Assessment of perennial ryegrass (Lolium perenne L.) for breeding. I Freezing tolerance

Summary Assessments of freezing tolerance, estimated in terms of temperature at which 50% mortality occurs (=LT₅₀), were obtained for 86 Lolium perenne accessions using a glycol bath test on naturally hardened field plants. Significant correlations were obtained between LT₅₀ and both heading dates of accessions and minimum temperature of the coldest month near their sites of origin. The effects of temperature and reproductive development on the hardening/dehardening of plants and their growth after freezing are discussed.