Section Linkage Map Construction In Maize DH Populations

Genetic linkage map reflects the relative relationship between genetic markers through linkage analysis.For a long time,to build genetic linkage map,genetic markers and phenotypic markers have restricted the process of the genetic map production due to the lack of polymorphism and limited number of them.Microsatellite markers with the advantages of rich polymorphism and wide distribution on the chromosomes have been widely used on construction of genetic linkage map.the basic idea of the construction of genetic linkage map is to find a polymorphic microsatellite marker at a certain distance in genome,when these markers reach adequate saturation(The average distance is not more than 20cM and can coverage more than 90 percent of the genome),we can make use of these microsatellite markers to find functional genes and quantitative trait loci(QTL) to operate and use them.A microsatellite linkage map of maize was constructed based on a doubled haploid population consisting of 240 lines.638 pairs of published PCR primers for amplifying microsateilite or simple sequence repeat (SSR) loci were used for the study.95 of them displayed polymorphism between the two parents, and therefore,84 of them were used for genotyping of the DH lines.Among the 84 SSR primers analyzed,53.6 percent behaved as seriously segregation distortion in the mapping population.The data of markers on chromosome 1 and 2 were analyzed using the software Mapmaker/ Exp3.0 to construct a genetic map.Two linkage groups were constructed based on the DH population.The map contained 30 SSR markers with the distance of 103.5cM(chromosome 1) and 141.6cM(chromosome 2) respectively and covered a total length of 245.1cM with an average distance of 9.15cM between adjacent markers.