Mechanism Of AM Fungi Promoting Growth Of Grasses In Saline-alkali Soil

In recent years,due to the dry climate,poor soil drainage,high groundwater level and other factors,the salinization of grass is becoming increasingly serious,resulting in the degradation of grass,lower production capacity.The available grass area is decreasing year by year,seriously affecting the economic development of grass livestock.It is an effective way to restore the economic development of grassland animal husbandry to understand and analyze the causes of grassland salinization and take corresponding control measures.At present,some studies use halophytes to restore grassland salinization,but halophytes grow slowly and have a long repair cycle.Studies have shown that AM fungi can significantly improve the salinity tolerance of plants and have good economic benefits for salinized grassland management,but little research has been reported on the mechanism of their effects on saline stress in pasture milk in salinized grassland.In this study,the effects of inoculation of F.mosseae in salinized soil on the growth,elemental uptake,ion homeostasis and regulation of the transcriptome in the shoots of Astragalus adsurgens were investigated in a greenhouse pot experiment.Meanwhile,the effects of inoculation with F.mosseae,R.intraradices and C.etunicatum on the growth and inter-rhizosphere soil bacterial community composition and diversity of Leymus chinensis were investigated to reveal the mechanism of action of AM fungi to improve the salinity tolerance of forage grass.The results show:(1)F.mosseae established a good symbiosis with both Leymus chinensis,Astragalus adsurgens and Stipagrandis,with mycorrhizal infestation rates ranging from 12.33% to 38.00%.In the soil with different degrees of salinization,inoculation of AM fungus caused a significant increase in the total dry weight of Astragalus adsurgens and Stipagrandis by 36.11%~303.13%,a significant increase in the content of N,P and K by 18.43%~1515.63%,and a significant improvement in K+/Na+,Ca2+/Na+ and P/Na+;inoculation of AM fungus caused a significant increase in the concentration of Na+ in the shoots and roots of Astragalus by significantly increased by 8.49%~248.50%;inoculation of AM fungus did not significantly improve the growth of Leymus chinensis.A total of 2491 differentially expressed genes were screened in the shoots of Astragalus of F.mosseae after inoculation,of which 849 were up-regulated and 1642 were down-regulated.The enrichment analysis showed that the differentially expressed genes were mainly associated with “ion transport”(GO:0006811),“cellular self-regulation”(GO:0019725),“oxidoreductase activity”(GO:0016491)and other GO terms.Meanwhile,differentially expressed genes are mainly enriched in KEGG pathways related to lipid metabolism,carbohydrate metabolism,amino acid metabolism,and biosynthesis of other secondary metabolites.The results show that AM fungi can enhance plant resistance to salinity stress by regulating photosynthesis-related pathways,water channel proteins,growth hormones,antioxidant enzymes and alglucose-related genes.(2)All three AM fungi inoculated with F.mosseae,R.intraradices,and C.etunicatum established a good symbiosis with Leymus chinensis,with mycorrhizal infestation rates ranging from 26.44% to 28.89%.Inoculation of F.mosseae and R.intraradices significantly increased the total dry weight of Leymus chinensis by 97.66% to 125.73% and the P content by 226.32% to 360.00%;inoculation of F.mosseae,R.intraradices and C.etunicatum significantly decreased the Na+ concentration of Leymus chinensis roots by 36.65%,32.42% and 29.12%,respectively,and significantly improved the ionic balance.The inoculation of R.intraradices significantly increased the soluble sugar content of Leymus chinensis leaves.Inoculation of AM fungi altered the abundance and diversity of the soil bacterial community in the inter-rhizosphere of Leymus chinensis,and different species of AM fungi had different effects.Inter-root soil bacterial richness(Sobs index)was significantly reduced after inoculation with R.intraradices.Inoculation with AM fungi resulted in a decrease in the proportion of Firmicutes and Proteobacteria and an increase in the proportion of Bacillus and Nocardioides in the inter-rhizosphere soil bacterial community of Leymus chinensis.Hydrogenophaga and Exiguobacterium dominant colonies were significantly enriched in the inter-rhizosphere soil of Leymus chinensis after inoculation with F.mosseae,and Nocardioides,Lysinibacillus and Ammoniphilus dominant colonies were significantly enriched in the inter-rhizosphere soil of Leymus chinensis after inoculation with R.intraradices.and these salt-tolerant and salt-loving dominant microorganisms could assist the forage to resist salinity stressThe results of the study showed that AM fungi significantly improved the growth of forage grasses and the accumulation of salt salts in salinized soils,and their effects were related to the species of AM fungi.Transcriptomic and inter-rhizosphere bacterial microbial findings suggest that AM fungi can improve salinity tolerance of forage grasses by regulating genes of Astragalus adsurgens and the composition of the inter-rhizosphere soil bacterial community of Leymus chinensis.The results of the study can provide basic data and theoretical basis for the combined plant-microbial remediation of salinized grassland.