Antagonismo de fitopatógenos por actinobactérias isoladas da caatinga

Abstract

Actinobacteria are known for their ability to produce antimicrobial substances and have gained prominence as alternatives to chemical pesticides. In order to explore their capacity to produce metabolites with antimicrobial potential against phytopathogenic fungi and bacteria that affect economically important crops, the biocontrol potential of four actinobacterial isolates obtained from the rhizospheric soil of species native to the Caatinga biome was evaluated. Direct antagonism tests were performed using the dual culture technique, indirect antagonism was assessed through the production of volatile compounds, and the antagonism index was analyzed. The phytopathogens tested in this study were: Lasiodiplodia pseudotheobromae, Fusarium sp., Pectobacterium carotovorum pv. carotovorum, Paracidovorax citrulli, Xanthomonas campestris pv. campestris, and Xanthomonas citri pv. viticola. The data indicate that, although with varying intensities, all isolates exhibited antagonistic activity and have potential for application in sustainable plant disease management strategies. Isolate J1 stood out among all others for its efficient production of antimicrobial secondary metabolites that significantly inhibited the growth of P. carotovorum pv. carotovorum and X. campestris pv. campestris through direct antagonism, with inhibition rates of 80.55% and 59%, respectively. In addition, it produced inhibitory volatile organic compounds against X. citri pv. viticola and P. citrulli, with inhibition rates of 96%. Isolate C5 showed the second-best performance, demonstrating inhibitory potential against the growth of X. campestris pv. campestris, with 45.5% inhibition in the direct antagonism test. It also produced volatile compounds with potential control over X. citri pv. viticola and P. citrulli, with inhibition percentages of 96% and 75%, respectively.