Virulence patterns of wheat yellow rust and effective resistance genes to Puccinia striiformis F. Sp. tritici in Pakistan

Yellow rust caused by Puccinia striiformis f. sp. tritici is a damaging wheat disease in many countries including Pakistan. Monitoring of pathogen virulences over time and space provides information for the host resistance improvement and deployment. Virulences were monitored in three wheat growing zones close to Himalayan region in Pakistan using yellow rust differentials AvSYr1NIL, AvSYr5NIL, AvSYr6NIL, AvSYr7NIL, AvSYr8NIL, AvSYr9NIL, AvSYr10NIL, AvSYr15NIL, AvSYr17NIL, AvSYr18NIL, AvSYr24NIL, AvSYr26NIL, AvSYr27NIL, AvSYr32NIL, AvSYrSPNIL, Jupateco R, Jupateco S, Avocet R and Avocet S during 2010 to 2013. No virulence was observed for Yr1 and Yr17 in the southern zone while Yr10 and Yr15 were found clean in the central and northern (Abbotabad) zones. Yr15 indicated susceptibility during 2011 and 2013 in northern zone (Swat). Performance of other genes fluctuated among locations and years. Virulences were observed for Yr5, Yr24, Yr26 and YrSp at different locations and years but rust severity of these genes were below 20% during 2010 to 2013 except Yr5 which was high at one location in the central zone. Similarity index (SI) among locations of three zones indicated a high degree of similarity between Peshawar 1 and Abbotabad (SI=0.13). All locations have little similarity among each other’s except Peshawar 1 and Bannu (SI=27.72) and Bannu and Abbotabad (SI=27.6) which had highest dissimilarity to each other. Both Yr10 and Yr15 can be used in the wheat improvement programs along with Yr18 to prolong the effective life span of cultivars for durable protection against yellow rust in Pakistan.