Evaluation the resistance of some CIMMYT wheat lines to tan spot disease

Document Type : Research Paper

Authors

• Mojgan Ghorbi ¹
• Hassan Momeni ²
• Varahram Rashidi ³
• Fahimeh Nazari ⁴
• Alireza Ahmadzadeh ⁵

¹ Department of Agronomy and Plant Breeding, Islamic Azad University, Tabriz, Iran.

² Plant Diseases Research Department, Iranian Research Institute of Plant Protection (IRIPP), Agricultural Research Education and Extension Organization (AREEO), Tehran, Iran.

³ Department of Agronomy and Plant Breeding, Islamic Azad University, Tabriz, Iran

⁴ Plant Diseases Research Department, Iranian Research Institute of Plant Protection (IRIPP), Agricultural Research Education and Extension Organization (AREEO), Tehran, Iran

⁵ Department of Agronomy and Plant Breeding, Islamic Azad University, Shabestar, Iran

Abstract

Keywords

• Pyrenophora tritici-repentis
• Evaluation
• Pathogen
• Wheat
• Resistance

20.1001.1.20084781.1402.54.1.3.3

Extended Abstract

Introduction

    Tan Spot disease caused by the pathogenic fungus Pyrenophora tritici-repentis is a destructive disease in wheat production areas around the world. The disease has a high prevalence and distribution in the Golestan, Mazandaran, and northern regions of Ardabil province. Due to the lack of suitable resistant varieties in the country, the damage caused by the disease is high. Few studies have been conducted in the country regarding the evaluation of the resistance of lines to the pathogen. In wheat breeding programs that have been carried out in the past in Iran, little attention has been paid to germplasms resistant to this disease. Unfortunately, for this reason, the spread of the disease in some northern provinces, including Golestan, is such that sometimes it is difficult to find a farm without symptoms of the disease.

Materials and methods

    In this study, the evaluation of 50 wheat lines resistance belonging to the 9HLBSN treasury of the International Maize and Wheat Research Center (CIMMYT) was investigated using the race1 of the pathogen. These investigations are carried out in a coherent and coordinated program centered on CIMMYT in a joint research program with different countries to accurately identify sources of disease resistance, and the results of this research will ultimately lead to the introduction of disease-resistant or tolerant cultivars. Two controls, Bolani and Salamouni, were also included as susceptible and resistant cultivars. According to previous evaluations, 90 to 100 percent of fungal isolates investigated in the infected provinces of the country, including Golestan, Mazandaran, and Ardabil, belong to race 1. Therefore, five isolates of race 1 from previous studies including IR 17, IR 46, IR 73, IR 172, and IR183 with a high ability to produce conidia were selected in pathogenicity tests in the greenhouse.

Results and Discussion

    By inducing the fungal isolates to produce abundant conidia, the infection was established in the wheat seedlings through the inoculation of the suspension of fungal conidia. Although 3 days after inoculation, the initial symptoms of the disease appeared on the wheat seedlings, but the final evaluation was done 7 days post-inoculation. The appearance of symptoms on wheat seedlings occurred from 4 to 7 days after inoculation, and the wheat lines were placed in different groups in terms of resistance or susceptibility to pathogenic fungi. Severe necrosis on cultivar Glenlea was the most common reaction observed, which indicated the production of Tox A by the isolates causing these symptoms. The production of chlorosis on line 6B365 was due to the production of Tox C. The emergence of resistance on line 6B662 was due to the lack of Tox B production in the investigated isolates. This is normal because race 1 of the pathogen does not produce Tox B and therefore no signs of sensitivity were observed on line 6B662. None of the isolates examined in this study were pathogenic on the Salamouni cultivar. As a susceptible variety against all fungal isolates, Bolani showed a high level of sensitivity and disease. The results of this study demonstrated that lines number 1, 17, 18, 22, 25, 29, 33, 34, 35, 36, 37, 38, 44, 45, and 47 had a susceptible reaction, and other lines which were 70% of investigated lines, were resistant. In addition, the mean disease index in different lines was calculated and compared. In terms of the mean disease index on the evaluated lines, 13 groups were obtained, which had 8, 8, 8, 4, 3, 5, 12, 23, 24, 28, 28, 26, and 22 members, respectively.

Conclusion

    Considering the susceptibility of most of the country's commercial cultivars to this disease, the resistant lines obtained in this study are good sources of resistance to be used in the breeding programs of wheat.