The identification of population-specific patterns in breeding programmes of Trifolium repens and related species

Abstract

The Trifolium family is a key legume family in agroecosystems of the world. White clover (Trifolium repens) is the most common pasture legume in New Zealand where it is usually grown with perennial ryegrass in swards and grazed in situ. White clover breeding in New Zealand started in the early 1930’s and due to the large economic value of white clover, there have been considerable research activities and development. The objective of this study was to identify population-specific patterns in Trifolium breeding programmes and to produce an overview of these patterns across time and human based decision making. Parental data for T. repens as well as other Trifolium species such as T. arvense, T. ambiguum, T. dubium, T. hybridum, T. medium, T. pratense and T. subterraneum, as well as an interspecific hybrid of T. repens x T. occidentale were collated from 1941-2016. These data sets, including breeding methods of bi-parental and single crosses and selections, backcrosses and polycrosses were constructed into pedigrees for the purposes of this study. Coefficients of coancestry and inbreeding were derived from biparental and single crosses in families. T. repens and T. pratense were the only species in the Trifolium family to show inbreeding. T. pratense had an average population inbreeding coefficient of 0.56% and a coancestry coefficient of 0.61%. Both commonly used families and unused families were identified from the pedigrees.