Abstract:

Xinjiang bermudagrass ecotypes have well-developed rhizomes and slender stolons， and exhibit extensive genetic variation in drought tolerance. In this study drought tolerant （C138） and drought-sensitive （C32） bermudagrass genotypes were exposed to natural drought for 7 days followed by 3 days of rehydration treatment and the differences in physiological response and gene expression levels of the antioxidant enzyme systems under drought stress and rehydration were evaluated. It was found that drought stress reduced the apparent quality of bermudagrass lawn， relative leaf water content and chlorophyll content， increased electrical conductivity and malondialdehyde （MDA） content， and these responses were expressed more significantly in C32 than in C138. With increased duration of drought exposure， the levels of O₂^·-， H₂O₂， and MDA in bermudagrass leaves increased significantly， and C32 increased more significantly than C138， while activities of superoxide dismutase （SOD）， peroxidase （POD） and catalase （CAT） initially increased and then decreased， and ascorbate peroxidase （APX） activities increased. Drought-resistant C138 and non-drought-resistant C32 showed high-levels of expression of antioxidant genes such as SOD， POD， APX， DHAR and GPX， while non-drought-resistant C32 showed the highest lipid peroxidation and the lowest antioxidant enzyme activity and gene expression levels. In the process of rehydration， POD activity plays a vital role in improving antioxidant capacity and removing reactive oxygen species. Drought stress induces the up-regulation of the expression of antioxidant enzymes and related genes， enhances the antioxidant defense in cells， helps bermudagrass maintain cell membrane stability， delays the dehydration of leaves， and improves the bermudagrass drought resistance ability.

Key words: drought stress, bermudagrass, antioxidant system, gene expression