In vitro Enzymatic and Antifungal Activity of Rhizobacteria against Fusarium oxysporum f. sp. lycopersici

Aim: This study was carried out to investigate the enzymatic activity of rhizobacteria in the rhizosphere of tomato plant in a farm at Elemi, Ado Ekiti Nigeria as well as to explore the possibility for control of Fusarium oxysporum, the causal agent of tomato wilt, using their antagonistic traits.

Place and Period of Study: The study was carried out in the Department of Microbiology, Faculty of Science, Ekiti State University, Ado Ekiti, Nigeria in August 2018.

Methodology: In this study, rhizobacteria were isolated from rhizosphere of healthy tomato plant in the fields. Using pour plate method, isolation was carried out from rhizosphere soil of tomato plant collected from a field located at Elemi farm, Ado Ekiti Nigeria. Standard methods of Enzyme assay was employed to determine the ability of isolated rhizobacteria to produce hydrolytic enzymes require for biocontrol of phytopathogenic fungi. Antagonistic assay was performed using dual culture method on Potato Dextrose Agar (PDA) Plates. Isolates were tentatively identified with help of Bergy’s manual for identification.

Results Five bacteria isolates coded as BaC1, BaC2, BaL, BaS, and CiF were identified from preliminary screening. Evaluation for hydrolytic enzyme activities such as cellulase, protease, chitinase and glucanase showed that the isolates have the ability to produce enzymes but BaC1 has the highest enzymatic activity in all except in protease, while the CiF has the lowest activity in the entire enzyme assay carried out. In antagonistic activity, BaC1 shows a maximum inhibition of 33.0% against Fusarium oxysporum f. sp. lycopersici B, after five days of incubation followed by BaS with an inhibition of 29.7%, BaL with an inhibition of 29.5%, and CiF with least inhibition of 15.9% against Fusarium oxysporum f. sp. lycopersici A. Based on cultural and biochemical characteristics, the isolates were identified as Bacillus cereus1 (Bac1), Bacillus cereus2 (Bac2), Bacillus licheniformis (Bal), Bacillus subtilis (Bas).

Conclusion: Thus, this present study concludes that these rhizobacteria isolates could serve as a good alternative biocontrol agent’s inoculant in the integrated management of soil borne diseases of tomato.