Characterization of two different genetic mechanisms involved in the rust resistance defense response in wheat

Abstract

Wheat leaf rust, stem rust, and stripe rust are major fungal diseases of wheat caused by Puccinia triticina, P. graminis f. sp. tritici, and P. striiformis f. sp. tritici, respectively. Development of wheat varieties with genetic resistance to pathogens is a common strategy to protect against significant yield loss. However, incorporating resistance is not always straightforward, and understanding the mechanisms responsible for triggering host resistance is key. Here, were characterized two different genetic mechanisms involved in the rust resistance defense response in wheat. Two spring wheat cultivars and their respective EMS mutants, which displayed enhanced resistance to leaf, stem, and/or stripe rust, were studied. The cultivar Canthatch possesses a stem rust resistance suppressor on chromosome 7DL. We characterized the spectrum of resistance of Canthatch and the mutant CTH-NS, confirming the specificity of this suppressor is stem rust-specific. The cultivar Alpowa mutant MNR220 displays broad-spectrum resistance to a number of wheat rust races at the seedling stage. We characterized the functional resistance of MNR220 to a race of leaf rust by sampling inoculated tissues at various time points and tracking the disease progress microscopically. The mutant MNR220 confers resistance at the pre-haustorial stage; formation of haustoria is delayed or inhibited in MNR220 relative to the wild type Alpowa.