Detection of tobacco rattle tobravirus and potato mop-top pomovirus in Swedish soil samples by the use of different bait plants and analysis by ELISA and biotest.

Abstract: Tobacco rattle tobravirus (TRV) and potato mop-top pomovirus (PMTV) are two known viruses in Sweden which impair the quality of potato tubers by causing spraing. This experiment aimed at finding the best bait plants (plants that is susceptible to infection) for acquiring virus particles from soil, and to analyse the acquired viruses by both ELISA and biotest. The results were finished after 8 weeks with findings that indicate differences in the ability of acquiring virus particles between the bait plants. Nicotiana clevelandii and N.debneyi seem to be the best bait plants to use. These plants were able to acquire both plant viruses in high concentrations. ELISA results also verify that the vector for PMTV, Spongospora subterranea f.sp. subterranea, and the vector for TRV, Trichodorus/Paratrichodorus were present in the soil. Another interesting discovery was that the only positive result of PMTV was found in soil samples that had been dried for at least two weeks. This could be confirmed by later tests that were made on a new batch of soil samples. Five different indicator plants (plants that develop symptoms after inoculated with virus) were used for the biotest and out of these Chenopodium amaranticolor and C.quinoa seem to be the best to use because of the clearly visible local lesions that were easy to count. The biotest results were compared to the ELISA results and the plants that showed local lesions matched with positive ELISA values but the amount of lesions could not be correlated to high or low ELISA values. A combination of these techniques could be used in future work to increase the certainty of the diagnosis.