Hill J H, Alleman R, Hogg D B, Grau C R
Department of Plant Pathology, Iowa State University, Ames 50011.
Department of Entomology, University of Wisconsin, Madison 53706.
Plant Dis. 2001 May;85(5):561. doi: 10.1094/PDIS.2001.85.5.561C.
The recent discovery of the soybean aphid, Aphis glycines Matsamura, in the North Central region of the United States is significant because it is the first time that a soybean-colonizing aphid has been detected in the New World. Although the aphid has the potential to cause physiological loss of up to 52% on soybeans (4), it can also transmit Soybean mosaic virus (SMV). Transmission of Alfalfa mosaic virus (AMV) has not been reported. SMV, and less commonly AMV, are found in soybeans in the North Central states and are transmitted by numerous aphids in a nonpersistent manner (2; Grau, unpublished). For SMV, potential exists for specificity of transmission between virus strain and aphid species (3). For these reasons, it was important to determine if an endemic isolate of these viruses could be transmitted by this introduced species of aphid in the North Central region. Transmission experiments were conducted as described (3), using 3, 5, and 10 aphids per plant. Ten plants of the soybean cultivar Williams 82 were used for each treatment. To preclude confounding results by possible seed transmission, plants used in all tests were grown from seeds harvested from virus-indexed plants grown in the greenhouse. For experiments involving SMV, the aphid-transmissible field isolate Al5 (GeneBank Accession no. AF242844) and, as a negative control, the non-aphid transmissible isolate N (GeneBank Accession no. D500507) were used. For experiments involving AMV, a field isolate of AMV, confirmed by ELISA and host range, was used. The aphid species Myzus persicae was maintained on broad bean and A. glycines was maintained on virus-free soybean. The protocol for transmission studies of AMV was identical to that used in the SMV study, except only A. glycines was tested. For experiments, plants were periodically observed for symptom development and tested by ELISA 4 to 5 weeks after inoculation access. No transmission of SMV-N occurred in any tests, which together involved 180 aphids each of M. persicae or A. glycines. For the Al5 isolate, transmission efficiencies of 30, 50, and 50% were obtained with 3, 5, and 10 individuals, respectively, of M. persicae per plant. Efficiencies for A. glycines were 30, 40, and 40%. Transmission levels by the two aphid species did not differ significantly (t-test, P = 0.01). For AMV, corresponding transmission efficiencies were 0, 0, and 20%. The data suggest that the introduced A. glycines can be an efficient vector of SMV, but a less efficient vector of AMV, in the North Central region. Transmission of AMV by M. persicae has been documented (1) but was not examined in this study. Transmission of SMV and AMV by A. glycines is of concern because it may increase SMV and AMV incidence. With the recent outbreak of Bean pod mottle virus (BPMV) in the region, the potential for synergism of SMV and BPMV is increased (2). References: (1) M. B. Castillo and G. G. Orlob. Phytopathology 56:1028, 1966. (2) G. L. Hartman et al., eds. 1999. Compendium of Soybean Diseases, 4th Ed. American Phytopathological Society, St. Paul, MN. (3) B. S. Lucas and J. H. Hill. Phytopathol. Z. 99:47, 1980. (4) C. L. Wang et al. Plant Prot. 20:12, 1994.
近期，美国中北部地区发现了大豆蚜（Aphis glycines Matsamura），这一发现意义重大，因为这是在新大陆首次检测到能在大豆上定殖的蚜虫。尽管这种蚜虫有可能使大豆生理损失高达52%（4），它还能传播大豆花叶病毒（SMV）。苜蓿花叶病毒（AMV）的传播情况尚无报道。SMV在中北部各州的大豆中存在，较少见的是AMV，它们由多种蚜虫以非持久性方式传播（2；Grau，未发表）。对于SMV，病毒株与蚜虫种类之间存在传播特异性的可能性（3）。基于这些原因，确定这些病毒的本地分离株是否能被中北部地区引入的这种蚜虫传播很重要。按照所述方法（3）进行传播实验，每株植物接种3、5和10只蚜虫。每种处理使用10株大豆品种Williams 82的植株。为避免种子传播可能带来的混淆结果，所有测试中使用的植株均由温室中病毒检测合格的植株收获的种子培育而来。对于涉及SMV的实验，使用蚜虫可传播的田间分离株Al5（基因库登录号AF242844），作为阴性对照，使用非蚜虫可传播的分离株N（基因库登录号D500507）。对于涉及AMV的实验，使用经ELISA和寄主范围鉴定的AMV田间分离株。桃蚜（Myzus persicae）饲养在蚕豆上，大豆蚜饲养在无病毒的大豆上。AMV传播研究的方案与SMV研究相同，只是仅对大豆蚜进行测试。实验过程中，定期观察植株症状发展情况，并在接种后4至5周通过ELISA进行检测。在所有测试中，SMV-N均未发生传播，这些测试总共使用了桃蚜或大豆蚜各180只。对于Al5分离株，每株植物接种3、5和10只桃蚜时，传播效率分别为30%、50%和50%。大豆蚜的传播效率分别为30%、40%和40%。两种蚜虫的传播水平差异不显著（t检验，P = 0.01）。对于AMV，相应的传播效率分别为0%、0%和20%。数据表明，引入的大豆蚜在中北部地区可能是SMV的高效传播介体，但对AMV而言传播效率较低。桃蚜传播AMV已有文献记载（1），但本研究未对此进行检测。大豆蚜传播SMV和AMV令人担忧，因为这可能会增加SMV和AMV的发病率。随着该地区近期菜豆荚斑驳病毒（BPMV）的爆发，SMV和BPMV协同作用的可能性增加（2）。参考文献：（1）M. B. Castillo和G. G. Orlob。《植物病理学》56:1028，1966年。（2）G. L. Hartman等人编。1999年。《大豆病害简编》，第4版。美国植物病理学会，明尼苏达州圣保罗。（3）B. S. Lucas和J. H. Hill。《植物病理学杂志》99:47，1980年。（4）C. L. Wang等人。《植物保护》20:12，1994年。
