http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
retention of maize dwarf mosaic virus by the greenbug, schizaphis graminum rondani and its implications for transmission mechanisms
For over five decades it was thought that aphids transmitted nonpersistent phytopathogenic viruses in what has been termed a "stylet-borne" manner. More recently, it has been proposed that aphids transmit virus as a result of "ingestion and egestion" of virus-containing plant sap. In the former case, virus is acquired and carried as a contaminant in the distal portion of the stylets. Ingestion-egestion, on the other hand, provides that virus is carried up to the maxillary food canal of the alimentary canal and perhaps beyond the pharyngeal gustatory organ. In the latter case there is greater opportunity for interaction between virus and both living and nonliving surfaces within the aphid. When the rate of loss of infectivity of MDMV (maize dwarf mosaic virus) was studied, early results suggested that both ingestion-egestion and stylet-borne contamination were operative mechanisms, the degree to which one predominates depending on the length of the acquisition period. Short acquisition times would result in aphids transmitting virus primarily because of stylet-borne contamination, whereas long acquisition times should result in primarily ingestion-egestion of virus-containing plant sap. Results indicate that the rate of loss of infectivity is independent of acquisition access time. There is a maximal amount of virus that can be acquired by aphids. The hypothesis that a dual-mechanistic approach can explain nonpersistent transmission is not supported. Nonlinear regression analyses can provide good predictions of transmission efficiency after extended retention time intervals. Possible implications of these findings are discussed.
Ph. D. in Philosophy Texas A & M University 1983
Includes bibliographical references (leaves 61-75).