Using Bulk-Hybrids for Breeding Adapted Genotypes of Subterranean Clover

Abstract

Changes were measured over 16 years in a self-regenerating, bulk-hybrid subterranean clover population, comprised of F2 seed from 253 crosses, sown at Nabawa and Mt Barker, low and high rainfall areas, respectively in south-western Australia. Seed banks were sampled annually and kept in cold storage. Population changes on 26 morphological, agronomic and chemical characters were measured three and 16 years after sowing, in comparison with the ancestral bulk-hybrid population. Changes in population means were observed in 20 characters at one or both sites, with much of this occurring within 3 years. Natural selection at Nabawa favoured early flowering of long duration, thick peduncles, high harvest index and high hardseededness, while at Mt Barker it favoured late flowering of short duration, large leaves and long, thick petioles at flowering, thick stems with long internodes, long, thin peduncles with a high burial angle, large plants at maturity, low hardseededness and high biochanin A and total oestrogenic isoflavone contents. High seed production capacity, with high seed weight and seeds per burr, was important at both sites. The use of bulk-hybrid populations is suggested as a low-input means of breeding and selecting well-adapted subterranean clovers.