Unique responses of three highly salt-tolerant wild Vigna species against salt stress

The genus Vigna contains important crops such as cowpea and mungbean. Wild Vigna showing higher salt tolerance than Vigna crops were screened and their tolerance mechanisms are discussed. Primary screening using 7 Vigna crops and 23 wild Vigna under 300 mM NaCl selected V. luteola, V. marina and V. vexillata. A study under different salt concentrations revealed the highest survival ability of V. marina. Diversity of salt tolerance in each species was revealed using a total of 230 accessions. Growth and physiological responses under 150 mM NaCl were then compared using two selected accessions from each species. The pattern of Na+ accumulation in roots, stems and leaves suggested that V. vexillata (V1) and V. luteola (L8, L9) are ‘Na+ excluder’ type, while V. marina (M1, M4) is ‘Na+ includer’ type. V. luteola (L8, L9) showed the highest dry matter production under control condition and well-maintained shoot dry weight under salt stress. Interestingly, V. luteola (L9) accumulated the highest Na+ in roots (3000 μM g−1) and increased root dry weight under salt stress, which might work as Na+ reservoir restricting Na+ transition to the leaves, leading to the increased photosynthetic rate. V. luteola has great potential in areas where moderate salt damage occurs. V. marina (M1, M4) accumulated Na+ at high level in roots, stem, and leaves. Under salt stress, they increased stomatal conductance, transpiration rate, and photosynthetic rate, which suggested the adaptational regulation of aquaporin gene expression. V. marina will be useful as food, pasture and phytoremediation legumes in highly salt-damaged areas.豇豆属（Vigna）包含豇豆、绿豆等重要栽培作物。本研究对耐盐性优于栽培豇豆的野生豇豆属种质进行了筛选，并探讨其耐盐机制。以300 mM氯化钠（NaCl）为盐胁迫浓度，对7份栽培豇豆及23份野生豇豆属材料进行初步筛选，最终筛选出V. luteola、V. marina与V. vexillata三个物种。不同盐浓度梯度下的试验表明，V. marina的存活能力最强。通过共计230份种质材料，明确了各物种间的耐盐性差异。随后，选取每个物种的2份代表性种质，对比其在150 mM NaCl盐胁迫下的生长与生理响应特征。通过分析其根、茎、叶的钠离子（Na+）累积模式，发现V. vexillata（V1）与V. luteola（L8、L9）属于‘排钠型’种质，而V. marina（M1、M4）则属于‘聚钠型’种质。V. luteola（L8、L9）在对照条件下的干物质积累量最高，且在盐胁迫下仍能维持较好的地上部干重。值得注意的是，V. luteola（L9）在根中累积的钠离子浓度最高（3000 μM g⁻¹），且盐胁迫下其根干重有所提升，这可能使其作为钠离子储库，限制钠离子向叶片转运，进而提高光合速率。V. luteola在中度盐渍化区域具有良好的应用潜力。V. marina（M1、M4）在根、茎、叶中均累积了高水平的钠离子。盐胁迫下，该物种的气孔导度、蒸腾速率与光合速率均有所提升，这表明其通过水通道蛋白基因表达的适应性调控来实现耐盐。V. marina可作为食用、饲用及植物修复用豆科植物，应用于重度盐渍受损区域。