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RNA-1 Dependent Seed Transmissibility of Cucumber Mosaic Virus in Phaseolus vulgaris. R. O. Hampton, U.S. Department of Agriculture, Agricultural Research Service, Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331; R. I. B. Francki, Department of Plant Pathology, Waite Agricultural Research Institute, University of Adelaide, Glen Osmond, South Australia, 5064. Phytopathology 82:127-130. Accepted for publication 4 September 1991. 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, 1992. DOI: 10.1094/Phyto-82-127.

Cucumber mosaic viral RNAs-1, -2, and -3 were isolated by successive gel electrophoresis and recombined between cucumber mosaic virus (CMV) strains that were (CMV-Pg) or were not (CMV-Le) seed transmissible in Phaseolus vulgaris ‘Top Crop.’ Twenty local-lesion isolates were derived for each of six pseudorecombinants, and selected isolates of each were assayed for seed transmissibility in cv. Top Crop. An average of 603 seedlings arising from Top Crop plants inoculated with respective pseudorecombinants were assayed for presence of seedborne CMV by means of double antibody sandwich enzyme-linked immunosorbent assay. Seedling symptoms of seedborne pseudorecombinants varied with seasonal differences in the greenhouse environment; in numerous cases infected seedlings were symptomless. Pseudorecombinants containing RNA-1 from CMV-Pg were seed-transmitted at a frequency of 64/2,032. Pseudorecombinants containing RNA-1 from CMV-Le were seed-transmitted at a frequency of 4/2,386. The latter seed transmissions were evenly divided among the three pseudorecombinants: LLP, 1/714; LPL, 2/1,091; and LPP, 1/581. Seed transmission rates of parental strains were, CMV-Pg, 22/60, and Le, 0/207. Thus, CMV RNA-l, co-governing viral replication and affecting virus movement, decisively influenced seed transmissibility of recombined CMV-Pg and CMV-Le genomic RNAs.