Objective Microorganisms antagonistic to Fusarium solani were isolated from the rhizosphere soil of healthy passion fruit plants and studied for potential application as a biocontrol agent.

Method Rhizosphere oil at the field of healthy passion fruit plants was sampled to isolate microbes antagonistic to F. solani using the confrontational culture method. Morphological observation and molecular identification were performed to determine the species and biological characteristics of the isolates. Potential as a biocontrol agent of the identified strains was evaluated on the extracellular enzyme detection plates, while possible growth promoting effect examined on tomato seeds.

Result Eight microbial strains antagonistic to F. solani were isolated from 7 soil specimens. Among them, NN-Q03-10, SL-Q02-05, and SL-Q02-06 exhibited the greatest inhibition rates of 57.81%, 57.34%, and 57.34%, respectively. Four of them belonged to Bacillus subtilis, and 4 to B. velezensis. All could produce proteases, cellulases, β-1,3-glucanases, and xylanases with genomes consisting of antibiotic bacA, FenB, and yanJ. In addition to those genes, SL-Q02-05, NN-Q03-01, NN-Q03-09, and NN-Q03-10 also contained MycB and ifuA.Validation of growth promoting effects using tomato seeds, and the results showed that six strains (SL-Q02-04、SL-Q02-05、SL-Q02-06、SL-Q03-01、NN-Q03-01、NN-Q03-10) could promote embryonic root growth, among them, SL-Q02-04 had the most significant promoting effect with a embryonic root length of 7.32 cm.

Conclusion The 8 Bacillus strains antagonistic to F. solani were identified. Their ability in producing protease, cellulase, β-1,3-glucanase, and xylanase and some of them having genomes containing mycB, ifuA, FenB, bacA, and yndJ related to antibiotic property strongly suggested a potential in serving as a biocontrol agent for F. solani infection on plants.