Maize streak is caused by the maize streak geminivirus (MSV). The disease was first reported in east Africa in the early 1900s and remains a major constraint to maize production in much of sub-Saharan Africa. MSV is transmitted by several species of Cicadulina leafhoppers.

Pathogen

Maize streak is caused by the maize streak geminivirus (MSV).

Vector: MSV is transmitted by species of Cicadulina leafhoppers.  Globally, 22 species of Cicadulina leafhoppers have been described, 18 of which are found in Africa. Of these, 8 species are confirmed vectors of MSV. Cicadulina mbila is the most predominant vector. The other vectors are C. storeyi, C. arachidis, C. bipunctat, C. lateens, C. parazeae, C. similes, and C. ghaurii.

Symptoms

Disease symptoms first become apparent about a week following infection. Small (0.1 to 2 mm in diameter), chlorotic, circular spots arise on the basal sections of young leaves that emerge after infection. Spots contrast sharply with surrounding healthy green leaf tissue. Numbers of spots increase with plant growth and can coalesce. In susceptible varieties, spots enlarge parallel to leaf veins, forming distinctive elongated, chlorotic streaks distributed evenly over the leaf surface. Infection with MSV commonly results in crop stunting and barren plants.

Confirmation

MSV can be detected using ELISA test kits. MSV is single stranded and non-enveloped. Under the electron microscope, characteristic geminate isometric particles (doublets) are visible. MSV has quasi-icosahedral particles that measure 18 × 30 nm.

Why and where it occurs 

Maize streak is predominantly a disease of maize in Africa although it has also been reported from south and south-east Asia. Outbreaks of the disease are infrequent, although severe epidemics can result in considerable yield loss. Outbreaks of maize streak have been associated with drought and irregular rain in west Africa.

Figure 1. Geographic distribution of maize streak virus.

As maize streak is vector transmitted, disease outbreaks are dependent on favorable conditions for Cicadulina species. Development period of Cicadulina species ranges from 22 to 45 days, depending on prevailing climatic conditions. Temperatures between 20-35°C are considered optimum for development.

Host range

MSV is known to infect a wide range of indigenous grass species in Africa in addition to various cereal crops, including wheat, oat, sugarcane, millet, rice, barley, rye and sorghum.

Life cycle

MSV can only be transmitted by leafhoppers of the Cicadulina species. MSV is not known to be seed-borne.

Vectors acquire the virus following feeding on an infected plant. A latent period of 6 to 12 hours is required before the vector can transmit the virus to another host plant. The virus does not propagate in the vector, although vectors transmit the virus for life even after molting. The virus overwinters in a wide range of graminaceous grasses and cereal hosts.

Damage

• Mechanism of damage: Yield loss is caused by plant stunting and the termination of ear formulation, development and grain filling in infected plants.
• When damage is important: Yield loss is caused by plant stunting and the termination of ear formulation, development and grain filling in infected plants.
• Economic importance:Maize streak remains an economically important disease of maize in much of Africa. Yield loss as high as 100% have been reported under conditions favorable for disease development (susceptible varieties and favorable climatic conditions for leafhopper development).

Global distribution

MSV is distributed throughout sub-Saharan Africa (Figure 1) including forest and savanna ecologies and from sea level to 1800m elevation. MSV has also been reported from Yemen and in various countries in south and south-east Asia, although little data is available on the identity and distribution of MSV in Asia. MSV is not reported from the New World.

Management principles

Host resistance

• Cultivation of resistant varieties offer the most practical and cost-effective means of disease management.
• Resistant varieties are widely available.
• Resistant varieties have been developed by IITA and CIMMYT and adapted for a wide range of growing conditions in Africa.

Vector management

• Management of vector populations through insecticide use can reduce rates of disease transmission.
• However, insecticide application is often uneconomical due to the uncertainity regarding disease outbreaks.

Cultural control

• As MSV is known to infect a wide range of graminaceous species, there are few cultural practices that can reduce disease severity.

References

Alegbejo, M.D.,S.O.  Olojede, B.D. Kashina and M.E. Abo. Maize streak mastrevirus in Africa: Distribution, transmission, epidemiology, economic significance and management strategies. Journal of Sustainable Agriculture 19: 35-45.

CAB International. 1997. Maize streak monogeminivirus. Distribution maps of plant disease. Edition 1 (December), Map 739. Wallingford, UK: CAB International.

CIMMYT. 2004. Maize Diseases: A guide for Field Identification. 4th Edition. Mexico, D.F.: CIMMYT.

Kyetere, D.T., R. Ming, M.D. McMullen, R.C. Pratt, J. Brewbaker and T. Musket. 1999. Genetic analysis of tolerance to maize streak virus in maize. Genome 42: 20-6.

Louie, R. 1999. Diseases Caused by Viruses In Donald G. White (ed), Compendium of Corn Diseases. St. Paul, Minnesota: The American Phytopathology Society. Pp. 49-55.

Peterschmitt, M., J.B. Quiot, B. Reynaud and P. Baudin. 1992. Detection of maize streak virus antigens over time in different parts of maize plants of a sensitive and a so-called tolerant cultivar by ELISA. Annals of Applied Biology 121: 641-53.

Contributor: Biswanath Das