For resistance evaluation, we used
the method of inoculation of tuber sprouts with fresh warts, containing
summer sporangia (Fig. 1). The procedure of inoculation and scale for
resistance evaluation were the same as described above for pathotype
determination. Results of resistance evaluation are considered authentic
if disease developed on not less than on 75% of tubers of the
susceptible cultivars Lorkh or Liza. The number of tubers per
replication and the number of replications depended on the availability
of tuber material (Table 1), but when possible we used ten tubers of
each accession per replication. We conducted two independent
replications for 19 potato accessions, three for 20 accessions, four
for 10 accessions, five for two accessions and six replications for one
accession. Average means for each replication were counted. If the
results of replications were different, the group of resistance was
determined on the basis of the maximum score in any replication.