Evaluation of indigenous Trichoderma spp. isolates in biological control of Botrytis cinerea, the causal agent of strawberry gray mold disease

Gray mold caused by Botrytis cinerea is the most important disease of strawberry in the greenhouse and in the field worldwide. The disease is also a serious problem during storage, transit and marketing stages. Nowadays, fungicide application is the most common strategy to control this disease. Consequently, strawberries are among the crops which may be contaminated with pesticide residues. Public concern about such residues in edible products and the environment, augmented by the practical problems arising from fungicide resistance in pathogen, has accelerated the search for the safe and effective alternative disease control strategies. One of the alternative strategies for the replacement of chemical methods could be biological control. Trichoderma species are ubiquitous fungi in soil with antagonistic activity against several plant pathogens. This study aimed to evaluate potential of indigenous Trichoderma strains against B. cinerea in in vitro and in the greenhouse. In dual culture tests, the majority of Trichoderma strains overgrew on B. cinerea colony with a high sporulation. More than 66% of strains were considered to be antagonists against B. cinerea. Furthermore, most strains were more or less capable of lysing sclerotia of the pathogen. The volatile metabolites of all Trichoderma strains significantly reduced the mycelial growth of the pathogen but, the inhibition rate was not above 55%. Culture filtrates of all strains at two concentrations significantly prevented the mycelial growth with maximum rate of 71% and 85% for 1 and 6 ml concentrations, respectively. The results obtained in the greenhouse experiments showed that disease infection was decreased in all treatments comparing to contro. Meanwhile, lowest and highest disease incidence (53.5 and 70.7%) was recorded for T. harzianum MS6-2 and TRICHO-MIX HV, respectively.