A SSR Genetic Linkage Map And Identification Of QTLs For Main Characters Of Sorghum Hybrid Sudanense

Sorghum hybrid sudanense was from a cross of bred by hybridization of sorghum X sudangrass, which is a forage with good characters of both parents. In the present study, using loose spike Sorghum and black sell sudangrass as parents, and their170F2individuals as mapping population, we constructed a genetic linkage map based on SSR markers, and identified the QTLs for8main agronomic traits of Sorghum hybrid sudanense. It lays the foundation for the future study of molecular marker assisted selection breeding in Sorghum hybrid sudanense. The main results were followed:1. Using the genome DNA of loose spike Sorghum, black sell sudangrass and one of F2individuals to select SSR primer pairs, we screened50suitable primer pairs from a total of120SSR primer pairs, then the screened SSR primers were used to amplified170F2individuals and obtained226polymorphic bands, on the average of4.5polymorphic bands each primer pair.2. According to the Chi-square test of the226SSR markers, a total of32markers showed segregation distortion, accounting for14.2%of all the loci.3. To construct a genetic linkage map of181SSR makers on10linkage groups, accounting for80.08%of the total SSR markers, of which15markers showed segregation distortion. The length of linkage groups ranged from5.8to52.3cM, and markers number of linkage groups ranged from3to45. The maximum and the minimum interval between markers were27.7cM and4.8cM. The map length was803.13cM, with the average distance between markers was4.38cM. It is a relatively high-density map.4. The8agronomic characters of F2mapping population such as hydrocyanic acid content, plant height and gain tiller showed continuous and normal distribution. There are significant correlation between different traits, in which13groups showed extremely significant correlation (P<0.01), and2groups showed significant correlation (P<0.05).5. A total of17QTLs for8agronomic traits were detected, including2QTLs for leaf number,4QTLs for stem diameter,2QTLs for gain tillers,2QTLs for leaf length,3QTLs for leaf width.2QTLs for panicle length,1QTL for plant height and1QTL for hydrocyanic acid. These QTLs were located on1to7and9linkage groups of the linkage map, respectively, explaining the the phenotypic variation from12.5%to25.6%, in which the QTLs for leaf width and hydrocyanic acid content explained the highest phenotypic variation.6. Of all the17QTLs,1QTL showed additive effect, accounting for5.88%,3QTLs showed partly dominance effect, accounting for17.65%,4QTLs showed dominance effects, accounting for23.53%, and9QTLs showed super dominance effect, which accounted for52.94%. It indicate that dominance effect and super dominance effect play a predominant role in the genetic basis of sorghum hybrid sudanense heterosis.