<i>Phytophthora acaciae</i> sp. nov., a new species causing gummosis of black wattle in Brazil
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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.
研究在巴西南部亚热带湿润地区的黑荆（Acacia mearnsii）人工林内，发现了一种与流胶病相关的新疫霉属（Phytophthora）物种。本文通过系统发育与形态学分析，将该新物种正式命名为金合欢疫霉（Phytophthora acaciae）。这是巴西黑荆人工林疫霉属病原复合群中第四种被发现可引发流胶病的疫霉物种，其余三种分别为烟草疫霉（P. nicotianae）、苎麻疫霉（P. boehmeriae）和寒生疫霉（P. frigida）。金合欢疫霉（Phytophthora acaciae）为异宗配合真菌，具雄器围生结构，孢子囊不脱落且带有乳突；基于核核糖体DNA内部转录间隔区（ITS1-5.8S-ITS2 = ITS）序列分析，该物种被归入疫霉属演化支2（Phytophthora clade 2）。针对金合欢疫霉分离株的多基因序列（包含3个核蛋白编码基因：β-微管蛋白、翻译延伸因子1α、Ras相关蛋白，2个线粒体蛋白编码基因：细胞色素c氧化酶亚基I与II，以及ITS序列数据）开展最大简约法与最大似然法系统发育分析，结果证实该物种可与其他已描述的疫霉属演化支2物种相区分，其分离自黑荆植株。致病性试验结果表明，该新物种可在植物茎部引发坏死病斑，且病斑可伴随或不伴随流胶症状。
