POPULATION-LEVEL PROCESSES IN RHIZOBIUM-LEGUMINOSARUM BV TRIFOLII - THE ROLE OF FOUNDER EFFECTS

The importance of genotype-specific selection between host and symbion t, founder effect, and clonal reproduction in Rhizobia leguminosarum b iovar trifolii populations is relatively unknown. A field experiment w as conducted to sample 1268 isolates of R. l. bv. trifolii from four g enotypically distinct Trifolium pratense plants for allozyme variation at nine loci. Genetic and genotypic variation, population genetic sub structure, and linkage disequilibrium were estimated. Of the 1268 isol ates 188 genotypically distinct strains (electrophoretic types or ETs) were identified with an average of 11.04 different ETs per plant. Tot al genetic diversity in the plot was 0.346 and most of the variation w as found within plants (approximate to 80%). Our data suggests that ge notype-specific selection between the rhizobia and the four host-plant genotypes tested does not influence local population structure, but e vidence of founder effect was present. Significant linkage disequilibr ium was observed and is most likely due to the clonal reproduction of R. l. bv. trifolii.