Unilateral Compatibility of Genome Segments from Two Distinct Strains of Red Clover Necrotic Mosaic Virus

Two strains of red clovcr necrotic mosaic virus (TpM 34 and TpM 48) were distinguished by their serological relationship, by the symptoms they induced in selected host plants and by Northern hybridization analysis. Purified RNA 1 and RNA 2 of the two strains were inoculated to he leaves of Chenopodium amaranticotor, Vigna unguiculata and C. quinoa in all possible combinations. It was demonstrated that a heterologous mixture containing RNA I of TpM 34 and RNA 2 of TpM 48 was infectious, resulting i lesion development whereas the reciprocal combination was not. The infectious pseudorecombinant wasisolated by several single lesion transfers in C. quinoa nd its genetic nature was confirmed by serology and Northern hybridization analysis. Inoculation of the pseudorecombinant d the two parental strains to five selected host plants revealed that symptom expression was determined by RNA 1. Red clover necrotic mosaic virus (RCNMV) is a member of the dianthovirus group of plant viruses (Matthews, 1982). The genome of RCN M V consists of two linear ssRNA molecules with estimated molecular weights of about 1.5 x 106 (RNA 1) and 0.5 × 106 (RNA 2) (Gould et aL, 1981). Two strains of the virus reported from Czechoslovakia, RCNMV-TpM 34 and RCNMV