Difference Of Hemicellulose Content And SNP Analysis Of Ramie(Boehmeria Nivea L.)

Hemicellulose,which is the most content of the colloid in ramie fibers,is most difficult to be removed in degumption process,so it has become the bottleneck of ramie industry and it is urgent for us to reduce the hemicellulose content in ramie fibers.For the genetic mechanism of ramie hemicellulose content is unknown and candidate genes and their functional molecular markers are lacking,we need to explore the gene and molecular markers related to hemicellulose content.In our study,we carried out genome-wide association analysis(GWAS)based on the studies of hemicellulose content differences in different parts of raw ramie and hemicellulose content differences caused by different peeling methods.The association analysis populations has been constructed in the earlier stage in two environments,including the first harvest ramie and the second harvest ramie.The GWAS The main results were as follows:1? We analyzed the chemical components in different parts of raw ramie of Zhongzhu No.3,Zhongzhu No.4,Zhongzhu No.5,Zhongzhu No.6 and X2016-?.The comparison between different parts of same species showed that the heads have more lipid wax,lignin,water soluble matter,pectin and hemicellulose than the middles and the roots in all 5 varieties,and no significant difference between the middles and the roots.Except variety Zhongzhu No.4,the content of cellulose in the middles were the highest in all 4 species.Because the cellulose quality can be affected by the other chemical compositions,so in the selection of high-quality parts in raw ramie,we should choose the middles,avoiding heads.We also compared the difference between varieties in the same part,and it showed that the lowest variety of water soluble matter and pectin were Zhongzhu No.3,the lowest variety of lipid wax and hemicellulose was X2016-?,Zhongzhu No.6 had the lowest lignin content,Zhongzhu No.3 had the highest content of cellulose,X2016-? had the highest content of hemicellulose.2? We set up 3 kinds of ramie decorticators: simple,pull-back drawing and reverse drawing decorticators,to discuss the effects of different peeling methods on the yield and quality of ramie.The results showed that the yield and quality of ramie fiber produced by different decorticators were significantly different.All kinds of fibers were nearly yellow,simple-peeled fiber was the brightest,while the color of reverse-peeled fiber was the reddest.There were no significant differences on the fresh weight stripping percentage between the simple and pull-back drawing decorticator,which was significantly lower than that of reverse drawing decorticator.However,the main reason for the higher fresh weight stripping percentage of the reverse drawing decorticator was the significantly higher total gum content(28.21%).There were significant differences in single fiber strength among 3 kinds of fibers,and the single fiber strength,from high to low,was simple peeled>pull-back peeled>reverse peeled(25.86cN).Therefore,the ramie peeled by simple ramie decorticator had the best quality.In the subsequent experiments,the samples of the associated groups were peeled by simple peeled machine.3? Associations between 1,336,689 SNPs and hemicellulose content were analyzed.Take-lg(P)>6.64 as the threshold,in the first harvest season ramie population,7 significant correlated SNPs were detected,which located in no.1,no.4,no.8 and no.14 chromosome.In the second harvest season ramie population,68 significant correlated SNPs were detected,which located in no.1,no.2,no.5,no.10,no.11 and no.14 chromosome.Common significant SNP sites were not detected in the two environments,but gene of ?-galactosidase were detected at different sites in two environments.In our study,nine candidate genes that may be related to hemicellulose content were detected in the germplasm of the first harvest ramie and the second harvest ramie.Two genes encoding ?-mannosidase and transcription factor genes encoding the NAC domain were specifically detected in the first harvest ramie.APL gene,MYB family transcription factor,which encodes glucuronyltransferase,and IRX9 H gene encoding ?-1,4-xylotransferase were specifically detected in the second harvest ramie.