Assembly of cereal crop fungal communities under water stress determined by host niche

Crop-associated fungi play an important role in agroecosystems. However, a comprehensive understanding of the ecological mechanisms governing fungal community assembly is lacking. Here, we established a wheat (Triticum aestivum) and oat (Avena sativa) cropping system and sampled crop associated fungal communities under different water stresses. The results show that fungal community assembly in the soil-plant continuum is mainly determined by host niches rather than water stress and genotype. However, within the same host niche, water stress and genotype significantly influenced the assembly of fungal communities. This finding was further supported by the network complexity and dissimilarity-overlap analysis. Epiphytes and leaf endosphere exhibited a complex network structure, characterized by strong positive interactions among the members of the mycobiome. The network complexity of the phylloplane increased under drought stress. The analysis of microbial source tracking revealed that the fungi in the roots primarily originated from the bulk soil, while most fungi in the leaves originated from unknown sources under different water stress. In addition, crop mycobiome was governed by a few dominant taxa, with Sordariomycetes identified as an important biomarker taxon for roots and Trichosporonales for leaves. This study provides comprehensive empirical evidence on the assembly mechanisms of crop fungal communities.