Research Programs |
Wheat Stem Rust Resistance
Wheat stem rust, caused by the fungus Puccinia graminis f. sp. tritici (Pgt), is a devastating disease that has caused multiple epidemics and associated crop failures throughout recorded history. Resistance to stem rust was a top priority in the “green revolution” wheat varieties bred by Norman Borlaug and coworkers beginning in the 1950s, and the combinations of resistance genes they created remained remarkably effective until the last decade. In 1999, a new strain of Pgt was identified from Africa that overcomes the major resistance genes used to combat stem rust. Commonly called Ug99, it has given rise to new strains to which 90% of the world’s commercial wheat varieties are susceptible. This pathogen, now spreading from sub-Saharan Africa across the Arabian peninsula, is predicted to move into central and south Asia, an area that produces 19% of the world’s wheat and home to 1 billion people, most of whom rely on the wheat crop for nutrition.
Throughout his career and right up until his passing in 2009, Dr. Borlaug had raised the alarm to mobilize the global plant breeding community to reinvigorate breeding for stem rust resistance. This activity has been supported through the Borlaug Global Rust Initiative, including the Durable Rust Resistance in Wheat project, funded by the Bill and Melinda Gates Foundation, and also the Food and Agriculture Organization. It is hoped that these on-going efforts in conventional breeding will result in new wheat varieties resistant to Ug99 and its progeny.
2Blades shares these concerns about stem rust and has initiated a project that focuses first on the pathogen, to identify the so-called“effector” proteins from Pgt that are recognized by resistance (R) genes in non-host plants of Pgt. The ultimate goal of this project is to use these fungal effectors as tools to isolate the corresponding R genes; the R genes will be introduced into wheat strains to produce durable resistance to stem rust. This biotechnological approach allows for the use of R genes from plant species that do not sexually hybridize with wheat, thus vastly increasing the genetic diversity of available resistances, and it will also permit the simultaneous insertion of multiple R genes at a single locus, greatly speeding introgression into commercial cultivars.
In addition, knowledge of fungal sequences will also allow us to understand in detail how the Pgt population changes over time in response to selective pressure imposed by resistance in the host crop.
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