Abstract
The present study focuses on the inhibitory effect of volatile metabolites released by Bacillus velezensis CT32 on Verticillium dahliae and Fusarium oxysporum, the causal agents of strawberry vascular wilt. The CT32 strain was isolated from maize straw compost tea and identified as B. velezensis based on 16S rRNA gene sequence analysis. Bioassays conducted in sealed plates revealed that the volatile organic compounds (VOCs) produced by the strain CT32 possessed broad-spectrum antifungal activity against eight phytopathogenic fungi. The volatile profile of strain CT32 was obtained by headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). A total of 30 volatile compounds were identified, six of which have not previously been detected in bacteria or fungi: (Z)-5-undecene, decyl formate, 2,4-dimethyl-6-tert-butylphenol, dodecanenitrile, 2-methylpentadecane and 2,2’,5,5’-tetramethyl-1,1’-biphenyl. Pure compounds were tested in vitro for their inhibitory effect on the mycelial growth of V. dahliae and F. oxysporum. Decanal, benzothiazole, 3-undecanone, 2-undecanone, 2-undecanol, undecanal and 2,4-dimethyl-6-tert-butylphenol showed high antifungal activity, with benzothiazole and 2,4-dimethyl-6-tert-butylphenol being the most potent compounds. These results indicate that the VOCs produced by B. velezensis CT32 have the potential to be used as a biofumigant for management of vascular wilt pathogens.
Highlights
IntroductionVascular wilt diseases, caused by Verticillium dahliae and Fusarium oxysporum, are devastating diseases of strawberry (Fragaria × ananassa Duch.) that severely affect the production of this crop
Vascular wilt diseases, caused by Verticillium dahliae and Fusarium oxysporum, are devastating diseases of strawberry (Fragaria × ananassa Duch.) that severely affect the production of this crop.Due to the fact that the persistent resting structures produced by the pathogens are able to survive in the absence of hosts for long periods of time, vascular wilt diseases are difficult to control [1,2]
Upon exposure to volatile organic compounds (VOCs) emitted by strain CT32, the mycelial growth of V. dahliae and FOF was reduced by 66.94% and 45.72%, respectively
Summary
Vascular wilt diseases, caused by Verticillium dahliae and Fusarium oxysporum, are devastating diseases of strawberry (Fragaria × ananassa Duch.) that severely affect the production of this crop. Due to the fact that the persistent resting structures produced by the pathogens are able to survive in the absence of hosts for long periods of time, vascular wilt diseases are difficult to control [1,2]. Due to the lack of resistant strawberry cultivars, soil fumigation with methyl bromide is an effective way to manage vascular wilt diseases, but this fumigant has been withdrawn from routine use under the Montreal Protocol [3]. Crop rotation is generally ineffective for Verticillium and Fusarium wilt of strawberry because of the wide host range of the pathogenic fungi. The need to develop eco-friendly and highly efficient biocontrol agents (BCAs) for sustainable strawberry production is extremely urgent
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