Pan-genome analysis reveals a highly plastic genome and extensive secreted protein polymorphism in Puccinia striformis f.sp.tritici

The obligate biotrophic basidiomycete fungus Puccinia striformis f.sp.tritici(Pst)is the causative agent of wheat stripe(yellow)rust,a disease that results in severe damage to global wheat production(Chen and Kang,2017).This pathogen has a mixed reproductive mode encompassing both asexual and sexual reproduction.The asexual stage is accomplished by reinfecting wheat with urediniospores,while the sexual cycle involves five different spore types and two phylogenetically unrelated plant hosts wheat,which is the primary host,and barberry,which is the alternate host(Zhao et al.,2016).This extremely complex lifecycle facilitates large genetic variation among Pst populations,which is conducive to the emergence of new virulent races that can overcome wheat resistance genes,resulting in epidemics(Chen and Kang,2017).Secreted effector proteins,the key virulence factors in fungal pathogens,can not only suppress plant immune systems but also trigger host immune responses following recognition by plant receptors(Toruno et al.,2016).