Surveys of soil and water from asymptomatic natural ecosystems in South Africa reveal a goldmine of Phytophthora diversity

Phytophthora species are well known as destructive plant pathogens, especially in natural ecosystems. However, little is known regarding the Phytophthora diversity in forests of South Africa. In this study, Phytophthora species were isolated using standard baiting techniques from 150 soil and water samples and these were identified based on ITS and coxI sequence data. The 162 resulting Phytophthora isolates resided in 11 taxa including four known species (P. multivora, P. capensis P. frigida, P. cinnamomi) the known but as yet unnamed, Phytophthora taxon PgChlamydo and P. taxon emzanzi and five new taxa. The most commonly isolated species from soil was P. multivora (75%), a species recently described from Western Australia where it has been extensively associated with dead and dying trees. P. capensis and P. taxon emzanzi have recently been described from the Cape region of South Africa and P. multivora was also reported from this region. The extensive isolation of P. multivora from asymptomatic natural vegetation suggests that South Africa may be the origin of this species. P. frigida was isolated for the first time from stream water and P. taxon PgChlamydo was isolated for the first time in Africa. The new species were isolated from water and not surprisingly belong to ITS Clades 6 and 9. With the exception of P. cinnamomi, very little is known regarding the biology, epidemiology or origin of these species.