大豆芽期耐高温评价方法构建及耐高温种质资源筛选

The frequent occurrence of extreme high temperature (HT) events causes continuous heat damage to soybean production, which seriously damages the yield components and quality traits. The seeds are sensitive to the changes of the external environment at germination stage. The rising temperature and the accompanying drought will affect the emergence of soybean seeds. The establishment of a set of scientific evaluation methods for HT tolerance at bud stage can provide a theoretical basis for the early identification of soybean, the breeding of HT tolerance germplasm, and the study of tolerance mechanism. In this study, 385 germplasm resources varieties were selected as the experimental materials, which creating a HT environment by artificial climate incubator and subjected to HT-stress for 3 d (40℃, 16 h light /8 h darkness) at bud stage of soybean. Compared with the control (25℃, 16 h light /8 h darkness), the hypocotyl length of soybean bud stage was significantly decreased 10.9% under HT stress (P < 0.05). The indices of fresh root weight, dry root weight, and root-shoot ratio increased by 13.10%, 22.20%, and 16.90%, respectively (P<0.01). The results showed that HT-stress significantly affected the surface and underground biomass distribution of bud stage in soybean. Meanwhile, the principal component analysis for the coefficient of HT-tolerance for each trait converted 11 indexes into two principal component factors. The comprehensive evaluation value (H-value) of soybean response to HT-stress was obtained by the standardized analysis of membership function, and cluster analysis was conducted for the tested varieties based on H-value. Ultimately, 385 germplasm resources were divided into 5 grades for the HT-tolerance at bud stage in soybean [namely: Grade I (tolerance), Grade II (strong tolerance), Grade III (medium), Grade IV (strong sensitive), and Grade V (sensitive type)] and four HT-resistant varieties based on the specific performance (H245, H070, H268, and H216) were initially selected combined with the actual heat resistance performance. After the stepwise regression analysis of each index, a predictive model for the comprehensive evaluation of HT tolerance (H-value) at bud stage of soybean was established: H = 0.191 + 0.017X₁ – 0.007X₂ + 0.013X₇ + 0.027X₈ – 0.009X₁₀ (R²=0.9752). Five indexes main including hypocotyl length (X₁), main root length (X₂), hypocotyl dry weight (X₇), root fresh weight (X₈), and simplified vigor index (X₁₀) were screened out as the evaluation indexes for HT tolerance at bud stage in soybean.