Selecting white clover (Trifolium repens L.) for sheep and cattle grazing environments

Abstract

Adaptation to different grazing systems is an important attribute in white clover breeding. A set of 41 white clover breeding lines and nine commercial cultivars were evaluated under two grazing systems, sheep and cattle, in Manawatu. The objective was to identify lines with either specific or broad adaptation to these two different grazing systems. The trials were established in late autumn 1997 and completed in autumn 2000. Visual scores of clover yield for spring, summer, autumn and winter of year 2 and spring, summer and autumn of year 3 were analysed. There was significant (P<0.05) genotypic variation among lines and cultivars for yield across all seasons within each grazing system. Variance component analysis across all seasons and grazing treatments, indicated significant (P<0.05) genotypic variation among the lines and cultivars, and also significant (P<0.05) genotype-by-grazing system interaction. There was a lack of genetic correlation between the sheep and dairy grazing treatments. Breeding lines with specific adaptation to the sheep and dairy grazing systems were identified. Also, there were breeding lines with superior broad adaptation across the two grazing systems. All the breeding lines identified, were significantly (P<0.05) superior in performance to the best performing commercial controls in each grazing system, indicating successful achievement of genetic advance for specific and broad adaptation. These superior breeding lines were experimental synthetics developed using germplasm with New Zealand and European background