Potato Leafroll Virus: Evaluation of Resistance in Potato Cultivars. R. H. Bagnall, Research Scientist, Agriculture Canada Research Station, Fredericton, NB, Canada E3B 4Z7. G. C. C. Tai, Research Scientist, Agriculture Canada Research Station, Fredericton, NB, Canada E3B 4Z7. Plant Dis. 70:621-623. Accepted for publication 16 January 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-621.

Thirty-six potato cultivars tested in the field for resistance to potato leafroll virus (PLRV) at Fredericton, NB, from 1972 through 1981 were separated into four resistance groups by Scott-Knott cluster analysis. Susceptible groups A (47.4–55.0% infection) and B (26-39.8%) and moderately resistant group C (11.6–24.8%) differed significantly from the resistant group D (0–4.4%) in a supplementary Duncan’s multiple range test. An additional 21 commercial cultivars and numerous seedlings from the Fredericton breeding program, which were in the trials for 5–9 of the 10 yr, could be classified by comparison with these four groups. Comparisons with official Dutch lists indicate that under higher selection pressure, group D cultivars could be split into several further categories. Through development and use of high-quality group D cultivars, PLRV could be reduced drastically in the northeastern seed-growing areas (Maine and New Brunswick). Even the moderate resistance of group C cultivars could temper the infrequent PLRV epidemics that occur in this area, but displacement of the PLRV-susceptible Russet Burbank, widely grown for french fry processing, is a formidable task for breeders.