Diversity of the RNAs in Thirteen Isolates of Beet Necrotic Yellow Vein Virus in Chenopodium quinoa Detected by Means of Cloned cDNAs

Complementary deoxyribonucleic acids (cDNAs) to the four ribonucleic acid (RNA) species of isolate YU2 of beet necrotic yellow vein virus (BNYVV) were prepared by reverse transcription. The duplexes of these cDNAs were incorporated in the plasmid pBR322 and cloned into E. coli strain 5K. The insert sizes of the cDNA clones ranged from 280 to 2100 base pairs. In Southern blot hybridizations not all cDNAs specific for a particular RNA of BNYVV cross‐reacted. This suggests that they are complementaryto different regions of the respective RNA. In dot blot hybridization experiments sixteen out of eighteen cDNA clones detected all thirteen BNYVV isolates which were obtained from sugar beets originating from Yugoslavia, Italy, Switzerland, France and various regions in Germany and which were maintained in Chenopodium quinoa. Two cDNA clones specific for RNA‐3 failed to detect one German isolate. Pronounced differences between the thirteen virus isolates were seen when the electrophoretic migration of their RNAs was compared in Northern blot hybridizations. RNA‐1 and RNA‐2 of all isolates had the same sizes of 7100 and 5200 bases, respectively. The size, number and relative concentration of the smaller RNAs, however, varied greatly with different, isolates.