New Phytophthora species in clade 2a from the Asia-Pacific region including a re-examination of P. colocasiae and P. meadii

Abstract

Five new taxa from Phytophthora ITS clade 2a are described from Cinnamomum cassia plantations and adjacent waterways in Van Yen, Vietnam, disturbed rainforest in the Hela Province of Papua New Guinea and from disturbed forest on Christmas Island. Phylogenetic analyses were performed using data from nuclear regions (ITS, β-tubulin; heat shock protein 90) and mitochondrial regions (cytochrome c oxidase subunit 1; cytochrome c oxidase subunit 2; NADH dehydrogenase subunit 1; ribosomal protein L10). The molecular data supported recognition of three species: Phytophthora insulinativitatica, P. multibullata and P. x vanyenensis, and two informal taxa: P. sp. germisporangia and P. sp. awatangi. P. x vanyenensis appears to be a hybrid between P. mekongensis and an unknown species. P. multibullata and P. sp. germisporangia are phylogenetically close to P. citrophthora, but morphologically distinct. P. insulinativitatica is most closely related to P. botryosa, but has distinct morphology. P. sp. germisporangia and P. sp. awatangi were morphologically distinct and separated in the phylogeny based on mitochondrial sequences, but their nuclear sequences were identical. When comparing the sequences of these new species to that available on GenBank, it became evident that some of these species shared similarity with isolates submitted to GenBank under other species names. A re-evaluation of all P. meadii and P. colocasiae ITS sequence data identified an additional 7 putatively new species all isolated from Asia. The results support the view that many more Phytophthora species remain to be discovered in the Asia-Pacific region.