F. Afshari - Seed and Plant Improvement Institute, P. O. Box: ۴۱۱۹, Karaj, Islamic Republic of Iran.

The stripe (Yellow) rust in wheat is one of the most important plant diseases in Iran. Since ۱۹۹۳ several epidemics have occurred in Iran causing the breakdown of widely util-ized sources of resistance in wheat cultivars. Twenty-seven pathotypes were identified during ۲۰۰۳ and ۲۰۰۴ in greenhouse tests. Pathotypes ۶E۶A+, ۶E۲۲A+, ۶E۱۳۰A+, ۶E۱۳۴A+, ۶E۱۴۲A+, ۶E۱۵۸A+, ۱۳۴E۱۳۰A+ and ۱۳۴E۱۴۲A+ were more common during the course of this study. Virulence on plant/s with gene/s Yr۲, Yr۶, Yr۷, Yr۸, Yr۹, Yr۲۴, Yr۲۵, YrSD, YrSP, Yr۳N, Yr۲+, Yr۶+, Yr۹+, Yr۷+, Yr۳۲+ and YrA was detected under greenhouse conditions. The majority of isolates with a high frequency (more than ۸۸%) showed virulence on plant/s with Yr۲, Yr۶, Yr۷, Yr۹, YrA and Yr۲۴ genes. No virulence was detected on plant/s with Yr۱, Yr۳V, Yr۴, Yr۵, Yr۱۰ and YrSU genes. In a greenhouse test, frequency of virulence to wheat genotypes with the Yr۳۲+, YrSP and YrSD gene was less than ۷%; frequency of virulence to all other wheat genotypes was between ۱۹ and ۱۰۰%. During three years of field study, virulence on wheat genotypes Heines Kolben (with genes Yr۲ and Yr۶), Kalyansona (Yr۲), Lee (Yr۷), Avocet R (YrA), Federation*۴/Kavkaz (Yr۹) and TP۱۲۹۵ (Yr۲۵) was common. No virulence was observed on plants with Yr۱, Yr۳V, Yr۳N, Yr۴, Yr۵, Yr۸, Yr۱۰, Yr۱۸, Yr۲۴, Yr۳۲+, YrSP, YrSD and YrSU genes in the trap nurseries. The coefficient of infection (C. I.) of the adult plant resistance gene, Yr۱۸, was between ۱۶-۶۴ with moderate susceptibility and is going to be used in the breeding program in combination with other resistant sources.

Wheat, Pathotypes, Puccinia striiformis, Resistance genes