Detection of novel genotypes in progeny from a controlled cross between isolates of Uncinula necator belonging to distinct phenetic groups

Sexual recombination and segregation in 18 ascospore progeny of Uncinula necator were analysed by mating type (Mat locus), RFLP and PCR markers. Progeny were analysed from a cross of parental isolates representing the genetically distinct phenetic Groups I (AHd2) and II (BNb2). A total of 27 markers was analysed, consisting of four single loci (Mat locus and three RFLP probes), 16 multi-loci (three multi-copy fingerprinting probes) and seven PCR loci. Novel hybrid genotypes were detected in 28% of the ascospore-derived progeny using the multi-copy RFLP probes, pUn122-11 and pUnP27, and the PCR primers (CAC)(5) and R1, confirming that recombination can occur between isolates representative of the two phenetic groups. This study provides evidence that out-crossing between isolates of U. necator generates novel genotypes and, as such, may have important implications for disease management practices, such as the durability of fungicides and host resistance.