In the beginning of the 1970’s, the occurrence of soil-borne viruses in 30 Finnish nurseries and experimental fields of garden plants at 3 research stations was mapped. Viruses were isolated on 26.9 % of the 672 plant and soil samples collected. The two most commonly found viruses were tobacco necrosis virus (TNV), 42.5 %, and tobacco rattle virus (TRV), 23.7 %. Tomato black ring virus (TBRV) and raspberry ringspot virus (RRSV) were isolated for the first time in Finland. The abundant occurence of TBRV in 32 samples was due to the abundance of Phlox paniculata samples. RRSV was isolated from only a few samples. The vectors of all of the above-mentioned viruses were found in many samples. The fungus vector of TNV, Olpidium brassicae, was investigated by examining the roots microscopically. The vector of TRV, the Trichodorus sp. nematodes, and the vector of TBRV and RRSV, the Longidorus sp. nematodes, were isolated from soil samples. In addition to the foregoing, tobacco mosaic virus was isolated from 31 samples of 6 nurseries and 2 experimental fields. Viruses were isolated from many weed samples, especially from roots of Senecio vulgaris and Stellaria media. Perennials proved to be virotic. All of the above mentioned viruses, especially TBRV and TRV, were isolated from Phlox paniculata; TBRV was also found in an Astilbe x arendsii sample. Dicentra spectabilis, like Phlox, was commonly infected with TRV. No clear results could be obtained from control experiments.
Transmission of Tobacco Necrosis Virus by Zoospores of Olpidium brassicae
