Department of Genetics, Forestry and Agricultural Biotechnology Institute, Faculty of Natural and Agricultural Sciences, University of Pretoria, Pretoria 0002, South Africa.
Fungal Biol. 2013 May;117(5):329-47. doi: 10.1016/j.funbio.2013.03.004. Epub 2013 Mar 29.
Surveys of Australian and South African rivers revealed numerous Phytophthora isolates residing in clade 6 of the genus, with internal transcribed spacer (ITS) gene regions that were either highly polymorphic or unsequenceable. These isolates were suspected to be hybrids. Three nuclear loci, the ITS region, two single copy loci (antisilencing factor (ASF) and G protein alpha subunit (GPA)), and one mitochondrial locus (cytochrome oxidase c subunit I (coxI)) were amplified and sequenced to test this hypothesis. Abundant recombination within the ITS region was observed. This, combined with phylogenetic comparisons of the other three loci, confirmed the presence of four different hybrid types involving the three described parent species Phytophthora amnicola, Phytophthora thermophila, and Phytophthora taxon PgChlamydo. In all cases, only a single coxI allele was detected, suggesting that hybrids arose from sexual recombination. All the hybrid isolates were sterile in culture and all their physiological traits tended to resemble those of the maternal parents. Nothing is known regarding their host range or pathogenicity. Nonetheless, as several isolates from Western Australia were obtained from the rhizosphere soil of dying plants, they should be regarded as potential threats to plant health. The frequent occurrence of the hybrids and their parent species in Australia strongly suggests an Australian origin and a subsequent introduction into South Africa.
对澳大利亚和南非河流的调查显示，在该属的第 6 分支中存在许多居住的 Phytophthora 分离株，其内部转录间隔区 (ITS) 基因区域高度多态或不可测序。这些分离株被怀疑是杂种。扩增并测序了三个核基因座（ITS 区、两个单拷贝基因座（反沉默因子 (ASF) 和 G 蛋白α亚基 (GPA)）和一个线粒体基因座（细胞色素氧化酶 c 亚基 I (coxI)），以验证这一假设。在 ITS 区观察到丰富的重组。这一点，加上对其他三个基因座的系统发育比较，证实了存在涉及三种已描述的亲本种 Phytophthora amnicola、Phytophthora thermophila 和 Phytophthora taxon PgChlamydo 的四种不同杂种类型。在所有情况下，仅检测到单个 coxI 等位基因，表明杂种是由有性重组产生的。所有杂种分离株在培养中均不育，其所有生理特征均倾向于与母体亲本相似。关于它们的宿主范围或致病性还一无所知。尽管如此，由于来自西澳大利亚的几个分离株是从垂死植物的根际土壤中获得的，它们应该被视为对植物健康的潜在威胁。杂种及其亲本种在澳大利亚的频繁出现强烈表明它们起源于澳大利亚，随后被引入南非。
