بررسی تنوع بیماریزایی جدایه های قارچ Puccinia graminis f. sp. tritici عامل بیماری زنگ سیاه گندم

Fungus Puccinia graminis f. sp. tritici (Pgt) is the causal agent of wheat stem rust disease that results in a significant yield loss at high severities. To overcome plant immunity system Pgt, like other biotrophs, produces considerable number of effectors for stealth infection. However, due to introducing new resistance genes, Pgt needs to escape from recognition by plant receptors. This arm race leads to frequent genetic variations and emergence of new Pgt races that are more virulent on effective resistance sources in wheat. The prevalence of race TTKSK and its related variants with virulence on germplasms carrying important resistance genes in Africa and also from Iran, is a clear example of these genetic changes. Monitoring highly virulent races of Pgt and their virulence factors assists to apply appropriate strategies in breeding of wheat carrying effective resistance genes. In this study, 36 wheat stem rust samples were collected from eight different provinces of Iran during the spring season of 2020. Samples were purified to single pustules on a susceptible wheat cultivar, Bolani, and for each isolate, infection types were assessed on the seedling stage of 20 North American stem rust differential lines carrying one of single genes Sr5, Sr21, Sr9e, Sr7b, Sr6, Sr8a, Sr9b, Sr35, Sr50,Sr9a Sr9g, Sr11, Sr36, Sr30, Sr17, Sr9d, Sr10, SrTmp, Sr38. Most virulence was observed on the differential lines carrying Sr5, Sr6, Sr8a, Sr9b, Sr30, Sr17, Sr21, Sr9e, Sr7b, Sr9d, Sr10, SrTmp, Sr38, and SrMcN. In addition, using PCR approach the presence of genes coding for AvrSr35 and AvrSr50 effectors was evaluated in the genome of all isolates. Also, these isolates were evaluated for their virulence ability on lines carrying Sr35 and Sr50. The evaluation of Pgt physiological races on differential lines as well as molecular and morphological studies related to AvrSr35 and AvrSr50 will be presented. Understanding the virulence variability of Pgt population could be useful for wheat improvement programs.