The citrus bark cracking viroid (CBCVd) was identified as causal agent for a severe stunting disease in hops. Viroids are highly stable parasitic RNAs, which can be easily transmitted by agricultural practices. Since CBCVd has recently been detected in two European countries a growing concern is that this pathogen will further spread and thereby threaten the European hop production. Biogas fermentation is used to sanitize hop harvest residues infected with pathogenic fungi. Consequently, the aim of this study was to test if biogas fermentation can contribute to viroid degradation at mesophilic (40 °C) and thermophilic (50 °C) conditions. Therefore, a duplex reverse transcription real-time PCR analysis was developed for CBCVd and HLVd detection in biogas fermentation residues. The non-pathogenic hop latent viroid (HLVd) was used as viroid model for the pathogenic CBCVd. The fermentation trials showed that HLVd was significantly degraded after 30 days at mesophilic or after 5 days at thermophilic conditions, respectively. However, sequencing revealed that HLVd was not fully degraded even after 90 days. The incubation of hop harvest residues at different temperatures between 20 and 70 °C showed that 70 °C led to a significant HLVd degradation after 1 day. In conclusion, we suggest combining 70 °C pretreatment and thermophilic fermentation for efficient viroid decontamination.

柑橘树皮开裂类病毒 (CBCVd) 被确定为啤酒花中严重发育迟缓病的病原体。类病毒是高度稳定的寄生 RNA，很容易通过农业实践传播。由于最近在两个欧洲国家检测到 CBCVd，人们越来越担心这种病原体会进一步传播，从而威胁欧洲啤酒花生产。沼气发酵用于消毒感染病原真菌的啤酒花收获残留物。因此，本研究的目的是测试沼气发酵在中温 (40 °C) 和高温 (50 °C) 条件下是否有助于类病毒降解。因此，开发了一种用于沼气发酵残留物中 CBCVd 和 HLVd 检测的双链逆转录实时 PCR 分析。非致病性啤酒花潜伏类病毒 (HLVd) 用作致病性 CBCVd 的类病毒模型。发酵试验表明，HLVd 在中温条件下 30 天后或在高温条件下 5 天后显着降解。然而，测序显示即使在 90 天后 HLVd 也没有完全降解。在 20 到 70 °C 之间的不同温度下培养啤酒花收获残留物表明，70 °C 导致 1 天后 HLVd 显着降解。总之，我们建议将 70 °C 预处理和高温发酵相结合，以实现有效的类病毒去污。测序显示，即使在 90 天后，HLVd 也没有完全降解。在 20 到 70 °C 之间的不同温度下培养啤酒花收获残留物表明，70 °C 导致 1 天后 HLVd 显着降解。总之，我们建议将 70 °C 预处理和高温发酵相结合，以实现有效的类病毒去污。测序显示，即使在 90 天后，HLVd 也没有完全降解。在 20 到 70 °C 之间的不同温度下培养啤酒花收获残留物表明，70 °C 导致 1 天后 HLVd 显着降解。总之，我们建议将 70 °C 预处理和高温发酵相结合，以实现有效的类病毒去污。