Screening of Saline–Alkali-Tolerant Rapeseed Varieties Through Multi-Index Integrated Analysis Across the Entire Growth Cycle

In order to identify saline–alkali-tolerant rapeseed varieties suitable for cultivation on moderately saline–alkali soils and to expand the use of such lands, six rapeseed varieties were selected as experimental materials. Field experiments were conducted to evaluate agronomic traits, photosynthesis, stress physiology, yield, and quality throughout the entire growth period. Statistical methods, including correlation analysis, principal component analysis, membership function analysis, and cluster analysis, were employed to evaluate and select saline–alkali-tolerant varieties. The results indicated that H62 and 20C14 yielded the highest seed production, reaching 2287.99 kg·hm−2 and 2277.15 kg·hm−2, respectively. During the mid-to-late growth stages, the majority of agronomic traits, photosynthetic parameters, and stress physiology indicators for 20C14 were significantly superior to those of the other varieties. The results of the principal component analysis showed that the total root length at maturity stage, root–shoot ratio at flowering stage, and proline content at maturity stage were the most important indicators for screening saline–alkali-tolerant rapeseed varieties. A comprehensive analysis of these indicators revealed the following descending order of saline–alkali tolerance among the varieties: 20C14 > 20C17 > 20C4 > H62 > H158 > 17C2. Cluster analysis was performed to classify the rapeseed into strong saline–alkali-tolerant type (20C14 and 20C17), moderate saline–alkali-tolerant type (20C4, H62, and H158), and weak saline–alkali-tolerant type (17C2). Consequently, 20C14 and 20C17 are recommended as suitable rapeseed varieties for cultivation on soda saline–alkali soils.