Phytophthora acaciae sp. nov., a new species causing gummosis of black wattle in Brazil

ABSTRACT

A new Phytophthora species was found associated with gummosis in black wattle plantations in the subtropical, humid, south of Brazil. The new species Phytophthora acaciae is formally named herein based on phylogenetic and morphological analyses. This is the fourth Phytophthora species found from this pathogen complex in black wattle plantations causing gummosis in Brazil. The other three species are P. nicotianae, P. boehmeriae, and P. frigida. Phytophthora acaciae is heterothallic with amphigynous antheridia, noncaducous, papillate sporangia and is placed in the Phytophthora clade 2 based on nuc rDNA internal transcribed spacer (ITS1-5.8S-ITS2 = ITS) sequences. Maximum parsimony and maximum likelihood phylogenetic analyses of P. acaciae isolates based on multigene sequences, including partial DNA sequences of three nuclear protein-coding genes (β-tubulin, translation elongation factor-1α, and ras-related protein), two mitochondrial protein-coding genes (cytochrome c oxidase subunits I and II), in addition to ITS sequence data, support the delimitation of this new species on Acacia mearnsii from the other previously described clade 2 Phytophthora species. Pathogenicity trial confirmed that the new species causes necrotic lesions on the plant stem, with either the presence or absence of gum.

KEYWORDS:

• Forest fungi
• Oomycetes
• phylogenetics
• Straminipila
• taxonomy
• 1 new taxon

ACKNOWLEDGMENTS

We thank the North Carolina Agricultural Research Service and the Department of Entomology and Plant Pathology of the North Carolina State University for hosting T.C.A.A.

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Funding

This study was financed in part by the National Council for Scientific and Technological Development (CNPq) of Brazil and the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Brazil (CAPES) (Finance Code 001), which awarded a scholarship to T.C.A.A. for a sandwich PhD program in the laboratory of J. Ristaino at the North Carolina State University.