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Molecular Plant Pathology

Sequence Relationships Among the Coat Proteins of Strains of Pea Mosaic, White Lupin Mosaic, and Bean Yellow Mosaic Potyviruses. N. M. McKern,Principal research scientist, Commonwealth Scientific and Industrial Research Organisation (CSIRO), Division of Biomolecular Engineering, 343 Royal Parade, Parkville 3052, Australia; O. W. Barnett(2), L. A. Whittaker(3), A. Mishra(4), P. M. Strike(5), X. W. Xiao(6), C. W. Ward(7), and D. D. Shukla(8). (2)Professor, Department of Plant Pathology and Physiology, Clemson University, Clemson, SC 29634-0377; (3)(4)(5)(6)(7)(8)technical officer, visiting scientist, experimental scientist, experimental scientist, chief research scientist, and senior principal research scientist, respectively, Commonwealth Scientific and Industrial Research Organisation (CSIRO), Division of Biomolecular Engineering, 343 Royal Parade, Parkville 3052, Australia; (4)Permanent address: Department of Plant Pathology, B. A. College of Agriculture, Gujarat Agriculture University, Anand 388110, India. Phytopathology 83:355-361. Accepted for publication 8 December 1992. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/Phyto-83-355.

The taxonomic relationships of 20 potyvirus isolates from the bean yellow mosaic virus (BYMV) subgroup were investigated by high-performance liquid chromatographic peptide profiling of tryptic digests of their coat proteins. The peptide profiles of the clover yellow vein virus (CIYVV) strains B, C81, LI, and Washington were almost identical to each other and were closely related to that of CIYVV-Pratt, confirming their status as strains of CIYVV and not strains of BYMV. The profiles of BYMV-GDD, G, WA8, WA22, and RL7 were almost superimposable on each other and were similar to the profiles of BYMV-Scott, S, G81, and F. indicating that their coat proteins were very similar. Comparisons of coat protein tryptic peptides from white lupin mosaic virus (WLMV) and three strains of pea mosaic virus (PMV) showed that the peptide profiles of WLMV and PMV-204-1 were very similar to those of BYMV-S, G81, and F, and that peptide compositions closely matched published sequences of BYMV strains. The profiles for PMV-I and Provvidenti were almost identical to that of BYMV-K but showed some differences to the majority of the BYMV profiles. Additional data such as amino acid composition and sequence analysis revealed that these differences were due to just a few amino acid substitutions in their coat protein sequences when compared to those of BYMV-GDD. Many of these substitutions matched those found in the published sequences of BYMV-S, CS, and Danish. The HPLC profiles, together with the amino acid composition and sequence data, indicate that the WLMV and PMV isolates, therefore, are strains of BYMV. Data for the coat protein of sweet pea mosaic virus (SPMV) were more limited and insufficient to establish the relationship of SPMV to the BYMV strains, although several of the sequence changes seen in SPMV were also seen in PMV-I, PMV-Provvidenti, and the published sequence for BYMV-CS. It was also observed that WLMV and the PMV isolates had a conserved C-terminal sequence identical to that of known BYMV sequences but which differed substantially from the conserved C-terminal sequence of the three CIYVV strains. These sequences are candidate epitopes that might assist the assignment of isolates from the BYMV subgroups as strains of BYMV or CIYVV.