A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases <http://www.isid.org>
Date: Sat 3 Nov 2012
Source: Leadership Newspaper, News Agency of Nigeria (NAN) report [edited] <http://leadership.ng/nga/articles/39126/2012/11/03/
Outbreak of rice blast reported in parts of Kaduna
The Kaduna State Government expressed concern on the reported outbreak of a rice disease known as rice blast, in some parts of the state. The Kaduna Agricultural Development Project (KADP) said that the outbreak had been reported in zones where the crop is cultivated in commercial quantity. Extension service workers had been deployed to the areas to take samples for laboratory analysis to ascertain the extent of the outbreak and the total areas affected.
They said the outbreak, in addition to the recent flood disaster, may likely affect the projected rice yield of the state. Farmers cultivate an average of 300 000 hectares [about 740 000 acres] per year, and the state produces an average of one million metric tonnes of rice.
They appealed to farmers not to panic, assuring that the state government had taken steps to ascertain the cause of the outbreak in order to control its spread.
[Rice blast is caused by the fungus _Magnaporthe oryzae_ (previously classified as a strain of _M. grisea_, synonym _Pyricularia oryzae_).
It is one of the most destructive diseases of rice worldwide with potential yield losses of more than 50 percent. Symptoms include lesions on all parts of the shoot, as well as stem rot and panicle blight. When nodes are infected, all plant parts above the infection die, and yield losses are severe. When infection occurs at the seedling or tillering stages, plants are often completely killed. More than 50 species of grasses and sedges can be affected by related pathogens, but most strains isolated from rice can only infect a limited number of cultivars.
Symptom severity and spread of the blast fungus are influenced by climatic conditions. The disease is also favoured by high nitrogen levels (for example from fertilizers) and high humidity. The fungus is spread by infected plant debris, mechanical means (including insect activity), water, and wind. Disease management may include fungicides and cultural practices but relies mainly on resistant varieties.
However, the fungus is highly variable, and this favours the emergence of new strains with increased virulence.
In a recent survey amongst a group of about 500 fungal plant pathologists, rice blast was perceived as the fungal disease with the highest potential scientific and/or economic importance. Reasons given were (1) that more than half of the world's population relies on rice as the main source of calories and (2) because the pathogen has also developed into a model system for the study of plant-pathogen interactions. (Ref: R Dean et al, 2012. Molecular Plant Pathology 13, 414-430. DOI: 10.1111/j.1364-3703.2011.00783.x; see link below)
Kaduna is the yellow state in the centre of the country.
Pictures of rice blast symptoms
Leaf, collar, node, and neck:
Information on rice blast:
<http://www.cbwinfo.com/Biological/PlantPath/PyG.html>, and <http://www.imtech.res.in/raghava/rbpred/home.html>
Perceived impact of fungal crop diseases:
_M. oryzae_ taxonomy:
Blast disease, rice - Australia: (NT) 20120217.1044294 Blast disease, rice - Malaysia: (KH) 20120103.0015
Blast disease, rice - Nepal: (JU) 20111111.3339 Blast disease, rice - Australia: (WA) 20110812.2442 Blast disease, rice - Philippines: (KA) 20110801.2311 Blast disease, rice - Kenya: (CE) 20110704.2025 Rice diseases - Costa Rica, Bangladesh 20110425.1289
Blast disease, rice - Thailand: (northeast) 20101201.4315 Blast disease, rice - Taiwan: (TA) 20101115.4146 Tungro, blast, bacterial blight, rice - India: (TN, OR) 20100912.3299 Blast disease, rice - Spain: (VC) 20100906.3194 Ragged & grassy stunt viruses, rice - Thailand 20100628.2155 Multiple disease, rice - Viet Nam 20100307.0749 Blast disease, rice - Viet Nam: (Mekong Delta) 20100129.0310
Blast disease, rice - Nepal: (JU) 20090731.2682 and older items in the archives]