| Maize streak virus | |
|---|---|
 Maize streak virus | |
| Common names | MSV, streak of maize |
| Causal agents | Maize streak virus |
| Hosts | maize, Urochloa panicoides |
| Vectors | leafhoppers ( C. mbila , C. storeyi , C. arachidis , C. dabrowski , other Cicadulina ) |
| EPPO Code | MSV000 |
| Distribution | sub-Saharan Africa |
| Maize streak virus | |
|---|---|
Virus classification  | |
| (unranked): | Virus |
| Realm: | Monodnaviria |
| Kingdom: | Shotokuvirae |
| Phylum: | Cressdnaviricota |
| Class: | Repensiviricetes |
| Order: | Geplafuvirales |
| Family: | Geminiviridae |
| Genus: | Mastrevirus |
| Species: | Mastrevirus storeyi |
Maize streak virus (MSV) is a virus primarily known for causing maize streak disease (MSD) in its major host, and which also infects over 80 wild and domesticated grasses. [1] It is an insect-transmitted pathogen of maize in the genus Mastrevirus of the family Geminiviridae that is endemic in sub-Saharan Africa and neighbouring Indian Ocean island territories such as Madagascar, Mauritius and La Reunion. The A-strain of MSV (MSV-A) causes sporadic maize streak disease epidemics throughout the maize-growing regions of Africa. [2] [3] [4] MSV was first described by the South African entomologist Claude Fuller who referred to it in a 1901 report as "mealie variegation". [5]
The development of conventionally resistant maize varieties has been a priority since the 1950s in Kenya, Nigeria, South Africa and elsewhere, with a good deal of success: however, there are several genes associated with resistance, and breeding is complex. Transgenically resistant or genetically modified maize varieties were under development in South Africa, [6] but the project has terminated without field trials of the candidate maize lines that were developed. Maize streak resistance is an important trait to maize breeders. [7] Forward genetics is increasingly being used. [7]
MSV is mainly vectored by Cicadulina mbila , and other Cicadulina species, such as C. storeyi , C. arachidis and C. dabrowski , are also able to transmit the virus.
Typical of all mastreviruses, MSV's circular, ~2.7-Kb monopartite single-stranded (ss) DNA genome encodes only four proteins. Bidirectional transcription from a long intergenic region (LIR) results in the virion-sense expression of a movement protein (MP) and a coat protein (CP), and the complementary-sense expression of the replication-associated proteins, Rep and RepA. Whereas the MP and CP are involved in virus movement and encapsidation, [8] Rep is an essential initiator of virus replication, and RepA is a regulator of host and viral gene transcription. [9] [10] [11] [12] Due to genome size restrictions, MSV usurps host DNA replication and double-stranded DNA break repair proteins to replicate its genome via, respectively, rolling-circle [13] and recombination-dependent mechanisms. [14]