تعیین فاکتورهای پرآزاری قارچ عامل زنگ سیاه گندم (Puccinia graminis f. sp. tritici) و کارایی ژنهای مقاومت به بیماری در ایران از طریق کاشت خزانه‌های تله طی سال‌های 1399 و 1400

Stem rust of wheat, caused by Puccinia graminis f. sp. tritici, is the most damaging rust among wheat rusts and the damage caused by the disease can be reached to a complete destruction of wheat fields. In order to production of rust-resistant wheat cultivars, it is necessary to have full information on the status of virulence factors of rust fungi and the efficiency of rust resistance genes in wheat in different parts of the country, so that it is possible to plan for the use of rust resistance sources and transfer of resistance genes to wheat. In the present study, virulence of P. graminis f. sp. tritici on 48 stem rust resistance genes (Sr genes) and the effectiveness of these genes were investigated by the development of trap nurseries consisted of 48 wheat stem rust differential cultivars/lines, each carrying an Sr gene, in different parts of the country during the two cropping years of 2019-20 and 2020-21 under natural field infection. To do the experiments, the differentials were planted at a rate of ≈7 gr. seed on one-meter long rows with 20-30 cm apart, and were brought to adult-plant stage. In order to help the spread of the disease in the nurseries, the susceptible check wheat cultivar, Morocco, was planted at the distance of every ten differentials and also around the nurseries. The differentials were scored for disease severity and infection type at hard dough stage when wheat stems/leaves were turning dry. A disease severity of ≥50 along with an infection type of susceptibility (S) was considered presence of virulence on the appropriate Sr gene. Any other combination of disease severity and infection type was considered effectiveness of an Sr gene. Considering that stem rust appeared in three locations including Kelardasht, Ardabil, and Miandoab in the first year of the experiment, and only in Kelardasht in the second year, the data collected from these environments were used for the final decision. Based on this, while the fungus had virulence on 33 out of 48 resistance genes at least in one place in one of the years tested, the resistance genes Sr9e, Sr14, Sr21, Sr23, Sr24, Sr26, Sr31, Sr32, Sr36, Sr37, Sr39, Sr40, and SrNin were effective in all locations in both years tested. There was not enough data to prove whether the other two genes were effective or not. These results indicate the absence of significant changes in virulence on stem rust resistance genes in the country compared to previous reports.