GENOTYPIC VARIATION IN PHYSIOLOGICAL TRAITS CONTRIBUTING TO DROUGHT AVOIDANCE AND ITS CONSEQUENCES FOR GROWTH AND YIELD IN WHEAT (TRITICUM AESTIVUM L.)

Abstract

Drought is the single most important abiotic constraint limiting wheat (Triticum aestivum L.) productivity, and identifying physiological traits that confer drought avoidance remains central to breeding resilient cultivars. In this study, thirty diverse bread wheat genotypes were screened under well-watered (control) and restricted irrigation (drought, imposed by withholding irrigation from 30 days after sowing) conditions in a randomised complete block design with three replications at the Crop Research Farm, RPCAU, Pusa, Bihar, during the 2021-22 rabi season. Six physiological traits associated with drought avoidance – canopy temperature (CT), tissue temperature (TT), normalised difference vegetation index (NDVI), relative water content (RWC), specific leaf weight (SLW) and SPAD-based greenness index – were recorded at the reproductive stage, and a cumulative response index (CRI) integrating all six traits was used to rank genotypes for drought responsiveness. Genotype, treatment and genotype × treatment interaction effects were highly significant (P<0.001) for all traits. Canopy and tissue temperature increased under drought while RWC, SLW, SPAD and NDVI declined in most genotypes, though the magnitude of change varied widely across the panel, indicating substantial exploitable genetic diversity. Based on CRI ranking, five genotypes (RAUW105 P10, HD2968, 11HPYT405, 41ESWYT102 P2 and SSN3) that maintained comparatively stable canopy temperature, tissue temperature, water content and greenness under drought were advanced for evaluation of growth and yield. In these genotypes, drought reduced plant height, spike length, grains per spike, test weight, grain yield and total biomass relative to the control, but the decline was consistently smaller in genotypes that had shown a favourable physiological response at the vegetative/reproductive screening stage, confirming a physiological basis for yield stability under water deficit. These results identify canopy temperature, tissue temperature, RWC, SLW and SPAD value as low-cost, high-throughput indicator traits for large-scale screening of drought avoidance in wheat, and RAUW105 P10, HD2968, 11HPYT405, 41ESWYT102 P2 and SSN3 as promising donors for incorporation into drought-tolerance breeding programmes.