关键词: 棉花, 萌发期, 耐冷性, 综合评价, 生理特性

Abstract:

【Objective】In this study, the purpose was to study the response of cotton seeds to chilling stress, and to identify the chilling tolerance of different test varieties during the germination period in Gossypium hirsutum. We were also committed to analyzing the cold-tolerance characteristics of tolerant and sensitive varieties at the physiological levels, and to provide a reference for further research on the molecular mechanism of cold tolerance during the germination period. 【Method】Fifty-three upland cotton varieties were used to determine the imbibition rate and relative imbibition rate under chilling stress. In addition, we also measured the cold tolerance indexes such as germination index, vigor index, mean germination time, average germination speed, germination potential, germination rate, seed germination coefficient, radicle fresh weigh, radicle dry weight, embryo fresh weight, embryo dry weight, productive efficiency and material growth rate under chilling stress. We used correlation analysis, principal component analysis, membership function analysis and cluster analysis to comprehensively evaluate the 15 morphological indexes in the imbibition and germination stage. We also measured the changes in antioxidant enzyme activities, osmotic adjustment substance concentration and the expression of antioxidant enzyme genes between different cold-tolerant varieties under chilling stress. 【Result】Under chilling stress, the relative water absorption and water absorption rate of cotton seeds showed a downward trend, and the cold tolerance indexes of 53 cotton varieties showed significant differences. There was a strong correlation between imbibition rate and relative imbibition rate during the imbibition stage, and their correlations with other germination indicators were not significant or negatively correlated. In addition, the correlation analysis also found that indicators such as radicle fresh or dry weigh, vigor index, average germination speed and mean germination time could better reflect the cold tolerance of different varieties. Principal component analysis showed that three principal components could be obtained through simplification, with contribution rates of 55.17%, 18.27% and 8.79%, respectively. The results of membership function and clustering analysis showed that the 53 varieties could be divided into four categories according to comprehensive evaluation value: high tolerant (5 varieties), tolerant (13 varieties), null-tolerant (26 varieties) and sensitive (9 varieties), of which Xinluzhong4 and Zhong103026 are the most resistant and sensitive variety to cold stress, respectively. After chilling treatment, the activity of SOD, POD and CAT in the seeds of Xinluzhong4 could be restored to the level close to or exceeding the control in a short time, the soluble protein concentration in Xinluzhong4 was significantly higher than that in Zhong103026. Gene expression analysis showed that the expression of GhPrx53 and GhCSD1 tended to be consistent with the changes of POD and SOD enzyme activity, respectively. 【Conclusion】The identification indexes of cold tolerance in upland cotton at the germination stage are diversified. The radicle fresh weight, radicle dry weight and vigor index can be used as positive indicators for cold tolerance, while the mean germination time and average germination speed can be used as negative indicator for cold tolerance during the germination period. Soluble protein concentration and the enzyme activities of POD, SOD and CAT can be used as physiological indicators for cold tolerance identification during cotton germination.

Key words: Gossypium hirsutum L., germinating stage, chilling tolerance, comprehensive evaluation, physiological characteristics