Using Stress Indices in Soybean for the Identification Genotypes Adapted to Non-Traditional Growing Seasons

Abstract

Soybean is a predominant kharif season crop in Telangana, recognized for its high yield potential and economic importance as a major oilseed. With the expansion of irrigation infrastructure in the region, there is growing potential to cultivate soybeans during the rabi season as well. However, the adoption of rabi soybean cultivation remains limited, primarily due to the absence of climate-resilient and photoperiod-insensitive varieties suitable for short-day winter conditions. The present study aimed to identify soybean genotypes with stable performance across both seasons by evaluating 50 genotypes, including advanced breeding lines and released varieties, during the 2021–2022 cropping. Field trials were conducted under optimal (kharif, Yp) and stress (rabi, Ys) environments. Seven widely used stress tolerance indices, Stress Susceptibility Index (SSI), Mean Productivity (MP), Geometric Mean Productivity (GMP), Tolerance (TOL), Stress Tolerance Index (STI), Harmonic Mean Productivity (HM), Yield Index (YI), and Yield Stability Index (YSI) were employed to assess genotype resilience based on grain yield performance. The indices STI, GMP, MP, and YI showed strong associations with both Yp and Ys, underlining their reliability in screening genotypes for seasonal adaptability. Genotypes were ranked using an average sum score derived from all eight indices. Based on this integrated evaluation, genotypes G50, G5, G15, G38, and G21 were identified as highly resilient and suitable for dual-season cultivation. These findings offer valuable insights for breeding programs aimed at developing soybean cultivars adapted to changing climatic conditions and expanding the sowing window beyond traditional kharif periods. Based on the average sum rank (ASR) derived from all eight stress indices, genotypes G50, G5, G15, G38, and G21 consistently exhibited high yield and stability across both seasons.  These genotypes are therefore promising candidates for cultivation under variable seasonal conditions due to their yield resilience and adaptability.