Purification and electron microscopy of some isolates of blackeye cowpea mosaic and cowpea aphid-borne mosaic potyvirus.

Two isolates of blackeye cowpea mosaic (BlCMV) and two of cowpea aphid-borne mosaic (CABMV) potyviruses were purified by three purification procedures. Variable virus yields of each isolate of each virus were obtained with different virus-host combinations and purification procedures. Highest average virus yields of 4.6 mu g and 3.4 mu g per 50 g of infected tobacco leaf tissue were obtained from CABMV isolate RN-7C and BlCMV isolate PU-7B. Method-3 was most effective for purification of both viruses. Carbon tetrachloride when used in combination with chloroform as a clarifying agent improved purification of the BlCMV isolates, but was harmful to CABMV isolates. Berate buffer was superior than phosphate for purification of both viruses. Addition of EDTA and Triton X-100 in extraction and resuspension buffers circumvented virion aggregation. Leaf dip or purified virus preparations of BlCMV or CABMV isolates, examined under the electron microscope, contained elongated flexuous particles of modal length of 742 nm and 725 nm for BlCMV and CABMV, respectively, and confirmed particle morphology of potyvirus group.