Yr26-virulent Puccinia striiformis f.sp. tritici pathotypes in China are genetically diverse

A Pst pathotype group named V26, virulent to wheat lines possessing Yr26 (=Yr24) has become the third most frequent group in China after races CYR32 and CYR33. Twenty four near-isogenic lines (NILs) and 19 Chinese differentials were used to identify the avirulence/virulence spectra of 36 Yr26-virulent isolates from four provinces (Qinghai, Gansu, Sichuan and Ningxia). Eight races were identified when tested on the NIL set, and 7 races were identified on the Chinese set. There was no relationship with province of origin. Three races identified on the NILs occurred at relatively high frequencies (23, 3, and 3 isolates). Virulence differences existed for Yr1, Yr4, Yr6, Yr9, Yr17, Yr25, Yr32, YrSp, and YrTr1. Among the 7 races identified on the Chinese differentials, one (CYR32 + Yr26 virulence) was represented by 13 isolates and another (CYR33 + Yr26 virulence) included 15 isolates. Among the entire group there were virulence differences on Trigo-Eureka (Yr6+), Lovrin 13 (Yr9+), Kangyin 655, Fengchan 3 (Yr1+), Lovrin 10 (Yr9+), and Hybrid 46 (Yr4+). All isolates were avirulent on Zhong 4 and T. spelta. Using 18 polymorphic simple sequence repeat (SSR) markers, we identified 35 genotypes clustered into two molecular groups (MGs) at a similarity coefficient level of 0.70. SSR analysis also indicated a high level of recombination within the V26 group. The considerable diversity indicates a threat not only to cultivars carrying Yr26, but also to other currently resistant materials.

Zhan
State Key Laboratory of Crop Stress Biology for Arid Areas and College of Plant Protection, Northwest A&F University, P.R. China
Primary Author Email: 
kangzs@nwsuaf.edu.cn