Variation among low rainfall white clover (Trifolium repens L.) accessions for morphological attributes and herbage yield

Abstract

The importance of passport data on rainfall at collection sites of accessions as a guide to identifying germplasm to be used in the genetic improvement was assessed by using 40 white clover accessions from the germplasm collection at Glen Innes, New South Wales. This set together with 2 standard cultivars, Haifa and Huia, were evaluated in the field. The objectives were to: (i) estimate the magnitude of genotypic variation among accessions for morphological attributes and herbage yield in a dryland summer rainfall environment; and (ii) compare estimates of genotypic variation for, and correlations among, the attributes and herbage yield for the 40 accessions with results from a study based on a random sample of accessions from the same collection. Herbage yield was measured in 4 seasons (autumn 1992-summer 1993) together with stolon and other plant attributes which were measured in 1 season (summer 1993). There was significant (P<0.05) variation for herbage yield among accessions. Hierarchical agglomerative classification was used to group the accessions based on herbage yield. This identified a single member group with greater herbage yield than the 2 groups which contained the cultivars Haifa and Huia. There was no association between the composition of the accession groups identified by classification and the passport data on average annual rainfall at the collection sites of accessions. There was some consistency between the estimates of repeatability, genotypic variation and genotypic correlations obtained from the low rainfall set of accessions used in this study and the random sample previously examined. It was concluded that selection of accessions from the collection for use in genetic improvement of herbage yield and the morphological attributes for dryland summer rainfall environments of the Northern Tablelands of New South Wales. should not be confined to specific groups originating from low rainfall regions.