Maize dwarf mosaic virus: purification, some physical properties, and yield of virus from several corn hybrids

To better understand the nature of maize dwarf mosaic virus (MDMV) and its interaction with susceptible and resistant corn hybrids, the purification of MDMV and its physical properties were re-evaluated and a rapid assay procedure was developed.

The virus was purified by chloroform clarification and differential and sucrose density-gradient centrifugation. Corn tissue was homogenized in 0.1 M sodium citrate plus 0.5% mercaptoethanol. The virus was resuspended after high speed centrifugation in 0.005 M sodium citrate, pH 7.0. Purified virus has an ultraviolet absorption spectrum typical for filamentous viruses having 5% RNA, shows birefringence, has an A260/280 of 1.18, and a sedimentation coefficient of 160-162 S. The virus is filamentous and appears to be a member of the potato virus Y group. A yield of 9.0-23.0 llg of virus/g fresh weigh.t of field-grown, mechanically inoculated Hy X Cl03 was determined by analytical sucrose density-gradient centrifugation. This represents a yield of purified virus of approximately 25% of that in the clarified sap. Results obtained from the density-gradient analysis were comparable to but more sensitive than those from the microprecipitin test and a systemic infectivity assay. The systemic infectivity assay on corn, analyzed by maximum likelihood and log log transformation, showed a yield of purified virus of 0.4% of that in the crude sap.