Safarali Safavi - Crop and Horticultural Science Research Department, Ardabil Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization, Ardabil, Iran.
Farzad Afshari - Department of Cereal Research, Seed and Plant Improvement Institute, Agricultural Research, Education and Extension Organization, Karaj, Iran.

Yellow (stripe) rust caused by Puccinia striiformis f. sp. tritici is an important disease that threatens wheat production where the weather conditions are congenial and susceptible cultivars are present. Host resistance is the most economical and environmentally safe control method to manage wheat yellow rust; and slow rusting resistance, a kind of quantitative resistance, has been reported to have more durability. We planned an experiment aimed to evaluate resistance durability to yellow rust in some wheat cultivars. This study was conducted in field plots under natural infection conditions against race(s) populations of stripe rust believed to have virulence against Yr۲, Yr۶, Yr۷, Yr۸, Yr۹, Yr۱۰, Yr۱۷, Yr۱۸, Yr۲۱, Yr۲۲, Yr۲۳, Yr۲۴, Yr۲۵, Yr۲۶, Yr۲۷, Yr۳۱, Yr۳۲, YrA and YrSU resistance genes. Slow rusting parameters, including final rust severity (FRS), apparent infection rate (r), relative area under disease progress curve (rAUDPC), and coefficient of infection (CI) were evaluated in a set of ۵۰ wheat genotypes along with susceptible control during a seven-year study from ۲۰۰۸ to ۲۰۱۴. Seedling reaction was also evaluated under field conditions. Based on evaluated resistance parameters, the cultivars (entries: ۳۴, ۴۰-۵۰) as well as susceptible check with the highest values of FRS, CI, r and rAUDPC, were considered as susceptible cultivars. Eight cultivars (entries: ۱-۷and ۹) were resistant at the seedling and adult plant stages. Thirteen cultivars (entries: ۱۳, ۱۵, ۱۶, ۱۷, ۲۰, ۲۱, ۲۴, ۲۸, ۲۹, ۳۲, ۳۳, ۳۵, ۳۷) showed resistance reaction at the seedling, but susceptible to moderate reactions at the adult plant stage. Sixteen cultivars (entries: ۸ ۱۰, ۱۱, ۱۲, ۱۴, ۱۸, ۱۹, ۲۲, ۲۳, ۲۵, ۲۶, ۲۷, ۳۰, ۳۱, ۳۸, ۳۹) were susceptible at the seedling stage, and had moderately resistant to moderately susceptible reactions at the adult plant stage. Accordingly, these later cultivars with low level of slow rusting parameters were supposed to have gene(s) for varying degrees of slow rusting resistance or high temperature adult plant (HTAP) resistance. The remaining cultivars may have low level of slow rusting resistance that need further study to elucidate their nature of resistance. Cluster analysis of wheat cultivars revealed four major groups/clusters, based on slow rusting resistance parameters and seedling infection types.

Wheat cultivars, durable resistance, yellow rust, Puccinia striiformis f. sp. tritici