Virulence structure of over-summering populations of Puccinia striiformis f.sp.tritici in Qinghai Province from 2014 to 2016
To explore the interrelationships between over-summering inocula of Puccinia striiformis f.sp.tritici(Pst)in different regions of Qinghai Province,we collected Pst samples from autumn wheat seedlings at the early stages of the disease during 2014-2016,identified their virulence on near isogenic wheat lines and assis-tant differential hosts,and analyzed the virulence diversity of these Pst populations by years and regions.The re-sults showed that a total of 65 virulence types were identified in 106 Pst samples.The Pst populations we tested in this study showed the highest virulence frequency to the stripe rust resistance genes Yr25,Yr29 and YrA,all with a value of 100％,followed by Yr44 of 99.07％.The virulence frequency of these Pst populations to Yr5 and Yr15 was 0,and to the other stripe rust resistance genes were between 45.56％and 97.78％except for the YrTr1 gene(1.76％).This indicated that except for Yr5,Yr15 and YrTr1,the resistance of the remaining 24 resistant genes had been reduced or lost in Qinghai Province.In comparison,the diversity of Pst virulence was the highest in 2016,followed by 2014 and then 2015;Hualong County had the highest virulence diversity,followed by Guide County and then Minhe County.The virulence frequencies of the tested Pst populations to Yr5,Yr15 and YrTr1 during 2014-2016 ranged from 0 to 2.8％,indicating that these three stripe rust-resistant genes are cur-rently effective in Qinghai Province and can be further utilized to control stripe rust of wheat.This study clarifies the virulence types of Pst populations in Qinghai Province and the difference in virulence between Pst popula-tions from different regions of Qinghai Province,providing a theoretical basis for the rational deployment of re-sistant wheat varieties in Qinghai Province.
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