Diversity Of Mycorrhizal And Symbiotic Microoganisms Of Six Rare Plants In Western Ordos Desert

West Ordos Desert is known as the distribution center of endemic genera of plants in Inner Mongolia Plateau and Central Asia.Rare plants such as Tetraena mongolica have adapted to the arid and barren habitat with different survival strategies.Exploring these plants' biological symbiosis characteristics of arbuscular mycorrhizal,mycorrhizal structure,diversity of arbuscular mycorrhizal fungi(AMF)in plant root and rhizosphere soils,and other microbial diversity of these plants,which is biologically important to reveal the plants biogeographic distribution and adaptationmechanisms of these plants to harsh environment.This thesis regards the rare and endemic shrub species,Tetraena mongolica,Sarcozygium xanthoxylon,Nitraria tangutorum,Ammopiptanthus mongolicus,Potaninia mongolica and Helianthemum songaricum and their communities,plant root and rhizosphere soils as the research objects.We assessed the community composition and mycorrhizal characteristics by collecting data of plant communities and soil physicochemical properties extensively in the study area.Based on this,we explored the AM mycorrhizal symbiotic biology of plant roots and the diversity of AM fungi and microorganisms with the help of multiple analytical methods such as morphological taxonomy and high-throughput sequencing technology.The effects of soil factors on AM fungal and microbial communities were analyzed with structural equation models.The main results include:1)The plant community investigated in the study area,which revealed that there were 27 species in 11 families and 22 genera in the community,of which 22.22%were Asteraceae,14.81% were Gramineae,and 11.11% were tribulaceae.According to the analysis of diversity indicators,the order of community diversity of the sample sites were as follows: Sihemu core plot(SA)>Hangjin Banner Baragon plot(HA)>Qipanjing plot(BA)>Qianlishan plot(QA).2)No arbuscular structure was found in the roots of three plants in the Tribulus family,Tetraena mongolica,Sarcozygium xanthoxylon,and Nitraria tangutorum,but vesicular and mycelial structures were identified,and microclerotia specialized structures were found in the root segments of Tetraena mongolica and Sarcozygium xanthoxylon.The AM mycorrhizal structure of Potaninia mongolica was very typical,with vesicles and arbuscular structures.In addition to vesicles,intercellular hyphae,and microsclerotia,some special hyphae structures of dark septate endophytic fungi were also found in the root segments of Helianthemum songaricum plants.Besides,through testing the mycorrhizal infection rate of dominant and common plants,AM fungi prefer to co-exist with plants such as Artemisia eriopoda,Stipa glareosa,Allium mongolicum,Cleistogenes squarrosa,and Potaninia mongolica.3)Based on the morphological characteristics of soil asexual spores of AM fungi,8 genera and 25 species with AMF spore morphological were identified from the rhizosphere soil of six plant species,including Acaulospora,Claroideoglomus,Diversispora,Funeliformis,Glomus,Rhizophagus,Septoglomus,and Scutellospora genera;G.hyderolabadensis,Sep.constrium,Sep.deserticola,A.spinosa,and R.intraradices were the dominant communities.Through statistics of the spore density,species richness and diversity index of the inter-rhizosphere soil of these plants,the results showed that the composition of AMF community in rhizosphere was varied from these plants,and the order of diversities from high to low was Helianthemum songaricum(BRHS)>Nitraria tangutorum(Nts)>Ammopiptanthus mongolicus(SDQS)>Potaninia mongolica(MCS)>Sarcozygium xanthoxylon(Sxs)>Tetraena mongolica(Tms).4)Genetic diversity of AMF,bacteria,and fungi in roots of six plants were measured by high-throughput sequencing,results were as follows:(1)There were 29 species of AMF in the six plant species root system,belonging to 6 families,9 genera,including Glomus,Rhizophagus,Septoglomus,Claroideoglomus and some unidentified species.Among theses,G.aggregatum,R.intraradices,and Sep.deserticola were dominant species.The findings revealed that their relative abundance were different.From high to low was Potaninia mongolica(MCR)>Helianthemum songaricum(BRHR)>Tetraena mongolica(Tmr)>Ammopiptanthus mongolicus(SDQR)>Nitraria tangutorum(Ntr)>Sarcozygium xanthoxylon(Sxr).