Crop-zone weed mycobiomes of the south-western Australian grain belt

In the absence of a primary crop host, secondary plant hosts may act as a reservoir for fungal plant pathogens of agricultural crops. Secondary hosts may potentially harbor heteroecic biotrophs (e.g. the stripe rust fungus Puccinia striiformis) or other pathogens with broad host ranges. Agricultural grain production tends towards monoculture or a limited number of crop hosts over large regions, and local weeds are a major source of potential secondary hosts. In this study the fungal phyllospheres of 12 weed species common in the agricultural regions of Western Australia (WA), were compared. We observed the presence of several major international crop pathogens, including basidiomycete rusts of the Puccinia spp., and ascomycete phytopathogens of the Leptosphaeria and Pyrenophora genera. Unrelated to crop production, several endemic pathogen species including those infecting Eucalyptus trees were also observed, which was consistent with local native flora. We also observed that differences in latitude or climate zones appeared to influence the geographic distributions of plant pathogenic species more than the presence of compatible host species. There was an increased proportion of necrotrophic Ascomycete species in warmer and drier regions of central WA, compared to an increased proportion of biotrophic Basidiomycete species in cooler and wetter regions in southern WA.

在缺乏主要作物宿主的情况下，次生植物宿主可作为农业作物真菌性植物病原菌的储存宿主。次生宿主可能携带转主寄生活体营养型真菌（例如条形柄锈菌Puccinia striiformis）或其他宿主范围广泛的病原菌。
大规模农业谷物生产往往趋向于单一种植或仅在大区域内种植有限种类的作物宿主，而本地杂草是潜在次生宿主的主要来源。
本研究对澳大利亚西部（WA）农业区域常见的12种杂草的叶围（phyllosphere）真菌群落进行了比较分析。我们检测到多种重要的全球性作物病原菌，包括柄锈菌属（Puccinia spp.）的担子菌锈菌，以及小球腔菌属（Leptosphaeria）和核腔菌属（Pyrenophora）的子囊菌植物病原菌。
与作物生产无关的是，本研究还观测到多种特有病原菌物种，包括侵染桉树（Eucalyptus）的病原菌，这与当地原生植被的分布特征相符。
此外我们发现，与亲和宿主物种的存在相比，纬度或气候区的差异对植物病原菌物种的地理分布影响更为显著。与西澳南部凉爽湿润区域的活体营养型担子菌物种占比升高的情况相对，西澳中部温暖干旱区域的死体营养型子囊菌物种占比有所上升。