Unravelling the evolutionary dynamics of a novel cercosporoid fungus

The fungus Pseudocercospora macadamiae has no known sexual state. It is novel, unique and spreading to new macadamiagrowing regions in Australia. As with other cercosporoid fungi, initial findings showed that the asexual spores mostly spread by rain-splash; however, the prevalence and virulence on different macadamia varieties and the distribution pattern of the fungus indicates the involvement of sexual spores. We tested the hypothesis that the sexual structure is produced only under specific conditions and is involved in the evolutionary dynamics of the fungus. The putative geographical isolation observed in the pathogen populations may account for the low level of recombination between strains from different regions. Primers designed for MAT 1-1 and MAT 1-2 genes differentiated the isolates into different mating types. Using both indirect and direct bio-assays, we identified significant (