Research On The Relationship Between Physical And Chemical Properties Of Rhizosphere Soil And Accumulation Of Endophytic Fungi And Aconite Alkaloids

Endophytic fungi can not only improve the environmental adaptability of host plants but also produce some secondary metabolites similar to or the same as host plants,which is an important part of the plant micro-ecosystem.Besides,soil's physical and chemical properties can also affect the community structure of plant endophytic fungi and the accumulation of plant secondary metabolites.Aconite is Aconitum carmichaeli Debx.of the genus Aconitum of Ranunculaceae.The seed root is a traditional bulk medicinal material in China,and it is customary to call the medicinal plant "aconite" in production.The main active components of aconite are alkaloids,but it is not clear which environment affects alkaloids' accumulation.At present,aconite is widely planted in Sichuan Jiangyou,Shaanxi Hanzhong,and Yunnan Dali.Still,the field management methods vary greatly,and the alkaloid content of aconite is also very different.Revealing the influence mechanism of the physical and chemical properties of rhizosphere soil and endophyte community structure on aconite alkaloids has important guiding significance for the elucidation of the mechanism of alkaloid synthesis and the research and development of scientific fertilization scheme.Based on this,in this study,the contents of many kinds of alkaloids in aconite were analyzed by UPLC-Q-TOF/MS,the community structure of endophytic fungi was determined by Miseq high-throughput sequencing,and the soil physical and chemical properties and the relationship between endophytic fungi and alkaloid content were analyzed,to provide support for revealing the mechanism of alkaloid accumulation and scientific planting plan.The main results are as follows:(1)Determination of alkaloid content of aconite root.By usingUPLC-Q-TOF/MStechnique and aconite database,38 alkaloids with high content were identified from 26 producing areas.The relative quantitative analysis of 38 alkaloids from 26 producing areas was carried out by TOF-MS,combined with heat map.The results showed that the contents of three alkaloids(benzoylhypacoitine,benzoylmesaconine,benzoylaconine)stipulated in Chinese Pharmacopoeia 2020 were in the middle of Fuzi in Sichuan Mianyang and Shaanxi Hanzhong.The alkaloid content in Yunnan Jiuhe,Shanxi Xiaxian,Yunnan Xiangyun,and Shaanxi Lantian was higher than that in other producing areas.In comparison,the alkaloid content in Sichuan Qingchuan,Yunnan Yunlong,Yunnan Ludian,and Guizhou Bijie was lower than that in other growing areas.(2)Study on the community structure of endophytic fungi in aconite.The species composition of endophytic fungi from aconite from different producing areas showed that 12 phyla,57 classes,149orders,363families,904 genera,and 1674 species were identified in 26 producing regions.The diversity and community structure of aconite endophytic fungi from different habitats were different.Alternaria,Phoma,Acremonium,Cladosporium,Boeremia,Fusarium,Lectera,Thelonectria,Olpidium,Titaea,Efibulobasidium,Ilyonectria,Cadophora,Gibberella,Mortierella,Plectosphaerella,Tetracladium,Didymella,Aspergillus,Oliveonia,and Neocosmospora were the dominant flora.Based on the cluster analysis of aconite endophytic fungi from different producing areas,the endophytic fungi were divided into three categories:Yunnan Zhanyi;Guizhou Shibing,Shaanxi Liuba,Guizhou Bijie,and Yunnan Kunming.The endophytic fungi are grouped into one group.Shaanxi Lantian,Hebei Anguo,Shaanxi Chenggu,Gansu Dingxi,Henan Nanyang,Yunnan Jiuhe,Yunnan Daxing Guizhou Xingfuli,Sichuan Qingchuan,Shaanxi Huxian,Hubei Enshi,Yunnan Longyang,Shanxi Xiaxian,Sichuan Mianyang,Yunnan Zhanyi,Yunnan Weixi,Yunnan Yongning,Guizhou Shibing,Shaanxi Liuba,Guizhou Bijie and aconite in Yunnan Kunming had the highest similarity in endophytic fungi.(3)Study on physical and chemical properties of rhizosphere soil of aconite.The physical and chemical properties of aconite soil samples from different areas were determined and analyzed by PB-10pH meter,SmartChem300 automatic discontinuous chemical analyzer,PW2403 X-Ray fluorescence spectrometer,and potassium dichromate volumetric method,which scientifically reflected the differences of pH value,ammonium nitrogen,nitrate nitrogen,phosphate,a large amount of elements and trace elements and organic matter in aconite soil from different areas.The results showed that there were differences in soil pH,organic matter content,a large number of elements,and trace elements in different producing regions.(4)Correlation between endophytic fungi,soil physical and chemical properties and alkaloids of aconite.The contents of Mn2+and Zn2+in rhizosphere soil were positively correlated with the abundance of endophytic fungi Cladosporium,Didymella,and Verticillium(p<0.001).The content of Mg2+ was positively correlated with the contents of songorine,mesaconitine,aconitine and beiwutine,but had no significant correlation with other alkaloids.The contents of pH in rhizosphere soil were positively correlated with salsolinol,lepenine,8-O-Cinnamoylneoline,karakoline,senbusine A and monoacetyltalatizamine,but not with other alkaloids.Olpidium,Cladosporium,Cadophora,Alternaria,Plectosphaerella,Efibulobasidium,Tricharina,Didymella,Oliveonia,Rhizoctonia,Vishniacozyma were positively correlated with other alkaloids.