| Rice blast is one of major rice diseases in the world, causing great loss every year. Breeding of resistant varieties is the most economical, effective and environmentally methods to control this disease. However, it is more and more difficult to breed the new varieties with high yield, high quality and high level resistance to diseases and pests through conventional breeding methods. The molecular breeding technology, including transgenic technology and molecular marker assisted selection (MAS) technology, could be used for improving some characters directionally and breeding the elite lines by aggregation of different genes. The transgenic breeding can break the hinderance between different species and improve some characters without influence from the genetic background. However, the safety of the transgenic food is suspected by public, so technology is restricted for widely used. In contrast, the MAS technology is safer and more reliable. But the selection efficiency is low because of the incorrect or inaccurate mapping results. The problem could be solved by developing the specific markers based on the sequence of cloned genes.Pi9is a cloned broad-spectrum blast resistance gene at Pi2/9locus, located on the short arm of rice chromosome6. The length of Pi9gene is9.5kb, which contains two introns and the Pi9cDNA was4009bp, including3099bp of Pi9coding sequence and910bp of3’-UTR. In this study the indica rice75-1-127containing Pi9gene was used as the donor and the molecular markers specific to Pi9gene were developed and employed to improve the blast resistance of23indica lines. The results are as follows:1. Based on sequence information of Pi9gene, four specific molecular markers, Pi9-a, Pi9-b, Pi9-c, and Pi9-d were designed. These markers showed obvious polymorphism, and appeared to be stable and could easily distinguish the23rice receptor lines from the Pi9donor line75-1-127. Pi9-b and Pi9-d have the same effect for selection with polymorphic rate of82.6%. The polymorphic rate of Pi9-b and Pi9-c were87.0%and95.7%, respectively; the primers Pi9-c could be used for differentiating the donor from receptor lines, combined with Pi9-a, Pi9-b, Pi9-d.2. The resistance spectra of23receptor lines and75-1-127were analyzed through indoor inoculation assay. The strains virulent to different lines were selected for phenotypic analysis of the progeny from backcross. The results showed that all the receptor lines needs to be improved and at least one strain was selected for different line. Among of them, T98B and Lunhui422have the narrowest resistance spectra. The rate of pathogenicity was90.9%and86.4%, respectively.3. Pi9-a, Pi9-b, Pi9-c and Pi9-d were used for screening of the individuals containing the target gene in each backcross populations from different crosses. Tianlongxiang103/75-1-127,25H003/75-1-127, Lunhui422/75-1-127, R288/75-1-127, and R747/75-1-127BC1F1populations were inoculated for phenotypic analysis and Pi9-a and Pi9-c were used for genotypic analysis. The results showed that the selection efficiencies of this two markers were over97%.4. BC4F1populations from10crosses between1701, Fengyuan B, E32, R228, R288, Ⅱ32B, Xiangfeng187,389, Xiangwanxianll, Tianlongxiang103and75-1-127were obtained; BC3F1populations from6crosses between Lunhui422, Xiangwanxian13,25H003,316B, R207and R747and75-1-127were obtained; BC2F, populations from5crosses between Jin23B、R996、198、527and R640and75-1-127were obtained; BC1F1populations from the crosses between T98B, Minghui63and75-1-127were obtained. The results will lay solid foundation for the further development of stable rice blast resistance lines. |
PDF Full Text Request