Aphis, Virus Relationship

Press, Volume CIV, Issue 30769, 5 June 1965, Page 9

Aphis, Virus Relationship

AS farmers who have suf- * fered from the effects of barley yellow dwarf virus in wheat well know, the relatively insignificant aphis plays a key role in the spread of this disease from plant to plant. At the sub-station of the Plant Diseases Division of the Department of Scientific and Industrial Research at Lincoln, Miss F. J. Wilson, who graduated from Canterbury University last year with a bachelor of science degree with honours in zoology, is looking into the relationship of the green peach aphis and pea leaf roll virus, the mechanism of transfer of the disease from aphis to plant and the effect of the virus on the aphis itself. A method has been devised of feeding aphides in a test tube with a virus infected solution. The aphis uses its mouth part to break through a film of material to draw off [the solution, containing sugar to make it more attractive to I the insect, from an upper [bowl or container which sits I in the top of the test tube. [Aphides have been kept alive

for up to 30 days under these conditions.

In the particular studies at present being made Miss Wilson is using the green peach aphis and is working with the pea leaf roll virus which is regarded as a typical example of a persistent type virus with a wide range of host plants. Dr. A. D. Thomson, officer in charge of the sub-station, is seeking to elucidate the basic properties of this virus which are at present unknown, and Miss Wilson is able to help to show whether solutions do contain the virus or not by feeding the aphides for a period of about three days and then putting the aphides on plants to determine whether symptoms of the virus develop. Another aspect of the study is the number of aphides that are needed to infect a plant so that symptoms of the disease are obvious. The indications are that 10 to 20 are required for this and that the more aphides there are the more marked are the symptoms. The possibility of certain plant sites being more susceptible than others to attack by the aphis comes into this study. Dr. Thomson says

that the presence of greater numbers of aphides on a plant may simply mean that there is a greater chance of an aphis attacking a susceptible area for entry of the virus and Miss Wilson will be restricting aphides to particular areas of plants to see if there is an effect of this nature. Miss Wilson is also interested in the possible effect of the virus on the aphis itself and whether it reduces the length of life of the insect. Dr. Thomson said that it had been shown overseas that where the leaf hopper was responsible for spreading virus it suffered as a result of being the carrier of the virus.

As has been observed with barley yellow dwarf virus it has been found that some pea plants, although infected with the virus, do not show the obvious symptoms. This is associated with the growing of these plants in soils high in nitrogen and Dr. Thomson said this week that it was hoped to do some simple field experiments using this knowledge and possibly one insecticidal spray to see whether high nitrogen in the soil enabled plants to overcome the effects of a virus.