LAUSR

Background: Adapting large-seeded soybean to drought stress is essential, requiring development drought-tolerant cultivars and management practices to sustain yield under water-limited conditions. This study aimed to evaluate and identify drought-tolerant soybean genotypes using drought indices in order to recommend promising genotypes for cultivation in drought-affecting regions. Methods: The experiment employed Split-Plot Design in Completely Randomized Design. The main plots were drought stress levels consisting of four levels, non-stress, 10% PEG6000, 20% PEG6000 and 65% field capacity. The sub-plots were 20 large-seeded soybean genotypes, replicated four times. Based on yield performance under non-stress (Yp) and drought stress (Ys), drought indices (Stress tolerance index, Stress adaptation index, geometric mean productivity, mean productivity, harmonic mean, yield stability index, yield index, drought response index, tolerance index, stress susceptibility Index) were calculated, Pearson correlation and PCA biplot analyses were computed. All statistical analyses were done using the SmartStatXL add-in. Result: Seed yield of large-seeded soybean genotypes varied significantly under different drought stress levels. Drought tolerance indices, STI, SAI, GMP, MP, HM, DRI and YSI, were strong positive correlated with yield, confirming their effectiveness in identifying drought-tolerant and stable genotypes. PCA biplot analysis effectively separated drought-tolerant from susceptible genotypes and classified Grobogan, Dega-1, KH-1 and Biosay-2 as tolerant under 10% PEG6000 » -0.19 MPa, Grobogan, Dega-1, KH-1 and Burangrang under 20% PEG6000 » -0.67MPa and Grobogan and Dega-1 under 65% field capacity. Of all the drought stress, Grobogan and Dega-1 consistently exhibited superior yield and drought tolerance, making them valuable genetic resources for breeding drought-tolerance soybean.