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Influence of testing procedure on evaluation of white clover (Trifolium repens L.)
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2009
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T.J. Gilliland, D. McGilloway and P. Conaghan. Influence of testing procedure on evaluation of white clover (Trifolium repens L.) Irish Journal of Agricultural and Food Research 48: 227–242, 2009
Abstract
This study examined data sets derived from the white clover cultivar evaluation
programmes of AFBI (N. Ireland), and DAFF (Republic of Ireland) to determine
whether elite performing genotypes are identifiable, independent of test procedure and
leaf size factors. Genetic variation in yield and persistency, independent of the leaf size
continuum effect, was observed. Identification of elite cultivars by breeders or testers
therefore required readjustment of assessment standards to account for the mostly curvilinear
relationships between performance and leaf size. The different testing procedures,
involving cutting or grazing at different heights, frequencies and nitrogen rates
changed the relative performances between the cultivars, making it difficult to predict
performance potential beyond specific test conditions. The underlying causes for these
changes in rankings was considered, including sensitivity to season and location, the
antagonistic affects of defoliation pressure and companion grass competition, the independence
of different seasonal profiles and the probable role of other morphological
characteristics. In is concluded that testing authorities must calculate the management
by leaf size relationships to adjust pass/fail standards if elite performing cultivars are
to be correctly indentified.