Investigations on potato mop-top furovirus in Sweden1

Potato mop-top furovirus (PMTV) was isolated for the first time in Sweden in 1985. During 1986 and 1987, soil samples from potato fields, mainly in the south-west of Sweden, were tested for PMTV. The virus was detected in 49 out of 305 samples tested. PMTV was also found to be present in soil collected from potato riddles during potato grading in early spring. The soil samples were tested by using Nicotiana clevelandii and N. debneyi as bait plants in a glasshouse. Seven potato cultivars were grown in a PMTV-infested field. PMTV symptoms in the tubers, i.e. external and/or internal brown rings and arcs (spraing), were observed in cvs Evergood, Provita, Saturna and Ukama but not in cvs Bellona, Bintje or King Edward. Very few, or no, PMTV symptoms were found in tubers of susceptible cultivars when examined 2-3 weeks after lifting. In later examinations spraing appeared and increased. The increase was greater in tubers stored at 9°C than in those at 4°C, and in cut than in uncut tubers.