The effects on adventitious root formation caused by chrysanthemum stunt viroid in Chrysanthemum morifolium and C. seticuspe

Chrysanthemum stunt viroid (CSVd) is a disease agent caused by a viroid from the genus Pospiviroid. The CSVd pathogen infects chrysanthemum plants and causes severe symptoms of stunting and significant yield loss in cultivation. Although many studies have focussed on this issue, the mechanism of CSVd‐infection remains to be clarified. In particular, the effects of CSVd on the underground parts of infected plants are not yet fully understood in Chrysanthemum. Here, we investigated whether the effects of CSVd on the root formation of infected plants varies among cultivars and wild Chrysanthemum species, C. morifolium and C. seticuspe, using transcribed RNA and in vitro assays. Furthermore, to compare infected plants with uninoculated plants, we assessed the symptoms and measured the CSVd RNA accumulation levels in several tissues using RT‐qPCR. Our findings indicated that CSVd‐infected plants exhibited severe root formation symptoms in both C. morifolium and C. seticuspe. RT‐qPCR revealed CSVd accumulation in the root tips and similar patterns of CSVd accumulation in each organ of C. morifolium and C. seticuspe. We propose that in vitro assays are useful for determining root formation in CSVd‐infected chrysanthemum plants. Such investigations are necessary to better understand CSVd infection in Chrysanthemum species and plant defences against such diseases.