Study of Some Biocontrol Bacterial Isolates and Evaluation of Their Antifungal and Insecticidal Effects

Abstract

The biological control of phytopathogenic diseases and other pests by the introduction of microorganisms beneficial of the rhizosphere has been proposed as an alternative to chemical control. The objective of our work is to determine the elements on which this interaction between antagonistic bacteria and bioagressors of cultures such as secondary metabolites, is based. The present work involves the identification of a collection of strains belonging to the Bacillus genus with the demonstration of the synthesis of secondary metabolites such as enzymes with hydrolytic effect and the characterization of their bioactive molecules as well as the study of their effect antagonist against Verticillium dahliae agent of the verticilliose and insecticidal effect against Galleria mellonela. These isolats are from the rhizosphere soil of three cultivated plants (Nefle, Barley and potato) in the region of Boumerdes (North Algeria). The macroscopic and microscopic identification tests allowed us to select strains with characteristics identical to those of Bacillus sp. The study of the different enzymes (amylase, cellulase, chitinase, caseinase) show for the majority of strains a good production, which explains their efficiency against Verticillium dahliae. In fact, the biological control tests carried out in vitro by these bacterial strains have shown that it is possible to limit the incidence of V. dahliae and that the use of this biological treatment makes it possible to maintain the disease at an acceptable threshold. These strains can therefore have a role in antagonism and plant biostimulation. Concerning the insecticidal effect of bacteria on the larvae of the wax moth Galleria mellonella, very significant results are achieved with 100% mortality recorded 8 days after treatment at the high dose (1.10 7 ufc/ml). It appears that these isolates could find their place in biotechnological applications aimed at improving yields and preserving the environment for sustainable development.