Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/26/2004
Publication Date: 1/15/2005
Citation: Harrison, B., Steinlage, T.A., Domier, L.L., D'Arcy, C.J. 2005. Incidence of soybean dwarf virus and identification of potential vectors in Illinois. Plant Disease. 89:28-32. Interpretive Summary: Soybean dwarf virus (SbDV) is closely related to Barley yellow dwarf virus, which has had a very significant impact on small grain production worldwide. Both viruses are transmitted by aphids in a persistent manner, which means that aphids retain the ability to transmit the viruses for days after feeding on an infected plant. Even though SbDV produces very severe yield losses in soybeans in Asia and is common in clovers growing next to soybean fields in the US, SbDV rarely infects soybean plants in the US. The inability of the SbDV to move from clovers to soybeans has been attributed to the absence of aphid vectors that colonize soybeans and have the ability to transmit the virus. In the summer of 2000, the Asian soybean aphid was reported in North America for the first time. These highly mobile aphids colonize soybeans and have been reported to transmit several viruses. To gauge the potential of endemic SbDVs to cause disease in Illinois, we determined the distribution of SbDVs in Illinois and evaluated the abilities of five aphid species, including the Asian soybean aphid, to transmit SbDV from infected clovers to soybean. We found that almost half of the red clover plants tested were infected with SbDV and that two aphid species native to North America that do not colonize soybean transmitted SbDV poorly from clover to soybean, but no transmission of SbDV by the Asian soybean aphid was detected. These findings suggest that the Asian soybean aphid will not be an important vector of SbDV in the US unless new virus strains or aphid biotypes appear. The information in this paper should be useful to other scientists who are studying virus epidemiology and distribution and aphid transmission of plant viruses.
Technical Abstract: Soybean dwarf virus (SbDV) causes an important disease of soybeans in Japan and is persistently transmitted by aphids. SbDV has been shown to be endemic in forage legumes in the United States. In 2000, Aphis glycines, an aphid species that colonizes soybeans, was reported in the Midwest. In 2001, we surveyed six species of clovers in 33 counties in the state of Illinois and tested them for the presence of SbDV by triple antibody sandwich enzyme-linked immunosorbent assay and polymerase chain reaction. We detected SbDV only in red clover (Trifolium repens), in 62% of the plants sampled. We also analyzed 981 soybean plants collected in Illinois in 2001, and 360 plants collected in 2002, but none tested positive for SbDV. We conducted transmission studies with aphid species that were found colonizing clover and soybean plants. Aphids of the species Nearctaphis bakeri and Aphis craccivora vectored SbDV among red clovers, and N. bakeri transmitted SbDV from red clover to soybean. However, A. glycines did not transmit SbDV; neither did two other clover-infesting aphid species, Acyrthosiphon pisum and Therioaphis trifolii.