Aphid and virus dynamics to improve forecasts of Barley Yellow Dwarf Virus risk

Abstract

The objective of the project was to quantify aspects of the epidemiology of Barley Yellow Dwarf Virus sufficiently to be able to contribute to a reliable scheme for forecasting the risk of infection in the different cereal growing regions of Britain. The project took place between August 1992 and July 1995.

A field experiment was continued in the first year from that started in project number 0003/3/89 (see Project Report No 87), incorporating four sites and five different sowing dates of winter barley at each site. The experiment was designed to study the effects of sowing date on the number and species of aphid vectors of BYDV and on virus incidence in the crop.

In addition, monitoring of the numbers of migrant aphid vectors and the proportion carrying virus continued for the three years of the project. The data provide valuable information on variation in aphid and BYDV incidence between regions and years using a standardised sampling method.

An experiment was done to investigate the effect of crop growth stage and temperature on virus progression and detectability in winter barley using artificial inoculations. The relationship between the time that a virus can be detected in a plant by ELISA, and the time at which a plant becomes a source for virus spread was also investigated.

Results showed that temperature in the period after inoculation was critical in determining the final virus levels regardless of growth stage at inoculation, but that the younger the plants when inoculated, the higher the level of virus when mature. However, plants inoculated at a later growth stage were a better source for subsequent virus transmission by aphids than those inoculated at an earlier growth stage.

Laboratory experiments were done to examine transmission of the virus from infected plants, through the aphid vector and into uninfected plants at a range of temperatures encountered in the autumn in the U.K. and in the two main vector aphid species. The results showed the crucial importance of autumn and winter temperature at all stages in the virus transmission cycle.

The results will be used, in conjunction with those of other HGCA-funded projects and information from the literature, in the assembly of a weather-driven mechanistic model of virus spread.