Classification Of Genetic Variation For Cadmium Tolerance In Bermudagrass Using Physiological Traits and Molecular Markers.

 Cadmium (Cd) is one of the most toxic pollutants causing severe threats to animal and human health. Bermudagrass is a dominant species in Cd contaminated soils, which can prevent Cd flow and spread caused by rainfall. The objectives of this study were to determine the genetic variations in major physiological traits related to Cd tolerance in six populations of bermudagrass collected from China, and to examine the genetic diversity and relationships among these accessions varying in Cd tolerance via molecular markers. Plants of 120 accessions (116 natural accessions and 4 commercial cultivars) were exposed to 0 (i.e. control) or 1.5 mM CdSO₄.8/3H₂O for 3 weeks in hydroponic culture. Turf quality, transpiration rate, chlorophyll content, leaf water content, growth rate showed wide phenotypic variation contributing to Cd tolerance in the collected bermudagrass. Membership function method of fuzzy mathematics was used to comprehensive evaluation Cd-tolerance. According to the average subordinate function value of the 7 physiological traits, 4 accessions were classified as the most tolerant genotypes and 4 accessions as Cd-sensitive genotypes. The trend of Cd tolerance among the seven populations was as follows: Hunan > cultivar > South China > North China > Central China> West South China and Xinjiang population. Edaphic conditions seemed to play an important role in genetic variation of bermudagrass Cd tolerance selection. Phylogenetic analysis revealed that the majority of accessions from the same or adjacent regions were clustered into the same group or subgroup based on the molecular markers and physiological traits, and the accessions with similar cadmium tolerance displayed a close phylogenetic relationship. Screening genetically diverse germplasm to identify superior Cd tolerance by combined the physiological traits and molecular markers could prove useful in developing Cd-tolerant bermudagrass for remediation of mill tailings and the heavy metal pullulated soils.