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ARS Home » Southeast Area » Charleston, South Carolina » Vegetable Research » Research » Publications at this Location » Publication #344421

Research Project: Biology, Etiology and Host Resistance in Vegetable Crops to Diseases and Nematodes

Location: Vegetable Research

Title: Variation in the AvrSr35 effector determines Sr35 resistance against wheat stem rust race Ug99

item Rutter, William
item SALCEDO, ANDRES - Kansas State University
item AKHUNOVA, ALINA - Kansas State University
item WANG, SHICHEN - Texas A&M Agrilife
item BOLUS, STEPHEN - University Of California
item Chao, Shiaoman
item Rouse, Matthew - Matt
item Szabo, Les
item Bowden, Robert
item AKHUNOV, EDUARD - Kansas State University
item DUBCOVSKY, JORGE - University Of California

Submitted to: Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/9/2017
Publication Date: 12/22/2017
Citation: Rutter, W.B., Salcedo, A., Akhunova, A., Wang, S., Bolus, S., Chao, S., Rouse, M.N., Szabo, L.J., Bowden, R.L., Akhunov, E., Dubcovsky, J. 2017. Variation in the AvrSr35 effector determines Sr35 resistance against wheat stem rust race Ug99. Science. 358(6370):1604-1606. https://doi:10.1126/science.aao7294.

Interpretive Summary: Wheat stem rust is a devastating disease of wheat caused by the fungus Puccinia graminis f. sp. tritici (Pgt). The most promising way to control this fungal pathogen is through the use of plant resistance genes. These plant resistance genes detect specific fungal factors (avirulence genes) and induce a resistance response within the host plant that ultimately kills the fungus. Pgt populations can become virulent against a specific plant resistance gene through mutational events that occur within the matching fungal avirulence gene. In this manuscript we have identified the first avirulence gene (AvrSr35) from the Pgt fungus. AvrSr35 is found within the hyper-virulent Pgt populations known as the 'Ug99 race group', which have caused catastrophic wheat losses over the past two decades. AvrSr35 is detected by the wheat resistance gene Sr35, which we now show confers resistance to any Pgt population expressing the AvrSr35 gene. With the identification of AvrSr35, Pgt populations can now be closely monitored for the presence of this gene, which will inform breeders and growers how and where to deploy wheat cultivars containing the Sr35 resistance gene. Ultimately, this provides stakeholders with valuable information that allows them make better stem rust management decisions in the field, and helps control an agronomically important fungal pathogen of wheat.

Technical Abstract: Puccinia graminis f. sp. tritici (Pgt) causes wheat stem rust, a devastating fungal disease. The Sr35 resistance gene confers immunity against this pathogen’s most virulent races, including Ug99. We used the comparative whole genome sequencing of chemically mutagenized and natural Pgt isolates to identify a fungal gene named AvrSr35 and required for Sr35 avirulence. The AvrSr35 gene encodes a secreted protein capable of interacting with Sr35 and triggering the immune response. We show that the origin of Pgt isolates virulent to Sr35 is associated with the non-functionalization of the AvrSr35 gene by the insertion of mobile element. The discovery of AvrSr35 provides a new tool for Pgt surveillance, identification of effector’s host target, and characterization of the molecular determinants of susceptibility and immunity in wheat.