| Introgression of superior genes into the common wheat from its wild relatives by distant hybridization is an important approach to creat new wheat germplasm, broaden the genetic basis of wheat breeding, and to promote the proceeding of wheat breeding programmes. It’s important to elevate the efficiency of germplasm usage in breeding by elucidating the genes controling superior agronomical traits and also their genetic behavior based on the development of novel germplasm. In this study, by exploiting a germplasm(Pubing7-4) derived from the hybrid between the wheat Fukuho(Triticum aestivum L.,2n=6x=42,AABBDD) and Agropyron cristatum(L.) Gaertn.(2n=4x=28,PPPP), we genetically analyzed its resistance against powdery mildew and the dwarf phenotype, through agronomic traits investigation and P genome detection. This study not only developed novel germplasm for wheat breeding, but also provided the theoretical guideline for efficient utilization of novel germplasm.1. The novel germplasm Pubing7-4 has many superior agronomic traits. After multiple years of field phenotyping observation in several environments, Pubing7-4 showed stable inheritance, with the typical characteristics of high resistance to powdery mildew during the whole growth period and also dwarfism. These traits include: the plant height was 52cm(ranges from 51.2 to 53.2cm), stem length under spike was 20.4cm(ranges from 19.5 to 21.2cm), effective tiller number was 18(range from14 to 21), kernel number per spikelet ranges from 4 to 5, spikelet number per spike was 20(ranges from 19 to 21), grain number per spike was 61(ranges from 56 to 73), and thousand grain weight was 25.1g and with plump kernels.2. Pubing7-4 carried genetic material from Agropyron P genome.GISH showed that there was no chromosome segment from P genome in Pubing7-4, but among 832 Agropyron specific molecular markers, three(Agc2970, Agc6287 and Agc21686) were detected in Pubing7-4, indicating that this germplasm was a wheat-Agropyron introgression line containing very small chromosomal segments from the P genome of Agropyron.3. Pubing7-4 carried a single dominant powdery mildew resistance gene and a broad resistance spectrum. In the disease resistance identification, Pubing7-4 showed high resistance to all the 21 Bgt isolates. Using F1, F2 population derived from the cross between Pubing7-4 and the susceptible cultivar Mingxian169 for identification of resistance to Bgt isolate E09, F1 plants showed high resistance to E09 and there was a separation ratio 3:1 in the F2 population. The above results showed that Pubing7-4 carried a single dominant gene, tentatively designated Pmpubing7-4.4. Pmpubing7-4 was a new powdery mildew resistance gene or allelic gene. Using F2, F2:3 population derived from the cross between Pubing7-4 and Mingxian169, genetic analysis was made by characterization of resistance to powdery mildew to the Bgt isolate E09, and constructed a genetic linkage map through molecular marker technology and bulk segregant analysis(BSA), Pmpubing7-4 was mapped on chromosome 5DS, flanked by SSR markers Xcfd81 and Xbwm25 at genetic distances of 2.6c M and 3.3c M, respectively. The comparism of resistance spectrum and linked markers showed that Pmpubing7-4 was distinct from other powdery mildew resistance gene on 5DS, and Pmpubing7-4 was a new gene or allelic gene.5.The dwarf phenotype of Pubing7-4 was semi-recessive. In addition, Pubing7-4 was insensitive to gebberellic acid. Using F1 derived from the crosses between Pubing7-4 and Mingxian169, Pubing7-4 and Zhongzuo9504 and Pubing7-4 and Fukuho and F2 population between Pubing7-4 and Mingxian169, phenotypic analysis of plant height showed that the dwarf phenotype of Pubing7-4 was semi-recessive and was quantitative traits controlled by main effect gene and micro-effect polygene.6. For QTL mapping of the drawf trait of Pubing7-4,we screened molecular markers in the whole wheat genome between Pubing7-4 and Mingxian169 and constructed genetic map using F2 population and F2:3 population. There QTL locis were detected on 4B, 4D and 5D chromosomes, named QPh-4B, QPh-4D and QPh-5D, respectively, and the PVE of them were 34.2%, 47.99%, 8.90%. Pubing7-4 was insensitive to gebberellic acid by the characterization of responses to GA at seedling stage.The above results indicated that, the novel germplasm Pubing7-4 presents a broad prospect in wheat improvement. The obtained specific markers, the exploration of the new powdery mildew resistance gene and its close linkage markers, and the genetic analysis of drawf trait plant height will lay theoretical foundation for improving the efficiency of utilization of this novel germplasm. |
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