A Caatinga biome-sourced <i>Streptomyces</i> sp. Act0014 for biological control of citrus canker caused by <i>Xanthomonas citri</i> subsp. <i>citri</i>

Copper bactericides are the most common and effective measure for controlling citrus canker caused by <i>Xanthomonas citri</i> subsp. <i>citri</i>. However, copper use can negatively impact the environment and promote the emergence of copper-resistant <i>Xanthomonas</i> strains, highlighting the need for sustainable alternatives. This study developed a biobactericide using <i>Streptomyces</i> sp. Act0014, for citrus canker management. Act0014 was fermented in ISP2 medium, and its purified extract, fermented broth, and spore suspension were assessed for curative and protective effects against citrus canker in the greenhouse. Furthermore, Act0014 was formulated and assessed for disease control over two consecutive seasons in a commercial sweet orange grove in the São Paulo state citrus belt, Brazil. After fermentation, Act0014 produced the antibacterial polyketide lysolipin I. The purified extract, spore suspension, and fermented broth acted protectively by reducing citrus canker severity on sweet orange leaves by more than 50%. No curative effect was observed after applying Act0014 fermented broth on pre-established lesions. In the field, formulated Act0014 significantly reduced the incidence of cankered leaves by up to 67.0% when used alone and by 86.5% when alternated with copper. These results highlight the potential of Act0014 as an environmentally friendly alternative to copper for citrus canker management.