A Variant of Cowpea Chlorotic Mottle Virus Obtained by Passage Through Beans

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Abstract
After continued propagation of the type strain (T) of cowpea chlorotic mottle virus (CCMV) in ''California Blackeye'' cowpeas [Vigna unguiculata ssp. unguiculata] for several months, the intensity of the chlorotic symptoms diminished. When ''Bountiful'' beans [Phaseolus vulgaris] were inoculated with sap extracts from such plants, a new variant of CCMV, designated M, was derived. M caused very mild symptoms on cowpeas, rather than the bright chlorosis of strain T. There was a close relationship between T and M in serology, replication, specific infectivity, host range and several biophysical properties. However, isolate T differed from M in symptoms produced on cowpeas, replication in resistant cowpea lines, ability to compete in cowpeas and beans, and in the nature of RNA species 3. Results of studies of pseudorecombination of the RNA of isolates T and M suggested that RNA-3 of CCMV has 2 genes, one controlling systemic symptoms and the other controlling coat protein.