Association mapping provides a powerful tool for dissecting genetic complex traits. The long-term goal of the objective is to conduct candidate gene-association mapping of drought and cold tolerance in perennial ryegrass (Lolium perenne L.). A total of 192 perennial ryegrass accessions were screened for drought and cold tolerance in three locations varying in climate and soil texture. Large variations in leaf wilting, canopy temperature, chlorophyll fluorescence, leaf water content, canopy reflectance and chlorophyll content were found among these accessions. Five genetic population structures (Q) were identified using 109 simple sequence repeat markers. No major relative kinship (K) was found. The candidate genes involved in major antioxidant pathways and other pathways have been sequenced to identify single nucleotide polymorphisms (SNP). Associations of genes with phenotypic traits are being analyzed. The results provide important information for future functional genomics study of drought and cold tolerance of perennial ryegrass.