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Etiology

Purification, Serology, and Particle Morphology of Two Russet Crack Strains of Sweet Potato Feathery Mottle Virus. B. B. Cali, Graduate student, Department of Plant Pathology, North Carolina State University, Raleigh 27650; J. W. Moyer, assistant professor, Department of Plant Pathology, North Carolina State University, Raleigh 27650. Phytopathology 71:302-305. Accepted for publication 15 June 1980. Copyright 1981 The American Phytopathological Society. DOI: 10.1094/Phyto-71-302.

Three strains of sweet potato feathery mottle virus (FMV) were isolated from roots and leaves of Ipomoea batatas ‘Porto Rico.’ Serial aphid and local lesion transfers, as well as dilution series, were used to separate isolates from mixed infections. Two strains of FMV were differentiated by lesion development in Chenopodium amaranticolor and the severity of russet crack (RC) lesions on I. batatas ‘Jersey’ roots. The third strain was FMV common strain, which did not infect C. amaranticolor and caused no external symptoms on Jersey roots. The normal particle lengths for the two RC strains were 850 nm and 833 nm, and are similar to those reported for the common strain (830–850 nm). Heterologous serological titrations indicated that the RC strains were related, but not identical, to the common strain. Attempts to purify the two RC strains by procedures used for the common strain resulted in severe aggregation; however, a method was developed to purify these two and the common strain. Evidence is provided that shows the two strains inducing russet crack to be strains of FMV.