Research On The Diversity And Function Of AM Fungi In The Rhizosphere Of Syneilesis Aconitifolia Of Songnen Saline-alkali Grassland

Arbuscular mycorrhizal（AM）fungi is one of the most important soil microbial groups distributed in various ecosystems.AM fungi can form a mutually beneficial symbiotic relationship with about 90%of plant species.Plants transport carbohydrates necessary for growth to AM fungi,and at the same time,AM fungi use their huge mycelia network to help host plants absorb various mineral nutrients and water in the soil,which has a positive impact on promoting plant growth and development and improving plant resistance.The community composition of AM fungi is often different in different ecological types,and the special habitats including saline-alkaline soil may contain AM fungi with special functions.Syneilesis aconitifolia is a kind of wild flower with peculiar leaf shape and long flowering period,which can be used as ground cover or floral arrangement.According to the investigation,S.aconitifolia can naturally grow in saline-alkali grassland of Songnen,and has a certain saline-alkali tolerance.However,no research has been found on the diversity of AM fungi around the root of S.aconitifolia and their impact on the saline-alkali tolerance of S.aconitifolia.This study investigated the diversity of AM fungi around the root of S.aconitifolia in Songnen saline-alkali grassland,and inoculated the AM fungi community as a microbial inoculum into S.aconitifolia plants,measured the changes of growth and physiological indicators of S.aconitifolia under NaCl and NaHCO₃stress,explored the role of AM fungi in improving the growth of plants under saline alkali stress in saline alkali land.This study aims to further understand the species of AM fungi in saline-alkali land,and also provides a reference for the application of the symbiont of S.aconitifolia and AM fungi in saline-alkali land greening.The main results of this study are as follows:（1）The results of symbiosis between S.aconitifolia and AM fungi in Songnen saline-alkali grassland showed that the roots of S.aconitifolia in 9 sample plots were colonized by AM fungi,and all of them formed Paris-type mycorrhizal structure.The colonization rate of S.aconitifolia roots in different plots reached 100%,and the colonization intensity was also high（40.57%-79.05%）.（2）The correlations between soil chemical properties around the roots of S.aconitifolia and AM fungi colonization index and diversity index were analyzed.The results showed that soil p H was significantly positively correlated with colonization intensity and vesicle abundance,soil organic matter content was significantly positively correlated with arbuscule abundance,and colonization intensity was significantly positively correlated with arbuscule abundance and vesicle abundance.Species abundance was positively correlated with Shannon index,and Shannon index was positively correlated with Simpson index.（3）By morphological method,13 genera and 34 species of AM fungi were isolated from the rhizosphere of S.aconitifolia,including 9 species of Glomus,8 species of Acaulospora,4species of Funneliformis,2 species of Ambispora,Rhizophagus,Septoglomus respectively,1specie of Claroideoglomus,Diversispora,Dominikia,Entrophospora,Gigaspora,Pacispora and Sclerocystis respectively.After species annotation of the effective sequence obtained by high-throughput sequencing,103 species of AM fungi belonging to 7 genera were identified from the rhizosphere of S.aconitifolia,among which Glomus has the most species,71 virtual species,which is consistent with the morphological results.（4）The important value of different AM fungi was evaluated,and it was found that the most dominant AM fungi genus in the rhizosphere of S.aconitifolia was Acaulospora,and the most dominant AM fungi specie was Septoglomus deserticola.At the same time,the results of high-throughput sequencing showed that the average relative abundance of Glomus was the highest in all fields,and it was the dominant AM fungi genus in the rhizosphere of S.aconitifolia,and Paraglomus Alguacil12a Para 1 VTX00348 was the dominant virtual specie of AM fungi community in the rhizosphere of S.aconitifolia.（5）The AM fungi community surrounding the roots of S.aconitifolia as a microbial inoculum was inoculated on S.aconitifolia plants and applied NaCl and NaHCO₃stress on it to observe the colonization results.It was found that although the saline-alkali stress had a negative impact on various colonization indicators of AM fungi,the overall colonization level was high,and the colonization rate reached more than 75%under different stress treatment conditions.（6）Under NaCl and NaHCO₃ stress conditions,AM fungi improved the growth and development of S.aconitifolia by increasing the fresh weight and dry weight.The stability of osmotic regulation system was maintained by increasing water absorption,photosynthetic pigment synthesis,soluble sugar,soluble protein and proline contents.At the same time,the activity of SOD,POD,CAT and the content of GSH in plants were increased and the content of malondialdehyde was decreased,so as to enhance the antioxidant capacity of S.aconitifolia,and finally improved the resistance of S.aconitifolia to saline-alkali stress.