ABSTRACT

Introduction.   Phytopathogenic fungi cause losses in tomato production and for this reason it is important and necessary to find alternatives aimed at managing antagonistic agents that are efficient and compatible with the environment.

Objective.  To determine the effectiveness of nativeand exotic strains of Trichoderma spp. against Fusarium spp. at laboratory level.

Materials and methods.  Commercial products of Trichoderma spp. with native (THM-03 and THM-04) and imported strains (THU-01 from the United States and THC-02 from Colombia) were used. Pathogen was isolated from diseased tomato plants, for which morphological and molecular analyses were used for identification. Dual culture technique was used to evaluate radial growth of the antagonist (RGA) and the pathogen, mycoparasitism and percentage of radial growth inhibition (PRGI).

Results.  T. asperellum, T. asperelloides and T. guizhouense were identified; the pathogen was identified as F. oxysporum. Mean RGA values of 25.6, 39.3, 41.2 and 32.1 mm were obtained for THU-01, THC-02, THM-03 and THM-04, respectively; and 42.75 mm for the control. Regarding mycoparasitism, THC-02, THM-03 and THM-04 presented complete invasion of the F. oxysporum colony, with sporulation and THU-01 only managed to invade a quarter of the pathogen's surface. PRGI was determined, in which significant differences were found between Trichoderma strains where the most effective strains were THM-03 and THC-02 with 67 and 63% inhibition, respectively.

Conclusion.  This in vitrostudy showed differences in the antagonistic capacity of different Trichoderma species against the pathogen F. oxysporum. Strains of T. asperellum(THC-02), T. asperelloides(THM-03) and the native strain T. guizhouense (THM-04) showed to be more aggressive in combat of the pathogen, regardless of its origin, thus the study could be expanded with the use of more isolates.

Keywords: Percentage of radial growth inhibition (PRGI); antagonist; native strains; biological control; mycoparasitism