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Characterization of Isolates of Four Aphid-Transmitted Sweet Potato Viruses. Mateo A. Cadena-Hinojosa, Graduate student, Department of Plant Pathology, University of California, Davis 95616; R. N. Campbell, professor, Department of Plant Pathology, University of California, Davis 95616. Phytopathology 71:1086-1089. Accepted for publication 5 February 1981. Copyright 1981 The American Phytopathological Society. DOI: 10.1094/Phyto-71-1086.

Isolates of four aphid-transmitted viruses (feathery mottle [FMV], russet crack [RCV], internal cork [ICV], and chlorotic leaf spot [CLSV]) from sweet potatoes were purified from mechanically inoculated plants of Ipomoea nil with yields of 818 mg of virus per kilogram of tissue. An antiserum was prepared for each isolate and the reciprocal titers were from 512 to 1,024 in homologous microprecipitin tests. Based on three serological procedures and particle morphology, the four isolates are closely related strains of sweet potato feathery mottle virus. In microprecipitin tests, the titers of each heterologous reaction were the same as the homologous reaction or one dilution step less; cross-absorption with each heterologous antigen removed all antibodies to the homologous virus; and intensities of homologous and heterologous reactions closely resembled those obtained with the ELISA technique. The normal length of the flexuous rod-shaped particles of FMV, RCV, ICV, and CLSV, were 829 38, 834 39, 838 38, and 845 32 nm, respectively. The four isolates caused similar symptoms in the foliage of Ipomoea spp., but differences were observed in the symptoms on roots of infected sweet potato plants. Plants of Jersey inoculated with RCV, ICV, and CLSV had russet crack symptoms that were not present in the FMV-inoculated plants or in the controls.