High performance of Amazonian Trichoderma strains in the control of southern blight caused by Sclerotium rolfsii in tomatoes

Abstract

The Trichoderma genus is considered one of the most promising in the control of phytopathogens. The mechanisms of antagonism that are common among Trichoderma species are mycoparasitism and competition for space and nutrients. Some species also show antibiosis through the production of secondary metabolites with antimicrobial activity, lytic enzymes and volatile compounds. Trichoderma species-mediated biocontrol can be exerted by indirect mechanisms such as induction of resistance. In the search for efficient isolates of Trichoderma spp. for the biological control of southern blight in tomato plants (Solanum lycopersicum), 33 isolates were evaluated for the Sclerotium rolfsii mycelial growth inhibition (MGI) via a dual culture method and for incidence of disease reduction in tomatoes (Yoshimatsu L-3 cultivar) under greenhouse conditions. The experiment was with five isolates that showed the best results in the biocontrol of southern blight, and these isolates were identified via phylogenetic analysis based on partial sequencing of the tef1-α gene. Three isolates completely inhibited the disease symptoms, namely, INPA 2473 (T. endophyticum), INPA 2951 (T. asperelloides) and INPA 2957 (T. rugulosum); while the T. asperellum isolates INPA 2959 and INPA 2961 reduced the disease incidence to 6.6 and 13.33%. Although all the isolates showed a mycelial growth inhibition rate of over 50%, curiously, the isolates with the best performance in the dual culture assays were not the best at controlling the disease under greenhouse conditions. In addition, this work reports new record of Trichoderma rugulosum in Brazil.