Comprehensive evaluation of salt tolerance during the germination period of tomato germplasm and Screening of key indicators

This study aimed to screen for salt-tolerant tomato germplasms at the germination stage and to identify key evaluation indicators for this trait. To determine the optimal stress concentration, six tomato germplasms were first treated with five NaCl stress concentrations (0.2%, 0.4%, 0.6%, 0.8%, and 1.0%) alongside a 0 control (CK). Based on radicle length measurements, 0.6% NaCl was identified as the optimal screening concentration. Subsequently, 20 tomato germplasms were treated with 0.6% NaCl, and eight indicators were measured, including germination rate, germination potential, germination index, vigor index, radicle length, hypocotyl length, and fresh weight. After calculating the salt tolerance coefficient for each indicator, a comprehensive evaluation of salt tolerance was conducted using correlation analysis, principal component analysis (PCA), the subordinate function method, and cluster analysis, followed by regression analysis to screen for key indicators. The results showed that NaCl stress exhibited a hormetic effect, where low concentrations (0.2%–0.4%) promoted radicle elongation in most germplasms, while the 0.6% treatment caused significant inhibition and higher concentrations (0.8%–1.0%) prevented germination in some materials. The salt tolerance coefficients of all indicators were significantly correlated (p<0.05). PCA extracted two principal components with a cumulative contribution rate of 78.114%. Cluster analysis classified the 20 germplasms as highly tolerant (2), moderately tolerant (15), or sensitive (3). Finally, regression analysis identified germination index, radicle length, and fresh weight as the key indicators for evaluating salt tolerance at the germination stage. This study established a comprehensive evaluation system for tomato salt tolerance during germination, screened superior germplasms and key indicators, and provides a foundation for future research on salt tolerance mechanisms and variety improvement.