Study On The Response Of Stylosanthes Spp. To Aluminum Toxicity Stress

Aluminum is the main abiotic factor limiting plant growth and productivity in acidic soils.Aluminum toxicity is the main abiotic factor limiting crop growth and productivity by inhibiting root growth.The main characteristic of aluminum poisoning is the rapid cessation of root growth.Although there is a large body of literature evidence and hypotheses about the toxicity of aluminum,the precise mechanism by which aluminum inhibits root growth remains unclear.Stylosanthes.Spp is a leguminous forage widely distributed in tropical and subtropical areas of the world.It is an excellent forage for studying the mechanism of response of legumes to aluminum toxicity stress.Therefore,screening excellent germplasm resources of Stylosanthes germplasm,analyzing the characteristics of Stylosanthes germplasm resistance to aluminum toxicity,conducting transcriptomics analysis and digging out the genes of Stylosanthes germplasm resistance to aluminum toxicity can provide a theoretical basis for popularizing Stylosanthes germplasm resistant to aluminum toxicity in the field and for subsequent research and breeding.This study first diversity in 10 varieties as material,through build resistance to aluminum toxicity evaluation system screening aluminum makers poison varieties of diversity,and the resistance of filter aluminum drug kinds of poison stress,on the physiological analysis and the analysis of the transcription,finally through the qRT-PCR technology to validate related genes,parsing the response mechanism of aluminum toxicity stress makers.The main results are as follows:1.Diversity will be 10 seed according to three different mathematical methods for resistance to aluminum toxicity evaluation,using diversity seed germination of the germination rate,germination potential,root length,bud length and fresh weight index and according to the principal component,the ASF value,A value,WAC and cluster analysis of 10 aluminium makers poison patience for sorting and classification,no significant differences between the three methods.Among them,TPRC2001-1 was the most resistant to aluminum,and TF234 was the most sensitive to aluminum.The evaluation system can quickly and efficiently identify the tolerance of Stylosanthes germplasm resources to aluminum toxicity.2.TPRC2001-1,the most aluminium-resistant drug previously screened,was treated with aluminum for 15 days,with 6 aluminum concentrations（0,50,100,150,200,400μM）respectively,and A₁₂（SO₄）³·18H₂O was used for aluminum treatment.The results showed that:（1）Al stress affected the Al content in the shoot and root of Stylosanthes.Among them,aluminum content of Stylosanthes root was mainly affected.With the increase of Al concentration,the Al content in the root also increased gradually.When the Al concentration was 200μm,the Al content in the root did not increase.However,there was no significant change of Al content in leaves when Al concentration was 0-100μm（P<0.05）,but it was significantly increased when Al concentration was 100-150μm and 200-300μm.The results showed that the aluminum toxicity was mainly concentrated in the roots of Stylosanthes spp.under slight aluminum toxicity stress.When the stress of aluminum toxicity increased,the leaves of Stylosanthes also enriched part of aluminum,and took part of the damage caused by aluminum toxicity for the roots.（2）The effects of aluminum stress on the activities of SOD,POD,CAT and APX of Stylosanthus were different.With the increase of Al concentration,the activities of SOD,POD and APX in shoot of Stylosanthes plants had no significant change（P>0.05）,but the APX activity decreased gradually from Al concentration 50μM.The activities of SOD and POD in Stylosanthes root were significantly increased when Al concentration was 0-200μM（P<0.05）,and reached the maximum value when Al concentration was 200μM,while the activities of CAT and APX had no significant changes（P<0.05）.These results indicated that three enzymes,SOD,POD and APX,were involved in the regulation of Stylosanthes plants under aluminum toxicity stress.APX regulated the shoot part,while SOD and POD regulated the root part.（3）With the increase of Al concentration,the total root length,relative elongation,total heel surface area,total heel volume and average root diameter of Stylosanthus alba root decreased.When Al concentration was50μm,total root length,relative elongation,total heel surface area,total heel volume and average root diameter were significantly decreased（P<0.05）,but all five indexes had no significant changes（P<0.05）when Al concentration was 0～50μm,which indicated that root morphological indexes were significantly affected when Al concentration was 50μm（P<0.05）.The total root length,relative elongation and total heel surface area reached the minimum values when the Al concentration increased to300μm,while the total heel volume and average root diameter reached the minimum values when the Al concentration increased to 200μm.The results showed that aluminum treatment significantly inhibited the root growth of Stylosanthes.3.The transcriptional level of Stylosanthes was analyzed and verified by qRT-PCR.Species distribution and identification of Stylosanthes and wild cultivated peanut are more closely related.At the same time,a total of 1206 up-regulated genes and 1709 down-regulated genes were identified.The up-regulated and down-regulated DEGs of GO analysis were mainly concentrated in two pathways,namely metabolic pathway and biosynthesis pathway of secondary metabolites.KEGG analysis showed the highest concentration of differential genes involved in metabolic pathways,followed by environmental adaptation and organic systems.Among them,the number of DEGs involved in global and global maps,carbohydrate metabolism,lipid metabolism,and other secondary metabolic biosynthetic metabolic pathways is high.The RNA-seq sequencing results were basically consistent with the qRT-PCR expression levels,showing a good correlation（R²=0.7213,P<0.01）,indicating that the changes in transcriptome expression results truly reflected the differences in the expression of corresponding genes in Stylosanthes plants.Diversity to sum up,this study determined the germplasm resistance to aluminum toxicity evaluation system and a preliminary screening of the aluminium drug kinds,at the same time to physical screening of drug resistance of aluminum and transcription level of analysis,the results of the study enriched the diversity root resistance to aluminum toxicity transcriptome information,provides valuable data for the molecular biology research in the future,and also provides reference for the breeding work.