Investigation of Resistance Responses in Elite Wheat Lines and Cultivars to Brown Rust (Puccinia triticina Eriks.) in the Moghan Plain

Background and Objectives

Brown rust or leaf rust of wheat caused by Puccinia triticina Eriks. It is considered one of the most damaging diseases of wheat all over the world, including Iran. Brown rust can reduce the yield of wheat in fields by 20 to 50% in epidemic conditions. The fungus that causes brown rust disease due to having a sexual cycle and new genetic recombinations resulting from it (presence of intermediate hosts in most regions), an asexual cycle in favorable weather conditions and Also, the probability of occurrence of phenomena such as mutation, migration and selection pressure by resistance genes in the hosts has high genetic diversity (variety of physiological breeds), genetic flexibility (variability) which by producing new breeds with Completely different pest patterns can overcome the created genetic resistance. The newly created breeds can be quickly transferred from one area to another through the wind and cause an increase in racial diversity in the disease population of other areas. The most reliable and fundamental method of its control and management is the use of genetic resistance. Accurate knowledge of the genetic structure of the pathogenic population in each region is the first step and road map to achieve effective and stable genetic resistance in wheat. This is possible through the monitoring of harmful pathogenic factors on the differential genotypes of brown rust in the trap vaults.

Materials and Methods

The effectiveness of resistance genes of international differential cultivars of brown rust was investigated in Moghan region of Ardabil province as one of the important poles of Iranian wheat production in two consecutive crop years (2022-2023). To identify the sources of resistance to the existing breeds in the region, the responses of 40 commercial varieties and 40 promising lines of wheat was evaluated. Investigating the resistance response in the full plant stage under natural pollution conditions, by the parameters of pollution coefficient (CI), final disease severity (FDS) and the relative value of the area under the disease progression curve (rAUDPC) in the research station of the Research and Training Center for Agriculture and Natural Resources of Ardabil Province (Moghan) were measured.

Results

The population of breeds in Moghan region were different from each other in both years. The results indicated that in both years of the test, the pathogenic mushroom population had immunity to differential cultivars carrying resistance genes Lr18, Lr19, Lr20, Lr22a, and Lr29. Therefore, these genes have the necessary efficiency to create effective resistance to brown rust pathogenic races in Moghan region. The differential cultivars carrying the resistance genes Lr2a, Lr2b, Lr9, Lr17, Lr21, Lr23, Lr10/Lr27/Lr31, Lr33, and Lr34 also showed relatively acceptable resistance to the pathogenic strains of brown rust in Ardabil region. The reaction of the genotypes carrying these genes was specific to the race. In other words, in one year they had a resistance reaction and in another year they had a semi-resistant to semi-sensitive reaction with an intensity of 5-20% contamination. Commercial cultivars and promising lines of wheat, which had an effective resistance response and the lowest value for the measured traits, as sources of effective genetic resistance to the brown rust pathogenic population in Moghan region and similar regions in The hot and humid climates of the country are introduced, which include Sahar, Rakhshan, Shush, Farin, Sirvan, Araz, Meraj, Danesh, Talai, Sana, Aran, Tirgan, Taban, Hana, Mehrgan, Avan, Arman, Fallah, Tektaz cultivars. and lines N-95-6, N-98-8, S-95-3, S-96-15, S-96-16, S-97-10, S-98-11, S-98- 22, M-97-12, M-97-18, M-98-18, CD-91-12, C-97-4, CD-97-19, C-98-7, C-98-8, They were CD-98-17, MS-92-5, MS-94-5, D-97-15, and D-97-16.

Discussion

Correct and conscious use of the combination of effective resistance genes identified in this research can create more stable resistance to brown rust. It is possible to use the resistance genes present in resistant genotypes identified in multi-breeding programs for the pyramiding of resistance genes in desirable wheat genotypes in terms of agricultural traits, yield and other physiological characteristics, in the production of stable resistant cultivars. Compared to the disease, he used a brown rust.