ANTAGONISTIC CAPACITY OF NATIVE Trichoderma spp. AGAINST Phytophthora parasitica AND Fusarium oxysporum ISOLATED FROM ROSELLE CROPS

Abstract

The black leg disease in roselle (Hibiscus sabdariffa L.) is mainly caused by Phytophthora parasitica Dastur and Fusarium oxysporum Schltdl. These pathogens cause losses in production of at least 50 % in the state of Guerrero, where the largest area of this crop is planted in Mexico. Fungicides used to control this disease are expensive, toxic and residual; thus, it is necessary to look for control alternatives within a context of sustainable agriculture. The objective of this study was to evaluate the in vitro antagonistic capacity of native strains of Trichoderma spp. against P. parasitica and F. oxysporum. Dual confrontations between pathogens and antagonistic agents were evaluated in Petri dishes under a completely randomized experimental design with four replications. The traits recorded were days at the first contact between hyphae, intersection zone, type of antagonism and percentage of inhibition. The information was submitted to analysis of variance and comparison test of means (Tukey, P ≤ 0.05). The five strains of Trichoderma overgrew P. parasitica and covered 100 % of the medium; in the case of the confrontation with F. oxysporum, Trichoderma grew only in two thirds of the medium. In the intersection zones, a variation of 0.0 to 4.8 cm was observed between pathogens and antagonists. The confrontation between T. inhamatum strain 14 and P. parasitica showed the largest contact between hyphae with 4.82 cm; Ti14, Ta10 and Ta9 showed the first contact between hyphae at 3 and 4 d in P. parasitica and F. oxysporum; the first strain had a higher inhibition percentage with 95 and 85 % for both pathogens. The Ti14 and Ta10 strains showed greater antagonism against both pathogens by time at first contact, sporulation, growth on the pathogens and percentage of inhibition. Trichoderma native strains represent a viable alternative for black leg control in roselle.