U.S.-New Zealand Cooperative Research: Breeding Improved Pasture Legumes from the Cross Trifolium ambiguum x T. repens

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This award will enable collaborative research between Dr. Elizabeth G. Williams of the University of Kentucky and Dr. Warren M. Williams and John Vanden Bosch of the Grasslands Division, Department of Scientific and Industrial Research located at Palmerston North, New Zealand. These researchers will produce interspecific genetic hybrids between white clover and kura clover in order to construct breeding populations of advanced generation hybrids and backcrosses to both parents. White clover, Trifolium repens, is a major pasture legume in both the U.S. and New Zealand. While this clover has the ability to withstand heavy grazing if moisture is adequate, thus improving the quality of grasslands both with respect to digestible energy and protein, and in terms of symbiotic nitrogen fixation, unfortunately its use is limited by a lack of persistence under lowered moisture conditions. Kura (Caucasian) clover, Trifolium ambiguum, possessess a vigorous underground perennial root and rhizome system and is both more drought resistant and shows resistance to a number of different viruses which affect white clover. The University of Kentucky staff will focus their activity on the generation of new hybrids through a seed embryo rescue technique which they have developed along with chromosome doubling and tissue culturing of hybrid materials. Virus testing studies will also be conducted in the U.S. The New Zealand investigators will focus their work on X-irradiation to enhance genetic exchange, the development of further advanced generation hybrids, and the selection for fertility and agronomic performance of the new hybrid materials. The collaboration between the U.S. and New Zealand investigators, working in the Northern and Southern Hemispheres, enables a doubling in the growing of experimental hybrid clover crops each year.