'Plant Breeding: Sustaining the Future' Abstracts of the XVIth EUCARPIA Congress, Edinburgh, Scotland, 10-14 September 2001 INTROGRESSION OF STRESS TOLERANCE TRAITS IN TRIFOLIUM A.H. MARSHALL, M.T. ABBERTON, T.P.T. MICHAELSON-YEATES, A.WILLIAMS Institute of Grassland and Environmental Research, Plas Gogerddan, Aberystwyth, Ceredigion, United Kingdom, SY23 3EB

Interspecific hybrids have been produced between the stoloniferous white clover (Trifolium repens L.) and the related rhizomatous species Caucasian clover (Trifolium ambiguum) M. Bieb) as a means of introgressing stress tolerance traits into white clover. Plants of the second backcross generation, with white clover as the recurrent parent, combine the stoloniferous growth of white clover with the rhizomatous growth of T.ambiguum. Six cycles of drought carried out in deep soil bins over 2 years showed that plants with rhizomes were significantly more tolerant of drought, maintaining a greater leaf relative water content and water potential than the white clover parent. Further studies are planned to investigate the cold tolerance of these hybrids and their ability to grow at low levels of soil phosphate.