Evaluation of the antagonistic potential of bacterial strains isolated from Algerian soils for the biological control of phytopathogenic fungi

Abstract

Antagonistic bacteria contribute to the management of plant diseases by stimulating the natural defenses in the host and/or by ensuring direct biocontrol of the aggressors. The objective of this work was to isolate, identify and evaluate (in vitro) various Bacillus spp. for their potential to control phyopathogenic fungi. Selection of the 40 strains of Bacillus previously isolated from the soil in various areas of western Algeria was carried out by direct confrontation on the mycelial growth of four phytopathogens (Fusariumoxysporumf.splycopersici, Alternaria tenuis , Phytophthorainfestans, Ascochytapisi). This strategy involved using the antagonistic potential of microorganisms found in the plant environment in Algeria. The second part of this work consisted of the characterization and identification of tested strainsThe identification of the selected strains was carried out by biochemical tests. The results obtained showed that at the end of the fifth day, the most promising isolates showed antifungal activity and reached an inhibition rate of the mycelial growth of phytopathogenic fungi, respectively, F. oxysporumf. splycopersici 75%, A. tenuis 80%, P. infestans 83.30%, Ascochytapisi 67%. The potential antagonist of Bacillus tested in vitro by direct confrontation against 04 phytopathogenic fungi showed that all strains of Bacillus decreased fungal mycelial growth. Two strains of Bacillus B30 and B41 were found to have the most efficacy against Fusarium oxysporum f.sp. lycopersici, Alternaria tenius, Phytophtora infestans et Ascochyta pisi, with an inhibition rate of  65.25 and 72.25% respectively These results demonstrate that Bacillus sp. presenteds a potential for biological control. However, it is important to understand the mechanisms implemented by these bacteria to develop effective protection strategies.