Development And Evaluation Of N553 Chromosome Segment Substitution Lines In Genetic Standard Line, Yangmai13 And Identification, Mapping Of A Dwarf, Compact Spike Mutant Rht23

Common wheat(Triticum aestivum, AABBDD,2n=42) is one of the most important food crops worldwide. China is the largest producer and consumer of wheat in the world. Nowadays, improvements in the standard of living in the country and continuously growth of population are expected to increase the demand of grain products. In the 1960s, dwarfing or semi-dwarfing genes were used in wheat breeding, selection and spreading of dwarf and semi-dwarf varieties triggered the wheat "green revolution". The average production of wheat in the world increased 3.4% annually. In addition, during the long process of the reproductive cycle of wheat, it is more susceptible to biotic or abiotic stress, such as FHB(Fusarium head blight), which has seriously affected the production and lead to food safety problems. Therefore, the improvement of ability of wheat disease resistance and ideal plant architecture is also the main task of wheat genetic improvement.Section I development and evulation of N553 chromosome substitution lines in genetic standard line, Yangmail3Narrow genetic base has become a main problem for genetic improvement of wheat scab. N553 is a newly discovered material possessing the same resistant level as Sumai 3, but better agronomic traits with unknown scab resistant genes. In our study, we attempted to develop a battery of CSSL lines in Yangmai13 background which could cover the whole genome of donor, N553. The main results were summarized as follows:1) The pedigree analysis for N553 A diverse collection of FHB-resistant and-susceptible wheat lines was characterized with microsatellite markers linked to FHB resistance quantitative trait loci (QTLs) on chromosomes 2DL,3BS (distal to the centromere),3BSc (proximal to the centromere), 4BS,5AS and 6BS identified in wheat lines Maringa, Sumai 3 and Wuhan 1(Yu et al.2006). Cluster analysis of 33 microsate’ite markers, mapping near six FHB resistance QTLs, grouped wheat lines with four major clusters. The second major was mainly composed of N553, Wangshuibai, F60096, Zhengyinl. Four wheat lines including N553, Ning894037, Ning7840, Taiwanxiaomai had the same haplotype as Sumai3 at the 3BS locus, whereas N553 possessed an independent haplotype at the 5AS locus that is different from Sumai 3 derived lines.2) Construction of Chromosome Substitution Segment Lines (CSSLs). The development of the CSSLs lines:the F1 was generated by a cross using Yangmai13 as the recipient parent and N553 as the donor parent. The N553×Yangmai13 F1 progeny were backcrossed with Yangmail3 until BC2F1 and self-pollinated to produce BC2S1. (Marker-Asisted-Selection)MAS were conducted to identify genotypes of 46 individual BC2F1 plants in the Yangmai13 background using 215 polymorphic SSR markers.27 plants from BC2F1 were selected to backcross with recurrent parent to generate BC3F1 population according to the results of MAS. A total of 270 BC3F1 individuals were also identified by MAS. Thus, a battery of N553 whole genome chromosome substitution Segment lines was developed.The CSSLs consist of 60 different lines. There are 14 segments on average in each individual and no single segment introgression lines were found. The length of the substituted segments covered 3404.1 cM in total with an average distance of segment by 17.13 cM. The substituted segments of each line are different in length, ranging from the shortest segment 6.54 cM to the longest 24.81 cM. The introgressed segments from N553 in the 60 lines covered 91.0% of the donor genome. All the identified BC3F1 have more 94.07% recipient genome composition (RGC) on average, which are higher than theoretical value. The backcross effect and deletion interval of N553 genome segments in BC2F1 and BC3F1 were analysed and compared with each other. We could initially predict that the absent segments were in the terminal and middle parts of each chromosome. The most length segment are absent in 5B(Centromere) and 7A(distal to Centromere), no absent segments in 6B. The BC3F1 heterozygous individuals were self-pollinated to generate homozygous BC3S1-3 lines for FHB surveying and QTL detection.2. In addition to traditional method of subspecies hybridization for producing recombinants, physical or chemical induction was also a useful method for creating new germplasm. Here, we reported a dwarf and compact spike mutant named NAUH164, which was derived form EMS treatment of Sumai 3. It is known for us that Sumai 3 is a common wheat variety with high resistance to wheat scab, but relatively poor agronomic traits. In order to investigate the molecular mechanism of mutated thraits and provide new genetic information for the development of plant and panicle stature in wheat breeding, researches on characteristic of mutant involved morphology, genetics, anatomy and physiology were conducted. The results were as followings:1) Morphology analysis. It was found that, starting at the jointing stage, the mutant showed obvious phenotypic differences with its wild type, mainly including reduced plant height, shortened spike length, along with altered leaf morphology and flowering time, decreased number of spikelets, deformed grain size, etc. The number of internodes in mutant did not change in comparison with its wild type, but the length of each them decreased, especially the Peduncle. Thus, the shorten spike could be attributed to the decreased length of rachis. According to genetic analysis, the dwarf and compact spike were controlled by single dominant gene, even showed pleiotrophic effect, which was desinated as Rht23. And it was mapped in the long arm of chromosome 5D after the linkage analysis based on BSA screening method using a (NAUH164x alondra’S) F2 population. The flanking marker was Gdm63 and Bare 110, with the genetic distances of 4.7 cM and 11.1 cM, respectively. Two microsatellite markers Whg50 and Whg52 were newly developed and confirmed to be closer to Rht23 loucs, which was located in a physical interval region of 8.5 Mb in Ae.tauschii. Finally, the ESTs of synteny between rice, Brachypodium and Ae. taushii genome could be useful for the further fine mapping and even map-based cloning of this new gene.3) Tissues from the peduncle (lcm above the 1 node) were cut into transverse and longitudinal sections adopting resin embedding protocol at heading and flowering stage. The results showed that, at the heading stage, the development of culm and vascular delayed. And the number of vascular bundles and the culm wall thickness of were significantly increased than that of in Sumai3 at anthesis. The length and width of parenchyma cells were both smaller than wild type, so that cell number per unit area in the mutant increased significantly. Seedlings of both NAUH164 and Sumai 3 are sensitive to exogenous gibberellins application, but the plant height of the mutant could not be restored to that of the wild type in a field experiment. Comparison of the induction of the a-amylase production in the aleurone using isolated mature wheat embryos in response to exogenous GA3 supplementation resulted in similar a-amylase activity in two genotypes. The second leaf sheath showed similar elongation ratio for both phenotypes when treated with different levels of GA3. These results indicated that the GA sensitiveness and a-amylase activity induction were same for the mutant and the wild type.