Studies on Genetic Variability, Heritability and Genetic Advance for Yield and Root Traits in Pup1-Introgressed Rice (Oryza sativa L.) Genotypes under Contrasting Phosphorus Regimes

Abstract

Background: Rice (Oryza sativa L.) is a globally important staple crop, fundamental to food security and livelihoods, particularly across Asia, but its productivity is increasingly constrained by nutrient limitations such as phosphorus deficiency. Enhancing phosphorus-use efficiency through genetic approaches, including the introgression of the Pup1 locus, is therefore essential for developing sustainable, high-yielding rice genotypes under low-input conditions. Aims: This study aims to evaluate genetic variability, heritability and genetic advance for yield and associated traits in rice genotypes introgressed with the Pup1 gene under contrasting phosphorus levels to identify phosphorus-efficient genotypes for low-input environments. Study Design: The experiment was conducted in a split-plot design with two phosphorus levels as main plots and 46 rice genotypes as sub-plots with two replications. Place and Duration of Study: The study was carried out during the kharif seasons of 2022 and 2023 at the Agricultural Research Station, Gangavathi, Karnataka, India. Methodology: A total of 45 rice (Oryza sativa L.) genotypes, including three phosphorus-deficiency tolerant checks (Swarna, Rasi and Vandana) and one susceptible check (Improved Samba Mahsuri), were evaluated under two phosphorus treatments: P₀ (0% recommended phosphorus) and P₅₀ (50% recommended phosphorus dose). Observations were recorded for phenological, yield and root-related traits such as plant height, number of tillers per plant, panicle traits, root length, shoot–root ratio, biomass traits and grain yield. Statistical analyses were performed to estimate phenotypic and genotypic coefficients of variation, broad-sense heritability and genetic advance. Results: Analysis of variance revealed significant differences among genotypes for all the traits studied, indicating substantial genetic variability. Phosphorus levels significantly influenced plant height, panicle length, number of tillers per plant, root length, shoot–root ratio and root dry weight. Significant genotype × phosphorus interaction for most traits indicated differential genotypic responses to phosphorus availability. High phenotypic and genotypic coefficients of variation, along with high heritability and genetic advance for several root and yield traits, suggested the predominance of additive gene action and greater scope for improvement through direct selection. Enhanced root growth under phosphorus-deficient conditions highlighted the adaptive advantage of Pup1-introgressed genotypes in sustaining yield under low phosphorus environments.         Conclusion: The study demonstrates that Pup1-introgressed rice genotypes possess significant potential for improving yield and phosphorus-use efficiency, making them well-suited for sustainable cultivation under phosphorus-limited conditions.