Cork oak forests are of immense importance in terms of economic, cultural, and ecological value in the Mediterranean regions. Since the beginning of the 20th century, these forests ecosystems have been threatened by several factors, including human intervention, climate change, wildfires, pathogens, and pests. Several studies have demonstrated the primary role of the oomycete Phytophthora cinnamomi Ronds in the widespread decline of cork oaks in Portugal, Spain, southern France, and Italy, although other congeneric species have also been occasionally associated. Between 2015 and 2019, independent surveys were undertaken to determine the diversity of Phytophthora species in declining cork oak stands in Sardinia (Italy). Rhizosphere soil samples were collected from 39 declining cork oak stands and baited in the laboratory with oak leaflets. In addition, the occurrence of Phytophthora was assayed using an in-situ baiting technique in rivers and streams located throughout ten of the surveyed oak stands. Isolates were identified by means of both morphological characters and sequence analysis of internal transcribed spacer (ITS) regions of ribosomal DNA. In total, 14 different Phytophthora species were detected. Phytophthora cinnamomi was the most frequently isolated species from rhizosphere soil, followed by P. quercina, P. pseudocryptogea, and P. tyrrhenica. In contrast, P. gonapodyides turned out to be the most dominant species in stream water, followed by P. bilorbang, P. pseudocryptogea, P. lacustris, and P. plurivora. Pathogenicity of the most common Phytophthora species detected was tested using both soil infestation and log inoculation methods. This study showed the high diversity of Phytophthora species inhabiting soil and watercourses, including several previously unrecorded species potentially involved in the decline of cork oak forests.

中文翻译：

---

撒丁岛（意大利）生活在下降的栎种群中的疫霉属物种概述

在地中海地区，软木橡树林在经济，文化和生态价值方面具有极其重要的意义。自20世纪初以来，这些森林生态系统受到多种因素的威胁，包括人为干预，气候变化，野火，病原体和害虫。数项研究表明，在葡萄牙，西班牙，法国南部和意大利，卵菌疫霉菌（Phytophthora cinnamomi Ronds）在软木橡树的广泛衰退中起着主要作用，尽管其他同属物种也偶有关联。在2015年至2019年之间，进行了独立调查，以确定疫霉菌的多样性撒丁岛（意大利）的软木栎下降种。从39个下降的软木橡木林中收集了根际土壤样品，并在实验室中用橡木小叶诱饵。此外，使用现场诱饵技术在遍布十个被调查橡树林的河流和溪流中测定了疫霉菌的发生。通过形态特征和核糖体DNA内部转录间隔区（ITS）区域的序列分析来鉴定分离株。总共检测到14种不同的疫霉菌。疫霉菌是根际土壤中最常分离的物种，其次是P. quercina，P。pseudocryptogea和tyrrhenica。相比之下，P. gonapodyides竟然是在溪水中最优势种，其次为P. bilorbang，P. pseudocryptogea，P.湖生，和P. plurivora。使用土壤侵染法和原木接种法测试了检测到的最常见疫霉菌的致病性。这项研究表明，生活在土壤和水道中的疫霉菌具有很高的多样性，其中包括一些以前未记录的可能与软木栎林衰退有关的物种。