Submitted to: Phytopathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/28/2002
Publication Date: 9/15/2002
Citation: GRAY, S.M., SMITH, D.M., BARBIERI, L., BURD, J.D. VIRUS TRANSMISSION PHENOTYPE IS CORRELATED WITH HOST ADAPTATION AMONG GENETICALLY DIVERSE POPULATIONS OF THE APHID, SCHIZAPHIS GRAMINUM. PHYTOPATHOLOGY. 2002. Interpretive Summary: Aphids are the most important & most numerous vectors of plant viruses and are responsible for significant crop losses each year. The knowledge of how viruses are transmitted by aphids has been increasing steadily in recent years, but much of the information has focused on the role of the virus in the transmission process. Much of the practical control of viruses is based don control of the vector yet we know very little about what makes an aphid a good vector. We examined several genetically distinct populations of a single aphid species that is know to be an efficient vector of several viruses that cause barley yellow dwarf disease. This disease is the most economically important virus disease of cereal crops worldwide. Several of the aphid populations were very efficient vectors of one or more of the five viruses tested, and aphid populations differed with respect to which viruses they transmitted. Several other aphid populations were very poor vectors of all the viruses. The ability to vector viruses was correlated with the host preference of the aphid. Those that are adapted to agronomic crops were poor vectors and those adapted to wild grasses were efficient vectors. In addition, some of the viruses are only vectored when virus is acquired by the immature stages of the aphid. This suggests a developmental regulation to transmission in addition to an underlying genetic regulation. Molecular techniques exist to quickly identify which defined population an aphid belongs to and now to determine if that aphid is able to transmit viruses. This will aid in insect and disease management decisions. Additionally, this information will form the basis for continuing studies on aphid genomics & the eventual identification of aphid genes responsible for allowing an aphid to transmit viruses.
Technical Abstract: Schizaphis graminum is an important insect pest of several grain crops and an efficient vector of cereal-infecting Luteoviruses and Poleroviruses. We examined virus transmission characteristics among several distinct populations of the aphid and among developmental stages of the aphid. Seven well characterized S. graminum biotypes maintained at the USDA, ARS laboratory in Stillwater, Oklahoma and two populations maintained in New York; one collected in Wisconsin in 1959, the other collected in South Carolina in 1995, were tested for their ability to transmit five viruses that cause barley yellow dwarf disease(BYD). Four biotypes from Oklahoma that are not commonly found colonizing agronomic crops and the Wisconsin population were efficient vectors of several viruses. Three biotypes from Oklahoma adapted to agronomic crops and the South Carolina population were poor vectors of all the viruses. Aphids from the various populations were able to acquire virus from infected plants and retention of virus was similar in vector and nonvector populations. The genetic diversity of S. graminum populations and their differential ability to transmit luteoviruses offers a unique system to study the cell biology, molecular genetics and inheritance of circulative virus transmission in homopterous insects.