Evaluation of the biocontrol potential of a new native Bacillus velezensis isolate “NH1 OQ711964” against Alternaria solani

One of the current challenges is meeting the increasing food demand and providing sustainable food resources. Hence, controlling plant diseases, especially those caused by phytopathogens has gained a significant interest to reduce the annual loss of plant crops. Although the control programs have traditionally relied on the use of agrochemicals, there is an urgent need to shift to biological control techniques because of the developed environmental and health concerns as well as the rise of microbial resistance. Bacillus velezensis is an emerging biocontrol agent that has shown a promising biocontrol potential. In the current study, a new native B. velezensis isolate has been isolated and tested for its antagonistic potential against Alternaria solani, the causal agent of a destructive disease affecting the solanaceous crops. The investigated isolate, Bacillus velezensis NH1 OQ711964, exhibited good antagonistic behavior against Alternaria solani in all tested methods. Its extracellular metabolites exerted a significant antifungal activity. Six phenolic, fatty acid, alkyne and pentadiene compounds have been estimated as the major metabolites in its extracellular ethyl acetate extract employing Gas Chromatography–Mass Spectrometry. These compounds in addition to Hydrocinnamic acid, a detected minor product, are well characterized by their antifungal activities which can explain the significant antifungal behavior of this isolate. Indeed, A. solani culture exposed to these metabolites has shown obvious mycelial growth inhibition, thinner hyphae with multiple fractures, coiling and distortions, in addition to cytoplasmic leakage combined with sparse cytoplasmic filling as illustrated by its scanning electron microscope imaging.