EFFECTS OF BEAN POD MOTTLE VIRUS ON SOYBEAN SEED MATURATION AND SEED-BORNE PHOMOPSIS SPP

Maturation rate, measured as length of late-season growth stage intervals, was studied in diverse soybean genotypes to determine if bean pod mottle virus (BPMV) infection altered the role of plant and seed drydown when seed infection by Phomopsis spp. increased. Foliage symptoms, stunting, and significant yield reductions due to BPMV occurred in all but one of the 12 soybean entries. Pod infection was consistently increased by BPMV, whereas seed infection was significantly increased in genotypes only if the virus infection delayed the rate of seed maturation. BPMV delayed maturity by extending the length of late-season growth stage intervals and increased seed infection in the soybean entries susceptible or moderately resistant to seed diseases. Effects of BPMV on soybean genotypes that matured under the same environmental conditions indicate that initial levels of seed infection are directly related to the rate of pod and seed maturation. Modifications by BPMV in the R7-R8 interval that delayed harvest maturity of soybean entries susceptible and moderately resistant to seed infection were correlated with increases in levels of seedborne Phomopsis spp.