The use of microorganisms with antagonistic activity against one or more pathogens can be an alternative to chemical control in agroecosystems. In this work, the potential for biocontrol by antagonism of a collection of environmental bacterial isolates against a phytopathogenic bacterium of Solanaceae, Xanthomonas vesicatoria, which causes bacterial spot in tomato and pepper, was evaluated. Control of this disease is usually limited by the lack of resistant hosts, the threat to the environment and the global health risks posed by the continued use of chemical agents.

Bacteria were isolated from different environmental samples from disease-free areas and tested for their in vitro antagonistic capacity against a reference strain of X. vesicatoria. The isolates with the greatest antagonistic activity were selected for initial ex vivo assays to determine this activity in plant material against the reference strain, using leaves from tomato plants of a variety sensitive to bacterial spot. The isolates with the greatest activity were further characterized for their capacity to produce hydrolytic enzymes, such as proteases, lipases, amylases and DNases, and for their nitrogen fixation capacity.

Overall, the results revealed the presence of bacterial isolates able to inhibit the growth of X. vesicatoria in vitro and reduce the severity of bacterial spot symptoms ex vivo, in addition to producing different hydrolases related to biological control and biotechnological use, and fixing molecular nitrogen. The prospects for improving biological control strategies against bacterial spot in tomatoes and peppers caused by X. vesicatoria are promising, thus promoting sustainable agricultural production that favors ecosystem balance.

Funding: This work is part of the R+D+i project PID2021-123600OR-C44, funded by MICIU/AEI/10.13039/501100011033 and by ERDF A way to do Europe, ERDF/EU.