Molecular Cytogenetic Study Of Wheat-rye Derivative Lines

Wheat is one of main food crops in China. Food is not only important strategic matter ofnational economic security and people’s livelihood, but also one of the most fundamentalresources. We choose a single wheat germplasm in wheat breeding and wheat geneticvariation is relatively small, which cased the comprehensive resistance to disease of wheat isless and seriously affect high and stable yield of wheat. However, the distant hybridizationcan transfer the beneficial genes of wheat relative species and genus of Triticum L. intocommon wheat, which we obtaine the excellent wheat germplasm and make a greatbreakthrough in wheat production. The introduction of alien chromosomes into wheat fromrelated species is an economical and important method for wheat improvement, particularlydisease resistance breeding. Rye (Secale cereale L.) is a reservoir of genes that resist bioticand abiotic stresses, which has been utilzed widely as a valuable source of alien chromosometranslocations during wheat breeding. In order to further excavate beneficial gene resources ofrye, we develop a hybrid LanR (2n=28, ABDR) in a previous study by crossing commonwheat cv. W770B (2n=6x=42, AABBDD) and Mexican Secale cereale L.(2n=2x=14,RR) via embryo rescue, before the LanR chromosome was doubled by treatment withcolchicine. Backcrossing with W770B and further embryo culture obtained a new wheat-ryegermplasm, Lanxiaohei (2n=8x=56, AABBDDRR), which was followed by furtherbackcrossing and six generations of selfing. A series of wheat-rye derivative lines wereisolated that exhibited stable agronomic performance.In the present study, The main objectives of this study were: a) to verify the chromosomeconfiguration of the lines based on cytological analyses and genomic in situ hybridization(GISH) during the mitotic and meiotic metaphases; b) to confirm the genome composition ofthe lines using specific molecular makers; and c) to evaluate the agronomic characteristics andresistance to powdery mildew of the lines. The results as followed:1、A novel1AL.1RS translocation line13-2-2with powdery mildew resistance wasdeveloped. The line was characterized based on cytological, genomic in situ hybridization(GISH), sequence-characterized amplified region (SCAR), and simple sequence repeat (SSR)analyses. The mitotic and meiotic investigations showed that the chromosome number andconfiguration of13-2-2were2n=42=21II. GISH using rye genomic DNA as a probe detected a pair of R genome chromosome arms with strong hybridization signals, which hadbeen introduced into13-2-2. Five rye genome-specific SCAR markers and three1RSchromosome-specific SCAR markers were used to identify13-2-2, and the results showedthat rye chromatin and1RS chromosome-specific bands were amplified in13-2-2. Wescreened320SSR primer pairs on the long or short arms from seven wheat homoeologousgroups in the translocation line and parents. However, only three1AS primers could not beamplified in line13-2-2, whereas the others were amplified. Thus, these markers suggestedthat the introduced R chromatin belonged to1RS, so we designated13-2-2as a1AL.1RStranslocation line. Line13-2-2was immune to powdery mildew after inoculation withBlumeria graminis f. sp. tritici isolate E05and E07during the adult plant stages. By contrast,the maternal parent W770B, Kavkaz with Pm8and Amigo with Pm17were heavily infectedwith spores and had reaction response scores of S. Thus, this new wheat-rye1AL.1RStranslocation line with resistance to powdery mildew could be a new and valuable donorsource for wheat improvement.2、A wheat-rye1BL/1RS translocation line14-1-2with big kernel traits was developed.Through observation of agronomic characters of three-year, we find the average thousandkernel weight of14-1-2is56.8g, the most of it is61.0g. The line was characterized bycytology, genomic in situ hybridization (GISH),SCAR and SSR. The mitotic and meioticinvestigations revealed that the chromosome number and configuration of14-1-2were2n=42=21II. GISH using rye genomic DNA as probe indicated that one pair of R chromosomearms with strong hybridization signals was introduced into14-1-2. Specific primers of ryewere screened, the result revealed that31RS chromosome specific SCAR primers amplifiedrye specific bands in the plant of14-1-2. SSR primers on the long arm and short arm of sevenwheat homoeologous groups were screened, but only4primers in1BS could not beamplified. Consequentially,1BS of wheat was substituted by1RS of rye and the derivativeline was confirmed as a1BL/1RS translocation line with big kernel trait.