Abstract:

Drought is an important stress affecting wheat production, which can reduce the quality of germination and seedling establishment. In order to understand the seed germination characteristics of wheat cultivars under drought stress, the germination characteristics under drought stress of 128 wheat cultivars widely used in production were identified by sand cultivation and water control method. Six wheat cultivars with significant differences in germination characteristics under drought stress ((Shannong 28 (SN28), Chang 6878 (C6878), Yannong 19 (YN19), Shannong 23 (SN23), Xinmai 296 (XM296), and Xinmai 38 (XM38)) were selected for physiological and biochemical analysis during seed germination under drought stress. The results showed that the germination characteristics under drought stress of 128 wheat cultivars were divided into 5 categories according to the drought tolerance coefficient of vigor index: good, the better, medium, the worse, and the worst. Eighteen wheat cultivars with good germination characteristics under drought stress, including SN28 and C6878, had fast seed germination and healthy seedlings. 26 wheat cultivars with poor germination characteristics under drought stress, such as XM38 and Lemai 185, had slow seed germination, dispersed germination time, low germination percentage (GP), and poor seedling uniformity. The physiological and biochemical indices of wheat cultivars with different germination characteristics under drought stress were further determined. The results showed that the relative expression level of TDP1 gene at the early stage of germination under drought in SN28 and C6878 with good germination characteristics under drought stress was significantly higher than the control. POD activity at the early stage of germination under drought was significantly higher than the control. The activities of α-amylase and cysteine protease were less affected by drought, and the soluble protein content at the late stage of germination was significantly higher than the control. However, the relative expression levels of DNA and protein repair genes in seed embryos of XM296 and XM38 with poor germination characteristics under drought stress were relatively delayed under drought stress. The activity of cysteine protease decreased significantly under drought stress. The above results indicated that wheat cultivars with good germination characteristics under drought stress showed strong macromolecular repair ability in seed embryos and antioxidant capacity in seed, early mobilization of storage substances during seed germination and seedling establishment under drought stress, and finally had fast germination speed and high seedling quality.

Key words: wheat (Triticum aestivum L.), drought stress, seed germination characteristics, decomposition and transformation of storage substances, macromolecular repair ability, antioxidant capacity