NUCLEOTIDE-SEQUENCE OF A RESISTANCE BREAKING MUTANT OF SOUTHERN BEAN MOSAIC-VIRUS

SBMV-S is a resistance-breaking mutant of an Arkansas isolate of the b ean strain of southern bean mosaic virus (SBMV-B-ARK) that is able to move systemically in Phaseolus vulgaris cvs. Pinto and Great Northern, whereas the wild-type SBMV-B-ARK causes local necrotic lesions and is restricted to the inoculated leaves of these hosts. Sequence analysis of the 4136 nucleotide genomes of SBMV-B-ARK and SBMV-S revealed seve n nucleotide differences, but only four deduced amino acid changes. A single amino acid change occurred in the C-terminal region of the puta tive RNA-dependent RNA polymerase and three differences were identifie d in the N-terminal portion of the virus coat protein. SBMV-B-ARK and SBMV-S were compared with other sobemoviruses and were found to contai n a high level of nucleotide sequence identity (91.3%) to SBMV-B. Unli ke SBMV-B however, SBMV-B-ARK and SBMV-S contained four putative overl apping open reading frames, making them more similar in genome organiz ation to the cowpea strain, SBMV-C. The possibility exists that mutati ons or even errors, that resulted in mis-identification of open readin g frames, occurred in previously published information on nucleotide s equence and genomic organization for SBMV-B.