Genetic Determinants Distributed in Two Genomic RNAs of Sweet Clover Necrotic Mosaic, Red Clover Necrotic Mosaic and Clover Primary Leaf Necrosis Viruses

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Abstract
Three serologically distinct polyhedral viruses, sweet clover necrotic mosaic virus (SCNMV), red clover necrotic mosaic virus (RCNM) and clover primary leaf necrosis virus (CPLNV), contain bipartite RNA with .apprx. MW of 1.35 .times. 106 to 1.55 .times. 106 (RNA 1) and 0.5 .times. 106 to 0.6 .times. 106 (RNA 2). The homologous and heterologous combinations of RNA 1 and RNA 2 of the 3 viruses were highly infectious, while individual RNA species were not. Electrophoretic mobility of genomic RNA from the pseudorecombinants showed that the progeny viruses maintained the heterologous RNA combinations identically with those in the original inocula. Serological specificity of the progeny viruses was determined by RNA 1. A mixture of isolated coat protein and RNA 1 was not infectious. RNA 1 of SCNMV was essential for systemic infection of sweet clover at 26.degree. C, while RNA 2 of SCNMV complemented RNA 1 of RCNMV in causing local infection in sweet clover at 26.degree. C. The heterologous combinations of CPLNV RNA 1 and RNA 2 of SCNMV or of RCNMV acquired the ability to infect white clover at 26.degree. C and also caused symptoms characteristically different from those induced by their parental viruses on Phaseolus vulgaris L. cv. Red Kidney.