Seed Coat Mottling in Food-Grade Soybean Cultivars in Response to Infection with BPMV and SMV.

In 2007, some lots of food-grade soybeans in the mid-Atlantic growing region were unusable due to seed coat mottling, presumably from virus infection. Anecdotal evidence suggests bean pod mottle virus (BPMV) incidence has increased in the same region in recent years. In 2008 the 74 entries (MG V and VI) in a regional food-grade large- and small-seeded soybean cooperative yield test were planted in three blocks with a soybean mosaic virus (SMV) inoculated treatment, BPMV inoculated treatment, and an uninoculated treatment and seeds were harvested at maturity. Blocks were scored visually for foliar symptoms of virus, and seeds were scored for percent of mottled seeds, degree and color of seed coat mottling, and seed size and quality. Thirty-four lines were resistant to SMV, but all lines were susceptible to BPMV with differential disease severity. Data were analyzed using ANOVA, Student's t-test, and PROC CORR, with data from lines resistant to SMV removed where needed to normalize the data set. Lines VS03-622, VS03-709, and TC02AXB-717 were resistant to SMV, and had very few percent mottled seeds in the BPMV treatment. Mean percent of mottled seeds was 59.9% in the BPMV treatment, 22.2% among susceptible lines in the SMV treatment, and 2.4% in the uninoculated treatment. Virus treatments significantly reduced seed quality but not seed size compared to the uninoculated treatment. Hilum color among lines ranged from yellow, to buff, to brown, to black but was not a significant source of variation for percent of mottled seeds, or degree and color of seed mottling. Seed size was not correlated with seed mottling symptoms. Severity of seed mottling was not correlated with foliar symptoms for either virus treatment, or both considered together. Resistance to SMV, or reduced SMV seed mottling and foliar symptoms among susceptible lines, were not associated with reduced BMPV seed mottling. Resistance or susceptibility to SMV foliar symptoms was a significant (P<0.05) source of variation for BPMV foliar symptoms