SSR Linkage Map Construction And QTL Identification For Resistance Gene Of MRDV In Maize

Maize (Zea mays L.) is an important food, forage and energy crop as well as a model plant for genetics in the world. In China, the maize yield has exceeded rice and plays an important role in the national economy. Maize rough dwarf disease, caused by MRDV (Maize Rough Dwarf Virus), is one of the most widespread and serious maize disease in most parts of China. In order to control the prevalent of deseases and reduce crop losses, developping and using resistance genes of maize for desease resistance breeding programs is an effective way to resolve the problem radically. Marker-assisted selection (MAS) may greatly increase the efficiency in plant breeding for resistance to MRDV compared to conventional breeding. This study mainly deals the screening of maize germplasm resources against MRDV and the mapping of QTLs concerning MRDV resistance, both of which are of great significance for maize breeding programs. The mainly results are as follows:A mapping population consisting of 205 F5 recombinant inbred lines (RILs), derived from the cross between maize inbred lines 80007 (the resistance line) and 80044 (the susceptible line), was used in this study. The polymorphisms between the parental lines were detected with 812 pairs of SSR markers, 199 (24.5%) of which showed polymorphisms between the two parents. However, totally 173 pairs of markers amplified desired polymorphic bands in the F5 RIL, and they were used to build the genetic linkage map. The total map length was 919.87 cM; the average distance between markers was 5.32 cM and the order of most of the loci on each chromosome are in agreement with that derived from MaizeGDB, indicating that the RILs and its corresponding genetic map are suitable for QTL mapping. The map provided a basis for the mapping of genes conferring resistance to MRDV and could also be used in the genetic improvement of the two parents and the inbred lines derived from 80007.The mapping results showed that five QTLs were identified for MRDV resistance using inclusive composite interval mapping method (ICIM), which were located on chromosome 1, 2 and 5 in Taian and explained a range of phenotypic variation from 4.69% to 17.74%; three QTLs for MRDV resistance were mapped on chromosome 1 and 2 in Feicheng, explaining phenotypic variation ranging from 4.95% to 19.13%. One common QTL detected on chromosome 2 were identified in both environments, explaining 17.74% and 8.76% of the phenotypic variation, respectively, which can be used for fining mapping and positional cloning.