Construction Of High-density Genetic Linkage Map And QTL Identification For Traits Such As Hydrocyanic Acid Content Of Sorghum-Sudangrass

The Sorghum-Sudangrass is the interspecific hybrids by a cross of Sorghum bicolor?Linn.?Moench×Sorghum sudanense?Piper?Stapf,which has strong heterosis.It synthesizes the advantages of high yield,strong stress resisitance and adaptability from sorghum,and large amount of grass and leaf,more tillering,good palatability and nutritional quality from sudangrass.The deficiency is that the Sorghum-Sudangrass has a relatively high hydrocyanic acid content in the stems and leaves,which can cause poisoning if livestock overfeeds.In order to breed new varieties of Sorghum-Sudangrass with super-low hydrocyanic acid content,high yield and good quality,our research group made a cross from loose panicle Sorghum×red shell Sudangrass and obtained F₁ hybrids,then,the F₂ separation population were obtained from the F₁ seeds bagging and selfing.In the present research,using 305 idividuals of Sorghum-Sudangrass F₂ population and their parents as materials,a high-density genetic linkage map of Sorghum-Sudangrass was constructed based on AFLP,SSR and SRAP molecular marker technique and Joinmap 4.0software.The quantitative traits loci?QTL?location was identified by the statistical value of 10 traits such as hydrocyanic acid content,fresh weight per plant,seed yield,tiller number,stem and leaf ratio in two years and two places and the Map QTL 4.0 software.So as to lay a foundation QTL fine localization,correlation functional gene map-based cloning and molecular marker breeding of important traits such as hydrocyanic acid content,yield and quality in Sorghum-Sudangrass.The main results were as follows:1.139 suitable primers were selected and amplified the genomic DNA of 305 F₂segregation individuals of Sorghum-Sudangrass and their parents,including 71 AFLP,57SSR and 11 SRAP primers.1310 polymorphic loci?716 AFLP,346 SSR and 248 SRAP?were detected by the PCR amplification.The percentage of polymorphism were 81.6%?85.2%and 93.6%respectively.2.Chi square test showed that a total of 1001 markers of 1310 polymorphism marker accorded with 3:1 Mendelian segregation ratio.A total of 309 markers deviated from segregation ratio,including 233 AFLP,43 SSR and 33 SRAP markers,and the average segregation ratio was up to 23.59%.3.A high density genetic linkage map of Sorghum-Sudangrass was constructed,consisting of 10 linkage groups and 1310 markers.The total length was 1488.5c M,and an average distance was 1.14 cM.4.The correlative analysis showed that the 10 traits such as hydrocyanic acid content,fresh weight per plant,stem and leaf ratio,tiller number and seed yield in two years and two places had significant or extremely significant correlative relationships.According to the QTL location analysis of 10 traits of the Sorghum-Sudangrass,93 QTLs were lacated in 10 linkage groups,with an average of 9.3 QTLs for each linkage group.5.Of all the 93 QTLs,four QTLs controlled hydrocyanic acid content,11 QTLs controlled dry weigh per plant,three QTLs controlled fresh weigh per plant and leaf number respectively,24 QTLs controlled stem-leaves weigh rate,five QTLs controlled stem diameter and tiller number respectively,21 QTLs controlled seed yield,two QTLs controlled panicle length,and 15 QTLs controlled panicle width,which could explain the phenotypic variation from 9.0%-38.4%.The research found that a total of 13 main QTLs could explain more than 20%of the phenotypic variation,including three QTLs controlled hydrocyanic acid content?Qcn1,Qcn2 and Qcn4?,one QTLs controlled dry weigh per plant?Qdwp4?and stem-leaves weigh rate?Qslrw3?respectively,two QTLs controlled tiller number?Qtn3 and Qtn5?,three QTLs controlled seed yield?Qyp2,Qyp8 and Qyp21?and panicle width?Qpw2,Qpw11 and Qpw12?,respectively.