Abstract:
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.
