Browsing by Person "Sprich, Elke"

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Composting and fermentation: mitigating hop latent viroid infection risk in hop residues
(2024) Hagemann, Michael Helmut; Treiber, Charlotte; Sprich, Elke; Born, Ute; Lutz, Kathrin; Stampfl, Johannes; Radišek, Sebastjan
Hop cultivation, integral to the brewing industry, faces challenges from viroids, especially the citrus bark cracking viroid (CBCVd) but also the hop latent viroid (HLVd) influences hop cone quality. We focused on the degradation kinetics of HLVd thereby covering compost, silage, and digestate made from hop residues. In this study, HLVd serves as a model for understanding CBCVd, which causes significant stunting and yield losses in European hop crops. Composting experiments revealed that although composting significantly lowers HLVd levels, complete degradation within 7 weeks is not guaranteed, with loose compost showing a more rapid reduction than compacted variants. Infectivity experiments conducted using inocula obtained from HLVd-infected hop plant residues exposed to composting, ensiling, and biogas digestate did not result in the transmission of HLVd to viroid-free plants. Also extracting and analyzing the soil-root mixture of plants inoculated with HLVd-infected hop residues did not show evidence for viroid persistence. Degradation experiments further differentiated between the physiochemical and biological influences on viroid and viroid-like random RNA stability, showing that higher temperatures of 50 °C enhance degradation over 40 °C, and pH levels of 5 or 7 are slowing degradation. In contrast deionized water or a pH of 4 or 9 enhances viroid degradation. Adding extracts from digestate accelerated the process indicating a role of biological activity. Interestingly, a viroid-like random RNA with similar physiochemical properties, showed to degrade faster compared to HLVd, suggesting high robustness of the actual viroid secondary structure. These findings offer valuable insights into managing HLVd in hops and potentially other crops, highlighting effective strategies to mitigate viroid spread, and contributing to broader understanding of RNA degradation in agriculture.
Degradation of hop latent viroid during anaerobic digestion of infected hop harvest residues
(2021) Hagemann, Michael Helmut; Born, Ute; Sprich, Elke; Seigner, Luitgardis; Oechsner, Hans; Hülsemann, Benedikt; Steinbrenner, Jörg; Winterhagen, Patrick; Lehmair, Erich
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.