| sorghum-sudangrass hybrid is an excellent annual forage grass produced by interspecific hybridization between sorghum and sudan grass,with strong heterosis.In this study,150 isolated individuals and their parents of F2population obtained by crossing sorghum biocolor and sorghum sudanense at the early stage of the research group were used as materials,the high-quality SNP molecular markers were developed based on whole-genome re-sequence technology,the ultra-high-density molecular genetic linkage map of sorghum-sudangrass hybrid was constructed with Lepmap3 software.The content of crude protein,crude fiber,crude fat,starch and calcium in the green hay at the jointing stage of sorghum-sudangrass hybrid under two different environments over two years was measured using a Spectra Star 2600XT near-infrared spectrometer made in the United States,and the location analysis was performed by Map QTL 6.0 QTL software.Then,transcriptome sequencing analysis was conducted on three major QTLs（q CP-3-4,q CP-8-1,q CP-8-2）with more than 20%of the genetic contribution rate of crude protein content,to explore candidate genes related to crude protein content.This study can lay a theoretical foundation for further research on QTL fine mapping,gene mapping cloning and functional analysis,and molecular marker-assisted breeding for nutritional quality traits in sorghum-sudangrass hybrid.The main results are as follows:1.A total of 5,656 high-quality SNP markers of sorghum-sudangrass hybrid were developed using whole-genome re-sequence technology.2.A high-density genetic linkage map of sorghum-sudangrass hybrid was constructed based on 5,656 SNP markers,which contained 10 linkage groups,with an average distance of 0.39 c M between markers and a total length of 2,192.84 c M covering the genome3.The phenotypic value of five nutritional quality traits of sorghum-sudangrass hybrid F2population,including crude protein,crude fiber,crude fat,starch and calcium content,showed a normal distribution in two different environments over two years,which showed the inheritance of quantitative traits.4.A total of 15 stable QTLs（LOD>3.0）were detected for five nutritional traits,including six QTLs for crude protein content,two QTLs for crude fat,crude fiber and starch content,and three QTLs for calcium content,with the variation of genetic contribution rate from 8.9%to 28.3%.5.Among the 15 stable QTLs,there were five major QTLs with a genetic contribution rate of more than 14%,among which three QTLs controlled crude protein content,namely q CP-3-4,q CP-8-1 and q CP-8-2,with a genetic contribution rates from 20.0%to 28.3%,21.8%to 24.1%,and 24.1%to 26.1%,respectively.One QTL for crude fat content and one for starch content were detected,which were q CFa-3-1 and q St-7-2,with the genetic contribution rates from 19.3%to 21.1%,and 14.3%to 16.6%,respectively.6.Transcriptome sequencing analysis was conducted on RNA gene pool samples of crude protein content of sorghum-sudangrass hybrid,and 31 differentially expressed genes related to crude protein anabolic metabolism were screened.7.After comparison with QTL mapping results of crude protein content,two candidate genes LOC8068026 and LOC8070372 may related to crude protein content were finally identified,encoding glutamate synthetase gene and glutamino-fructose-6-phosphate aminotransferase gene,respectively. |
