Cyclical Transmissibility of Barley Yellow Dwarf Virus from Oats with Increasing Age of Infection

C. C. Gill

Contribution No. 308, Canada Department of Agriculture, Research Station, 25 Dafoe Rd., Winnipeg 19, Manitoba.
Accepted for publication 7 June 1968.

ABSTRACT

English grain aphids occasionally transmitted barley yellow dwarf virus from oats two days after the seedlings were inoculated. There was usually a marked increase in the proportion of aphids that transmitted virus on the 4th day after start of the inoculation of the source plants, and a first major peak of transmission always occurred on the 6th day. An average of 94% of the aphids transmitted virus at this time. Subsequently, virus transmission from individual or composite samples of leaves on the main culm fluctuated in a cyclical pattern. The first major valley occurred on about the 11th day when 62% of the aphids transmitted virus. In one trial the level of virus transmission from individual second and third leaves on the main culm remained high for a period of about 30 days after the initial peak in the transmission curve. Five major peaks in the transmission curve occurred during this period. Symptoms in the virus source plants appeared at an average time of 4.2 days after the first major peak of transmission. A larger proportion of aphids transmitted virus from the first and second leaves of source plants inoculated with 12 viruliferous aphids each, than from plants inoculated with three viruliferous aphids, during the first 4 days that virus was transmissible. Phytopathology 59: 2 3-2 8.

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