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Alternate hosts for the yellow rust pathogen and their role in generating new virulence

Zhensheng Kang: Northwest A&F University

<div>Wheat stripe rust, caused by <em><i>Puccinia striiformis </i></em>f. sp. <em><i>t</i></em><em><i>ritici</i></em><em><i> </i></em>(<em><i>Pst</i></em>), is a damaging disease of wheat in the world. Epidemics of the disease cause severe yield reduction. Use of wheat resistant cultivar is an economic, effective approach for control of wheat stripe rust. However, the resistance of wheat was often overcome by new races. Mutation, somatic recombination and sexual recombination were proven to cause virulence variation to produce new races in rust fungi. But, sexual cycle of <em><i>Pst</i></em> has not been known for centuries until recent discovery of barberry (<em><i>Berberis</i></em>) identified as alternate host for <em><i>Pst</i></em>. To date, many barberry species, native to China (mainly), USA, and European countries, have been identified as alternate hosts for <em><i>Pst</i></em>. Importantly, <em><i>Pst</i></em> samples recovered from rusted barberry species have been reported in China, but not in other countries. This indicated that <em><i>Pst</i></em> completes sexual cycle on barberry in nature in some regions of the world. Sexual hybridization of <em><i>Pst </i></em>can produce a high diversity in virulence either single race or between races, greatly higher than asexual reproduction. This can be explained high diverse of <em><i>Pst</i></em> population in some areas of the globe, especially in China and Pakistan. Barberry plays an important role in occurrence of stripe rust of wheat in China but not in other countries so far, indicating that function of barberry in generating new virulence for <em><i>Pst</i></em> and providing inoculums for wheat may vary in different countries.</div>

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