''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. It is an insect-transmitted

maize Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American English, North American and Australian English), is a cereal grain first domesticated by indigenous peoples of Mexico, indigenous ...

pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a g ...

in the genus ''Mastrevirus'' of the family '' Geminiviridae'' that is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...

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. MSV was first described by the South African entomologist Claude Fuller who referred to it in a 1901 report as "mealie variegation". 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 Genetically modified maize (corn) is a genetically modified crop. Specific maize strains have been genetically engineered to express agriculturally-desirable traits, including resistance to pests and to herbicides. Maize strains with both trait ...

varieties were under development in South Africa, 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 A breeder is a person who selectively breeds carefully selected mates, normally of the same breed to sexually reproduce offspring with specific, consistently replicable qualities and characteristics. This might be as a farmer, agriculturalist, o ...

Forward genetics Forward genetics is a molecular genetics approach of determining the genetic basis responsible for a phenotype. Forward genetics provides an unbiased approach because it relies heavily on identifying the genes or genetic factors that cause a partic ...

is increasingly being used. MSV is mainly transmitted by ''Cicadulina mbila'' Naude, but other

leafhopper A leafhopper is the common name for any species from the family Cicadellidae. These minute insects, colloquially known as hoppers, are plant feeders that suck plant sap from grass, shrubs, or trees. Their hind legs are modified for jumping, and ...

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, Rep is an essential initiator of virus replication, and RepA is a regulator of host and viral gene transcription. 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 and recombination-dependent mechanisms.

References

{{DEFAULTSORT:Maize Streak Virus Maize diseases Viral plant pathogens and diseases Geminiviridae