Roots act as a biological filter that exclusively allows only a portion of the soil-associated microbial diversity to infect the plant. This microbial diversity includes organisms both beneficial and detrimental to plants. Phytophthora species are among the most important groups of detrimental microbes that cause various soil-borne plant diseases. We used a metabarcoding approach with Phytophthora-specific primers to compare the diversity and richness of Phytophthora species associated with roots of native and non-native trees, using different types of soil inocula collected from native and managed forests. Specifically, we analysed (1) roots of two non-native tree species (Eucalyptus grandis and Acacia mearnsii) and native trees, (2) roots of two non-native tree species from an in vivo plant baiting trial, (3) roots collected from the field versus those from the baiting trial, and (4) roots and soil samples collected from the field. The origin of the soil and the interaction between root and soil significantly influenced Phytophthora species richness. Moreover, species richness and community composition were significantly different between the field root samples and field soil samples with a higher number of Phytophthora species in the soil than in the roots. The results also revealed a substantial and previously undetected diversity of Phytophthora species from South Africa.

根作为一种生物过滤器，仅允许与土壤相关的微生物多样性的一部分感染植物。这种微生物多样性包括对植物有益和有害的生物。疫霉属是导致各种土壤传播的植物病害的最重要的有害微生物群之一。我们使用了与疫霉菌特异性引物结合的元条形码方法，使用从原生林和人工林中收集的不同类型的土壤接种物，比较了与原生树和非原生树的根相关的疫霉菌物种的多样性和丰富性。具体来说，我们分析了（1）两种非本地树种（桉树和相思树）的根）和本地树木，（2）体内植物诱饵试验的两种非本地树种的根，（3）田间采集的根与诱饵试验的根，以及（4）根系和土壤样品领域。土壤的起源以及根与土壤的相互作用极大地影响了疫霉菌的物种丰富度。此外，田间根样品和田间土壤样品之间的物种丰富度和群落组成显着不同，土壤中的疫霉菌数量比根中的多。结果还显示了来自南非的疫霉属物种的大量且以前未发现的多样性。