| Paspalum vaginatum is a warm-season perennial grass of the Gramineae family.It has many excellent resistances to abiotic stresses,such as salinity,cadmium and drought.And some studies have shown that it is one of the warm-season turfgrasses with strong resistance to cadmium.P.vaginatum has strong resistance to cadmium,but its mechanism is still unclear.In this study,morphological indicators were used to evaluate the cadmium tolerance of P.vaginatum accessions,and the correlation between cadmium tolerance and cadmium content was analyzed.In order to study the physiological mechanism of the extreme germplasm of P.vaginatum,the changes of chlorophyll and proline content were analyzed.And the transcriptome of USA17-2,USA17-2 1d,USA17-2 3d;USA17-16,USA17-16 1d,USA17-16 3d;USA17-47,USA17-47 1d,USA17-47 3d was analyzed.The main contents of this study are as follows:1.Optimization of cadmium-tolerant system of P.vaginatum accessionsSelect two P.vaginatum materials（USA17-41 and HN17-2）,use hydroponic method,and treat with cadmium sulfate solution（8Cd SO4·3H2O）,set 0,0.5,1.0,1.5,2.0,2.5,3.0mmol·L-1concentration gradients for cadmium resistance screening.The results showed that when the P.vaginatum was subjected to 0～1.5 mmol·L-1 cadmium stress,its leaf firing was less than 50%,and the turf quality was higher than 4 points.The turf quality of P.vaginatum reduced to 2～3 points,the leaf firing was greater than 60%,resulting in the large area of P.vaginatum wilt,and when the P.vaginatum received 1.5～2.0 mmol·L-1,the turf quality and the leaf firing are significant differences.Therefore,1.5 mmol·L-1was selected to evaluate the cadmium tolerance of a large number of P.vaginatum accessions.2.Evaluation of Cadmium Tolerance of P.vaginatum accessionsAt a concentration of 1.5 mmol·L-1cadmium sulfate（8Cd SO4·3H2O）,hydroponic method was used to evaluate the cadmium tolerance of 90 P.vaginatum accessions.The turf quality,leaf firing,dryweight aboveground and underground were determined.Evaluate the cadmium tolerance of P.vaginatum accessions by the recording function method,Comprehensive evaluation shows that USA17-2 and USA17-45 are cadmium-tolerant germplasm,while USA17-47 and HN17-35 are cadmium-sensitive germplasm.The cadmium content of 50 P.vaginatum accessions was determined.The results showed that most of the cadmium was mainly distributed in the roots of the P.vaginatum,and the cadmium content of USA17-16 and HN17-35 were mainly distributed aboveground.According to the correlation between the cadmium content and the cadmium tolerance index,the underground cadmium content is significantly correlated with the relative aboveground dry weight（P<0.05）,and the correlation coefficient is 0.281.3.Study on physiological difference e of P.vaginatum accessions in Cd treatmentThe Proline and chlorophyll were determined of extreme resources for cadmium tolerance（cadmium resistance:USA17-2,USA17-30 and USA17-37,sensitive cadmium:USA17-24,USA17-42,USA17-47 and HN17-35）.It shows that the content of proline and chlorophyll in cadmium-tolerant P.vaginatum after cadmium stress was significantly（P<0.05）higher than that of cadmium-sensitive P.vaginatum.It is speculated that maintaining a high content of proline and chlorophyll is an important physiological mechanism of P.vaginatum cadmium tolerance.4.Transcriptome analysis of P.vaginatum accessions in Cd treatmentThrough transcriptome analysis of P.vaginatum accessions plants（USA17-2,USA17-16 and USA17-47）,a total of 36,201 DEGs were detected,GO and KEGG analysis of DEGs revealed that photosynthesis,Ion transport,metabolism related genes play an important role in cadmium stress of P.vaginatum.In this study,28 genes related to promote the synthesis of chlorophyll and proline of P.vaginatum USA17-2 and USA17-47 were discovered,These genes were significantly up-regulated in the plants of P.vaginatum USA17-2 after cadmium stress,and promoted the synthesis of chlorophyll and proline in the leaves,but they were down-regulated or not expressed in the plants of P.vaginatum USA17-47.The results are consistent with Mechanism research.18 genes related to cadmium transport of P.vaginatum USA17-16 and USA17-47,These genes were significantly down-regulated or not expressed in the roots and leaves of P.vaginatum USA17-47,and up-regulated in USA17-16,which promoted the transport of cadmium to the aerial parts,consistent with the results of cadmium transport and distribution（The cadmium content of the aboveground part of USA17-47 is lower than that of the underground part,while the cadmium content of the aboveground part of USA17-16 is significantly（P<0.05）higher than that of USA17-47）.It provides basic data for further research on gene cloning and functional verification of P.vaginatum. |
