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The etiology of a previously unknown disease of Streptopus amplexifolius (L.) DC. (twisted stalk) that occurred in south central Alaska was elucidated. Symptomatic plants with yellow-green dashes and streaks on their leaves contained distinct viruses belonging to the family Potyviridae and (or) tentatively to the family Flexiviridae genus Carlavirus . Each virus’ identity was confirmed by a combination of morphology, serology (ELISA and (or) Western analysis), and sequences obtained from reverse transcriptase – polymerase chain reaction products previously generated by potyvirus- or carlavirus-specific primers. The mechanical transmission of particles (purified from twisted stalk as a mixture of both viruses or as a single preparation of each virus) to S. amplexifolius, Chenopodium amaranticolor Coste et Reyn, and Chenopodium quinoa Willd., fulfilled Koch’s postulates. The relatively high incidence of infected plants and associated severe symptoms in populations from several sites in south central Alaska gave evidence that native plants are susceptible to, and are adversely affected by viral diseases. Even though Streptopus species grow throughout the temperate regions of the world, this is the first report of a pathogen(s) infecting plants in the genus Streptopus. |
