Phytoplasma - forage grass
Contributors to this page are: CIAT, Colombia (Maritza Cuervo, Cesar Medina, Jose Luis Ramirez, Socorro Balcazar, Josefina Martinez, Daniel Debouck); ILRI, Ethiopia (Jean Hanson, Janice Proud, Juvy Cantrell).
Napier Grass Stunt Disease
Phytoplasma belonging to 16SrXI (rice yellow dwarf) group; 16Sr111 group
Reduction in plant biomass by 20 to 40% poses a major problem to small-holder cattle producers (milk and meat). It is threatening the livestock industry and food security in east and central Africa.
Etiolation, reduction in leaf size, proliferation of tillers and shortened internodes
Pennisetum purpureum, Medicago sativa, Cynodon dactylon
East and Central Africa
Biology and transmission
The method of plant propagation and the presence of insect vectors promote the spread of NGSD over long distances. Napier grass produces small, unviable seeds thus propagation is vegetative either by stem cutting or clump splitting.
Transmission of the pathogen among plants is facilitated by leafhoppers. Leafhoppers generally spend their life on one plant but can transfer to another plant during cropping or when blown by wind. Transmission of pathogen in plants happens after the latent period when phytoplasma multiplies in the body and migrates to the salivary glands of the insect. While feeding on phloem sap, the insect inoculate the pathogen into the plant.
Strains were most similar (96%) to Bermuda grass white leaf phytoplasma (Accession 16388).
Detection/indexing method in place
- at CIAT: Not applicable
- at ILRI: NASH, PCR method
- If the disease is present then all symptomatic plants should be removed and burnt.
- Measures to control the spread of NGSD can be effective only if there is sufficient knowledge on vector lifecycle in relation to phytoplasma transmission.
- For high infection check for disease free seeds tillers to re-establish plots.
Procedure followed at the centers in case of positive test
- All individual plants tested, clean plants retained and infected plants rogued and material burnt
References and further reading
Arocha Y, Zerfy T, Abebe G, Proud J, Hanson J, Wilson M, Jones P, Lucas J. 2008. Identification of Potential Vectors and Alternative Plant Hosts for the Phytoplasma Associated with Napier Grass Stunt Disease in Ethiopia. Journal of Phytopathology. Published Online: 11 Nov 2008.
Diekmann M, Putter CAJ. (eds.) 1995. FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm. No. 14. Small Grain Temperate Cereals. Food and Agriculture Organization of the United Nations, Rome/International Plant Genetic Resources Institute, Rome.
Frison EA, Putter CAJ. (eds.). 1993. FAO/IBPGR Technical Guidelines for theSafe Movement of Sugarcane Germplasm. Food and Agriculture Organization of the United Nations, Rome/ International Board for Plant Genetic Resources, Rome.
Jones P, Arocha Y, Zerfy T, Proud J, Abebe G, Hanson J. 2007. A stunting syndrome of Napier grass in Ethiopia is associated with a 16SrIII Group phytoplasma, Plant Pathology, 56, 345.
Jones P, Devonshire BJ, Holman TJ, Ajanga S. 2004. Napier grass stunt: a new disease associated with a 16SrXI Group phytoplasma in Kenya. [online] Available from URL: http://www.bspp.org.uk/ndr/july2004/2004-19.asp Date accessed 13 April 2010
Mulaa M. Nov. 2004. A Survey to Collect and Identify Potential Vectors of Napier Grass stunting disease Associated with Phytoplasma in Western Kenya. Nov. 25-29, 204. ILRI, Unpublished material.