(2)Based on the fungi of six plants' root,fungi community including Agaricomycetes,Dothideomycetes,Sordariomycetes,Eurotiomycetes and others.Sordariomyceteswas the most abundant in the roots of Tmr,Sxr,Ntr,and BRHR belonged,and their relative abundances were 52.07%,1.68%,29.07% and 22.91%,respectively.Shannon-Wiener index of fungal community ranged from 0.791 to 3.153,Simpson index ranged from 0.081 to 0.674.From high to low was BRHR >Ntr >SDQR >MCR >Sxr >Tmr.(3)The bacteria genetic diversity of six plants root included Cyanobacteria,Actinobacteria,Gammaproteobacteria,Alphaproteobacteria,Acidobacteria.Actinobacteria has the highest abundance in the root of BRHR,SDQR and MCR,accounting for 29.94%,47.27% and 36.59%,respectively.The Shannon-Wiener index of root bacterial community in the rare plant ranged from 2.053 to 5.864,Simpson index ranged from 0.007 to 0.446.The order of these indexes were as follows: BRHR >SDQR >MCR >Tmr >Ntr >Sxr.5)Genetic diversity of AMF,bacteria,and fungi in the rhizosphere of six species was determined by high-throughput sequencing.(1)A total of 164 OTU and 32 AMF belonging to 10 genera and 6 families were detected in the rhizosphere soils of six species,Glomus,Rhizophagus,Septoglomus,Claroideoglomus,and some species were not identified.G.aggregatum,R.intraradices,Sep.deserticola,and C.claroideum were the dominant species.The relative abundances of AMF in different plants rhizosphere soil were different.The AMF community Shannon-Wiener index ranged from 1.560 to 2.670,and the Simpson index ranged from 0.664 to 1.234.The order of these indexes were as follows: Sxs > BRHS > MCS > Nts > SDQS > Tms.(2)The soil fungi in the 6 plants' rhizosphere mainly included Dothideomycetes,Sordariomycetes,Saccharomycetes,Eurotiomycetes,Tremellomycetes,and Pezizomycetes.The fungal abundance in rhizosphere soils of different plants were varied.Dothideomycetes was the most abundant in Tms,Sxs,SDQS,and MCS,the Shannon-Wiener index of fungal community ranged from 3.186 to 4.115,and the Simpson index ranged from 0.036 to 0.117.The order of these indexes were as follows: BRHS >Sxs >MCS >Nts> SDQS >Tms.(3)At the class level,the soil bacterial species in 6 plants' rhizosphere mainly included Cyanobacteria,Actinobacteria,Gammaproteobacteria,Alphaproteobacteria,and Acidobacteria.Alphaproteobacteria was the most abundant in the rhizosphere soils of Tms,Sxs,and BRHS.The Shannon-Wiener index of bacterial community ranged from 1.928 to 5.632,and Simpson index ranged from 0.038 to 0.335.The order of these indexes were as follows: BRHS > MCS >Sxs>Tms>Nts> SDQS.6)The p H value of the rhizosphere soil of the six plants were between 8.01 and9.06,and there were no significant difference(P>0.05).Total nitrogen were0.174-0.273 mg/g,total phosphorus were 0.170-0.233 mg/g,organic matter were3.342-7.212 mg/g.The content of organic matter in rhizosphere soil of Helianthemum songaricum was higher than that of Potaninia mongolica and there was significant difference between them(P<0.05).The content of EGG and T-GRSP were0.319-0.389 mg/g and 0.323-0.347 mg/g in rhizosphere soil,and there was no significant difference among plant species(P>0.05).7)Microbial diversity and soil factor correlation analysis showed that total soil nitrogen and organic matter directly and positively influenced bacterial and fungal diversity.The relationship between AMF diversity and different soil factors varied.Available phosphorus(AP),available potassium(TK),organic matter(OM)and p H were the main factors affecting the community structure of AMF.AMF species richness was significantly positively correlated with soil moisture content and soil enzyme activity(P<0.01).The fungal community was positively correlated with alkaline phosphatase,organic matter,total nitrogen,and total phosphorus contents(P<0.01),and the bacterial community was positively correlated with p H value,ammonium nitrogen content,total phosphorus,and acid phosphatase content(P<0.01).Combining the results obtained by both morphological taxonomy and molecular biology methods of identification,it is clear that AMF is commonly associated with desert plants in western Ordos Desert.The roots and rhizosphere soil of six major rare plants are rich in AMF diversity,and microbial abundance varied from different plant species.In addition,the symbiosis of soil microorganisms(AMF,bacteria,and fungi)with these plants and their interaction with soil factors are important characteristics of desert for plants adapting to the arid and infertile environments.Therefore,further study on the diversity of microbial of rare desert plants can provide an important theoretical basis for the protection and utilization of rare desert plants.