EVALUATION OF Trichoderma spp. AGAINST PATHOGENIC Fusarium spp. ISOLATED FROM CASSAVA ROOTS (Manihot esculenta)

VARGAS AD; MADRASSI LM ; MÓNACO CI; ZAPATA PD; ALVARENGA AE

Congreso; LVII SAIB Meeting - XVI SAMIGE Meeting; 2021

In Misiones province, cassava crops are affected by a variety of phytosanitary problems. Among them, cassava root rot disease (CRRD) caused by edaphic fungi, particularly Fusarium spp., is of major concern. This condition produces economic losses and, even though there are no standardized procedures against it, farmers use agrochemicals. In recent years, it has been investigated how to deal with CRRD using Trichoderma spp. as a biocontrol agent. These are widely studied microorganisms which are capable of controlling the development of pathogens, either through their competitive capacity or because they feed on them. However, no studies have been carried out to estimate the antagonistic capacity of Trichoderma spp. against root rot cassava pathogens in Misiones. The objective of this work was to evaluate the antagonistic potential of native Trichoderma spp. strains against CRRD pathogens belonging to Fusarium spp., in vitro. Co-culture tests were carried out between three Trichoderma spp. strains (1BA, 8A, and Tob6) and five pathogenic Fusarium spp. strains (33F, M2aF, P1, P3, and 3.4F). In this test, portions of the pathogen and antagonist mycelium, taken with a sterile 4 mm punch, were placed 6 cm apart and 1 cm from the edge of 90 mm Petri dishes. These plates contained 20 ml of sterile potato-dextrose agar and were incubated at 28ºC ± 2ºC during 10 days. As a negative control, pathogen mycelium was inoculated alone, under the same conditions mentioned above. Each confrontation test was carried out by triplicate. After the end of the cultivation period, pathogenic colony growth radius (mm) was measured as the distance between the center and the edge of the fungal colony. Then, the percentage of pathogenic growth inhibition (PICP) was calculated as (control colony size - treatment colony size) / control colony size * 100. It was observed that all the antagonists reduced Fusarium spp. colony growth radius (18-77% inhibition) and that the majority of them grew over the pathogenic mycelium. Trichoderma 1BA produced the highest PICP values against P1 and 33F, while Trichoderma 8A and Tob6 showed the highest inhibition against M2aF and 3.4F respectively. From the results of the present work, it is concluded that native Trichoderma spp. strains could be potential biocontrollers of CRRD caused by Fusarium spp., due to its ability to inhibit pathogen mycelial growth in vitro.