Enrichment of microbial taxa after the onset of wheat yellow mosaic disease

Soil-borne Chinese wheat mosaic virus causes yellow mosaic disease in winter wheat and is transmitted by its vector—Polymyxa graminis—in rhizosphere soil. However, the mechanism underlying the protective effect of belowground plant-associated microbes against infection by soil-borne viruses is unknown. Here, we used comprehensive bacterial 16S rRNA gene and fungal internal transcribed spacer region sequencing to explore changes of belowground plant-associated microbes and their network associations in response to wheat yellow mosaic disease. Following infection, the alpha diversity of root-associated microbiota significantly increases, whereas the microbial community structure becomes more homogeneous from the bulk soil to the root endosphere. Nevertheless, significant differences occur in taxonomic composition with different degrees of plant disease. For example, certain phyla, including Firmicutes, Gemmatimonadetes, Bacteroidetes, Chloroflexi, Nitrospirae, Armatimonadetes, and Acidobacteria, as well as specific genera, namely, Streptomyces, Stenotrophomonas, Bradyrhizobium, Sphingomonas and Bacillus, are greatly enriched following disease outbreak and may contribute to pathogen suppression. Moreover, following disease occurrence, the scale, connectivity, and complexity of the rhizosphere and root endosphere co-occurrence network increased compared with those of healthy plants. Moreover, the rhizosphere and root endosphere co-occurrence network of diseased plants contains more plant beneficial taxa and nitrogen cycle-related bacterial taxa as the keystone taxa, including the genera Bosea (Bradyrhizobiaceae), Stenotrophomonas, Thermomonas (Xanthomonadaceae), Novosphingobium (Sphingomonadaceae), and Methylibium (Comamonadaceae), implying that these potential beneficial taxa may regulate microbial networks and prevent the collapse of belowground microbial networks after disease emerging. It also implies that there is potential niche competition between beneficial bacteria and pathogen. In conclusion, our findings provide important insights into the relationship between the occurrence of soil-borne virus diseases and changes in the belowground microbial communities. This work may facilitate future research on the use of specific rhizosphere microbial communities to inhibit soil-borne virus infection.