Screening Of Molecular Markers Linked To Maize Dwarf Mosaic Virus Resistance Gene And Marker-assisted Selection

Maize dwarf mosaic is one of the devastating and widespread viral diseases caused by maize dwarf mosaic virus (MDMV) in the world. The virus is transmitted in a nonpersistent manner by several aphid species. Although insecticides are effective in controlling aphid populations, they cannot prevent the introduction of virus by migrant aphids. The occurred and prevalent of maize dwarf mosaic disease owing to the narrow genetic base of test material and the use of large number of susceptible inbred lines.The research had shown that the resistance to maize dwarf mosaic virus is significantly different in different inbred lines and varieties. Breeding and cultivation resistant maize varieties are the efficient method to control MDMV. In order to control the maize dwarf mosaic disease, the researchers need to explore resistance resources and analyze the characteristics of resistance genes. This can help discover new disease-resistant genes and provide an important basis for the material. The accurate location of resistance loci is the prerequisite and the infrastructure of breeding for disease resistance.The resistance genes of maize inbred lines Huangzaosi, X178 and Siyi have been identificated and used. The resistance of the maize inbred line Huangzaosi to the maize dwarf mosaic virus strain B was conditioned by a major gene and polygene.With the allelism test and genetic analysis,Wu jianyu and so on identify a recessive resistance gene to Maize dwarf mosaic virus strain B of the maize inbred Huangzao 4. The gene is located on the long arm of chromosome 6 and was proposed to designate as mdm1 (t).The present investigation was carried out to develop DNA markers closely linked to the resistance gene mdm1(t). Linkage between the markers and phenotypes was confirmed by analyzing an F2 population obtained from a cross between a resistant parent'Huangzaosi'and a susceptible parent'Mo17'. The results were as follows:1. AFLP technology was used to analyze the parents and the F2 populations. Two AFLP markers were found in the maize dwarf mosaic resistant plants through the test.2. Positioning the AFLP amplification products with RFLP analysis. The positioning results indicated that the two amplified fragment length polymorphism (AFLP) markers, RHC-1and RHC-2, from the amplification products of primer/enzyme combination E-AAC/M-CAG and E-AGG/M-CAC showed linkage with the mdm1(t) gene. The genetic distances between markers and the gene were calculated, which showed markers RHC-1 and RHC-2 flanking the resistance gene on chromosome 6 were 1.6cM and 2.0cM respectively.3. We analyze the sequences of the two AFLP fragments and design two pairs of SCAR primers according to the base sequences of the 5,end taking into account the principle of PCR primer design. To test the specificity of the markers, we use the SCAR primers designed for PCR amplification in the parents and the F2 populations. One primer could amplify a discriminating band (401bp) from resistant parent and resistant F2 individuals, while no product was obtained from the susceptible parent or susceptible F2 individuals. Another primer also can amplify polymorphism between resistant individuals and susceptible individuals.4. We amplified the F2 plants with the SCAR markers transformed. The results were as basically same as the results that were amplified with the SCAR primers. This indicates that the AFLP markers have been successfully transformed into SCAR markers. The new SCAR markers will be valuable to distinguish resistant plants from susceptible plants in plantlets. The close-up molecular markers provide a solid foundation for marker-assisted selection and the clone for disease resistance gene.