Species composition of Trichoderma isolates from the rhizosphere of vegetables grown in Hungarian soils

The species composition of Trichoderma isolates from the rhizosphere of different vegetables collected at different locations in Hungary was examined during this study. Trichoderma strains were isolated from the rhizosphere samples on dichloran-rose bengal medium. After purification of genomic DNA, the PCR amplification of the internal transcribed spacer (ITS1-5.8S rDNA-ITS2) region and its sequence analysis were used for the identification of the isolates at the species level. Altogether, 45 Trichoderma isolates were identified from the examined samples. The detected Trichoderma species were T. asperellum, T. atroviride, T. citrinoviride, T. gamsii, T. hamatum, T. harzianum, T. koningiopsis/T ovalisporum, T. longibrachiatum/H. orientalis, T. pleuroticola and T. virens. Besides species known as opportunistic pathogens of humans (T. longibrachiatum / H. orientalis, T. citrinoviride) or as causative agents of mushroom green mould disease (T. pleuroticola), beneficial taxa (T. harzianum, T virens, T. atroviride) widely used for the biological control of plant pathogenic fungi could also be identified in the examined samples, suggesting that the rhizosphere of vegetables may be a rich source of potential biocontrol agents. In vitro antagonism was examined in dual culture tests and the Biocontrol Index (BCI) values were determined for the particular isolates. Certain T. asperellum, T. virens and T. atroviride isolates proved to possess good in vitro antagonistic activities against plant pathogenic Fusarium solani and F. oxysporum strains, suggesting that they might be promising for the development of Trichoderma-based biocontrol strategies for the suppression of plant pathogenic fungi in the rhizosphere of vegetables produced in organic farmland soils.