EN
Tomato black ring virus is a quarantine pathogen of many plants worldwide. In Institute of Plant Protection – National Research Institute we collected several TBRV isolates from zucchini, tomato, potato and Robinia pseudoaccacia L. They have single stranded RNA genomes of positive polarity that are divided into two genomic RNAs. Moreover, the presence of defective RNA (D-RNA) associated TBRV was observed. Defective RNAs arise from some viral genomes during prolonged incubation into a host species. In addition, defective interfering RNA (DI-RNA) can modulate virus symptoms, accumulation and replication as well as other important functions therefore influence virus evolution. The serial passage in Chenopodium quinoa of two TBRV isolates TBRV-L1 (obtained from robinia) and TBRV-KC (from zucchini) resulted in arising small RNA in case of TBRV-L1. It was also associated with milder symptoms induced by virus. It indicated the interfering character of small RNA observed. In case of TBRV-KCV after 24 passages no additional bands were observed in gel electrophoresis.