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

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