Laboratory of Phytopathology, Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium;
CBS-KNAW, Fungal Biodiversity Centre, P.O. Box 85167, 3508 AD Utrecht, The Netherlands.
Persoonia. 2013 Dec;31:63-76. doi: 10.3767/003158513X668554. Epub 2013 May 14.
Despite its association with important agricultural crops, Phytophthora clade 8b is a poorly studied group of species. The clade currently consists of three officially described species (Phytophthora porri, P. brassicae and P. primulae) that are host-specific pathogens of leek, cabbages and Primula spp., respectively. However, over the past few decades, several other clade 8b-like Phytophthoras have been found on a variety of different host plants that were all grown at low temperatures in winter seasons. In this study, a collection of 30 of these isolates was subjected to a phylogenetic study using two loci (the rDNA ITS region and the mitochondrial cox1 gene). This analysis revealed a clear clustering of isolates according to their host plants. To verify whether these isolates belong to separate species, a detailed morphological study was conducted. On the basis of genetic and morphological differences and host specificity, we now present the official description of three new species in clade 8b: Phytophthora cichorii sp. nov., P. dauci sp. nov. and P. lactucae sp. nov. Two other groups of isolates (Phytophthora taxon castitis and Phytophthora taxon parsley) might also represent new species but the data available at this time are insufficient for an official description. This brings Phytophthora clade 8b to a group of six species that are all host-specific, slow-growing and specifically infect herbaceous crops at low temperatures.
尽管与重要的农业作物有关，但 8b 谱系的 Phytophthora 是一个研究较少的物种群。该谱系目前由三个正式描述的物种组成（韭菜疫霉、白菜疫霉和报春花疫霉），它们分别是葱、甘蓝和报春花属植物的专性病原菌。然而，在过去的几十年里，在各种不同的冬季低温生长的宿主植物上发现了其他几个类似 8b 谱系的 Phytophthoras。在本研究中，对 30 个此类分离株进行了基于两个基因座（rDNA ITS 区和线粒体 cox1 基因）的系统发育研究。该分析根据宿主植物清楚地对分离株进行了聚类。为了验证这些分离株是否属于不同的物种，我们进行了详细的形态学研究。基于遗传和形态差异以及宿主特异性，我们现在正式描述了 8b 谱系中的三个新物种：慈姑疫霉、牛蒡疫霉和莴苣疫霉。另外两个分离株群（芹菜疫霉和欧芹疫霉）可能也代表了新物种，但目前的资料不足以进行正式描述。这使 8b 谱系的 Phytophthora 达到了一个包含六个物种的群组，它们都是专性宿主、生长缓慢，并且专门在低温下感染草本作物。
