Phenotypic and molecular characterization of resistance to stem rust in wheat cultivars and advanced breeding lines from Iran and Syria

Seedling and adult-plant response to stem rust of ۱۰۳ Iranian and Syrian bread and durum wheat genotypes was investigated using stem rust races TKTTC and TTKSK in seedling tests and TKTTC and TTKST at the adult-plant stage. The same genotypes were characterized with simple sequence repeat (SSR), sequence tagged site (STS) and cleaved amplified polymorphic sequence (CAPS) markers linked to Sr۲, Sr۲۲, Sr۲۴, Sr۲۵, Sr۲۶, Sr۳۱, Sr۳۶, Sr۳۹, and Sr۴۶. In seedling tests, three phenotypic groups were identified: those lacking effective resistance genes, those postulated to carry Sr۳۱, and those that were resistant to TKTTC and TTKSK. Adult-plant assessment indicated the presence of adult-plant resistance (APR) to TKTTC and TTKST mainly due to Sr۲ and uncharacterized resistance gene(s). Using molecular markers, Sr۲ was confirmed as the most common resistance gene detected in Iranian genotypes. It was detected alone in ۳۸ genotypes, in combination with Sr۳۱ in ۱۱ genotypes, and combined with Sr۳۱+Sr۲۵ in one genotype. In total, Sr۳۱ was postulated in ۱۹ genotypes. Among Syrian genotypes, Sr۲ was detected alone in one and in combination with Sr۳۱ in two bread wheat cultivars. No diagnostic DNA fragment associated with the markers was present in the durum wheat genotypes. Haplotype analysis of ۱۰۳ genotypes using Sr۲-linked markers csSr۲ and STS#Sr۲ indicated that csSr۲ was a better predictor of the presence of Sr۲ gene in wheat.