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Serological Relationship Between Beet Western Yellows and Beet Mild Yellowing Viruses. James E. Duffus, Plant Pathologist, Agricultural Research Service, United States Department of Agriculture, U. S. Agriculture Research Station, Salinas, California 93901; G. E. Russell, Principal Scientific Officer, Plant Breeding Institute, Trumpington, Cambridge, England. Phytopathology 65:811-815. Accepted for publication 7 February 1975. DOI: 10.1094/Phyto-65-811.

A possible relationship between beet western yellows virus (BWYV), the most common virus of sugarbeet in the United States, and beet mild yellowing virus (BMYV), the most prevalent virus of sugarbeet in Europe, has long been suspected. Differences between the viruses in regard to symptomology on beets, epidemiology and host range and the lack of a serological test has hampered studies on their relationships. Twelve BMYV isolates from sugarbeet in England were transferred by Myzus persicae to Capsella bursa-pastoris and studied in regard to host range, membrane feeding, and serology. The BMYV isolates produced a common reaction on certain key indicator hosts. Beta vulgaris, Capsella bursa-pastoris, and Claytonia perfoliata were all susceptible whereas Raphanus sativus, Lactuca sativa, Brassica pekinensis, and Brassica rapa were all immune. Numerous early trials with membrane feeding of BMYV failed and was thought to be another factor pointing to the differences between BMYV and BWYV. However, early in 1971, by use of highly concentrated preparations, BMYV was transmitted by M. persicae which had acquired virus by feeding on purified preparations through artificial membranes. In density-gradient columns, the positions of infectious zones of BMYV corresponded closely with those in gradients containing BWYV. Differences in transmission efficiency through membranes between common BWYV isolates and the BMYV isolates tested seems to be related to virus concentration differences in their hosts. Antisera prepared against 10 strains of BWYV from the United States and England neutralized infectivity of all isolates of BMYV tested. Antisera prepared against the English isolates of BMYV neutralized the infectivity of the American and English BWYV strains, and also the BMYV isolates. The results of these investigations establish a close serological relationship between BWYV from the United States and BMYV from Europe.