Wheat leaf showing symptoms of stem rust (Puccinia graminis), in this case the virulent Ug99 race. The reddish brown pustules contain masses of urediospores, and may occur on both sides of the leaves, on the stems, and on the spikes. These pustules coalesce during heavy infections.
This wheat is being grown, and will be assessed for symptoms, as part of an ongoing screening program at the Njoro research station in Kenya. The station is part of the Kenya Agricultural Research Institute (KARI), which is working in partnership with CIMMYT to identify sources of resistance to Ug99. This strain of the disease, which emerged in Uganda in 1999, is already endemic in the area, making it possible to use Njoro as a testing ground for wheats from all over the world. Around 30,000 wheat lines are now being screened each year.
For more information on the disease, see CIMMYT’s Wheat Doctor: http://wheatdoctor.cimmyt.org/en/pests-a-diseases/list/122?task=view.
For more on CIMMYT’s ongoing work on Ug99, see the following e-news stories:
2010, “Planting for the future: New rust resistant wheat seed on its way to farmers”: http://www.cimmyt.org/newsletter/231-2010/716-planting-for-the-future-new-rust-resistant-wheat-seed-on-its-way-to-farmers.
October 2009, “From Cairo to Kabul: Rust resistant wheat seed just in time”: http://www.cimmyt.org/newsletter/38-2009/460-from-cairo-to-kabul-rust-resistant-wheat-seed-just-in-time.
December 2008, “Report from the field: Wheat stem rust resistance screening at Njoro, Kenya”: http://www.cimmyt.org/newsletter/37-2008/110-genetic-resources-program.
December 2006, “Threat level rising”: http://www.cimmyt.org/newsletter/82-2006/263-threat-level-rising.
September 2005, “The WorldÃs Wheat Crop is Under Threat from New Disease”: http://www.cimmyt.org/newsletter/86-2005/331-the-worlds-wheat-crop-is-under-threat-from-new-disease.
Photo credit: Petr Kosina/CIMMYT.