Non-target effects on the soil microbiome of a plant root exudate biocontrol for Fusarium wilt

Crop rotation and intercropping with Allium spp. (e.g. garlic, onion) are recognized as biological controls of Fusarium wilt in several crops. However, the non-target effects of this strategy on the soil microbiome are largely unknown. We evaluated the effect of cultivating Musa basjoo, Allium tuberosum (Chinese leek), and their co-cultivation on the rhizosphere and bulk soil microbiome under glasshouse conditions. We do not report the impact of Chinese leek on Foc abundances, as this has been previously reported. The bacterial and fungal communities in the rhizosphere and bulk soil varied depending on the plant type. The microbiomes of allium and bananas were consistently dissimilar, and the co-cultivation treatment contained constituent taxa from both. However, the effect of allium on soil community composition was outweighed by that of bananas in the co-cultivation scenario. Discriminative taxa for allium included members of the genera Sphingomonas, Microbacterium, Flavihumibacter, Brevundimonas, Pseudolabrys, Ramlibacter, Trichoderma, Mortierella and Fusarium. In the case of bananas, predominant biomarkers encompassed members of Rhizobacter, Noviherbaspirillum, Pseudarthrobacter, Aquabacterium, Pseudomonas, Tausonia and Humicola Biomarkers and predictions of functional gene abundances suggest that shifts in the soil microbiome induced by allium are correlated with increases in microorganisms exhibiting potential disease suppression and antibiotic or antifungal traits, whereas those in bananas are associated with plant-growth-promoting microorganisms. The biocontrol efficacy of allium co-cultivation may there involve shifts in the soil microbiome as well as direct impacts of root exudate chemistry on Fusarium plant pathogens.