productive tillers per plant, number of grains per panicle, root length (RL) at 45 days after sowing and single plant yield (SPY) in Cross I and L/B ratio, RL, root : shoot ratio (RSR), drought recovery and SPY in Cross II. Correlation studies revealed significant positive genotypic correlations of SPY with productive tillers per plant, number of grains per panicle and spikelet fertility in Cross I and these yield-attributing traits are valuable for improving grain yield. Path coefficient analysis revealed that productive tillers per plant and number of grains per panicle were the primary direct contributors to SPY in Cross I. These findings provide a quantitative basis for trait-based selection and genotype advancement in MAGIC rice breeding programmes targeting drought-prone environments.