Comprehensive Evaluation of Salt Tolerance of Processing Tomato Germplasms at Seedling Stage

Soil salinization constitutes a major abiotic constraint limiting global crop productivity, and breeding salt-tolerant cultivars represents a pivotal strategy to addressing this challenge. In this study, 50 processing tomato genotypes with diverse genetic backgrounds were cultivated hydroponically in Hoagland nutrient solution and subjected to either 0 (control) or 150 mM NaCl at the four-leaf stage. Nine seedling traits, encompassing plant height, stem diameter, and antioxidant enzyme activities, were measured on the 9th day after treatment initiation. Comprehensive evaluation of salt tolerance was performed using principal component analysis (PCA), fuzzy membership function analysis, and cluster analysis. The coefficients of variation (CVs) for all measured traits ranged from 21.54% to 92.69%, with relative proline content exhibiting the highest CV (92.69%) and relative stem diameter showing the lowest (21.54%). Correlation analysis revealed a highly significant positive correlation between relative plant height and relative stem diameter, and a highly significant negative correlation between relative plant height and relative proline (Pro) content. PCA reduced the nine seedling traits to four principal components, which collectively accounted for 67.529% of the total variance. Based on the combined results of fuzzy membership function and cluster analyses, the 50 genotypes were classified into three distinct categories: highly salt-tolerant (six genotypes), moderately salt-tolerant (26 genotypes), and salt-sensitive (18 genotypes). These findings provide a theoretical foundation and valuable germplasm resources for breeding salt-tolerant processing tomato varieties.