Evaluation of salt stress indices and morpho-physiological attributes to identify high-yielding, salt-tolerant guar (Cyamopsis tetragonoloba L.) genotypes

) in a factorial RCBD design. Salinity imposed highly significant reductions in relative chlorophyll content, relative water content, leaf area, plant height, root length, and all reproductive traits, while markedly increasing CO₂ concentration, electrolyte leakage, MDA accumulation, and proline content. Genotypes differed widely in their sensitivity, and strong genotype × salinity interactions were observed for most traits, particularly chlorophyll stability, water status, oxidative stress indicators, phenological delays, and seed and gum yields. Seed yield and gum yield, respectively were declined by 25.1 and 43.9% at 15 dS/m (p < 0.001). Among the evaluated genotypes, RGC-986 (genotype 1) consistently displayed superior performance across salinity levels, maintaining the highest relative chlorophyll content, leaf area, seed number per plant, 100-seed weight, gum percentage, and final seed yield. In contrast, Pishen (genotype 15) was the most adversely affected, exhibiting sharp declines in morphological attributes, delayed phenology, and substantial reductions in reproductive output at high salinity. Stress-tolerance indices (STI, GMP, YSI, HMP) further confirmed the strong salt-tolerant behavior of genotypes RGC-986 (G1) (STI = 1.0), S6673 (G2), BR-99 (G3) and Saravan (G10), while genotypes RGC-1066 (G14) and Pishen (G15) ranked among the most susceptible (STI = 0.63). Overall, the study demonstrated substantial genetic variability in guar responses to salinity and highlighted key physiological traits such chlorophyll retention, osmotic adjustment, membrane stability, and growth maintenance as essential determinants of tolerance. Genotypes identified as salt-tolerant represent valuable candidates for breeding programs and for sustainable guar cultivation in salinity-affected regions.