Screening of native Trichoderma harzianum isolates for their ability to control verticillium wilt of strawberry

In this research, the antagonistic potential of native Trichoderma harzianum isolates toward important strawberry pathogen Verticllium dahliae was studied. For this purpose, fungi were isolated from the rhizosphere and soil from five different strawberry production sites in Estonia over two growing seasons and were investigated under laboratory and greenhouse conditions. T. harzianum colonies were recovered using a selective medium after 12 days and confirmed through species-specific primers. In the laboratory, although all isolates of Trichoderma produced volatile and non-volatile metabolites, seven isolates which had the strongest inhibitory effects on mycelial growth of pathogen were selected for greenhouse assays. In the greenhouse, the disease severity was measured in a split plot treatment design with seven antagonist isolates applied to the two main treatment factors (soil and root), in which all levels of each factor were used in combination with all other factor levels. The result of greenhouse experiments showed that there was no significant difference among T. harzianum treatments but, among selected T. harzianum isolates, TU79 was the most effective isolate for inhibiting the effects of strawberry Verticillium wilt. In the cross-interaction between the antagonist isolates and their treatments, the minimum disease severity was significantly recorded when both soil and roots were treated with TU79 isolate. However, there was no statistically significant difference when this isolate was applied to the soil alone. The results of this study demonstrated that native T. harzianum isolates collected from Estonian fields have potential biocontrol ability so that they may be extensively used to control Verticillium wilt in strawberry nurseries. © 2016, Lithuanian Institute of Agriculture. All rights reserved.