| 1 | Population Diversity of Puccinia graminis is Sustained Through Sexual Cycle on Alternate Hosts显示文摘A high degree of virulence diversity has been maintained in the population of Puccinia graminis f.sp.tritici(Pgt)in northwestern United States.Although Berberis vulgaris is present in the region and Pgt has been isolated from aecial infections on B.vulgaris,the population is too diverse to be explained by the limited presence of B.vulgaris alone.Since2008,we have isolated P.graminis from aecial infections on fruits of Ma honia repens and Mahonia aquifolium from northwestern United States.These two native woody shrub species,widely distributed in western North America,were once classified as resistant to P.graminis based on artif icial inoculations.By isolating P.graminis from aecia,we established that M.repens and M.aquifolium along with B.vulgaris(albeit infrequent)serve as the alternate hosts of P.graminis in the region.The isolates of P.graminis from Mahonia of North America had diverse virulence patterns and most of the isolates could be differentiated on Morocco,Line E,Chinese Spring,Little Club,LMPG-6,Rusty,and other genotypes that are considered to be universally susceptible to most Pgt isolates.This discovery explained the persistence of virulence diversity of Pgt observed in isolates derived from uredinia on cereal crops in the region.In addition to cereal crops,uredinial stage of the P.graminis population is sustained by wild grasses,especially Elymus glaucus,a native grass sharing the same habitat with the rusted Mahonia spp.Although virulence to some important stem rust resistance genes was observed in some isolates derived from Mahonia of North America when tested against single stem rust resistance gene stocks,the overall virulence is very limited in these isolates.This is likely a result of limited selection pressure on the rust population.In contrast to northwestern United Sates,the Pgt population in east of the Rocky Mountains of North America has declined steadily with a single race,QFCSC,being predominant in the last decade.This decline is likely due to a combination of factors,of which a lack of sexual recombination in the region is perhaps the most important one. | Yue Jin Matt Rouse Jim Groth | 2014 | Journal of Integrative Agriculture2014，13，2： | 2 |
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