Alkaline stress and selenium dioxide induce differential physiological, biochemical, and transcriptional responses in Vigna mungo genotypes

Alkaline stress limits plant productivity. This study examined selenium dioxide (SeO₂) seed priming (100 μM, 6 h) on responses of two Vigna mungo L. landraces, Iranian (IR) and Indian (IN), to alkaline stress (pH 9). High pH reduced shoot length (23% IR, 22% IN) and root length (29% IR, 12% IN); SeO₂ priming improved shoot length by 45% in IR but only 2% in IN. Shoot fresh weight declined under stress (32% IR, 42% IN), dropping further with SeO₂ in IR but rising 45% in IN. Glycine (Gly) rose sharply under stress in both genotypes, while alanine (Ala), methionine (Met), tryptophan (Trp), and phenylalanine (Phe) increased in IR (96-202%) but decreased or became non-detectable in IN. Under SeO₂ + alkalinity, IN showed further rises in Gly and Ala, with Phe and Met newly detectable, while IR showed mixed amino acid responses. Relative to alkalinity alone, combined treatment markedly raised CAT and POD activities (101-124%) in IR, with inconsistent responses in IN. qRT-PCR revealed NAC upregulation (128%) in IN and downregulation (89%) in IR. Overall, SeO₂ priming produced genotype-dependent effects, enhancing biomass and amino acid metabolism in IN, and strengthening antioxidant defense and shoot elongation in IR, supporting genotype-specific priming strategies for legume resilience in alkaline soils.