Screening for cadmium tolerance of 21 cultivars from Italian ryegrass (Lolium multiflorum Lam) during germination

The cadmium (Cd) tolerance of 21 Italian ryegrass (Lolium multiflorum Lam.) were investigated in this study by evaluating the process of seed germination on exposure to excess Cd. Excess Cd resulted in the significant growth inhibition, particularly of root growth. The relation between Cd concentrations and inhibition rate of root or shoot elongation can be well described by a logarithmic equation. The maximum values of IC50 (Cd concentration when the root or shoot elongation decreased to 50% compared with control) were observed in root and shoot of IdyII', whereas the minimums showed in Nioudachi' and Harukaze'. Cadmium dramatically inhibited the seed germination of 21 cultivars. By comparison of physiological parameters including the absolute and relative value of root and shoot length, germination rate, germination energy, germination index and vigor index, all the tested cultivars exhibited variation when exposed to the same strength of Cd stress. In addition, the values of evaluation index, subordinate function were used to evaluate the Cd tolerance among cultivars treated with excess Cd. As a result, cultivar IdyII' was identified to be most tolerant to Cd stress, cultivar Tachiwase' was the most sensitive one. Cluster analysis indicated that 21 cultivars of Italian ryegrass can be classified into four groups, Cd-tolerant, moderate Cd-tolerant, low Cd-tolerant and Cd-sensitive groups. The results will be basic information for cultivating forage crops used as bioenergy crops in Cd polluted environments.