Browsing by Subject "Risk assessment"

Now showing 1 - 2 of 2

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.
Rubber production in Continental Southeast Asia
its potentialities and limitations
(2019) Golbon, Reza; Sauerborn, Joachim
This thesis focuses on three climate-related aspects of Para rubber (Hevea brasiliensis) cultivation in areas where altitudes and latitudes higher than its endemic range create conditions which are labeled nontraditional, suboptimal or marginal for rubber cultivation: 1. rubber yield in relation to the meteorological conditions preceding harvest events, 2. potential geographical shifts in rubber cultivation through climate change and 3. assessment of climate driven susceptibility to South American leaf blight (Pseudocercospora ulei) of rubber.