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Vector Relations

Ultrastructure of Fungal Plant Virus Vectors Polymyxa graminis in Soilborne Wheat Mosaic Virus-Infected Wheat and P. betae in Beet Necrotic Yellow Vein Virus-Infected Sugar Beet. Willem G. Langenberg, Agricultural Research Service, U.S. Department of Agriculture and Department of Plant Pathology, University of Nebraska, Lincoln 68583; L. Giunchedi, Istituto di Patologia Vegetale, University of Bologna, 40126 Bologna, Italy. Phytopathology 72:1152-1158. Accepted for publication 8 January 1982. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1982.. DOI: 10.1094/Phyto-72-1152.

The association of Polymyxa graminis with the viruses it transmits is thought to be internal; zoospores of Polymyxa do not acquire soilborne wheat mosaic virus (SBWMV) in vitro and cystosori of Polymyxa in dry SBWMV-infected roots remain able to transmit SBWMV to wheat seedlings for a long period of time. The ultrastructure of various stages in the life cycles of P. graminis and P. betae were examined in SBWMV-infected wheat and beet necrotic yellow vein virus (BNYVV)-infected sugar beet roots, respectively. Although particles of both viruses were observed in close contact with the fungal vector in the host tissue, they were always outside the fungal structures. Owing to the density of the fungal cytoplasmic contents, virus particles were not seen within fungal plasmodia, zoosporangia, or cystosori.