THE DISTRIBUTION AND ORIGIN OF GENES FOR RACE-SPECIFIC RESISTANCE TO MELAMPSORA-LINI IN LINUM-MARGINALE

The genetic basis of resistance in wild flax (Linum marginale) to its host-specific pathogen Melampsora lini was investigated in seven lines collected from a single population growing at Kiandra, New South Wale s and in an additional ten lines collected more widely across southeas tern Australia. All lines showed different phenotypic patterns of resi stance and susceptibility. Genetic analyses indicated the presence of single dominant genes for race-specific resistance in all but one of t hese lines. That particular line appeared to carry two linked dominant genes for resistance. Intercrosses between lines in each of these gro ups of L. marginale detected substantially more linkage between the re sistance genes in the Kiandra population sample than between those in the broader geographic collection. This result is interpreted to indic ate a possible mechanism whereby resistance genes are generated in nat ural populations.