EFFET INVIVO DE BIOCONTROLE D’UN ENDOPHYTE BACTERIEN SUR LE DEVELOPPEMENT DES MALADIES PHYTOPATHOGENES.

Abstract

Fungal phytopathogenic diseases represent a major constraint for cucumber cultivation, causing significant losses in yield and quality. Given the limitations of chemical control and its environmental impacts, biocontrol using endophytic bacteria emerges as a sustainable and promising alternative. The objective of the present study was to evaluate the in vitro and in vivo effects of a bacterial strain belonging to the genus Bacillus on the development of two phytopathogenic fungi: Alternaria sp. and Diaporthe sp. The study began with the revival and characterization of the bacterial strain through morphological observation, Gram staining, spore staining, as well as several biochemical and physiological tests (catalase, starch hydrolysis, and salt tolerance). The evaluation of the antagonistic potential of Bacillus was carried out by direct confrontation on agar medium as well as through the use of secondary metabolite extracts. The results showed a significant inhibition of the mycelial growth of both pathogens, with inhibition rates of 22.5% for Alternaria sp. and 37.5% for Diaporth sp., reflecting a strong antifungal activity. In vivo trials on cucumber plants also revealed a reduction in disease severity in bacteria-treated plants compared to the infected controls. This protection resulted in a decrease in the severity rate from 85% to 17% against Alternaria, and from 60% to 4% against Diaporthe sp. These results confirm the potential of Bacillus as an effective biological agent in protecting cucumber against fungal diseases. In conclusion, this study highlights the value of endophytic bacteria in biological control strategies and underscores their potential for a more sustainable and environmentally friendly agriculture.