| Soil cadmium pollution has become a serious threat to food safety production.Ramie is an important fiber crop in China,and it is a very promising plant for remediation of heavy metal cadmium contaminated land.In order to further evaluate and identify the cadmium enrichment characteristics of ramie germplasm,and select excellent ramie germplasm with high cadmium enrichment ability,so as to understand the enrichment mechanism of heavy metal cadmium in Ramie.In this study,269 Ramie germplasms were used to compare the phenotypic characters of agronomic characters,cadmium content and cadmium accumulation ability under the condition of cadmium pollution.The association analysis was conducted between 168 pairs of polymorphic EST-SSR primers and 269 Ramie germplasms including agronomic characters,cadmium content and cadmium accumulation.On this basis,through high-throughput sequencing technology,discover the genes of ramie germplasm in response to cadmium stress,and a pot experiment was conducted to study the ability of various components of ramie germplasm cell wall to accumulate heavy metal cadmium.The main results are as follows:1.In the soil with cadmium pollution concentration of 1.63～9.06 mg kg-1,the results for2 years indicating that 269 ramie germplasm had rich phenotypic variation.Based on the correlation analysis of agronomic traits of 269 ramie germplasm resources,the results for 2years showed that the fiber yield of ramie was significantly positively correlated with plant height,stem diameter and skin thickness.Biological yield was significantly positively correlated with plant height,stem diameter,skin thickness and fiber yield.In 2017,the cadmium content and cadmium accumulation of the underground part was significantly higher than that in the aboveground part,which were 1.42 and 1.96 times.11 Ramie germplasm resources with high cadmium enrichment ability were selected,the average accumulation of cadmium in 2016 and 2017 were 41.47,17.84 g·hm-2,respectively.The enrichment coefficient in 2016 and 2017 were 2.86,0.91,respectively.And the translocation coefficient in 2016 and 2017 were 2.89,0.92,respectively.2.The number of alleles of the 168 pairs of markers ranged from 2 to 4,with an average of 2.38.The range of Shannon index was 0.3980-1.2677,with an average of 0.6988,and the range of polymorphic information content was 0.2076-0.6364,with an average of 0.3709.According to the analysis of population structure,269 ramie germplasms were divided into 4subgroups and 1 mixed subgroup（MP）.Using Tassel 3.0 to analyze the association of agronomic traits,cadmium content and cadmium accumulation,52 locis were significantly associated with agronomic traits,cadmium content and cadmium accumulation.Among them,40 locis were significantly associated with two years:plant height（3）,stem diameter（9）,skin thickness（9）,ramet number（7）,effective plant rate（1）,fiber percentage（2）,biological yield（1）,aboveground cadmium accumulation（1）,underground cadmium accumulation（5）,single plant cadmium accumulation（2）.3.The results of different ramie varieties and different cadmium concentrations showed that the cadmium content of root,stem and leaf cell wall of ramie increased with the increase of cadmium concentration.When cadmium concentrations were 25 mg kg-1 and 75 mg kg-1,the cadmium content in root cell wall were significantly higher than that in stem and leaf.which were 2.73～5.08,2.76～4.14 times higher than that in stem,and 4.86～7.55,4.56～7.21times higher than that in leaf.The results indicating that root is the main organ for accumulating cadmium.At the same cadmium concentration,the hemicellulose cadmium content of root,stem and leaf was significantly higher than that of pectin,cellulose and lignin.When cadmium concentrations were 25 mg kg-1 and 75 mg kg-1,the cadmium content of hemicellulose in root were 1.96～2.70,2.23～2.65 times higher than that of pectin,and2.07～2.64,1.79～2.16 times higher than that of cellulose and lignin.The cadmium content of hemicellulose in stem were 2.77～4.20,3.29～3.96 times higher than that of pectin,and3.12～4.03,2.33～3.88 times higher than that of cellulose and lignin.The cadmium content of hemicellulose in leaf were 2.52～3.12,2.72～3.68 times higher than that of pectin,and2.52～4.23,2.10～3.20 times higher than that of cellulose and lignin.It shows that hemicellulose is the main component of heavy metal cadmium in cell wall.4.2 Ramie germplasms with different cadmium accumulation ability,Bni-1 and Bni-2,were sequenced by high-throughput sequencing,and a total of 56039 Unigene were obtained after assembly.There were 3914 genes differentially expressed in ramie germplasm Bni-1with low cadmium enrichment ability,which significantly less than 4243 genes in ramie germplasm Bni-2 with high cadmium enrichment ability.There were 1692 up-regulated genes and 1615 down-regulated genes in Bni-1,1907 up-regulated genes and 1729down-regulated genes in Bni-2.The results of KEGG metabolic pathway enrichment analysis showed that the main metabolic pathways with significant enrichment of up-regulated differential genes shared by Bni-1 and Bni-2 are amino sugar and nucleotide sugar metabolism,carbon fixation in photosynthetic organisms,galactose metabolism,inositol phosphate metabolism,and so on;the main metabolic pathways that share the down-regulated expression of differential genes are significantly enriched are glutathione metabolism,glycine,serine and threonine metabolism,aminoacyl-t RNA biosynthesis,butanoate metabolism,and so on.Bni-2 specific up-regulated expression genes are significantly enriched in the main pathways such as phenylpropanoid biosynthesis,plant-pathogen interaction,tyrosine metabolism,isoquinoline alkaloid biosynthesis,cutin,suberine and wax biosynthesis,and so on.34 differentially expressed genes related to heavy metal cadmium were screened by analyzing the differentially expressed genes shared by Bni-1 and Bni-2,which were 1 ABC gene,1 HMA gene,3 WRKY genes,13 ATPase genes and 16 MYB genes.The up-regulated genes of Bni-2 were analyzed,the results showed that18 differentially expressed genes related to high cadmium accumulation,which were 4 MYB genes,2 WRKY genes,1 HAM gene,8 ATP enzyme genes and 3 ABC genes. |
PDF Full Text Request