Assessing the Influence of Fumigation and Bacillus Subtilis-Based Biofungicide on the Microbiome of Chrysanthemum Rhizosphere

Abstract

Chrysanthemum is an important ornamental species in China. However, sustained monoculture often leads to a decline in soil quality, in particular to the build-up of pathogens. Fusarium wilt, a severe disease in chrysanthemum monoculture systems, was effectively controlled by fumigation and/or the application of a biofungicide in our previous study. However, the mechanisms underlying disease suppression remain elusive. Here, a series of greenhouse experiments were conducted to characterize the effect on the chrysanthemum rhizosphere microbiome of the fumigant dazomet (DZ) and of a biofungicide based on Bacillus subtilis NCD-2 (BF). The results indicated that the BF treatment increased bacterial diversity by 4.2%, while decreasing fungal diversity by 21.3%. After two seasons of BF treatment, the abundance of microbes associated with disease suppression such as Bacillus spp. and Trichoderma spp. increased 15.1-fold and 4.25-fold more than that of the control, while the pathogenic Fusarium oxysporum was decreased by 79.20% when compared to the control. Besides, the DZ treatment reduced both bacterial and fungal diversity 7.97% and 2.73% respectively, when compared with the control. The DZ treatment controlled Fusarium wilt disease and decreased the abundance of F. oxysporum in the first year, but the abundance of the F. oxysporum was 43.8% higher after two years in treated soil than in non-treated soil. Therefore, the application of BF has a great potential for the control of Fusarium wilt disease in chrysanthemum by changing soil microbiome structure and function.