Hop (Humulus lupulus L.) production is threatened by many pathogens, including viroids. Viroid CBCVd causes severe hop stunt disease. For studies of the interactions between the CBCVd viroid and hop cells, we attempted to establish suspension cultures of three hop cultivars, Celeia, Styrian Cardinal, and Styrian Wolf. The initiation of suspension cultures of the Styrian Cardinal cultivar was unsuccessful. We have successfully established suspension cultures of cultivars Celeia and Styrian Wolf. Dimeric in vitro transcripts of viroid CBCVd were used for establishing infected suspension cultures. We sought to determine the effects of CBCVd infection on cell viability and biomass accumulation. No differences in cell viability and biomass accumulation were observed between viroid-free and CBCVd-infected cell suspension cultures. RT-qPCR was used to confirm the presence of CBCVd RNA in samples from suspension cultures. The RT-qPCR results indicate that we successfully infected cells in suspension cultures of the susceptible cultivar Celeia and the cultivar Styrian Wolf, which is among the supposedly resistant cultivars. By regularly sampling biomass from infected suspension cultures of Celeia cultivar, we determined the occurrence of viroid RNA of negative polarity. Results indicate that synthesis of the negative strands of the viroid CBCVd begins in the cells of the suspension cultures at approximately two weeks postinfection. By establishing suspension cultures infected with the viroid CBCVd, we obtained a model to study the interactions between hop cells and the CBCVd viroid.
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