Community composition and distribution of Phytophthora species across adjacent native and non-native forests of South Africa

The diversity of Phytophthora species associated with various ecological niches is poorly understood. In this study, the community composition and distribution of Phytophthora species associated with non-native plantation trees, Eucalyptus grandis and Acacia mearnsii, was compared with adjacent natural forests in South Africa using soil baiting and metabarcoding approaches. Through soil baiting, 85 Phytophthora isolates were recovered representing five taxa: P. alticola, P. cinnamomi, P. frigida, P. multivora and P. pseudocryptogea. Metabarcoding revealed molecular operational taxonomic units corresponding to 32 Phytophthora taxa. Among these, 14 were new reports from South Africa, including seven undescribed taxa. The community composition of Phytophthora species clustered according to vegetation type. Most species in plantations were present in the natural forest sites, but few species were exclusively associated with the non-native plantations. Overall, the results revealed a substantial diversity of Phytophthora species that includes both described and novel phylotypes previously unknown from South Africa.