A stunting syndrome of Napier grass in Ethiopia is associated with a 16SrIII Group phytoplasma
1 Global Plant Clinic, Plant Pathogen-Interactions Division, Rothamsted Research, Harpenden, Hertfordshire, UK
2 National Centre for Animal and Plant Health (CENSA), Apdo 10. San José de Las Lajas, Havana, Cuba
3 Forage Genetic Resources, International Livestock Research Institute, PO Box Addis Ababa, Ethiopia
Accepted: 02 Jul 2006
Napier or elephant grass (Pennisetum purpureum) is a perennial grass grown widely in East Africa as a fodder crop. It is being promoted in Ethiopia for use by cut and carry (zero grazing) smallholder livestock keepers. In Kenya, Napier grass stunt is associated with a phytoplasma belonging to the 16SrXI (Candidatus Phytoplasma oryzae) group. The impact of Napier stunt is such that the viability of the smallholder dairy industry in Western Kenya is seriously threatened by this disease (Jones et al., 2004). The International Livestock Research Institute (ILRI) in Ethiopia maintains a germplasm collection of Napier at its field stations in Debre Zeit and Zwai, under the auspices of FAO as a global public good. In 2004 symptoms were observed of stunting in some of the accessions and a phytoplasma infection was suspected. Leaf samples of healthy and affected Napier were collected from Debre Zeit and Zwai and the DNA extracted. This was used as a template for nested PCR analysis using primers P1/P7 and R16F2n/R16R2 (Arocha et al., 2005), and bands of the expected size (1.25kb) were produced in 8/11 diseased and 3/9 apparently healthy samples. These amplicons were sequenced directly, the sequences aligned, subjected to BLAST analysis and deposited in GenBank (Accession No. DQ305977). The highest similarity was with the African sugarcane yellow leaf phytoplasma (Accession No. AF056095), a member of the 16SrIII (Candidatus Phytoplasma pruni) group (IRPCM Phytoplasma/Spiroplasma Working Team–Phytoplasma taxonomy group, 2004) but not to the Napier grass stunt phytoplasma found in Kenya (GenBank Accession No. AY736374) or others of the 16SrXI group. Latent infection by phytoplasmas has previously been reported for yellow leaf syndrome of sugarcane in South Africa (Cronjé et al.,1998) and in Cuba for sugarcane and weeds (Arocha et al., 2005). This is the first report of a 16SrIII group phytoplasma infecting Napier grass.
Work in the UK was done under Defra licence No PHF 174D/5185(08/2005). Sequencing was done by the Sequencing Service (School of Life Sciences, University of Dundee, Scotland, www.dnaseq.co.uk) using Applied Biosystems Big-Dye Ver 3.1 chemistry on an Applied Biosystems model 3730 automated capillary DNA sequencer.
- Cronjé CPR, Tymon AM, Jones P, Bailey RA, 1998. Association of a phytoplasma with a yellow leaf syndrome of sugarcane in Africa. Annals of Applied Biology 133, 177-186.
- Jones P, Devonshire BJ, Holman TJ, Ajanga S, 2004. Napier grass stunt: a new disease associated with a 16SrXI Group phytoplasma in Kenya. Plant Pathology 53, 519. (First published online: New Disease Reports 9
- Arocha Y, López M, Fernández M, Horta D, Piñol B, Peralta EL, Almeida R, Carvajal O, Picornell S, Wilson MR, Jones P, 2005. Transmission of sugarcane yellow leaf phytoplasma by the delphacid planthopper Saccharosydne saccharivora, a new vector of sugarcane yellow leaf syndrome. Plant Pathology 54, 634-642.
- IRPCM Phytoplasma/Spiroplasma Working Team – Phytoplasma taxonomy group, 2004. ‘Candidatus Phytoplasma’, a taxon for the wall-less, non-helical prokaryotes that colonize plant phloem and insects. International Journal of Systematic and Evolutionary Microbiology 54, 1243-1255.
This report was formally published in Plant Pathology
©2006 The Authors