Rice is a highly water-demanding crop and climate change–driven water scarcity is making sustainable production increasingly difficult. Enhancing water-use efficiency through improved photosynthesis and reduced transpiration is therefore a key breeding objective. In this study, 70 rice genotypes were evaluated for 16 morpho-physiological traits under non-stressed conditions. Analysis of variance revealed significant genotypic differences for most traits. High genotypic and phenotypic coefficients of variation were recorded for stomatal conductance, transpiration rate (TR), photosynthetic rate (PR), intrinsic water-use efficiency (iWUE) and single plant yield, accompanied by high heritability (>97 %) and genetic advance, indicating strong selection potential. Single plant yield showed significant positive correlations with plant height, days to 50 % flowering, panicle length, spikelet fertility and harvest index, demonstrating that yield is governed by growth, physiological and agronomical components. Photosynthetic rate increased with stomatal conductance, whereas iWUE declined, reflecting a carbon–water trade-off and suggesting an optimal range of moderate conductance. Path coefficient analysis identified plant height (0.38), days to 50 % flowering (0.34), harvest index (0.33), spikelet fertility (0.27), iWUE (0.12) and stomatal density as major direct contributors to yield. Principal component analysis showed that the first 2 components explained 35.94 % of total variation, while cluster analysis grouped genotypes into 5 clusters, indicating substantial genetic divergence. The results suggest that moderate stomatal conductance, high iWUE, panicle length, spikelet fertility and harvest index are important selection criteria for improving yield and water-use efficiency in rice breeding programmes.
Srimathi et al. (2026) studied this question.