Evaluation And Mechanism Of Aluminum Toxicity Of Cajanus Cajan Germplasm Resources

As the sixth largest edible legume in the world,pigeonpea has high crude protein content in branches and leaves,and has great potential as a high quality protein feed.Aluminum toxicity is one of the most important abiotic stresses inhibiting plant growth in acid soil,which seriously restricts the development of planting industry in acid soil area.Pigeonpea is mainly distributed in areas with serious soil acidification and is extremely vulnerable to aluminum toxicity.Therefore,it is an important guarantee to promote the sustainable production of new cultivar of pigeonpea by researching the physiological mechanism of pigeonpea resistance to Aluminum toxicity and exploiting the excellent gene resources of Aluminum toxicity resistance.In this paper,an identification system was established for the resistance to aluminum toxicity in the sprout stage of pigeonpea,and 51 pigeonpea germplasm were evaluated for the resistance to aluminum toxicity,and the resistant and sensitive germplasm were obtained.The physiological mechanism of resistance to Aluminum toxicity was explored by measuring the Aluminum content and organic acid content of resources with different response to Aluminum toxicity.At the same time,association analysis was used to find the marker sites that were significantly associated with the Aluminum toxicity resistance of pigeonpea.The main research results are as follows:1.A series of experiments under Al³⁺concentration stress showed that the relative root elongation decreased significantly with the increase of Al³⁺concentration.Under 20μmol·L^-1Al Cl₃·6H₂O（p H=4.5）stress for 24 h,the relative root elongation decreased significantly to about 50%,and the relative root elongation was significantly different among different germplasm（P<0.05）,which was an appropriate method for evaluating the resistance of germplasm to Aluminum toxicity at the pigeonpea.The results showed that the relative root elongation of different germplasms was 8.22%～49.89%,and 9 germplasm resources that were resistant to aluminum toxicity and 5 germplasm resources that were sensitive to aluminum toxicity were obtained.2.The results of hematoxylin staining and aluminum content determination showed that the relative root elongation of the seeds was negatively correlated with aluminum content.The organic acids（malic acid,citric acid and succinic acid）secreted from seed roots increased significantly after aluminum toxicity,but the types of organic acids secreted from seed roots of different germplasm resources were different.However,the contents of endogenous organic acids（oxalic acid,tartaric acid,malic acid,citric acid and succinic acid）decreased significantly after aluminum toxicity,and the types of endogenous organic acids decreased in seed roots of different pigeonpea germplasm were different.3.Forty-two polymorphic markers were selected from 96 SSR markers,and the genetic diversity and population structure of 46 samples were analyzed.A total of 118 alleles were detected in 42 SSR markers,with an average of 2.8 alleles per marker.Clustering analysis showed that 46 pigeonpea resources could be divided into 4 groups,but the clustering results were not consistent with geographical sources.The analysis of population structure showed that 67.39%of the germplasm had a single genetic background and 32.61%of the germplasm had a complex genetic background.The MLM model was used to analyze the association between SSR markers and root relative elongation.A total of four related marker sites were found,with interpretation rates ranging from 8.85%to 13.60%.