Antagonistic Activity of Streptomyces spp. Waksman & Henrici Isolated from Larrea tridentata (Sesse’ & Moc. Ex DC.) Coville and Rhizosphere Soil Against Fusarium spp.

Agriculture is an essential activity in Mexico, representing the main source of income of numerous families. Crops are negatively affected by many diseases, particularly caused by phytopathogenic fungi, whose control by biological agents emerges as an advantageous alternative. The aim of the present study was to evaluate the antagonistic activity of microorganisms isolated from Larrea tridentata L. (Sessé & Moc. Ex DC.) Coville leaves, stems, roots, and rhizospheric soil against Fusarium spp. and other phytopathogen fungi. We identified 54 microorganisms: 30 bacteria species and 24 actinobacteriota. Initial dual-confrontation experiments with phytopathogenic fungi determined the bacillus and actinobacteriota inhibited growth from 57 to 100% and 42 to 83%, respectively. Based on our initial results, selected isolates were confronted with Rhizoctonia sp. and two Fusarium spp. isolates (orchid and garlic isolates). All microorganisms inhibited Rhizoctonia, but only 13 bacillary bacteria and eight actinobacteriota isolates inhibited Fusarium and were selected for the third confrontation, in which firmicutes –Bacilli:Bacilliales- and actinobacteriota isolates inhibited Fusarium spp. growth from 55 to 92% and 14 to 74%, respectively. In addition, supernatant fluids from six selected actinobacteriota were evaluated, and the results determined that the strains OP-AGsD3, OP-AGsM4R7, and OP-AGsM1R5 possessed the highest antagonist activity against all Fusarium spp. isolates. Molecular identification analysis indicated that actinobacteriota belonged to the Streptomyces genus. Our results revealed the potential of native Streptomyces spp. from L. tridentata rhizosphere soil as biocontrol agents against phytopathogenic Fusarium spp.