Genotypic Variation in Salinity Tolerance of Perennial Ryegrass

Soil salinity can severely affect crop production. The long term goal of our research is to identify genes linked to salinity tolerance using association mapping approach in perennial grass species. We have assembled a mapping population of perennial ryegrass (Lolium perenne L.) consisting of 192 globally distributed diploid accessions. This population showed high genetic diversity and exhibited five population structures. Responses of 56 accessions to salinity stress (300 mM NaCl) were initially evaluated. Salinity stress decreased plant height, chlorophyll content, leaf water content, dry weight and leaf ratio of K⁺/Na⁺, but increased total water-soluble carbohydrate and leaf Na⁺ contents. Large variations in growth and physiological traits were found among the accessions exposed to NaCl stress. Sequence diversity in candidate genes involved in salt tolerance such as antioxidants, dehydrin, aquaporin, signal transduction and Na⁺, K⁺ transporters are being analyzed. The results can be used to further dissect genotypic variation in salinity tolerance and to conduct gene-trait association analysis of perennial ryegrass.