Salinity is one of major environmental stresses that dramatically threaten plant growth, and variations in genetic structure and functional traits have important effects on the salt tolerance of perennial ryegrass (Lolium perenne L.). The objectives of this study were to: (i) assess the inter-clonal variation of functional traits of accessions among geographic groups or between wild and commercial groups in response to salt stress; (ii) develop a mathematical model to effectively assess salt tolerance of perennial ryegrass accessions originating from different geographic populations; and (iii) determine the relation between spatial genetic structure and salt tolerance in perennial ryegrass. Wide variations were found among the accessions for seven functional traits. One regression model (F = 0.49 × F1 + 0.303 × F2 + 0.207 × F3) was established to ascertain salt tolerance of each accession. The highest variation of the traits and salt tolerance were obtained for accessions from the European group. Wild accessions exhibited more variation in functional traits and salt tolerance than commercial cultivars. Both molecular marker techniques and functional traits were used to conduct phylogenetic analysis, and the majority of accessions from the same or adjacent regions were clustered into the same group or subgroup. The perennial ryegrass accessions with similar salt tolerance had a close phylogenetic background. The patterns in functional trait variations associated with salt tolerance might allow acceleration of the process for improving salt stress resistance in perennial ryegrass.

Experiments were conducted to study the relationship between autumn (fall) dormancy rating (FDR) and salt tolerance of lucerne (alfalfa, Medicago sativa L.). Seeds of eight cultivars with different FDRs (range 2.0–10.2) were germinated in a growth chamber under five concentrations of NaCl (range 0–1.2%). A subordinate function value method was adopted for comprehensive evaluation of salt tolerance of the lucerne cultivars. Seed germination rate and germination potential, and seedling electrolyte leakage, shoot length, root length, fresh weight, root : shoot length ratio, Na+ and K+ concentrations and K+ : Na+ ratio were used as the indices of evaluation. Under 1.2% salt treatment, salt-tolerance ranking of the cultivars was WL656HQ > WL440HQ > WL712HQ > WL525HQ > WL343HQ > WL319HQ > WL363HQ > WL168HQ, with respective FDRs of 9.3, 6.0, 10.2, 8.2, 3.9, 2.8, 4.9 and 2.0. The results of this study show that non-dormant cultivars were generally more salt tolerant than dormant cultivars.