Potentials of Indigenous Bacillus thuringiensis Isolates from the soil in controlling Fusarium wilt of Cucumber cause by Fusarium oxysporum f.sp cucumerinum

Abstract

Cucumber (Cucumis sativus L.) production is generally low in Nigeria due to continuous soil nutrient limitation and diseases. However, the persistence in the use of agrochemicals for cucumber production in Nigeria is associated with high cost and deleterious effects on man, animal and the environment. This study was conducted to investigate the potentials of indigenous Bacillus thuringiensis (Bt), a spore-forming bacterium known for its insecticidal properties in controlling Fusarium wilt of cucumber. Bacillus thuringiensis strains were isolated from soil samples collected from different farm sites in Abeokuta, Nigeria, and identified phenotypically and molecularly. The in-vitro antagonistic activity of B. thuringiensis strains on F. oxysporum f.sp. cucumerinum was evaluated by dual culture method, followed by pot experiment in the screen house. 16S rRNA gene sequencing was performed on the antagonistic B. thuringiensis to confirm Bt species. The results of the in-vitro antagonistic activity revealed that most indigenous B. thuringiensis strains showed significant growth inhibition of Fusarium oxysporium f. sp. cucumerinum. Similarly, application of B. thuringiensis A and C isolates significantly suppressed the incidence of Fusarium wilt of cucumber in the screen house when compared to the control. The 16S rRNA gene sequencing technique identified the isolates A and C as Bacillus thuringiensis strain LTS-209 and Bacillus thuringiensis strain VITSJ-01, respectively. Hence, indigenous B. thuringiensis A and C isolates should be incorporated into cucumber cultivation for controlling Fusarium wilt disease of cucumber. Keywords: Cucumber, Bacillus thuringiensis, Fusarium wilt, 16S rRNA gene