Anti-PSbMV polyclonal antibody [AP]

Amplification of pea seed-borne mosaic virus (PSbMV) in field pea (Pisum sativum subsp. arvense) seed was studied under near-natural growing conditions at two locations. The level of virus amplification varied significantly from year to year but was not affected by location. High densities of the pea aphid Acyrthosiphon pisum did not increase amplification of the virus in seed in field plots. In field plots, the incidence of seed infection was 4% or less in cultivars Century and Trapper, but it usually was 10-20% in cv. Fortune. In the greenhouse, however, infected plants of cv. Century produced seed with an incidence of 18% infection. In the field the virus was self-limiting. In cvs. Century and Trapper, the level of seed infection at harvest dropped if the infection rate at seeding was 2% or higher. In cv. Fortune, amplification declined as the level of infection at seeding increased, but it did not drop below 1.0 until the level of infection at seeding reached at least 20%. Cultivar susceptibility is more important than self-limitation in affecting transmission and amplification of seed infection. PSbMV is not likely to have a significant effect on field pea production in Manitoba if cultivars such as Century, Trapper, Bellevue, Titan, or Topper are grown, but if cultivars such as Fortune and Express are grown continuously, significant yield reduction could result.

Field experiments examined the effects of sowing field pea seed with different amounts of infection with Pea seed-borne mosaic virus (PSbMV) on virus spread, seed yield, and infection levels in harvested seed. Plots were sown with seed with actual or simulated seed transmission rates of 0.3 to 6.5% (2005) or 0.1 to 8% (2006), and spread was by naturally occurring migrant aphids. Plants with symptoms and incidence increased with the amount of primary inoculum present. When final incidence reached 97 to 98% (2005) and 36% (2006) in plots sown with 6.5 to 8% infected seed, yield losses of 18 to 25% (2005) and 13% (2006) resulted. When incidence reached 48 to 76% in plots sown with 1.1-2 to 2% initial infection, seed yield losses were 15 to 21% (2005). Diminished seed weight and seed number both contributed to the yield losses. When the 2005 data for the relationships between percent incidence and yield or yield gaps were plotted, 81 to 84% of the variation was explained by final incidence and, for each 1% increase, there was a yield decline of 7.7 to 8.2 kg/ha. Seed transmission rates in harvested seed were mostly greater than those in the seed sown when climatic conditions favored early virus spread (1 to 17% in 2005) but smaller when they did not (0.2 to 2% in 2006). In 2007, sowing infected seed at high seeding rate with straw mulch and regular insecticide application resulted in slower spread and smaller seed infection than sowing at standard seeding rate without straw mulch or insecticide. When data for the relationship between final percent incidence and seed transmission in harvested seed were plotted (all experiments), 95 to 99% of the variation was explained by PSbMV incidence. A threshold value of <0.5% seed infection was established for sowing in high-risk zones.