Investigation Of Resistance To Wheat Leaf Rust And Resistance Genes In Wheat-wheatgrass No.33 At Seedling Stages

Wheat leaf rust is an important disease in wheat production, screening and breeding for resistance cultivars are considered to be the most economical, environmental and effective appropriate strategy to reduce damages due to this disease. Therefore, it is an important basis for utilizing the resistance cultivars, and is very reasonably to make clear the constitutes and genetic characteristics of the resistance genes in our country's wheat production cultivars and important germplasm. Wheat-wheatgrass No.33 was a germplasm which bred by Northeast Normal University and Jilin Academy of Agricultural Sciences, and derived from 468-6-7 hybriding with Xinshuguang No.1 wheat through the technique of alien addition lines. In 1995, Wheat-wheatgrass No.33 was examined and approved and began to spread. Now, this wheat variety has been grown in many provinces. It was a variety of high-yield, high protein, and multi-resistance to diseases, so it was important in wheat breeding and production practice. In this paper, took the wheat cultivar Wheat-wheatgrass No.33 as experiment materials, through the identification of leaf rust resistant ability, genes postulation, the genetic analysis of resistance, Marker-assisted Selection and Single Sequence Repeatd (or Microsatellite) technique did some researches on the leaf rust resistance of Wheat-wheatgrass No.33, the results were as follows:1. Wheat- wheatgrass No.33 displayed immunity, high resistance or middling resistance to 212 isolates of 214. It indicated that this cultivar was resistant to the majority of Puccinia triticina isolates prevailing in our country. Wheat-wheatgrass No.33 possessed high resistance to races of Puccinia triticina from China and broad resistant spectrum, and had a broad applied prospect in production.2. Through genes postulation, postulated resistance genes against to wheat leaf rust were detected by comparing the infectiontypes on Near-isogenic Lines and Wheat-wheatgrass No.33 induced by 19 Puccinia triticina races which were previously characterized of avirulence or virulence gene combination. Among 49 known Lr resistance genes used in the test, Lr2a, Lr3a, Lr23, Lr44 and one unknown resistance genes were deduced be present in Wheat-wheatgrass No.33.3. Wheat-wheatgrass No.33, F₁ populations (Wheat-wheatgrass No.33 crossed with the susceptible wheat 'Thatcher'), F₂ populations and F3 families were tested for analysis of wheat leaf rust resistance at seedling stages with specific Puccinia triticina isolate 04-5-32-1(Prt code KHDN). The genetic analysis results showed that the resistance of Wheat-wheatgrass No.33 was controlled by two pairs of dominant and overlapped or controlled independently genes to wheat leaf rust isolate 04-5-32-1. In addition, genetic analysis showed that the resistance segregations of Wheat-wheatgrass No.33 to most isolates was not distinct or the boundary among resistance types are unclear. F₁ populations, and F₂ populations appeared mixed infection types when score the resistance. In genetic,this condition is the resistance possiblly to be controlled by several major genes and a large number of minor genes.4. Microsatellite technique was used to mark the wheat leaf rust resisting genes in Wheat-wheatgrass No.33. Puccinia triticina isolate of 04-5-32-1 was used to score the resistance in F2 generation. DNA samples extracted from the F2 individuals were pooled into two separate groups for Bulked Segregant Analysis(BSA) to identify the molecular markers linked to the resistant genes, 79 pairs of microsatellite primers were screened between the parents and progenies. 69 primer pairs on 2 A, 2B, 7D chromosome of wheat generated no PCR polymorphism between the resistant pool and the susceptible ones. However, one SSR markers Xgwm33 located on 1A chromosome of wheat generated about 135bp specific band between the resistant pool and the susceptible ones. It indicates that a deduced unknown resistance gene located on Chromosome 1 A. Therefore, further research should be focused on this fragment so as to ascertain whether it was linked with a new leaf tust resistance gene.5. A series of optimized systems and programmes were established, which were suitable for marking wheat leaf rust resistance genes with good stability and repeatability. The markers linked to resistance genes Lr9, LrlO, Lrl9, Lr20, Lr24, Lr29 and Lr35 were found to be unique and specific in Thatcher background NILs. Marker-assisted Selection for leaf rust resistance in Wheat-wheatgrass No.33 was approached by using above STS or SCAR markers, PCR amplification results showed that Wheat-wheatgrass No.33 did not contain Lr9, Lrl9, Lr20, Lr24, Lr29, Lr35, but possessed LrlO.This experiment concluded that the Wheat-wheatgrass No.33 was a cultivar which possessing multiple leaf rust resistance genes. As an important resistance cultivar, it can undoubtedly be used as an important breeding material to prevent the extension varieties from losing disease resistance.