Expression Analysis of Candidate Genes in Response to PEG Induced Osmotic Stress in Soybean [Glycine max (L.) Merrill]

Drought stress poses a significant challenge to soybean production, necessitating the understanding of molecular mechanisms underlying stress tolerance for breeding resilient varieties. This study evaluated the expression of three drought-responsive candidate genes-GmLEA2-1, GmXTH1, and DREB-in seven soybean genotypes with varying tolerance levels under mild (0.5% PEG 6000) and severe (1% PEG 6000) osmotic stress, induced by immersing 3-week-old seedlings in PEG 6000-modified 1/10 strength MS nutrient solution for 18 hours. Semi-quantitative RT-PCR and spot density analysis revealed that tolerant genotypes, such as EC 538828 and EC 602288, exhibited significant upregulation of GmLEA2-1 and GmXTH1, emphasizing their roles in cellular stabilization and water uptake. DREB expression varied, with tolerant genotypes maintaining consistent or enhanced expression, while sensitive genotypes, such as NRC 37, showed downregulation under stress. Notably, MACS 330, a sensitive genotype, exhibited a delayed but significant response under severe stress. The findings underscore the utility of PEG 6000 as an effective osmotic agent for simulating drought stress, while highlighting the potential of these genes as molecular markers for breeding drought-resistant soybean varieties, offering insights into improving crop resilience in water-limited environments.