| Sorghum-sudangrass,a hybrid by parents of sorghum and sudangrass,which has the characteristics of high grass production,strong adaptability,superior quality,are widely used in animal husbandry and aquaculture.At present,most of the seeds of high-quality forage crops in China still rely on importation,especially compared with the main crops,such as rice,wheat,cotton and corn,the study on genetic breeding of new forage crops(e.g.Sorghum-sudangrass)considerably lags behind.Therefore,the study of high-density genetic maps and QTL mapping of the main agronomic traits of Sorghum-sudangrass significantly contribute on genetic breeding of Sorghum-sudangrass.In this study,the genetic population of RIL recombinant inbred lines constructed by M81(Sweet Sorghum)and Sa(Sudangrass)was used to sequence by RAD-seq technique,to obtain SNP molecular markers and construct a high-density genetic map for Sorghum-sudangrass.In addition,QTLs for agronomic traits,such as plant height,stem diameter,tiller number,fresh weight per plant,dry weight per plant,spike length,sugar content etc.,were localized.The conclusions as follows:1.Taking 174 recombinant inbred lines(female parent Sweet Sorghum M81 ×male parent Sudangrass Sa)as the drawing population,constructing a library with the size of 300-500bp and sequencing by RAD-Seq technique,to obtain accurate data and construct a high-density genetic linkage map of Sorghum-sudangrass.The results showed that the map contains a total of 790 marker locus and 10 linkage groups(LGs),as well as the coverage of total 2101cM genetic distance,the average 2.65cM distance between markers,and the average 91.57%coverage.2.According to the frequency distribution map of each of agronomic traits in the RIL population of Sorghum-sudangrass,in addition to one trait of sugar content deviating from the normal distribution,the other 6 traits are nearly normal distribution.3.Correlation analysis of seven main agronomic traits,such as plant height,stem diameter,tillering number,fresh weight per plant,dry weight per plant,spike length,sugar content,etc.,showed that the dry weight per plant was significantly and positively correlated with fresh weight per plant,spike length,and sugar content.The correlation coefficient between dry weight per plant and fresh weight per plant was the largest,reaching 0.79;Secondly,the tillering number was significantly correlated with fresh weight per plant and dry weight per plant,with the correlation coefficients of 0.46 and 0.56,respectively;Stem diameter was also significantly and positively correlated with fresh weight per plant,dry weight per plant,and sugar content;stem thickness was significantly correlated with ear length with a correlation coefficient of 0.11;stem diameter was negatively correlated with tiller number,with no significant correlation.4.The QTL location analysis of the main agronomic traits of Sorghum-sudangrass,a total of 18 QTL loci were detected.Among them,there are 4 QTLs controlling plant height,2 QTLs controlling stem diameter,8 QTLs controlling fresh weight per plant,3 QTLs controlling dry weight per plant,and only 1 QTL controlling sugar content.5.According to the contribution rate,a total of 5 main QTLs were found.Two QTLs(fresh weight and plant height)were located on LG 3,two QTLs(dry weight and sugar content)were located on LG 10,and one main QTL controlling stem was located on LG 8.6.Gene clusters that controlled the expression of QTL for two traits,fresh weight and dry weight per plant,were detected on the LG 9 and LG 10 chromosomes at the same locus,further confirming that the same QTL locus greatly contribute multiple function. |
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