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An isolate of the "Kranich" race of the basidiomycete Puccinia striiformis f.sp. tritici (Pst), which causes yellow (stripe) rust on wheat, was selfed on Berberis vulgaris, the alternate (sexual) host for several rust fungi infecting cereals and grasses. Since 2011, the "Kranich" race has been detected in several European countries and it has contributed to the replacement of the pre-existing European Pst population. A sexual origin of the "Kranich" race has been suggested due to the high capacity of teliospore production and the genetic similarity to the populations in the centre of diversity of Pst in the near-Himalayan region. For the completion of the sexual life cycle, B. vulgaris was inoculated with basidiospores derived from germinating teliospores. Pycnia appeared on the adaxial side of the leaves 8 days after inoculation (dai) and subsequent fertilization resulted in the development of aecia on the abaxial side of the leaves from 15 dai. Inoculation of wheat seedlings with aeciospores from bulked aecia resulted in 124 progeny isolates. Twenty-three of these were randomly selected and genotyped using 19 simple sequence repeat (SSR) markers, which confirmed the parental origin of the progeny isolates. Eight heterozygous markers in the parental isolate revealed segregation in the progenies resulting in 18 novel multilocus genotypes, confirming recombination following sexual reproduction. This study demonstrated a high sexual capacity of the "Kranich" race, which highlights the risks associated with sexual reproduction under suitable conditions for rust development. [ABSTRACT FROM AUTHOR]

Isolates of recently spreading races of yellow rust from wheat and triticale in Europe were analysed using virulence phenotypic data of 2605 isolates sampled in 12 countries between 2000 and 2014. A subset of 239 isolates was investigated by microsatellite markers. At least three races of non-European origin, termed 'Warrior', 'Kranich' and 'Triticale aggressive', were identified in the post-2011 population. The Warrior race was already present in high frequencies in the first year of detection in most European countries and to a large extent it replaced the pre-2011 European population. In contrast, the two other exotic races were localized to certain regions and/or crop type. The presence already of at least six multilocus genotypes of the Warrior race and five genotypes of the Kranich race in the first year of detection and across large areas is consistent with a hypothesis of aerial spread from genetically diverse source populations. A comparison with reference isolates sampled from six continents suggested that the Warrior and Kranich races originated from sexually recombining populations in the centre of diversity of the yellow rust fungus in the near-Himalayan region of Asia. However, the Triticale aggressive race was most similar to populations in the Middle East/Central Asia. The study illustrated the potential role of sexual Puccinia striiformis populations as a reservoir for new races replacing distant clonal populations. [ABSTRACT FROM AUTHOR]