BREAD: Inactivating Rust Resistance Suppressors to Unlock Multiple Defense Responses in Wheat

01 May 2010 30 Apr 2018

Li Huang (PI) , Evans Lagudah (CoPI), Sridhar Bhavani (CoPI)


PI: Li Huang (Montana State University)

CoPI: Evans Lagudah (CSIRO Plant Industry-Black Mountain, Australia)

Collaborators: Linda Tabe (CSIRO Plant Industry-Black Mountain, Australia), Junhua Peng (Chinese Academy of Sciences, Wuhan Botanical Garden/Institute, Wuhan, China) and Davinder Singh (CIMMYT, Village Market, Nairobi, Kenya)

Wheat is a staple cereal for most of the world's population. It is estimated that approximately 50% of the world's wheat is grown in developing countries, where it serves as a staple food for a large proportion of subsistence farmers. Rusts are fungal pathogens that cause some of the most damaging diseases of wheat. Leaf rust (caused by Puccinia triticina), stem rust (caused by P. graminis f. sp. tritici) and stripe rust (caused by P. striiformis f. sp. tritici) are the most widely distributed diseases of wheat. These diseases reduce plant fitness and result in grain yield losses from 5-95%, depending on the rust species and the development stage at which it infects the crop. Historically, breeding durable resistance to rust diseases relies largely on continually introgressing new resistance genes into adapted varieties, often from wild relatives. This long genetic process is not always completely successful in eliminating unfavorable characteristics brought in by linkage drag. Furthermore, there is genetic evidence that the functions of introgressed resistance genes are often suppressed in the hexaploid wheat genetic background. However, little is known about the nature of these "suppressors" or the mechanism by which they act. This project will investigate two suppressors of rust resistance in wheat that preliminary studies have shown, when inactivated, unmask robust resistance to the newly emerged virulent stem rust strain, Ug99, which currently threatens food security in Africa and the Middle East. The project will deploy a multi-national team to 1) characterize these two suppressors and their mechanism of action(s); 2) transfer this new resistance to wheat breeding programs in both Kenya and China; and, 3) screen project germplasm for resistance against other emerging rust disease threats across this broad region.

The work has the potential to unlock an extensive array of cryptic rust resistance genes in the hexaploid wheat genome that are either currently unrecognized or have been poorly utilized. Suppressors of rust resistance have not been characterized in any experimental system, so project results will provide fundamental new information about the nature and mode of action of a previously-unstudied class of negative regulators of plant defense responses. This research will have direct benefits for agriculture in the developing world by providing new, useful sources of rust resistance, with associated molecular markers. With respect to training and outreach, the project will provide an exchange program to introduce young researchers from Kenya and China to cutting-edge technologies, and to create opportunities for young researchers from the USA and Australia to learn from local knowledge in Kenya and China. The exchange program will train four young scientists who will work in the two labs in Kenya and China to deliver cultivars and to educate smallholder farmers of their nations. In addition, the project will generate three video protocols available on-line to reach a broader audience, including students, biology teachers, and wheat breeders in both developed and developing countries. All data and biological resources generated by the project will be available to the public. Gene expression data will be submitted to the Gene Expression Omnibus (GEO; http://www.ncbi.nlm.nih.gov/geo/). Mapping and marker data will be submitted to GrainGenes (http://wheat.pw.usda.gov/GG2/index.shtml) and germplasm and breeding line information will be available through the website for the USDA-National Institute of Food and Agriculture supported Durable Rust Resistance in Wheat (DRRW) project (http://maswheat.ucdavis.edu/). Wheat lines used and/or developed by this project will be available through the USDA-ARS National Small Grain Collection (NSGC).