Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 3/15/2007
Publication Date: 8/1/2007
Citation: Singh, R., Jin, Y., Huerta-Espino, J., Njau, P., Ward, R. 2007. Progress in the identification and utilization of adult-plant resistance to Puccinia graminis tritici race Ug99 (TTKS) in CIMMYT spring wheats. Phytopathology. 97:S136.
Technical Abstract: The spread of race Ug99 (TTKS) of Puccinia graminis tritici, the causal organism of stem (or black) rust, from East Africa to Arabian Peninsula poses a major threat to wheat production worldwide due to the susceptibility of a majority of current cultivars and breeding materials. Testing of wheat seedlings in the greenhouse and adult plants under high disease pressure in the field have identified wheat materials that carry high to moderate but adequate levels of adult-plant resistance (APR). Among these materials are included old-tall Kenyan cultivars, 4-5 minor, additive genes carrying APR wheat stocks developed by D. R. Knott in late 1970s, older semidwarf CIMMYT-derived cultivars, and new high-yielding materials. The best APR wheat line from CIMMYT displayed a very low disease score (5MR) during both years of field testing. A common feature of all the above APR lines was the presence of known durable slow rusting gene Sr2 in combination with other unknown number of minor genes referred as the "Sr2-Complex". Because complex APR is expected to be durable, a breeding scheme that includes shuttling of segregating populations between Mexico and Kenya has been implemented to enhance the incorporation of APR in a wider range of popular wheat cultivars and promising wheat germplasm. Identifying APR genes and linked molecular markers are also being pursued to aid selection of APR in the presence of effective race-specific resistance genes.