In vitro evaluation of Trichoderma and Gliocladium antagonism against the symbiotic fungus of the leaf-cutting ant Atta cephalotes

The antagonistic activity of Trichoderma and Gliocladium isolates against A ttamyces sp., a symbiotic fungus of the leaf-cutting ant Atta cephalotes, w as investigated. A. cephalotes cultures this fungus as the primary food sou rce. Most of the Trichodema and Gliocladium isolates tested in vitro (82.6% ) inhibited the Attamyces sp. mycelial growth, which was probably due to th eir colonization ability and competition for nutrients, both of them known mechanisms of some species of these genera. T. lignorum strain T-26 was the strongest inhibitor achieving a colonization of 23%. Microscopical observa tions indicate that the inhibitory effect was caused by an interaction that took place in close contact with the host hypha, causing wall deformation that led to the collapse of the turgor pressure.