Quality of harvested seed associated with soybean cultivars and herbicides under weed-free conditions

Different herbicides were applied to soybean plants in field plots planted to different soybean cultivars located at four locations in Illinois between 1997 and 2000. Treatments varied from hand weeded to preemergence herbicides to postemergence herbicides. Soybean seeds were harvested and evaluated for different seed quality parameters. The percentage of seeds infected with Phomopsis spp. ranged from 1 to 40%, and the percentage of seeds infected with Cercospora kikuchii was low, ranging from 0 to 4%. Herbicides had little or no effect on seed quality parameters such as percent germination and incidence of seed pathogens or on protein and oil concentrations. Soybean seed quality was affected by Phomopsis spp. in that there were significant (P ≤ 0.05) inverse correlations between Phomopsis spp. incidence and percentage seed germination. It appears that Phomopsis spp. may be a more prevalent seed pathogen than C. kikuchii for soybean fields in central to northern Illinois.