AFLP and RFLP (RG57) fingerprints can give conflicting evidence about the relatedness of isolates of Phytophthora infestans

Selected isolates of Phytophthora infestans from around England and Wales were fingerprinted using both RG57, a multi-locus RFLP probe, and Amplified Fragment Length Polymorphisms (AFLPs). The larger number of polymorphisms delectable with the AFLP method allowed resolution of several similar AFLP genotypes among isolates with identical RG57 fingerprints. However, some isolates with the same RC37 genotype had remarkably dissimilar AFLP genotypes, suggesting that there has been convergent evolution of some RG57 Fingerprints. Also, some isolates with dissimilar RG57 fingerprints had similar or identical AFLP fingerprints. Both techniques distinguished isolates of mitochondrial DNA haplotype Ia from those of haplotype IIa, However, with AFLPs only, most of the isolates of A2 mating type were very similar and were distinguished from those of A1 mating type, suggesting that gene flow between A1 and A2 genotypes is limited and that sexual recombination is rare.