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Wheat stripe rust: Are recent pandemic races associated with the sexual cycle of the pathogen?

Julian Rodriguez Algaba: Aarhus University

<div>A changing climate and increasing travel and trade may be important drivers for inter-continental spread of yellow (stripe) rust to new areas and spread of new races to previously resistant crop varieties. The latter was the case when the NW European <em>Puccinia striiformis</em> population in 2011 was replaced by new races of non-European origin. The ‘Warrior’ race was present at many locations in the first year of detection, whereas the ‘Kranich’ race was predominant only in few regions. Presence of several multi-locus genotypes of both races was consistent with a hypothesis of aerial spread of spores from genetically diverse source populations. Both races produced more telia on the wheat host than previously detected races in Europe, and teliospores were able to germinate and produce basidiospores infecting the alternate host, <em>Berberis</em> <em>vulgaris</em>. Sexual reproduction was completed under experimental conditions by recovery of progeny isolates from wheat inoculated by aeciospores from <em>B. vulgaris.</em> Based on informative microsatellite markers and reference isolates from six continents, it was concluded that the ‘Warrior’ and ‘Kranich’ races originated from the centre of diversity of the yellow rust fungus in the near-Himalayan region. The study illustrated the potential role of sexual reproduction of wheat rust fungi, serving as a reservoir for new races replacing distant clonal populations, and causing disease epidemics at continental scales on previously resistant crop varieties.</div>

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