Evaluation of the antifungal activity of some Azospirillum strains for their possible role as biocontrol agents

Abstract Two strains of the N2 fixing, plant growth promoting bacterium Azospirillum were isolated as endophytes from roots of wheat seedlings grown in the spermosphere model that was inoculated with aliquots of two rhizosphere soil samples. Azospirillum isolate 3Re was recovered after inoculation with Sisamum irio rhizosphere soil and the other isolate (12Re) was recovered after inoculation with Triticum aesativum rhizosphere soil, both were brought from Dalja village, . Some physiological and biochemical characteristics of Azospirillum strains were determined. One of the physiological studies on these Azospirillum strains exhibited that they have a chitinolytic activity. This study aims to evaluate the antagonistic activity of these isolates against the phytopathogenic fungus Fusarium. The investigation exhibited a positive effect for the in vitro control of Fusarium growth through the production of the fungal cell wall degrading enzymes (chitinase and β-1,3-glucanase) in addition to the production of volatile and non volatile antifungal compounds. The microscopic examination of the lysed fungal hyphae was recorded as a result of Azospirillum's fungal cell wall degrading enzymes produced. Moreover, in pot experiment Azospirillum overcame pathogenicity of Fusarium on wheat seedlings' growth and showed 100% of seedlings growth compared with 30% growth of control infested seedlings only. These results suggest that Azospirillum has an excellent potential to be used as biocontrol agents against phytopathogenic fungi.