Comparison and Evaluation of Low-Temperature Tolerance of Different Soybean Cultivars during the Early-Growth Stage

Low temperatures have seriously affected crop growth owing to climate change and frequent extreme weather. Low-temperature disasters easily affect the early-growth stages of planted soybeans in Northeast China. In the present study, the comprehensive evaluation method using low-temperature (4 °C) simulation at soybean germination and seedling stages was used to compare soybean cultivars. The results revealed that low temperatures inhibited the germination ability of soybean seeds and prolonged the average germination time (about 7–13 days under low temperatures). Simultaneously, low-temperature stress at the seedling stage decreased plant height and dry weight, but accumulated proline and soluble sugar. The soluble protein content of most cultivars decreased at low temperatures. Peroxidase activity was significantly decreased in henong70, suinong82, and heinong83, and opposite in the other cultivars. Additionally, MDA content increased in cultivars heinong69, dongnong42, and dongnong55. The final comprehensive evaluation showed that Suinong42 had better low-temperature tolerance, whereas Kendou40 was more sensitive to low temperatures. The grey correlation analysis also showed that dry weight and proline can be used as the target traits for cultivar improvement.