نوع مقاله : مقاله پژوهشی

نویسندگان

• مرتضی صادقی ¹
• رامین روح پرور ²
• منصور کریمی جشنی ¹

¹ گروه بیماری شناسی گیاهی، دانشکده کشاورزی دانشگاه تربیت مدرس، تهران، ایران

² بخش تحقیقات علوم زراعی و باغی، مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان آذربایجان‌شرقی، سازمان تحقیقات، آموزش و ترویج کشاورزی، تبریز، ایران. بخش تحقیقات غلات، موسسه تحقیقات اصلاح و تهیه نهال و بذر، سازمان تحقیقات، آموزش و ترویج کشاورزی، کرج، ایران

چکیده

کلیدواژه‌ها

• تنوع
• تیپ آلودگی
• ژن‌های مقاومت
• پارازیت اجباری
• پرآزاری

عنوان مقاله [English]

Identification of races of Puccinia graminis f. sp. tritici, the causal agent of wheat stem rust, in the west and north west of Iran in 2021-2022

نویسندگان [English]

• Morteza Sadeghi ¹
• Ramin Roohparvar ²
• Mansoor Karimi-Jashni ¹

کلیدواژه‌ها [English]

• diversity
• infection type
• resistance gene
• obligate parasite
• virulence

Extended Abstract

Introduction

 The fungus Puccinia graminis f. sp. tritici (Pgt) is an obligate biotrophic fungus and causes stem rust disease in wheat. This fungus evolves continuously, threatening commercial wheat varieties with resistance genes. The emergence of virulent strains, particularly, has undermined the resistance of cultivated varieties. Understanding the population genetics and pathogenicity genes of this fungus is crucial for managing resistant wheat varieties, especially given the significance of wheat in the region. To identify Pgt races, field surveys conducted in mid-June to mid-July of 2021 and 2022 in western and northwestern Iran involved the collection of 35 samples from Ardabil, Hamadan, and Lorestan provinces. The rust samples were postulated and purified on the susceptible wheat cultivar Morocco. The physiological races of 18 pure isolates were analyzed using 20 differential cultivars with known resistance genes. Infection types were scored based on a 0-4 standard scale and races were determined using a 5-letter standard coding system. Results showed that most of the differential lines carrying specific genes were susceptible to the evaluated isolates. These findings indicated that these isolates belonged to two TTTTF and TKTTF races. Fungal virulence was observed in the majority of lines carrying Sr genes, and only the Sr24 and Sr31 genes exhibited full effectiveness against all these isolates.

Materials and Methods

Infected wheat samples containing Pgt pustules were collected from Ardabil, Hamadan, and Lorestan provinces (Fig. 1). To purify and multiply all isolates, seedlings of the sensitive cultivar Morocco were inoculated at 25 °C with 80–90% relative humidity, light intensity of 12,000 lx, and 16 h light: 8 h dark for 2 weeks. Virulence study of Pgt isolates was evaluated on 20 North American standard differential lines comparable to those of the purification. Infection types were assessed at 14 dpi based on the 0 to 4 scale. Infection types 0 to 2 are regarded as incompatible reactions, and infection types 3 and 4 are considered as compatible reactions (Fig. 2). The physiological race of isolates was indicated based on the five-letter code of the North American nomenclature system for Puccinia graminis f. sp. tritici (Fig. 3), using infection types 0 to 2 as low (L), and infection types 3 and 4 as high (H). The frequency of each race, their distribution in different geographic regions, and the frequency of virulence among the isolates for each resistance gene were determined.

Results and Discussion

 In this study, among 18 Pgt isolates collected from the 3 provinces, 2 physiological races (TTTTF, TKTTF) were identified (Table 1). According to sampling from Ardabil, Lorestan and Hamedan provinces, the pathogenicity spectrum of TKTTF strains was recorded at 76% and TTTTF strain at 24% (Table 2). TTTTF strain is one of the strains with the widest pathogenicity spectrum and the most destructive stem rust. The TKTTF race has also been reported from Lorestan, Hamedan, Ardabil, and Mazandaran provinces in previous years, and the TTTTF race has been reported from Golestan, Lorestan, Ardabil, and Hamedan provinces. Based on the genomic polymorphism grouping, most of the isolates related to these two races belong to clade IV (Szabo et al., 2022). The dominant population of wheat stem rust strains in Iran has shifted from the Ug99-related group (clade I) to group IV. These two races have also been identified in previous studies (Khanboluki et al., 2024; Omrani et al., 2018). TTTTF strain has a pathogenicity formula that is almost similar to TKTTF but is distinctly different from the stem rust strain TTKSK (Ug99), as the TTKSK strain is not pathogenic on both Sr24 and Sr31. Varieties containing Sr11, Sr24, and Sr31 are effective against TKTTF strain, but varieties containing Sr11 are susceptible to TTTTF strain. Overall, the present study demonstrates that the disease had a lower prevalence and racial diversity in 2022 and 2023. If environmental conditions are favorable in the coming years, these two races could become more prevalent and cause regional epidemics.

Author Contributions

MKJ and RR conceptualized the project. MS and MKJ performed the experiments and wrote the manuscript. MKJ and RR edited the manuscript. All authors read and approved the manuscript.

Data Availability Statement

Data are available upon request from the authors.

Acknowledgements

We acknowledge TMU, Seed and Plant Improvement Institute, Agricultural and Horticultural Sciences Research centers of Lorestan and Ardebil, Azerbaijan, for their hosting and financial support.

Ethical considerations

The authors avoided data fabrication, falsification, plagiarism, and misconduct.

Conflict of interest

The authors declare no conflict of interest.