Abstract: Hot-dry windy climate is the weather phenomenon of low humidity, high temperature, and wind stress occurring simultaneously, which causes great reduction of wheat yield in northern China during grain filling. As a compatible solute in cells, glycinebetaine plays an important role in tolerance to environmental stresses of plants. In this study, we used three betA transgenic wheat lines and their wild type (WT) to disclose the effects of glycinebetaine accumulation on the growth and yield components of wheat plants suffering from hot-dry windy stress for three days. After the hot-dry windy treatment, the transgenic plants maintained more vigorous growth compared with the WT and showed slower dehydration rates of flag leaf with significantly larger green blade area than that of WT. Under the hot-dry windy stress, the photosynthetic ability and the activities of sucrose phosphate synthase (SPS) and sucrose synthase (SS) in flag leaf were reduced in both transgenic lines and the WT. However, the reductions were smaller in the transgenic lines than in the WT. After 3-day of stress, the net photosynthetic rates of the transgenic lines fell to 2.3–3.7 μmol CO₂ m^-2 s^-1, while that of the WT plant was 1.2 μmol CO₂ m^-2 s^-1. After the 3-day stress, the activities of SPS and SS were decreased to 62.3–69.8% of the levels before stress treatment in the transgenic lines of those before stress, whereas those were decreased to 56.5–64.5% of the levels before treatment in the WT plant. The glycinebetaine contents in flag leaf were increased in all lines, especially in the transgenic lines (18–87% higher than that of WT). Based on these results, we concluded that under the protection of glycinebetaine, the transgenic plants could maintain higher net photosynthetic rate than that of the WT plant, resulting in more accumulation of carbohydrate and higher grain yield per plant and 100-grain weight after the stress of hot-dry windy stress. Therefore, the betA transgenic wheat might be practical in improving tolerance to the hot-dry windy climate in winter wheat.

Key words: Wheat, betA transgene, Glycinebetaine, Resistance to hot-dry windy, Yield