Studies On Quantitative Characteristics Of AMF In Grazing Grassland Of Seriphidium Desert And Its Growth-promoting Effects On Host Plants

Seriphidium desert plays an important role in Xinjiang's animal husbandry production.In recent years,overgrazing and changes in climatic conditions have led to a significant degradation of desert grasslands.Among them,a large number of arbuscular mycorrhizal fungi(AMF)in the soil can effectively resist the effects of grazing and drought on desert grassland vegetation to a certain extent.Obiective: To clarify the species diversity,spore density,and root infection status of AMF in soil of Seriphidium desert grassland at different grazing intensities,and the selection preference of different AMF to host plants.At the same time,the AMF species or specie combinations with the best growth-promoting effects and drought resistance on Seriphidium transiliense plants were screened.Finally,the role of AMF in stress resistance and its physiological mechanism was explained.Methods: In the Seriphidium desert grassland,GPS was used to set four grazing intensities of mild,moderate,severe,and extreme.From April 2018,soil samples and roots of plants(S.transiliense,S.capillata,F.ovina,C.liparocarpos)were taken monthly.On this basis,using S.transiliense as the research object,inoculating AMF(Fm,Ri,Gv,mixed H),and controlling the relative soil water content by pot weighing,and water stress 2 months after emergence,every 20 days,the leaves of the plant were taken to determine its root activity,water-holding capacities and related drought-resistant physiological indexes.The membership function method was used to comprehensively evaluate and select the AMF species and specie combinations with the best effect on plant growth-promoting and drought resistance.Results:(1)Tthe spore density and species richness and diversity index of AMF and root colonization rate of plants decreased significantly with the increase of grazing pressure(P<0.05).The spore density,species richness and root colonization rate in the 0-10 cm soil layer were significantly higher than those in the10-20 cm and 20-30 cm soil layers(P<0.05)under the same grazing,and the diversity index showed no significant difference with the increase of soil depth(P>0.05).Meanwhile,It was also found that the infection rate of roots of different host plants by AMF was in order: S.transiliense > F.ovina > C.liparocarpos.The AMF spore density,species richness,and plant root infection rate all showed a "double-peak" phenomenon with seasonal changes,reaching the peak in June and September,which were almost synchronized with the growth rhythm of grassland vegetation of Seriphidium desert.(2)Under the same relative soil water content and the same inoculation method,inoculation withAMF significantly(P <0.05)enhanced the plant height,root length,ground diameter,biomass,infection rate,leaf water-holding capacities,root activity.Under water stress,plants have higher dependence onAMF.Different AM species have different growth-promoting effects on plants,and the overall inoculation effect is H> Fm> Ri> Gv> CK from large to small.The demucus treatment of Seriphidium seed inhibited the growth and development of the plant.(3)Under the same relative soil water content and the same inoculation method,inoculation withAMF significantly(P <0.05)enhanced the soluble sugar and soluble protein content,SOD and POD activities,significantly decreased(P <0.05)the content of proline and malondialdehyde.The inoculation of different strains also had different effects on the drought resistance of the plants.The results showed that the effect of the AM species on the drought resistance of the plants was H> Fm> Ri> Gv> CK.At the same time,it was found that in the treatment with the mucus group,except for malondialdehyde,the other indicatorsmentioned above were significantly higher(P <0.05)as a whole than the treatment without the mucus group.Conclusion: The greater grazing pressure inhibited the reproduction and development of AMF spores and host plant root infection,and under the same grazing conditions,as soil depth increased,spore density,species diversity,and root infection rate decreased.Inoculation with AMF can significantly enhance the plant's growth-promoting effect and drought resistance.Among them,it was found that mixed inoculation had significantly better plant growth-and drought-resistance effects than single inoculation.At the same time,the growth-promoting effect and drought resistance of plants with mucilage were higher than those without mucilage.