Development Of Molecular Markers And Mapping Of Resistance Gene To Sugar-cane Virus In Maize

Maize dwarf mosaic virus is one of the most important virus diseases of maize and causes serious yield losses in the world. The most effective way to control the disease is to breed and popularize resistant hybrids based on screenings of resistant materials and understanding on the inheridity of resistance. In our previous study, one inbred line Siyi with elite agronomy traits was singled out and its inheritance of resistance to SCMV was studied. Two dominant complementary genes were detected to determine the resistance to sugarcane mosaic virus in Siyi.They were mapped on chromosome 3 and chromosome 6, respectively using microsatellite markers. They were named RSCMV2 and RSCMV1. Many people were found resistance genes or disease resistance QTL in these regions. Action mode analysis of two dominant complementary genes using NILs. These results suggest that RSCMV1 is likely a predominant gene and shows basal resistance to SCMV, while RSCMV2 shows specific resistance at adult stage. Separation of the two resistance gene is important for the resistance breeding practice and the analysis of its molecular mechanism of disease resistance. Combination of maize genome sequencing information, development of molecular markers and mapping of resistance genes by using near isogenic lines in Maize is base of map-based cloning. The results were obtained as following:1. 674 F2 individuals derived from Mo17AaBB were used to mapping of the RSCMV1 in 2007. The resistant gene RSCMV1 was flanked by SSR markers umc1018 and umc2311. The physical distance between the two SSR markers is 6.83 MB, which contained about 50 BAC. Based on 41 BAC's sequences of different regions by randomly selected , 47 pairs of BAC-SSR primers and 17 pairs of ILP primers were developed, 13 pairs of primers exhibited polymorphisms between Siyi and Mo17 and 4 pairs of exhibited dominant phenotyp . Consequently, the resistant gene RSCMV1 was mapped between A16-18 and a1-1, The physical distance between the two markers is 2.6 MB. This result is proved by the offsprings of recombinat plants phenotype. 1279 F3 individuals derived from Mo17AaBB were used to conduct fine mapping of the RSCMV1 in 2008.finally, the resistant gene RSCMV1 was located in a 0.8×106 bp long region on chromosome 6 and co-segregation markers A4-3, A4-2 and a2-1were detected.2. In 2007, 549 F2 individuals derived from Mo17AaBB were used to mapping of the RSCMV2. The resistant gene RSCMV2 was located in SSR markers bnlg1456and umc2020. The physical distance between the two SSR markers is 16.61MB, which contained 113 BAC. Based on 14 BAC's sequences of different regions by randomly selected , 129 pairs of BAC-SSR primers were developed and 26 pairs of primers exhibited polymorphisms between Siyi and Mo17 .Consequently, the resistant gene RSCMV2 was located between bnlg1456 and 3-AC16-20. This result is proved by the offsprings of recombinat plant's phenotype. in 2008, 7000 F3 individuals derived were used to conduct fine mapping of the RSCMV2.finally, the resistant gene RSCMV1 was located in BAC-SSR markers 3-ac36-9 and 3-AC16-20, the physical distance is 5.54MB. Totally 154 individual plants showed recombination between RSCMV1 and SSR markers.