Population structure of Cylindrocladium parasiticum peanuts (Arachis hypogaea) in Georgia, USA

Cylindrocladium parasiticum is an important pathogen of peanut (Arachis hypogaea) causing the disease Cylindrocladium black rot. The genetic structure of this haploid pathogen was determined for populations associated with peanut in Georgia, USA. Ten polymorphic microsatellite markers were used to determine genetic and genotypic diversity among three sub-populations representing the geographic distribution of peanut production in Georgia. Among 200 isolates collected, only 10 unique multilocus haplotypes were identified, with one multilocus haplotype occurring 176 times. Although no evidence for random mating was observed, the existence of loops in a constructed haplotype network hint at the possibility of recombination events. The absence of random mating might therefore be attributed to the homothallic nature of C. parasiticum as well as the clonality of the population, without excluding the possible occurrence of recombination. Cylindrocladium parasiticum thus appears to consist of a genetically homogeneous population throughout Georgia with mainly clonal reproduction or inbreeding contributing to the observed population genetic structure.