Bio control mechanism of endophytic beauveria bassiana in three tomato (lycopersum esculentum) varieties

Abstract

Beauveria bassiana has gained considerable attention as biological control agent for most agricultural pests, however environmental variability has affected its efficacy and persistence. There is need to improve the delivery mechanism for B. bassiana, such as it’s use as an endophyte for protection from harsh environmental conditions. Endophytic fungi vary in their mode of action for insect and disease control. A clear understanding of the mode of action involved in biological control of Tetranychus evansi by endophytic Beauveria bassiana is important for successful application in the field. B. bassiana is known to synthesize hydrolytic enzymes such as lipase and protease which assist in degrading of the insect cuticle components. B. bassiana isolate IC 35 colonized tomato varieties Cal J, Kilele and Anna F1 in the screen house. The objective of this study was to determine the production of extracellular enzymes such as lipase and protease by endophytic B. bassiana isolate IC 35 on solid medium. To test the production of lipases, endophytic B. bassiana IC 35 from the three tomato varieties was grown for a-week on Sabourand Dextrose Agar and point inoculated on medium containing sorbitan monolaurate. To assess the protease activity, IC 35 was point inoculated on gelatin medium. The control plates lacked enzyme– specific substrates. All petri dishes were incubated for one week under laboratory conditions of 270c and 70% Relative Humidity. The diameters of the clear zone of inhibition and of fungal colonies were measured. Control plates had no clear zone since no enzymes were produced in them. Maximum lipase value of 2.15 cm and protease values of 2.2 cm activities were recorded on day 5 and there were significant difference among the tomato varieties for the treatments and control. These enzymes are important since they correspond to the main chemical integuments of the insect body, hence assist in breaking it down for effective biological control.