Abstract
Chrysanthemum stunt viroid (CSVd) was inoculated into two chrysanthemum (Chrysanthemum morifolium) cultivars, the CSVd-susceptible cultivar Piato and the CSVd-resistant cultivar Mari Kazaguruma. For CSVd inoculation, grafting and Agrobacterium-mediated inoculation were used. In grafting experiments, CSVd was detectable in Mari Kazaguruma after grafting onto infected Piato, but after removal of infected rootstocks, CSVd could not be detected in the uppermost leaves. In agroinfection experiments, CSVd systemic infection was observed in Piato but not in Mari Kazaguruma. However, agro-inoculated leaves of Mari Kazaguruma accumulated circular CSVd RNA to levels equivalent to those in Piato at 7 days post-inoculation. In situ detection of CSVd in inoculated leaves revealed that CSVd was absent in phloem of Mari Kazaguruma, while CSVd strongly localized to this site in Piato. We hypothesize that CSVd resistance in Mari Kazaguruma relates not to CSVd replication but to CSVd movement in leaves.
Highlights
Viroids are small, circular, highly structured RNAs of approximately 250–400 nt without a proteincoding region
Piato and Mari Kazaguruma plants were inoculated with Chrysanthemum stunt viroid (CSVd) and CChMVd by grafting onto infected Piato
In Piato, CSVd was detected in all tested leaves at 20 days post grafting and the titers reached a plateau at 40 dpg (Figures 2A,B)
Summary
Circular, highly structured RNAs of approximately 250–400 nt without a proteincoding region. They are the smallest infectious agents in plants and cause various symptoms (Diener, 2003). They have been found to infect various economically important crops, including vegetables, field crops, fruits or palm trees and ornamentals, and in sometimes severe symptoms cause significant reduction in productions (Hadidi et al, 2017; Hammond, 2017; Rodriguez et al, 2017; Verhoeven et al, 2017). The biosynthesis of Pospiviroidae is achieved via asymmetric rolling-circle replication in a host nucleus (Flores et al, 2009).
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