Molecular Identificaiton Of Wheat Leaf Rust Resistance Gene And Research On Genetic Diversity At Locus Lr10

Leaf rust, caused by Puccinia triticina, is one of the most severe diseases of commonwheat (Triticum aestivum L.) all over the world. The study of the diversity and distribution ofleaf rust resistance genes in wheat cultivars is of great significance to protect geneticresources of leaf rust resistance genes, to guide the scientific use of resistance genes, andfinally to effectively control the wheat leaf rust. There are two ancient haplotypes and severalsub-haplotypes at locus Lr10for leaf rust resistance, which is of great significance for thestudy of genetic evolution and genetic diversity. In this study,247of Chinese wheat cultivars(lines) and7different wheat genetic groups were used to detect allelic variation at the Lr10locis. Moreover,12specific molecular markers for various leaf rust resistance genes wereused for molecular detection of leaf rust resistance genes possibly existed in58wheat linesused in this study. The major results are as follows:1. Both H1and H2were detected in the above wheat cultivars (lines), However,95.2%of the189cultivars showed H2haplotype, and a similar rate (96.6%) of the58breeding linesturned to be H2, strongly suggesting that the H2haplotype is most dominant in the Chinesewheat gene pool.2. Two haplotypes at locis Lr10are polymorphic and genetic diversities resulting fromrecombination and other types of chromatin reorganizations (e.g., the origin of the H2haplotype and the polymorphism for the Lr10) have been going on since the formation of thehexaploid wheat. Nine sub-haplotypes had been detected in this study and five novelsub-haplotypes were revealed present in the cultivars, namely H1-2, H2-4, H2-5, H2-6, andH2-7, which have not been reported until this report.3. New genotypes at locis Lr10could be generated by hybridization. Except forgenotypes of parents, new genotypes emerged in offsprings of different genetic groups.Genotype H1-2, resulting from recombination between H1and H2is unstable and it could turn to H1-1through crossing whith other genotypes.4. Recombination sites between the H2subhaplotypes were possibly within regionslocated on the5′coding and non-coding regions of the RGA2-b and3′coding regions of theRGA2-a. The frequencies of H2-1, H2-2and H2-5were higher than other sub-haplotypes inthe above wheat cultivars (lines). And hybridization between H2-1and H1can get H2-2,while hybridization betweent H2-2with and H1can also get H2-1. Sub-haplotype H2-5hadno fragments amplified from the primer A which located in the region of5′coding andno-ncoding regions of the RGA2-b, while subhaplotypes of H2-1and H2-2had fragmentsamplified from the primer A.5. Genetic diversity at locus Lr10affected by the modern breeding to a certain extent.According to correlation analysis, genotypes at locus Lr10was extremely significantlycorrelated with grain yielt (P<0.01), and there were significant correlations betweengenotypes at locus Lr10and origins of wheat cultivars (P<0.05)and thousand kernel weightof wheat (P<0.05).6. According to the results of moleculer detection, we preliminary concluded that mostof the selected wheat lines contain leaf rust resistance genes with different numbers. Lr29were detected most frequently appeared in the selected strains, indicated it may played acertain role on resistanting leaf rust in most of the texted wheat lines.