Biodiversity and antifungal activities of actinomycetes isolated from the rhizosphere of Inga edulis in an urban forest fragment of the amazon

Abstract Actinobacteria are major producers of antibacterial and antifungal metabolites and are targets of increasing research in the search for substances of biotechnological interest, especially for use in agriculture. The Amazon soils is potentially rich in actinobacteria; therefore, we prospected actinobacteria from the rhizospheres of three individuals of Inga edulis found on the campus of the Federal University of Amazonas, the largest urban forest fragment in the Amazon. We isolated 64 strains of actinobacteria, which were distributed in 16 morphogroups. A total of 20 strains representing these 16 groups were subjected to morphological analysis, genotyping using the 16S rRNA gene, and assays against pathogenic fungi of important agricultural plants in the region that also cause annual losses of millions of dollars to world agriculture. Using GenBank-NCBI and EzBioCloud data, 90% of the strains were identified as Streptomyces and 10% as Kitasatospora, indicating at least 16 different species and possible new species. All showed antagonisms for two or more phytopathogen strains of Corysnepora cassiicola, Colletotrichum sp., Colletotrichum guaranicola, Pestalotiopsis sp., and Sclerotium coffeicola. Two stood out for their broad spectrum and better results against phytopathogens of the guarana plant (Paullinia cupana), an important crop for the regional economy and one of the best sources of caffeine in the world, whose powder is used in the food industry and traditional medicine. Complementary analyses ratified the potential of these strains as sources of highly effective antifungal substances. In general, the results exemplify the high diversity and richness of the actinomycetes in the Amazon.