Survival of Alternaria alternata during anaerobic digestion of biomass in stirred tank reactors.

The survival of Alternaria alternate during anaerobic digestion was investigated in context of a joint research project. The aim of this project was to estimate the phytosanitary risk of dissemination of pathogens by returning treated biomass as organic fertilizer to arable land. The studies were carried out in lab-scale stirred tank reactors under mesophilic conditions. After insertion of infected plant material into the reactors the influence on the viability of the fungal pathogen was studied concerning exposure time, pretreatment and storage of the digestates for four weeks or six months. The results clearly showed that anaerobic digestion leads to a complete inactivation of A. alternate already after an exposure time of six hours.

Control of mechanical viroid transmission by the disinfection of tables and tools.

Viroids are of practical importance as the cause of several economically significant infectious diseases. Potato spindle tuber viroid (PSTVd) causes severe yield losses in several crops, because the pathogen spreads fast within the culture. Viroids are small molecules, a few hundred nucleotides long, with a high degree of secondary structure. They do not code for any polypeptides and replicate independently of any associated plant virus. Viroids are readily transmitted by contaminated tools and tables. Furthermore PSTVd is transmitted through the pollen and true seed and can remain its infectious activity in seed for long periods. Vector transmission of PSTVd was reported to occur at low frequency. However, the mechanical transmission is the predominant factor and in this case we discuss the efficient disinfection of tools and tables as a main prophylactic trail to avoid viroid transmission. In previous studies we have tested the efficiency of several disinfectants to eliminate virus contamination. This paper demonstrates the efficient disinfection of MENNO-Florades (Menno-Chemie-GmbH, Norderstedt, Germany. A selection of different concentrations of the disinfectant and various times of incubation were applied in regard to practical use. The tests were confirmed by biological assays using suitable indicator plants, tissue print hybridization, gel electrophoresis and by nucleic acid hybridization. It was shown that PSTVd was eliminated when using the determined combination: 2% of the disinfectant while incubating for one minute or alternative 3%, 30 seconds. The possibility of viroid inactivation by a chemical method of disinfection--while plants are not affected--opens a new perspective to control viroid transmission via tools and tables.