ABSTRACT
Totals of 960 and 286 certified potato seed lots from locations across North America were planted in trials in Washington and Oregon, respectively, in 2001 to 2003 and tested for strains of Potato virus Y (PVY). The incidence of PVYO-infected lots averaged 16.4 and 25.9% in the Washington and Oregon trials, respectively. There was a general trend of increasing incidence of the PVYO, PVYN:O, and PVYN strains during this period, as evidenced by more infected cultivars, sites of seed origin, and number of seed growers providing infected seed lots. In particular, there was a dramatic increase in seed lots with the PVYN:O strain from 2002 to 2003. PVYN:O, in contrast to PVYO, which only causes yield reduction, also causes internal and external damage to tubers, making them unmarketable. In 2003, PVYN:O occurred in seed lots originating in eight states and three Canadian provinces. The increased incidence of PVYN:O was likely due to the difficulty in differentiating this strain from PVYO. The prevalence of PVY in potato seed lots documented herein poses a threat to potato production in the United States and suggests that current measures to reduce the incidence of this virus are inadequate.
ABSTRACT
Tuber yield and quality of cv. Russet Norkotah potato plants grown from seed infected with potato leaf roll virus (PLRV) were compared with tuber yield and quality of adjacent plants grown from virus-free seed. Plants from PLRV-infected seed produced at least 60% less total yield and 88% less marketable yield (tubers >85 g) than plants grown from healthy seed. PLRV-infected seed also produced plants with fewer and smaller tubers than plants grown from healthy seed. No compensatory yield was measured in plants grown from PLRV-free seed growing adjacent to plants from PLRV-infected seed.
ABSTRACT
The effects of seedborne potato virus Y (PVY) in Shepody and Russet Norkotah, two new cultivars that express mild disease symptoms, were determined by comparing tuber yield and specific gravity of plants grown from PVY-infected seed with those of adjoining plants grown from virus-free seed. Seedborne PVY-infected Shepody plants produced 28.7% less total yield in 1994, and 41.1 and 47.3% less in two trials in 1995. Marketable yield was reduced 55.8 and 79.4% in 1995 trials. PVY infection did not affect specific gravity in Shepody. Seedborne PVY infections in Russet Norkotah reduced total yield by 45.5 and 48.8% in the 1994 and 1995 trials, respectively. During the 1995 trial, marketable yield from seedborne infected plants was reduced 65.1% compared with adjacent plants grown from noninfected seed. Additionally, specific gravity was lower for tubers from seedborne infected Russet Norkotah plants than from plants grown from noninfected seed in 1994. Seedborne infected plants of both varieties had fewer and smaller tubers than did plants grown from virus-free seed. No compensatory yield increase was measured for plants originating from PVY-free seed and growing adjacent to seedborne infected plants for either variety. Rather, yield reduction was observed in Russet Norkotah plants growing adjacent to seed infected plants in 1995. Enzyme-linked immunosorbent assay (ELISA) on Shepody in 1995 showed most plants grown from PVY-free seed became infected within 6 weeks of emergence.
