Streptomyces Strains from Amazonian Sediments as Plant Growth Promoters and Biocontrol Agents of Anthracnose in Postharvest Capsicum chinense

Postharvest diseases represent a critical challenge for global agriculture, resulting in substantial economic losses and threatening worldwide food security. Species of the genus <i>Colletotrichum</i> stand out among the main phytopathogens for being responsible for up to 40% of postharvest losses in various crops, including <i>Capsicum</i> species. This study evaluated the antifungal activity of two <i>Streptomyces</i> strains isolated from Amazonian sediments against different <i>Colletotrichum</i> species, with a focus on <i>C. scovillei</i>, the causal agent of anthracnose in <i>Capsicum chinense</i> fruits. Multilocus phylogenetic analyses indicated that strain APUR 32.5 possibly represents a new species, while MPUR 40.3 was identified as <i>Streptomyces murinus</i>. Both strains exhibited in vitro antifungal activity against seven <i>Colletotrichum</i> species, with inhibition percentages ranging from 56.3% to 88.6%. In fruit bioassays, <i>S. murinus</i> MPUR 40.3 reduced the incidence of anthracnose by 95%, while <i>Streptomyces</i> sp. APUR 32.5 achieved a 39.25% reduction. Scanning electron microscopy revealed complementary mechanisms of antifungal action, with MPUR 40.3 acting during the early infection stages through germination tube lysis, while APUR 32.5 targeted established mycelial structures through hyphal degradation. Additionally, both strains demonstrated plant growth-promoting capacity and exhibited biotechnologically relevant characteristics, including production of hydrolytic enzymes, siderophores, and phosphate solubilization ability. These results highlight the biotechnological promise of these Amazonian isolates as multifunctional agents for the sustainable management of anthracnose in <i>Capsicum</i> peppers.