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Disease Note.

First Report of Alfalfa Mosaic Virus in Lupins in Australia. E. V. Alberts, South Australian Research and Development Institute (SARDI), G.P.O. Box 397, Adelaide, SA 5001. F. W. Nutter, Jr., Visiting Scientist SARDI, and Department of Plant Pathology, Iowa State University, Ames 50011; A. J. Corbett, Mallee Research Station, Department of Natural Resources and Environment, Walpeup, Victoria, 3507; and D. K. Graetz, SARDI. Plant Dis. 80:1302. Accepted for publication 4 September 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-1302A.

During spring 1995, sudden death of narrow-leafed lupins (Lupinus angustifolius L.) grown in the Mallee region of Victoria, Australia, was observed. Tip necrosis and progressive dieback resulted in rapid plant collapse. Most lupin crops grown throughout the region were affected to some degree, with estimated incidence levels ranging from 5 to 60%. Yield loss for the region was estimated to be 25%. Lupin plants exhibiting mild to severe symptoms from seven affected lupin crops were tested for bean yellow mosaic potyvirus (BYMV), pea Seedborne mosaic potyvirus (PSbMV), tomato spotted wilt tospovirus (TSWV), clover yellow vein potyvirus (CYVV), alfalfa mosaic alfamovirus (AMV), and cucumber mosaic cucumovirus (CMV), by double antibody sandwich-enzyme-linked immunosorbent assay (DAS ELISA) or dot immuno binding assay (DIBA). BYMV, PSbMV, TSWV, and CYVV were not detected in any of the samples. Forty-seven percent of samples tested positive for CMV alone, 13% for AMV alone, and 21% positive for both AMV and CMV. Although CMV-infected seed is known to be the primary source of inoculum to initiate CMV epidemics in lupins (I), AMV is not known to be seed-transmitted in lupins (1) and, therefore, potential exogenous sources of AMV inoculum were investigated. Forage legumes, primarily annual medics (Medicago spp), were arbitrarily sampled (25 to 50 plants per pasture) from pastures in closest proximity to AMV/CMV-infected lupin fields, and tested for the presence of AMV and CMV by DAS ELISA. CMV was found to be present in just 1 of 9 pastures and incidence in the affected pasture was very low (2%). AMV was detected in 8 of the 9 pastures and incidence ranged from 4 to 100%. AMV incidence exceeded 20% in 6 of the 9 pastures sampled, 2 of which were found to be 100% infected. These results indicated medic pastures may be an important AMV reservoir for potential spread to neighboring lupin fields. This is the first documented report of AMV infection in lupins in Australia and also reports the occurrence of mixed infection of AMV with CMV.

Reference: (1)R A. C. Jones and G. D Mclean. Ann. Appl. Biol. 114:509, 1989.