| Wheat (Triticum aestivum L.) is an important food crop and economic crop all over the world. Stripe rust and powdery mildew are globally serious fungal diseases to production of wheat, which could result in tremendous damage to wheat productivity. China is the largest and relatively independent disease epidemic area. Production practice showed that cultivating and breeding resistant cultivars is the most cost-effective and sustainable measure to control these diseases. At present, several resistance genes for stripe rust and powdery mildew have been identified and mapped on almost all the wheat chromosomes in different carrier varirties (lines). Durable resistance breeding can be sped up by using relative resistance genes and their closely linked molecular markers through molecular marker assistant breeding.Alien resistance gene transfer is the most effective way of increasing the amount of resistance diversity. Thinopyrum (Thinopyrum or Elytrigia Desv.) belongs to the tribe Triticeae (Triticum) of Poaceae (syn. Gramineae), and is a member of the third gene pool of wheat, which consisting of a vast source of genetic diversity and disease resistances such as stripe rust and powdery mildew. Species of Thinopyrum have been considered as excellent gene donors in wheat breeding program, Thinopyrum ponticum and Thinopyrum intermedium are the most widely used speices in wheat improvement.In this thesis, four resistance new genes origined from Thinopyrum were mapped using wheat-Thinopyrum derivatives and corresponding mapping population as material. Among the four genes, three (Yr69, YrCH5026 and YrCH7124) are stripe rust resistant, and one (pmCH89) is powdew mildew resistant. The main results are as follows:1. CH7086 is a stable and stripe rust resistant wheat-Th. ponticum introgression line. CH7086 exhibited immunity to P. striiformis f. sp. tritici (Pst) pathotypes CYR23, CYR29, CYR31, CYR32, CYR33, SY11-4, SY11-5, SY11-7 and CH42 at the seedling stage. The Pst resistance in CH7086 is similar to that in XY7430 and its wild parent Th. ponticum. The chromosomal location and inheritance of Yr gene was determined by susceptive wheat cultivar TC 29 crossed with line CH7086. The disease screening demonstrated that CH7086 and its donor XY7430 as well as the wild parent were resistant at the seedling and adult stages to CYR32, whereas all the wheat parents involved were susceptible, indicating that the CH7086 was possibly derived from Th. ponticum. Molecular characterization of the alien introgression and genomic in situ hybridization (GISH) failed to identify alien chromatin. We couldn’t testify that CH7086 had alien chromosomal segments from Th. ponticum. Genetic analysis of the crossed populations from susceptive wheat cultivar with CH7086 showed that a single dominant gene resistance to CYR32. We detected SSR, STS and EST-SSR markers linked to Yr resistance gene. The gene was linked to six SSR markers, one STS marker and one EST-SSR marker. The two flanking markers were X2AS33 and Xmag3807, and their genetic distances with resistance gene were 1.9 cM and 3.1 cM, respectively. Using the CS tool materials, the Yr gene and the polymorphic markers were located in deletion bin 2AS5-0.78-1.00. Furthermore, based on the source of the Yr gene, allelism test and chromosome location, the gene might be a novel stripe rust resistance gene, which is formally named Yr69.2. CH09W89 was derived from susceptible wheat cultivars crossing with TAI7045. TAI7045 was a wheat-Th. intermedium partial amphiploid. CH09W89 exhibited highly resistant or immunity to Blumeria graminis f.sp. tritici (Bgt) pathotypes, at the seedling stage. It showed that CH09W89 had powdery mildew resistance similar to its donor TAI7045 and Th. intermedium, it dicating that the powdery mildew resistance gene in CH09W89 derived from Th. intermedium. Based on GISH of mitotic chromosomes, no Th. intermedium chromatin was detected. To determine the chromosomal location and inheritance of Pm gene, two susceptive wheat cultivars were crossed with CH09W89. Genetic analysis showed a single recessive gene controlled the adult resistance to Bgt E09 in CH09W89. The two flanking markers were Xwmc310 and Xwmcl25, genetic distances were 3.1 cM and 2.7 cM to Yr gene. Using the CS tool materials, the polymorphic markers and the resistance gene were located in the chromosome bin 4BL-0.68-0.78. The gene might be a new Pm resistance which is temporarily named pmCH89.3. CH5026 is a stable introgression line carrying resistance genes of Th. intermedium, which was found to be resistant to stripe rust and powdery mildew. Th. intermedium, CH5026 and its resistant parent amphiploid TAI7045 as well as all wheat parents were evaluated by inoculated races in the seedling stage (CYR31, CYR32 and CYR33) and adult stage (CYR32). Through races test, CH5026 showed similar phenotype to its donor parent TAI7045 and the wild parent Th. intermedium, which indicated the resistance of line CH5026 was derived from Th. intermedium. No Th. intermedium chromatin has been detected according to GISH assay. Genetic analysis on the crossed populations from resistant line CH5026 with susceptive wheat cultivar showed that a single dominant gene resistance to Pst CYR32. Three SSR primers, Xgwm210, Xwmc382 and Xgpw7101 were identified to be linked to the resistance gene. The genetic distances of Yr gene and two flanking markers, Xwmc382 and Xgpw7101, were 6.0 cM and 4.7 cM. Using the CS tool materials, Yr gene and its linked polymorphic markers were assigned to chromosome 2AS. According to the source of the Yr gene, the stripe rust resistance gene in CH5026 was likely different from the known resistance genes on chromosome 2AS. The gene might be a novel stripe rust resistance new gene which is temporarily named YrCH5026.4. CH7124 was a homogeneous BC2F6-derived wheat lines using TAI8335 as the donor parent. Through races test, CH7124 showed similar phenotype to its donor parent TAI8335 and the wild parent Th. intermedium, which indicated the resistance of line CH7124 was derived from Th. intermedium. To investigate the inheritance of stripe rust resistance, CH7124 was crossed to susceptible cultivars to obtain segregating populations. The F1, F2 and F2:3 populations were tested for segregation of stripe rust resistance. The results showed that there is a single dominant gene to Pst CYR32 in adult stage, which is temporarily named YrCH7124. SSR markers screening results showed that four polymorphic markers were linked to the resistance gene. The two flanking markers were Xgwm614 and Xwmcl54, and genetic distances to Yr gene were 8.6 cM and 10.5 cM. Based on the marker loci and the origination, YrCH7124 might be a new gene to wheat stripe rust on 2BS chromosome.In summary, total three dominant stripe rust reisitance genes and one recessive powdery mildew resistance gene which derived from wheat-Th. ponticum or wheat-Th. intermedium cryptic translocations were genetically analysised and mapped. Moreover, molecular markers which were closely linked to the resistance genes are developed. These resistance genes discovery provided new gene sources for wheat breeding, and the establishment of molecular markers which closely linked to the resistance genes laid a solid foundation for using them in marker assisted breeding program. |
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