Severe hop stunt disease caused by CBCVd and HLVd viroids is one of the worst diseases in hop. In this dissertation, we analyzed the host specificity of CBCVd, tohether with stability, spread and impact of the disease on hop. We developed methods for artificial infection, simultaneous detection and quantification of viroids. Woody nightshade (Solanum dulcamara) was infected with CBCVd and cannabis (Cannabis sativa) with HLVd. Analyzing the stability of CBCVd, the viroid was detected in residues and soil up to one year after the destruction and burial of infected plants. Analyzing the spread of the disease, we determined an 8.5 % rate of spread (no. of symptomatic pants/year) and a 50 % increase in the number of diseased plants in seven years. The impact of the disease on hop yields was negative with pronounced disease symptoms: 10-fold decrease in growth rate, 70 % drop in α-acids, 55 % drop in β-acids, 85 % lower essential oils, 40 % shorter length and up to 70 % lower cone weight. For efficient viroid detection, we developed multiplex methods: mRT-PCR for detection of all 4 hop viroids and endogenous control, and mRT-qPCR for detection of CBCVd, HLVd and HSVd. We next determined the seasonal dynamics and tissue colonization of CBCVd and HLVd in hop. Synergy and a positive correlation were confirmed between the viroids, they accumulated in similar localization patterns with respect to tissue. In leaves and generative organs, the highest titer of viroids was in July and August, in the roots in May. The research determined the biology of the CBCVd, developed methods for artificial infection and detection of viroids, and was the first to analyze the seasonal dynamics of viroids in hop.
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