Transmission of bean pod mottle virus in soybeans and effects of irregular distribution of infected plants on plant yield

Factors affecting bean pod mottle virus (BPMV) progression in soybeans and the effect of plants escaping virus infection on yield reduction were investigated. In 1980, 4 wk after inoculation with BPMV, rows of tall soybean genotypes (120 cm) adjacent to rows of relatively short genotypes (85 cm) had 35 percent more symptomatic plants than adjacent short lines. Differences became less as the season progressed. In 1982, tall lines (100 cm) next to short lines (78 cm) had a significantly higher number of BPMV-infected plants than adjacent short lines whereas no differences in BPMV disease incidence were found in adjacent soybean lines that were similar in plant height. Disease incidence within soybean cultivars Ransom and Centennial planted on 25 June 1982 increased two to three times faster than within these cultivars planted on 11 May. Virus spread within rows appeared to be nonrandom at the beginning of the epidemic and became random as the epidemic progressed. Individual Centennial and Ransom soybean plants without virus symptoms adjacent to BPMV infected-plants yield 50 and 16 percent more, respectively, than did healthy plants adjacent to other healthy plants