The work was carried out during 2008 in Saltillo, Coahuila with the aim of isolating actinomycetes in different culture media and assess their in vitro antagonistic effect against plant pathogenic fungi of economic importance. For the isolation of actinomycetes we sampled rhizosphere of plants, soil, ant larvae and adults, the samples were treated with water and seeded phenolized diffusion in artificial culture media: Potato Dextrose Agar (PDA), Starch Casein Agar (ACA), Actinomycetes agar (AA) and Czapek Dox Agar (CDA). The isolates obtained were evaluated preliminarily by confrontation and observation. 70 isolates were obtained mainly from actinomycetes in soil; 25 showed antagonistic effects, four of tem APA2, AASH48, AAH53 and APC70 were selected for their inhibitory activity and permanence over time. In vitro bioassays antibiosis against phytopathogenic fungi such as Alternaria sp., Rhizoctonia sp., Fusarium sp. and Colletotrichum sp. on PDA and ACD mediums, the antagonistic effects (%-inhibition) were statistically different (p= 0.05). The best results were obtained with inhibition of Streptomyces spp., APC70 against (57.6%); while Streptomyces spp., AAH53 was for Rhizoctonia, Fusarium and Colletotrichum in 53.08%, 49.36% and 61.57%, respectively. The saprophytic actinomycetes showed antagonistic potential and inhibitory activity against phytopathogenic fungi.
Keywords: Antibiosis, antagonism, confrontation,