Abstract
Drought is a key abiotic factor limiting soybean productivity, particularly during early development stages.This study comprehensively evaluated drought tolerance of soybean varieties and lines during germination and initial seedling growth using PEG-6000-induced osmotic stress, comparing laboratory parameters with field yield.Under control and stress conditions, relative germination rate, root length index, shoot length index, and proline content in seedlings were evaluated as morphophysiological and biochemical indicators.Laboratory parameters were integrated with field yield data via an integrated stress index (ISI) based on trait ranking, analyzed separately for ultraearly and early maturing groups.Results showed high genotypic variability in response to osmotic stress.Seedling growth indicators had partially independent dynamics, indicating multicomponent early drought tolerance.Proline accumulation under PEG-6000 was statistically significant, reflecting stress intensity but not independent tolerance.Integral assessment identified promising genotypes combining stable lab performance with high field productivity.Highest ISI in ultra-early: Chera-1-3, line 32-21-1, Nuralem-1, OAK Prudence.In early maturing: Belgorodskaya 7, Nadezhda, line 111-21-1, Milyausha.The approach PEG screening, morphophysiological, biochemical parameters integrated with field data is an effective tool for early-stage breeding diagnostics of soybean drought tolerance, applicable for parental selection in water-limited environments.