Sodium hydrosulfide alleviation of alkalinity stress is differentially modulated through changes in polyphenolic levels and NAC transcription factor in two black mung bean genotypes

Alkaline stress presents a major challenge in agriculture, significantly limiting plant growth and productivity. This study introduces a new, integrated experimental framework for assessing stress tolerance in Vigna mungo , combining genotype comparisons with external application of sodium hydrosulfide (NaHS). Two genetically distinct genotypes were studied to understand the links between genetic background and physiological, biochemical, and molecular responses to alkaline stress. The results showed genotype and tissue-specific increases in both enzymatic and non-enzymatic defense mechanisms, with the Indian genotype revealing a stronger antioxidant response. Under combined NaHS + alkaline stress, chlorogenic acid and rosmarinic acid levels increased significantly in the Iranian genotype (by 108.70 % and 250 %, respectively), while they declined in the Indian genotype (by 21.88 % and 50 %). In contrast, coumaric acid, rutin, and quercetin levels decreased in the Iranian genotype but rose markedly in the Indian genotype (by 50 %, 31.65 %, and 77.42 %, respectively), highlighting distinct genotype-specific polyphenolic responses to stress. At the molecular level, the Iranian genotype exhibited significant upregulation of the NAC gene under alkaline stress (214 %), whereas the Indian genotype showed notable downregulation (90 %), compared to the control. These findings imply that NAC may play a more key role in the Iranian genotype’s adaptation to alkaline conditions. This study presents a pioneering, integrative analysis of alkaline stress tolerance in Vigna mungo , combining physiological, biochemical, and molecular approaches. The findings offer novel insights into stress adaptation mechanisms and suggest promising strategies for improving crop resilience in alkaline soil environments. • NaHS + alkaline stress raised chlorogenic acid 108.7 % in the Iranian genotype. • Coumaric acid rose 50 %, rutin 31.65 %, quercetin 77.42 % in Indian genotype. • NAC gene upregulated 214 % in the Iranian genotype, downregulated 90 % in the Indian. • Indian genotype showed stronger antioxidant defense under alkaline stress. • Study links genotype-specific polyphenol shifts to stress adaptation traits.