Genetic variation of salinity tolerance in Chinese natural bermudagrass (Cynodon dactylon (L.) Pers.) germplasm resources

Bermudagrass (Cynodon dactylon (L.) Pers.) is a widely used turfgrass in tropical, subtropical and warm-temperate regions in the world. It is a salinity-tolerant plant, but much genetic variation exists among its genotypes. Genetic diversity has been shown to exist from a morphologic level to a molecular level among Chinese natural bermudagrass germplasm resources; however, the extent of variation in their salinity tolerance has remained unclear. We conducted greenhouse hydroponic and sand culture experiments to evaluate the variation in salinity tolerance of natural bermudagrass germplasm resources obtained from their main areas of distribution in China and treated at a 33 dS m(-1) salinity level for three weeks. Compared with non-saline controls, salinity stress significantly decreased shoot clipping weight (46.5% and 44.2%) and increased leaf firing (41.1% and 37.6%) in hydroponic and sand culture experiments, respectively, across all genotypes. However, significant genetic variations in relative leaf firing percentage (RLF) and relative shoot weight (RSW) were found among genotypes in both experiments, and their coefficients of variation ranged from 25.5% to 41.6%, indicating that considerable variation exists in the salinity tolerance of Chinese natural bermudagrass germplasm resources. Shoot Na+ concentrations increased under salinity stress for all genotypes in both experiments. However, significant genetic variations were also found in shoot Na+ concentrations. Salinity tolerance in bermudagrass genotypes was found to be significantly negatively correlated with shoot Na+ concentrations in both experiments. Using a cluster analysis of RLF and RSW data, all genotypes were classified into four groups with different salinity tolerances. The results of our evaluation indicate that there is much potential for improving salinity tolerance among Chinese natural bermudagrass cultivars.