Department of Plant Pathology, The Ohio State University, Wooster, Ohio
Department of Plant Pathology, University of Wisconsin, Madison
Soybean has been increasing in importance and acreage over wheat and corn for the past decade in Ohio and is now planted on 4.5 million acres. Previous surveys in Ohio of viruses infecting soybean failed to identify Bean pod mottle virus (BPMV) and soybean virus diseases have rarely caused economic losses (1). During 1999, producers in Ohio noticed virus-like symptoms in soybeans in a few isolated locations. Soybeans with green stems, undersized and “turned up pods” were collected from Union, Wood and Wyandot Counties during October 1999 and soybeans with crinkled, mottled leaves were collected in Henry, Licking and Sandusky during August 2000. Five to six plants were collected from a single field from each county each year. In 1999, samples were sent to the University of Wisconsin-Madison, where one symptomatic leaflet/sample was ground in 3 ml of chilled phosphate buffered saline (pH 7.2). Leaf sap was placed in 1.5-ml centrifuge tubes and stored at 4°C for 24 h. Sap was assayed for the presence of BPMV using an alkaline phosphatase-labeled double-antibody sandwich enzyme-linked immunosorbent assay (DAS ELISA) for BPMV (AgDia Inc., Elkhart, IN). All samples tested were positive for BPMV. Samples collected in 1999 were also maintained at The Ohio State University in Harosoy soybean and in 2000 assayed serologically along with samples collected in 2000 for BPMV and Soybean mosaic virus (SMV) by ELISA and for Tobacco ringspot virus (TRSV) and Bean yellow mosaic virus (BYMV) by a host-range symptom assay; SMV, BYMV and TRSV had been identified from soybean in previous Ohio surveys. Soybean leaf samples were assayed using F(ab′)2-Protein A ELISA with antiserum prepared in 1968 to a southern U.S. isolate of BPMV and to an Ohio isolate of Soybean mosaic virus (SMV) prepared in 1967, both stored at −20°C. Diseased and non-symptomatic soybean leaf samples were ground in 4 ml 0.025M Tris pH 8.0, 0.015M NaCl and 0.05% Tween 20. Extracts were tested for BPMV and SMV by ELISA following a protocol described elsewhere (2). All of the samples collected during 1999 and maintained in the greenhouse tested positive for both BPMV and SMV while all of those samples collected during 2000 tested positive for BPMV and negative for SMV. Host-range symptom assays were conducted with leaf extracts prepared by grinding 1 g tissue:10 ml potassium phosphate buffer, pH 7.0. Extracts were inoculated by leaf rub method to Harosoy soybean, Phaseolus vulgaris cvs. Red Kidney and Bountiful, cowpea, and cucumber. The host-range symptom assays of both the 1999 and 2000 samples were negative for TRSV and BYMV; cowpea failed to express local lesions and cucumber systemic mosaic characteristic of TRSV infection and the two Phaseolus cultivars the yellow mosaic characteristic of BYMV infection. These results indicate that both BPMV and SMV were present in the samples in 1999 but only BPMV in 2000. The distribution of BPMV within Ohio and economic impact of this virus have yet to be determined. This is the first report of BPMV in Ohio.
References: (1) A. F. Schmitthenner and D. T. Gordon. Phytopathology 59:1048, 1969. (2) R. Louie et al. Plant Dis. 84:1133--1139, 2000.