The Spatiotemporal Distribution And Inoculation Effect Of Dark Septate Endophytes Of Hedysarum Scoparium

Hedysarum scoparium Fisch.et Mey.belongs to the semi-shrub of the genus Astragalus.It has developed roots and strong resistance to stress.It is naturally distributed in the desert areas of northwest China and is the dominant plant for wind and sand fixation.Dark septate endophytes(DSE)are widely colonized in plant roots and are not pathogenic and have potential ecological functions.We selected seven typical plots of Erdos,Dengkou,Wuhai and Alxa in Inner Mongolia,Shapotou in Ningxia,Minqin and Anxi in Gansu,and collected the soil and root samples in rhizosphere of H.scoparium.This study included DSE colonization and species diversity in different plots,and the effects of precipitation,spatial variables and soil factors on DSE distribution and activity.Twe strains of DSE were screened and inoculated onto the roots of H.scoparium to study the effect of DSE on plant growth,and provideed a basis for rational utilization of DSE strain resources and promotion of desert plant growth and vegetation restoration.The main test results are as follows:1.DSE formed typical septate hyphae and microsclerotia structure in the roots of H.scoparium.The hyphae in Wuhai,Minqin and Anxi plots were thicker,and hyphae circles were occasionally found in Ordos and Alxa plots.The morphology of microsclerotia varied significantly in different plots,most of which were discrete in Anxi,Beaded in Shapotou and clustered in other plots.2.The colonization rate of DSE and soil factors have obvious temporal and spatial heterogeneity.There were significant differences in DSE colonization rates among the seven plots.Ordos was significantly higher than other plots,but the lowest in Dengkou.During the interannual period,the maximum colonization rate of DSE in Ordos,Alxa and Minqin plots was in 2017,and the minimum was in 2015.The maximum colonization rate of DSE in Dengkou,Wuhai and Anxi plots was in 2016.Except for soil pH,the contents of other soil factors in all plots decreased in four years.3.The correlation analysis showed that pH was negatively correlated with DSE mycelial colonization rate and total colonization rate,while urease was positively correlated with mycelial colonization rate.4.The results of variance decomposition show that: Soil factors,spatial variables and precipitation account for 44.7% of the variation of DSE colonization rate.Among them,spatial variables account for the most,accounting for 28.0%,which is the main factor affecting the ecological distribution of DSE.5.In this study,a total of 11 genera and 15 species of DSEs were isolated and identified,among which Alternaria tennuissima,Alternaria longissima,Alternaria gansuensis,Paraphoma pye,Subramaniula flavipila,Fusarium acuminatum,Thielaviopsis basicola,Herpotrichia striatispora,Acrocalymma vagum,Darksidea alpha and Paeosphaeria sp.were first reported in H.scoparium of desert plants.Paraphoma sp.,Alternaria sp.and Peosporales sp.are the dominant species of H.scoparium.6.The growth-promoting effect of DSE on plants is closely related to the inoculation amount.The 20 mL inoculation of DSE has the best effect on plants.When the inoculation amount of DSE is 20 mL,the number of leaves,branches,plant height and root growth of underground parts of plants can be increased.