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Etiology

Purification, Partial Characterization, and Serology of Blackeye Cowpea Mosaic Virus. J. Albersio A. Lima, Department of Plant Pathology, University of Florida, Gainesville, FL 32611, Present address of senior author: Department of Plant Science, University of Ceara, Fortaleza, Ceara, Brazil, 60,000; D. E. Purcifull(2), and E. Hiebert(3). (2)(3)Department of Plant Pathology, University of Florida, Gainesville, FL 32611. Phytopathology 69:1252-1258. Accepted for publication 24 May 1979. Copyright 1979 The American Phytopathological Society. DOI: 10.1094/Phyto-69-1252.

Blackeye cowpea mosaic virus (BlCMV) was increased in cowpea, Vigna unguiculata ‘Knuckle Purple Hull’, and infected leaves were used for purification of virus and cytoplasmic inclusion bodies. Either n-butanol or a combination of chloroform and carbon tetrachloride was used in the clarification process. Polyacrylamide gel electrophoresis of sodium dodecyl sulfate (SDS)-dissociated inclusions and virions revealed that the inclusions consisted of a single protein estimated to have a molecular weight (MW) of about 70,000 whereas freshly purified BlCMV consisted of a main protein component with a MW of 34,000 and two smaller proteins with MWs of 29,000 and 27,000. Purified BlCMV had a A₂₆₀/A₂₈₀ ratio of 1.2 and a modal length of 753 nm. Freshly purified BlCMV preparations showed a single sedimenting peak with s₂₀ = 157–159S. Storage of purified BlCMV at 4 C for more than 30 days resulted in a reduction of the virion S value, a reduction in the molecular weight of the capsid protein, and a partial loss of antigenic determinants. The purified BlCMV cytoplasmic inclusions had absorption spectra characteristic for proteins. Antisera reactive in SDS-immunodiffusion were obtained against untreated virions, pyrrolidine-dissociated coat protein, and untreated BlCMV cytoplasmic inclusions. Double immunodiffusion tests (with SDS-treated antigens and antiserum to BlCMV) showed that the BlCMV is serologically unrelated to six potyviruses and serologically related to, but distinct from, the following potyviruses: bean common mosaic (BCMV), bean yellow mosaic, cowpea aphid-borne mosaic (CAMV), dasheen mosaic, lettuce mosaic, tobacco etch, potato Y, soybean mosaic, and watermelon mosaic-2. The intragel cross-absorption technique also was used to distinguish BlCMV from CAMV and BCMV. Five of 20 cowpea cultivars were resistant to BlCMV, whereas all 20 were susceptible to CAMV.