Comprehensive evaluation of salt tolerance and identification of elite salt-tolerant germplasm in 331 peanut accessions at seedling stage

Soil salinization is a major constraint limiting the expansion and yield of peanut cultivation. Screening salt-tolerant peanut germplasm and identifying related traits provide a foundation for breeding salt-tolerant varieties and investigating the mechanisms underlying salt tolerance. In this study, the salt tolerance of 331 peanut accessions was evaluated at the seedling stage using a hydroponic system. Eight parameters were measured: SPAD value, plant height, shoot fresh weight, root fresh weight, shoot dry weight, root dry weight, fresh weight root/shoot ratio, and dry weight root/shoot ratio. A comprehensive evaluation of salt tolerance was conducted using principal component analysis (PCA), membership function analysis, and cluster analysis. Under different salt concentrations, six parameters—plant height, shoot fresh weight, root fresh weight, shoot dry weight, fresh weight root/shoot ratio, and dry weight root/shoot ratio—showed significant differences among accessions. Salt stress inhibited peanut growth and significantly reduced four of these parameters compared with the control. Correlation analysis revealed significant relationships among the salt tolerance coefficients of all eight parameters, with the strongest correlation observed between root fresh weight and root dry weight (<italic>r</italic> = 0.83). PCA reduced the eight parameters to three principal components, accounting for a cumulative variance of 76.22%. Based on <italic>D</italic>-values (comprehensive evaluation scores), cluster analysis grouped the 331 accessions into five categories: Group I (highly salt-tolerant, 11 accessions), Group II (salt-tolerant, 33 accessions), Group III (intermediate, 104 accessions), Group IV (salt-sensitive, 42 accessions), and Group V (highly salt-sensitive, 141 accessions). A stepwise regression analysis yielded a predictive equation for evaluating salt tolerance in peanut seedlings: <italic>Y</italic> = 0.032 + 0.163<italic>X</italic>₄ + 0.137<italic>X</italic>₃ + 0.073<italic>X</italic>₁- 0.158 <italic>X</italic>₂ + 0.111<italic>X</italic>₅ + 0.080<italic>X</italic>₆. The <italic>D</italic>-value proved effective for assessing salt tolerance at the seedling stage, and 11 salt-tolerant germplasms, including Huashi 2, AM-Ceorganic, and Zhonghua 6, were identified. Plant height, root dry weight, and shoot dry weight were identified as key indicators for evaluating peanut salt tolerance at the seedling stage.