Weeds (Forage grasses)

Weeds

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

Scientific name

Phytoplasma belonging to 16SrXI (rice yellow dwarf) group; 16Sr111 group

Significance

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.

Symptoms

Etiolation, reduction in leaf size, proliferation of tillers and shortened internodes

Hosts

Pennisetum purpureum, Medicago sativa, Cynodon dactylon

Geographic distribution

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

Treatment/control

• 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.

http://www3.interscience.wiley.com/journal/ 

Safe transfer of maize germplasm

Contributors to this page: CIMMYT, Mexico (Etienne Duveiller, Monica Mezzalama, Eloise Phipps, Thomas Payne, Jesper Norgaard), Independent consultant (Jesse Dubin). IITA, Nigeria (M. Ayodele, L. Kumar).

CIMMYT, as one of the 15 CGIAR centers, has the mandate for care and maintenance of maize germplasm. The Wellhausen-Anderson Genetic Resources Center provides secure, long-term storage for critical maize genetic resources; facilitating their use to solve practical breeding problems; improving knowledge about genetic diversity; developing and assessing complementary strategies for in situ and ex situ conservation; exploring genetic diversity at the molecular level; helping develop global databases on maize genetic resources.

The Plant Genetic Resource Center’s specially designed vaults currently hold some 22,000 samples of maize and teosinte, a wild relative of maize. The Center also maintains a living collection of Tripsacum, a more distant maize relative.

Both CIMMYT and IITA have responsibilities for maize and the information on quarantine regulations and guidelines is presented for both institutions.

 Information is included on: 

• Import and export requirements for CIMMYT and IITA. 
• Technical guidelines for the safe movement of germplasm and detection of relevant pathogens and pests. 
• Best practices in place at CIMMYT.

References and further reading

Compendium of Corn Diseases. 1999. Third Edition. Editor, Donald White. APS Press, St. Paul, MN. USA. ISBN 0-89054-234-1.

Import/export of maize germplasm

Contributors to this page: CIMMYT, Mexico (Etienne Duveiller, Monica Mezzalama, Eloise Phipps, Thomas Payne, Jesper Norgaard), Independent consultant (Jesse Dubin).

It is very important to remember that an International Phytosanitary Certificate is always required for any plant germplasm exchange.

The requirements of countries that received seed from CIMMYT Headquarters located in Mexico, have been collected from the permits granted to CIMMYT for exportation of maize experimental seed. The information in this table was updated to September 2011. IITA import requirements are included.

• The information received from the same country may vary from a permit to another, therefore the latest has been considered the valid one.
• It is advisable before sending a shipment to contact the consignee in the recipient country to confirm the information reported in this table.
• Some of the pathogens listed are not proved to be seed borne (for example Burkholderia andropogonis, Cercospora zeae-maydis), nevertheless due to the fact that these pathogens are listed among the country requirements they were included.