Root architectural traits and their contribution to yield in F₂ populations of selected rice crosses under contrasting soil catena conditions

Rice yields in Sri Lanka’s Wet Zone are frequently constrained by soil and drainage limitations, yet root traits remain underutilized in breeding programs. This study evaluated four F₂ populations of rice crosses, their parents, and two check varieties at the Rice Research Station, Labuduwa, under upper and lower catena positions to evaluate genotype × environment effects under contrasting drainage conditions and to (i) compare root and shoot morphological traits and (ii) quantify associations between root traits and yield components. Plot-level means were analyzed using a two-way model with Cross and Catena effects, and significant Cross × Catena interactions were detected for several traits. Across environments, Crosses 2 and 4 exhibited superior root architecture, characterized by greater root zone width, number of roots, root strength, root volume, and root dry weight, along with competitive yield components. Moderate to high phenotypic and genotypic coefficients of variation for key root and yield traits indicated substantial scope for selection. False discovery rate–controlled correlation analysis revealed positive associations of root zone width, number of roots, root strength, and root volume with effective tiller number, shoot biomass, and total panicle weight. These findings demonstrate the value of targeted selection for root traits to enhance yield stability under contrasting drainage conditions in the Wet Zone of Sri Lanka.