Botryosphaeriaceae are a diverse group of endophytic fungi colonizing the inner tissue of many woody species. As opportunist pathogens, they have been increasingly involved in diebacks worldwide. Nonetheless, the diversity of Botryosphaeriaceae, especially in asymptomatic plants, remains largely unknown. Using an innovative and mixed strategy of metabarcoding, this study aims to investigate the diversity of the fungal endophyte community, with a focus on Botryosphaeriaceae, which colonize grapevine and adjacent oak and pine trees in a French landscape. These data were used to test if the differentiation between hosts is more important than geographical effects for shaping the Botryosphaeriaceae communities and whether that similarity is higher between communities of grapevine and oak (both Angiosperms) than between oak and pine trees. We revealed a high level of diversity in Botryosphaeriaceae fungi, in both grapevines and forest trees, with a greater richness for grapevines. Contrasting results were obtained for the endophytic community, which was more diverse in forest trees. Our results support the hypothesis that host factors prevail on geographic effects to explain the diversity of Botryosphaeriaceae at the studied spatial scale. However, the features of the agroecosystem, such as management practices, were suggested to be more important than phylogeny to structure the fungal community. This highlights the importance of management practices for the microbiome of plants. [Formula: see text] Copyright © 2020 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Oomycetes (commonly known as 'water moulds') include several plant pathogens belonging to the genera Phytophthora, Pythium and Phytopythium. Phytophthora pathogens in particular are an increasingly important threat to forests and other natural and semi-natural ecosystems in Europe causing devastating declines and dieback of important tree species (Jung, Colquhoun & Hardy, 2013). Human activities, including the international plant trade, have facilitated spread of Phytophthora species. Nursery stock of woody ornamentals may inadvertently contain infectious propagules in soil, organic debris and on roots, which may serve as vectors to gardens, urban landscapes and natural habitats where they are subsequently planted (Jung et al., 2016). Once established, air-and soilborne Phytophthora species can attack other, potentially new, hosts causing foliar dieback or root and collar rot, which affects the growth, vitality and survival of woody plants and trees. Recent analyses revealed several alien Phytophthora species in southern Swedish landscapes (Cleary et al., 2017). Here, we wanted to evaluate the risk of potentially important pathogenic Phytophthora species entering natural environments via planting of ornamental nursery stock. | MATERIAL S AND ME THODSBetween June and August 2017, herbaceous and woody ornamental plants showing chlorosis, withering and/or necrotic lesions on foliage were anonymously purchased from 13 horticultural garden centres or nurseries in southern Sweden (Figure 1). Plants (totally 44) represented the following taxa: