Features of the white clover lines collected from two distinct climate regions in Hokkaido revealed by coefficients of variation between and within lines
There are two types of farming areas in Hokkaido which are classified based on their climate in winter : a soil-freezing area, mainly located the eastern part of the island, and a snowy area, mainly located in the southern, central and northern parts. There are different factors in these two areas which contribute to the overwintering ability of forage crops. In this study, we conducted a field evaluation to detect the differences in phenotypic character among white clover (Trifolium repens L.) lines collected from various regions in Hokkaido. Seventy-eight collected lines and 6 control cultivars were evaluated for 32 traits, including morphology, overwintering and disease damage, for two years. The process of analysis was 1) detection of the traits with statistically significant difference among lines, 2) comparison of coefficients of variation (CVs) between and within lines for each trait, 3) comparison of the mean values of traits exhibitng lower CVs than those of the cultivars, and 4) grouping the lines by principal component analysis using those traits. Significant differences were found in thirty of 32 traits among lines and 22 traits showed lower CVs in collected lines than in the cultivars. In five traits, plant size, leaf density, vigor in the seeding year, budding and vigor in the spring of the 2nd year, differences were found between two groups based on the whether the collecting site was in a soil-freezing or snowy area. The results can be applied to a breeding program of white clover, especially to improve adaptation to soil-freezing areas.