Streptomyces como biocontroladores in vitro de Exserohilum rostratum y productores de sustancias promotoras del crecimiento vegetal

The aim of the study was to evaluate the antifungal activity of Streptomyces spp. against Exserohilum rostratum strain CIAD_CP01 (synonym Setosphaeria rostrata ), as well as their ability to produce plant growth promoting substances. The antagonistic capacity in vitro of six Streptomyces strains was evaluated by direct confrontation and through volatiles against E. rostratum , isolated from maize leaves in the state of Chihuahua, (this being the first report of occurrence in this State) and was calculated by the percentage of inhibition of radial growth (PIRG). Likewise, the capacity of Streptomyces to produce indole acetic acid (IAA) and siderophores was determined, in addition to the fixation of atmospheric nitrogen and solubilize phosphates. The obtained PIRG ranged from 34.9 to 95.7% by direct confrontation and from 0.6 to 2.2% through volatiles.  Streptomyces cangkringensis strain CIAD-CA07 (A7) and Streptomyces misionensis strain CIAD-CA27 (A27) were able to produce IAA, with 3 and 29 ?g mL-1, respectively. All strains were able to produce the siderophore trihydroxamate (ferrioxamine), ranging from 7.8 to 39.3 % siderophore units, and to fix atmospheric nitrogen. Based on these results, Streptomyces strains could be used as biological control agents for E. rostratum and as biofertilizers in horticultural crops.