Hilum bleeding as a diagnostic method for estimating percent soybean mosaic virus or bean pod mottle virus occurrence in soybean seed: Variety Bolivar as a case study

In 2000 and 2001, four greenhouse and two field studies were conducted at the Rodney R. Foil, Plant Science Research Farm, Mississippi State University, MS to determine if the seed symptom hilum bleeding, in the soybean variety Bolivar, indicates the presence or survival of Soybean mosaic virus (SMV), or Bean pod mottle virus (BPMV). Treatments were selected based on the percent of hilum bleeding within seven seed lots including: <1 (control), 1, 2, 4, 25 (trt. 2x) and 35%, per year. The treatments were further subdivided in the greenhouse studies based on severity of hilum bleeding including: none, intermediate hilum bleeding, and severe hilum bleeding. Stand counts, plant heights, visual disease ratings, enzyme-linked immunosorbent assay (ELISA), and electron microscopy (EM) data were used to compare the seven treatments. The results from the stand counts, plant heights, and visual disease ratings did not show any association with differences in percent hilum bleeding of the seed lots. When differences did occur, no trends were noted. Furthermore, only one plant tested positive for SMV in the greenhouse or field studies but in the field 59% tested positive for BPMV. In the greenhouse only one plant from the study tested positive for BPMV. It was observed that insect feeding caused transmission of BPMV from symptomatic plants growing outside the field study area. Results from all field, greenhouse, and laboratory investigations indicate that hilum bleeding, regardless of percent within a seed lot, does not indicate the presence or survival of SMV or BPMV in Bolivar soybean seeds.