Objective To screen and identify highly efficient antagonistic bacteria against banana Fusarium wilt.

Method Antagonistic bacteria against Fusarium oxysporum f. sp. cubense tropical race 4 (Foc TR4) were screened from the rhizosphere soil of healthy banana plant by plate confrontation method. The antagonistic strain was identified by morphological observation, physiological and biochemical tests, and phylogenetic analysis of multiple genes including 16S rDNA, GyrB, RpoB and TyrB. The effect of the antagonistic strain on Foc TR4 hyphae morphology and conidial germination was evaluated using microscopic examination, and its anti-fungal spectrum was investigated by plate confrontation method. Volatile organic compounds (VOCs) from the antagonistic strain were analyzed through gas chromatography-mass spectrometry (GC-MS). The biological control effect and growth-promoting efficiency was evaluated by pot experiment in greenhouse.

Result An antagonistic strain (named GD7-17) was screened with an inhibition rate of 72.1% on hyphal growth of Foc TR4, which was identified as Streptomyces aureoversilis. The strain GD7-17 inhibited Foc TR4 hyphal growth by causing malformation, and showed a broad-spectrum antifungal activity against plant pathogenic fungi. VOCs produced by the strain GD7-17 significantly inhibited fungal mycelial growth, with an inhibition rate of 76.9%. Six VOCs were identified through GC-MS, including well-known geosmin and 2-methylisoborneol. Furthermore, S. aureoversilis GD7-17 exhibited a biocontrol efficiency of 59.6% against banana Fusarium wilt disease and effectively promoted banana growth. The strain GD7-17 was able to degrade lignin, secrete proteases and dissolve inorganic phosphate.

Conclusion S. aureoversilis GD7-17 exhibits good biocontrol potential against banana Fusarium wilt. This study provides a potential microbial agent for biocontrol of banana Fusarium wilt.