Molecular And Cytogenetic Characterization Of A Common Wheat And Thinopyrum Intermedium Chromosome Translocation Line Conferring Resistance To Powdery Mildew

Wheat powdery mildew, caused by Blumeria graminis f. sp. Tritici is one of the most devastating diseases of common wheat worldwide. The utilization of resistant cultivars is is the most efficient and environmentally friendly approach to control this disease. It is urgent to identify new genes for diversifying sources of resistance genes and for pyramiding genes for different types of resistance in order to achieve high levels of durable resistance for sustainable control of powdery mildew in wheat breeding and production. The wild relative species of wheat has many excellent and resistant genes, which is beneficial for wheat genetic improvement. Thinopyrum intermedium(2n=42), a grass relative of wheat was reported to be immune to wheat powdery mildew. This species is easily hybridized with wheat and therefore is of potential value for wheat improvement.A stable wheat line723, selected from the progenies of hybrid between common wheat and Thinopyrum intermedium is immune to powdery mildew in field and has similar phenotype with its wheat parent. In present study, the chromsome constitution of line723was identified by GISH, FISH and Giemsa C-banding techniques, the inheritance of powdery mildew resistance gene was determined by line723crossed with susceptible cultivars Mianyang26to yield segregating populations. And the relationship between the translocated chromosome fragment and powdery mildew resistance gene was also investigated.1. Genetic analysis of the F1, F2and F2:3populations from powdery mildew resistant line723with susceptible cultivars Miangyang26(MY26) revealed that resistance was controlled by a single dominant gene.2. The cytogentical results indicated line723has nomal chromosome number with chromosome configuration of2n=42=21â…¡, suggesting that it is cytologically stable.3. A interstitial translocation from J or JS chromosome fragment of Th. intermedium was found to be transferred into one pair of wheat chromosomes short arms by genomic in situ hybridization analysis using Th. Intermedium and Psudoegoeria straffic DNA as probes.4. The A genome chromosomes were involved in the translocation by two-color fluorescence in situ hybridization (FISH) with the probes of pAs1and pSc119.2.5. Sequential Giemsa C-banding and genomic insitu analyses revealed that the translocation was involving the wheat chromosome5A.6. Indivadual plant of F2segregating population of line723with susceptible wheat cultivar MY26was randomly selected to analyse chromsome constitution by genomic in situ hybridization with Th. Intermedium DNA as probe and it was found that the F2plant was resistanc to powdery mildew when there is as least one translocation chromosome in the analysed F2plant, otherwise the F2plant is susceptible to powdery mildew. These results suggested the translocation fragnent carried the powdery mildew resistance gene and it might be a novel powdery mildew resistance gene.