Abstract
Perennial ryegrass (Lolium perenne L.), one of the most widely utilized forage grasses for temperate regions, has differentiated in winter survival among various cultivars. Freezing hardiness is one of the primary factors associated with winter survival. The purpose of this study is to elucidate the inheritance of freezing hardiness in perennial ryegrass. The results obtained are summarized as follows : 1) We made a diallel analysis with F_1 progenies of a diallel cross among four cultivars which showed different levels of freezing hardiness. Each cultivar was represented by 2 genets which were understood to provide each cultivar mean. 2) Freezing hardiness varied significantly among the genotypes ; the variation was largely attributable to the between-cultivar component. 3) Both additive and dominance components were detected with the magnitude of the former component being higher than that of the latter one. The heritability value was extremely high, suggesting that selection for freezing hardiness may be successful. 4) The average reciprocal effect was found to be significant, suggesting also that cytoplasmic factors contribute to freezing hardiness in perennial ryegrass.
