Population genetic structure of Rhizoctonia solani AG 3-PT from potatoes in South Africa

Abstract

Rhizoctonia solani AG 3-PT is an important potato pathogen causing significant yield and quality losses in potato production globally. However, little is known about the levels of genetic diversity and population structure of this pathogen in South Africa. A total of 114 R. solani AG 3-PT isolates collected from four geographic regions were analyzed for genetic diversity and structure using eight microsatellite loci. Microsatellite analysis found high intrapopulation genetic diversity, population differentiation and evidence of recombination. A total of 78 multilocus genotypes (MLGs) were identified with few MLGs shared among populations. Low levels of clonality (13-39 %) and high levels of population differentiation were observed among populations. Most of the loci were in Hardy-Weinberg equilibrium and all four field populations showed evidence of a mixed reproductive mode of both clonality and recombination. The PCoA clustering method revealed genetically distinct geographic populations of R. solani AG 3-PT in South Africa. This study showed that populations of R. solani AG 3-PT in South Africa are genetically differentiated and disease management strategies should therefore be applied accordingly. This is the first study of the population genetics of R. solani AG 3-PT in potatoes in South Africa and results may help to develop knowledge-based disease management strategies in South Africa and elsewhere.