Maize Streak Virus (Geminiviridae)

Abstract

Maize streak virus (MSV) is the type species of the genus Mastrevirus of the family Geminiviridae and the causal agent of maize streak disease (MSD), one of the most important viral diseases of maize in sub-Saharan Africa. The virus remains largely uncontrolled in most parts of the continent and in epidemic years it contributes to widespread yield losses and famine. Eleven major MSV strains have been identified so far, of which only the MSV-A strain is known to produce economically important infections in maize. Apart from maize, however, these various MSV strains infect over 80 other grass species including wheat, barley, and rye. The epidemiological complexity of MSD contrasts starkly with the genomic simplicity of MSV. The MSV genome contains two intergenic regions and only three genes. Whereas the intergenic regions are involved in replication and the regulation of gene expression, the genes encode four different proteins. Two of the proteins, Rep and RepA, are expressed from a single alternatively spliced gene and are involved in genome replication and the regulation of host and virus gene expression. The two other proteins, MP (movement protein) and CP (coat protein), are involved in systemic spread within plants and the encapsidation of viral DNA within characteristic geminate particles. Control of MSV is primarily via insecticide targeting its leafhopper vector and the use of resistant maize genotypes that have been derived through traditional breeding approaches.