Virus diseases of sweet potato in East Africa. I. Identification of the viruses and their insect vectors

1957

A:PS

At least 2 viruses attack sweet potatoes in East Africa. Virus A, found in only 1 locality, causes a relatively mild disease and is transmitted by Myzus persicae (Sulz.), which can acquire it in a 2-minute feeding. Virus B is widespread throughout East Africa. It is transmitted by Bemisia tabaci (Genn). The virus-vector relationships are obscure; under the experimental conditions used, B. tabaci acquired the virus in 5 minutes but it was a very inefficient vector. Virus B exists in a number of strains, the mildest of which may cause no symptoms in some sweet potato varieties whereas others cause extremely severe diseases. Infection with virus A does not protect a plant from infection with virus B, but infection with a mild strain of the latter protects against infection by a severe strain. Neither virus is transmitted mechanically to healthy sweet potatoes. Infection by virus B may be masked or not fully systemic in dull, cold conditions, but all attempts to inactivate it in the tubers before germination by heat treatment or by chilling failed. Virus a might be the same as one of the sweet potato viruses described from the United States, but virus B is distinguished from them by its insect vector. [AS]

v.47:582-590, PHYTOPATHOLOGY

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