Biocontrol effect of <I>Paenibacillus polymyxa</I> BRF-1 and <I>Bacillus subtilis</I> BRF-2 on fusarium wilt disease of cucumber and tomato

Cucumber is an important vegetable crop in China. Fusarium wilt is a soil-borne disease that can significantly reduce cucumber yields. Paenibacillus polymyxa WLY78 can strongly inhibit Fusarium oxysporum f. sp. Cucumerium, which causes Fusarium wilt disease. In this study, we screened the genome of WLY78 and found eight potential antibiotic biosynthesis gene clusters. Mutation analysis showed that among the eight clusters, the fusaricidin synthesis (fus) gene cluster is involved in inhibiting the Fusarium genus, Verticillium albo-atrum, Monilia persoon, Alternaria mali, Botrytis cinereal, and Aspergillus niger. Further mutation analysis revealed that with the exception of fusTE, the seven genes fusG, fusF, fusE, fusD, fusC, fusB, and fusA within the fus cluster were all involved in inhibiting fungi. This is the first time that demonstrated that fusTE was not essential. We first report the inhibitory mode of fusaricidin to inhibit spore germination and disrupt hyphal membranes. A biocontrol assay demonstrated that fusaricidin played a major role in controlling Fusarium wilt disease. Additionally, qRT-PCR demonstrated that fusaricidin could induce systemic resistance via salicylic acid (SA) signal against Fusarium wilt of cucumber. WLY78 is the first reported strain to both produce fusaricidin and fix nitrogen. Therefore, our results demonstrate that WLY78 will have great potential as a biocontrol agent in agriculture.

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

Agriculture ◽

10.3390/agriculture9120255 ◽

2019 ◽

Vol 9 (12) ◽

pp. 255

Author(s):

Huijie Chen ◽

Jiamiao Zhao ◽

Jing Jiang ◽

Sumei Chen ◽

Zhiyong Guan ◽

...

Keyword(s):

Bacillus Subtilis ◽

Fusarium Wilt ◽

Fungal Diversity ◽

Severe Disease ◽

Wilt Disease ◽

Disease Suppression ◽

Soil Microbiome ◽

Trichoderma Spp ◽

Treated Soil ◽

Fusarium Wilt Disease

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.

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