2.2.66
MOLECULAR VARIATION IN WHEAT YELLOW RUST IN NORTHERN EUROPE

MS HOVMØLLER1, CJ RIDOUT2 and JKM Brown3

1Department of Plant Protection, Danish Institute of Agricultural Sciences, Research Centre Flakkebjerg, 4200 Slagelse, Denmark; 2Sainsbury Laboratory and3Cereals Research Department, John Innes Centre, Norwich Research Park, Colney, Norwich NR4 7UH, UK

Background and objectives
Wheat yellow rust, or stripe rust, caused by the fungus Puccinia striiformis f. ;sp. tritici (Pst) is a damaging disease on wheat in many temperate regions throughout the world. Pst is a basidiomycete and the epidemics are caused by asexually produced urediniospores; so far no alternative host has been found to complete sexual reproduction. Despite the existence of pathotypes with different virulence spectra, not much molecular variability has been observed within a single population of wheat yellow rust. In order to study the population dynamics of Pst we used amplified fragment length polymorphism (AFLP) to analyse molecular variation in isolates from Denmark and Britain.

Materials and methods
Isolates of P. striiformis were collected in Denmark as single lesions from infected plants in the field from different locations and varieties between 1993 and 1995. The British isolates were provided by the National Institute of Agricultural Botany, Cambridge. DNA was extracted from freeze-dried urediniospores using CTAB, and subsequently a standard AFLP procedure was followed [1]. Data were analysed by different statistical procedures.

Results and conclusion
The population had a clear clonal structure with no indication of sexual or somatic recombination. It was concluded that isolates from UK and Denmark belong to a single population, indicated by the amount of molecular variation within and among Danish and British isolates, respectively. Further, isolates of the same pathotype occasionally shared AFLP pattern, supporting that dispersal of virulent clones over large distances occur. The results emphasize the importance of diversity for disease resistance in the wheat germ plasm used in the same geographical region, to achieve sustainable disease control by the use of host resistance.

References
1. Vos P, R. Hogers, M Bleeker, M. Reijans, T Lee, M Hornes, A Frijters, J Pot J Peleman, M Kuiper and M Zabeau 1995. Nucleic Acids Research, 23 4407-4414.