'Plant Breeding: Sustaining the Future' Abstracts of the XVIth EUCARPIA Congress, Edinburgh, Scotland, 10-14 September 2001 FIELD EVALUATION AND DEVELOPMENT OF TRANSGENIC GERMPLASM WITH VIRUS RESISTANCE IN WHITE CLOVER R. KALLA, P. CHU, Z. JAHUFER, K. SMITH, G. SPANGENBERG Plant Biotechnology Centre, Agriculture Victoria, La Trobe University, Victoria 3086, Australia

White clover is a major component of improved pastures throughout the temperate world.  Virus diseases reduce white clover pasture production potential by up to 30% through reduced foliage yield and quality, reduced nitrogen fixing capacity and reduced persistence under primary and secondary biotic and abiotic stress conditions.  The most widely spread virus diseases in white clover are alfalfa mosaic virus (AMV), white clover mosaic virus (WCMV), and clover yellow vein virus (CYVV).  Transgenic white clover plants with individual immunity to these viruses were produced and evaluated under containment conditions.  Selected transformation events need then to be field tested to assess immunity to the virus and transgene flow.  Design and results from the field evaluation of world's first transgenic white clover plants with immunity to AMV are described.  After field evaluation, selected transformation events are used to produce elite transgenic germplasm for cultivar development.  Strategies being implemented for the development of elite transgenic germplasm and selection of superior parental lines with transgenes conferring virus immunity at the homozygous state will be outlined.