Isolation and identification of Streptomyces aureoversilis GD7-17 and its biocontrol potential against banana Fusarium wilt

Objective To screen and identify effective biocontrol agent 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 plants by plates 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 TrpB. The effect of the antagonistic strain on Foc TR4 hyphae morphology and conidial germination was evaluated using microscopic examination, and its antifungal spectrum was investigated by the 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 plant growth-promoting effect were evaluated by pot experiments under greenhouse conditions.

Result A strain, designated GD7-17, was isolated and identified as Streptomyces aureoversilis. It exhibited strong antagonistic activity against Foc TR4, inhibiting mycelial growth by 72.19% and inducing abnormal hyphal morphology. Furthermore, the strain showed broad-spectrum antifungal activity against plant pathogenic fungi. VOCs produced by strain GD7-17 significantly inhibited fungal growth, with an inhibition rate of 76.9%. Six VOCs were identified through GC-MS, including geosmin and 2-methylisoborneol. Furthermore, S. aureoversilis GD7-17 exhibited a biocontrol efficacy of 58.2% against banana Fusarium wilt disease, and simultaneously exerted a significant growth-promoting effect on banana plants, resulting in an 18.0% increase in fresh weight, an 8.2% increase in corn diameter, and a 16.7% increase in plant height. Strain GD7-17 was able to degrade lignin, secrete proteases and solubilize inorganic phosphate.

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