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Subgenomic RNAs in Virions of Southern Bean Mosaic Virus. K. A. Weber, Postdoctoral fellow, Department of Plant Pathology, University of Missouri, Columbia 65211; O. P. Sehgal, professor, Department of Plant Pathology, University of Missouri, Columbia 65211. Phytopathology 72:909-913. Accepted for publication 17 December 1981. Copyright 1982 The American Phytopathological Society. DOI: 10.1094/Phyto-72-909.

The proportion of subgenomic RNAs in southern bean mosaic virus bean strain (SBMV-B), relative to the infectious genomic (25S) RNA, is ~2.3 times greater in late- versus early-progeny virions. The specific infectivity of late-progeny SBMV also is lower than that of the early-progeny virions. Apparently, a proportion of late-progeny SBMV lacks 25S RNA; attempts to resolve them were unsuccessful. Subgenomic SBMV RNAs neither inhibit nor stimulate the infectivity of 25S RNA. When virions are exposed at 45C for 2 hr, subgenomic components complex with genomic RNA, but this treatment causes no marked decline in the infectivity. Exposure at a somewhat higher temperature (65 C, 10 min) is necessary for SBMV inactivation with genomic compaction. Subgenomic RNAs were detected in SBMV-B virions synthesized in necrotized tissue of Phaseolus vulgaris ‘Pinto’ as well as in the 50S subviral nucleoprotein. Two additional SBMV strains, viz, cowpea and Nigerian, also encapsidate the subgenomic components.