Submitted to: Phytopathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/4/2001
Publication Date: N/A
Citation: Interpretive Summary: Barley yellow dwarf is the most economically important virus disease of cereal crops and is responsible for significant crop losses each year in all production areas. The disease is caused by a group of related viruses in the Luteoviridae family all of which are dependent upon aphids for transmission between plants. A majority of the information on the dispersal lof the virus and the development of disease epidemics is based on studies using laboratory adapted viruses and aphids. The emerging story is that the viruses and the aphids actually responsible for disease epidemics in the field are much more diverse than those studied in the laboratory. To be able to develop disease control recommendations we must first understand how the viruses and their aphid vectors behave in the field. This study examines the diversity in populations of one virus and two of its aphid vectors that are prevalent in cereal crops grown in the northern regions of fthe United States. The results indicated that virus populations can differ significantly in how well they are transmitted between plants. More importantly aphid populations differ significantly in how well they can transmit virus. Temperature can have a profound effect on how well the virus is transmitted and under certain conditions an aphid that is normally considered to be unimportant in the development of disease epidemics can play a major role in moving the virus between plants. The most significant finding was that the aphid species that inoculates virus into a plant can influence how well different aphid vectors can take up virus from the plant once it becomes infected. These findings will help in the understanding of how barley yellow dwarf epidemics can develop and help in the development of methods to predict and control disease epidemics.
Technical Abstract: RMV is an unassigned member of the Luteoviridae that causes barley yellow dwarf in various cereal crops. It has previously been referred to as BYDV-RMV. The virus is most efficiently vectored by the aphid Rhopalosiphum maidis, but can also be vectored inefficiently by R. padi & Schizaphis graminum. Field collections of alate aphids migrating into the emerging winter wheat crop in the fall of 1994 in central New York identified a hig proportion of R. padi transmitting RMV. This prompted a comparison of the RMV isolates & the R. padi populations found in the field with type virus & aphid species maintained in the laboratory & used to differentiate various luteoviruses responsible for barley yellow dwarf. A majority of the field isolates of RMV were similar to each other & to the type RMV isolate in disease severity on oat & in transmission by the laboratory population of R. maidis & a field population of R. maidis. Several field populations of R. padi differed in their ability to transmit the various RMV isolates. Th transmission efficiency of the R. padi clones was increased if acquisition & inoculation feeding periods were allowed at higher temperatures. In addition, the transmission efficiency of RMV was found to be significantly influenced by the aphid that inoculated the virus source tissue. In general RMV transmission by R. padi was higher if R. padi was the aphid that had inoculated the source tissue than if R. maidis has been the inoculating aphid. The magnitude of the change varied among virus isolates & R. padi clones. These results indicate that under certain environmental conditions R. padi can play a significant role in the epidemiology of RMV. This may be especially significant in regions where corn is a major source of virus & aphids that will migrate into a fall planted wheat crop.