Effects of seedborne potato virus Y on Russet Norkotah performance

Research plots were established in 1996 and 1997 at Klamath Falls and Hermiston, Oregon and Tulelake, California to determine: 1) the extent of seedborne PVY spread during the growing season; 2) effects of seedborne PVY on yield and grade of Russet Norkotah; and 3) the economic consequences of varying levels of seedborne PVY infections. A series of 5 treatments evaluated initial PVY infection levels of 1 to 60% in 1996 and 1 to 98% in 1997. Virus spread occurred earlier and was more extensive at Hermiston than at Klamath Falls or Tulelake. Plants derived from PVY-free seed were nearly 100% PVY infected at early senescence at Hermiston. Comparisons of potatoes grown from PVY-free seed versus potatoes grown from seed where initial PVY infection levels were 60% in 1996 and 100% in 1997 showed seedborne PVY infection at these levels reduced U.S. No. 1 yields by an average of 40% at Hermiston, 20% at Tulelake, and 12% at Klamath Falls. Predicted total yield losses were 0.19, 0.12, and 0.08 Mg ha^?1 for each percent of PVY infection at HAREC, IREC, and KES, respectively. Reductions in gross crop value were estimated at 39, 26, and 14%, respectively, based on regression analyses.