An approach to field screening potato genotypes for potato leaf roll virus resistance

Eight potato cultivars and two advanced breeder selections were assessed for field resistance to the potato leaf roll virus (PLRV) following field exposures in which PLRV-infected Russet Burbank plants were used as inoculum sources within treatments. This screening protocol provided consistent PLRV resistance ratings despite year-to-year variation in PLRV pressure. Secondary disease incidence based on enzyme-linked immunosorbent assay (ELISA) of foliage from tuber progeny ranged from 0–87% in 1990 and 0–67% in 1991, and was consistent with reported PLRV resistance ratings for eight of ten genotypes. Agreement between visual assessment and ELISA on plants from harvested tubers was 94% in 1990 and 83% in 1991, for all genotypes. However, agreement data were inconsistent from year-to-year, with the exception of three genotypes. In both years, current season infection, based on ELISA of foliage, was detected in less than two percent of the plants and, was inadequate as a measure of secondary PLRV incidence. Green peach aphid (GPA) populations did not differ among genotypes at sampling times during the season, but the PLRV concentration in GPA colonizing Russet Burbank plots was significantly higher than in GPA colonizing any other genotype.