VIEW ARTICLE

Physiology and Biochemistry

Decline of Bean Pod Mottle Virus Specific Infectivity in Vivo Correlates with Degradation of Encapsidated RNA-1. S. Kartaatmadja, Department of Plant Pathology, University of Missouri, Columbia 65211, Present address: Sukamandi Research Institute for Food Crops, Sukamandi-Subang, West Java, Indonesia; O. P. Sehgal, Department of Plant Pathology, University of Missouri, Columbia 65211. Phytopathology 80:1182-1189. Accepted for publication 26 March 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/Phyto-80-1182.

The specific infectivity (SI) of bean pod mottle virus (BPMV) recovered from inoculated primary leaves of bean (Phaseolus vulgaris ?Pinto?) and soybean (Glycine max ?Williams 82?) at 20?25 days post inoculation was only 2% that of virus at 3?5 days post inoculation. Similarly, BPMV from systemically invaded older soybean leaves possessed a lower SI than that from younger leaves. There were no differences in either the structure or stability of high and low SI BPMV. Differences were detected in electrophoretic migration patterns of virions and in the molecular weight of the small coat protein subunit, but these did not contribute to the infectivity decline. The bottom component RNA (RNA-1) of low SI BPMV was degraded but not the middle component RNA (RNA-2). Replacing the bottom component in preparations of low SI with that from high SI restored infectivity. These results suggest that a selective in situ degradation of one of the two genomic RNAs leads to BPMV inactivation, a mechanism that appears unique among multicomponent plant viruses. Additionally, RNA-1 was degraded preferentially when BPMV was exposed briefly to high alkaline conditions, indicating that RNA-1 may be physically less stable than RNA-2.