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Etiology

Identification of Small Single- and Double-Stranded RNAs Associated with Severe Symptoms in Beet Western Yellows Virus-Infected Capsella bursa-pastoris. B. W. Falk, University of Florida, Agricultural Research and Education Center, Belle Glade 33430; J. E. Duffus, USDA, SEA WR, P.O. Box 5098, Salinas, CA 93915. Phytopathology 74:1224-1229. Accepted for publication 23 April 1984. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1984. DOI: 10.1094/Phyto-74-1224.

An isolate (ST9) of beet western yellows virus (BWYV) that caused severe stunting symptoms in infected plants of Capsella bursa-pastoris was compared with two isolates (ST1 and STFL) that caused typical symptoms. Yields of purified virions were 10 times greater from C. bursa-pastoris infected with ST9 than with ST1 or STFL. Purified ST9 virions contained two single-stranded (ss-) RNAs of 1.9 and 0.93 × 10⁶ M_r whereas ST1 and STFL virions each had only one ss-RNA of 1.9 × 10⁶ M_r. The ST9-infected plants also contained two prominent double-stranded RNAs (ds-RNAs) that were not found in ST1- or STFL-infected plants. These RNAs were 2.2 × 10⁶ M_r and smaller than 4.6 × 10⁵ M_r. Both new ds-RNAs were present in much higher concentrations than were the other ds-RNAs from the ST9-or STFL-infected plants. No differences in proteins or densities were detected between the ST9 and the STFL or ST1 virions. The association of the extra RNAs with the ST9 isolate and the resulting severe symptom development on C. bursa-pastoris is discussed.