Species Diversity And Ecological Response Of Dark Septate Endophytes In The Roots Of Haloxylon Ammodendron In Desert

Haloxylon ammodendron is a pioneer plant for vegetation restoration in desert areas of Northwest China.The morphological and physiological characteristics adapted to arid habitat have been formed in the long-term evolutionary process.In addition,the symbiotic relationship between H.ammodendron and endophytic fungi is important for its adaptation to extreme environments.Dark septate endophytes(DSE)are a kind of small endophytic fungi colonizing plant roots,which can improve the tolerance of plants to stresses and enhance the ecological adaptability.In this study,H.ammodendron was used as the target plant,and soil and root samples from 0-30 cm depth of H.amendamentum roots were collected from Wuhai and Dengkou of Inner Mongolia,and Anxi and Minqin of Gansu Province in different years and seasons.Based on the analysis of colonization characteristic,community structure,species diversity of DSE,as well as the soil factor,the spatial and temporal distribution of DSE fungi of H.ammodendron roots and soil habitat response characteristics were explored.The purpose of this study was to explore the strategy of plant-DSE symbiosis to adapt to desert environment and explore beneficial DSE fungi resources,and to provide a basis for DSE fungi to promote the growth and ecological restoration of desert plants.The main results showed as follows:1.The healthy roots of H.ammodendron all could be highly infected by DSE fungi,forming typical dark septic hyphae and microsclerotia structures.The predominant colonization structure was hyphae in Inner Mongolia and microsclerotia in Gansu.The average DSE colonization rate of Anxi was the highest among years(hyphae colonization rate: 90.0 %,microsclerotia colonization rate: 78.9 %,the total colonization rate: 93.3 %),and the average total DSE colonization rate among seasons was the highest in July(85.56%),and significantly higher than that in December(66.67%)and September.2.Different colonization structures of H.ammodendron showed obvious spatial and temporal heterogeneity.The average hyphae septum interval(34.29 ?m)and diameter(4.67 ?m)in Anxi were significantly higher than in other sampling sites.The average microsclera diameter in Minqin was the largest(7.71 ?m),which was significantly higher than in Dengkou(5.75 ?m),Wuhai(5.67 ?m)and Anxi(5.54 ?m).The average hyphae septum interval was July(34.52?m)> December(20.65 ?m)> September(20.32 ?m),and the microsclerotia diameter was the largest(9.25 ? m)in December.3.The spatial and temporal distribution of DSE colonization is closely related to soil factors.Soil p H and AP were negatively correlated with DSE colonization.Microsclerotium colonization was positively correlated with SOC and U,and significantly positively correlated with microbial community composition.Among them,p H and AP were the main soil factors affecting DSE colonization rate.The hyphae septum interval was significantly positively correlated with Hum and U,and negatively correlated with AP.The hyphae diameter was significantly positively correlated with AN,while the microsclera diameter was significantly negatively correlated with AN and soil microbial metabolic function.Among them,Hum,AP and AN were the main soil factors affecting the DSE colonization characteristic.4.There are abundant germplasm resources of DSE fungi in the roots of H.ammodendron.DSE isolates from the roots of H.ammodendron were identified to 14 genera and 24 species,among which 10 species of DSE fungi produced sporulation.Herpotrichia striatispora and Alternaria tellustris were the common species in the sampling sites.Canariomyces microsporus,Alternaria alstroemeriae,Botryotrichum murorum,Alternaria sorghi and Lophotrichus fimeti were reported as DSE for the first time in a desert environment.5.The dominant species of DSE in H.ammodendron roots were Alternaria tellustris and Neocamarosporium chichastianum,with separation frequencies of 27.76 % and 19.57 %respectively.The separation rate of DSE strains was higher in 2018(53.88 %)than in 2019(23.34 %)in different years,and that was higher in December(46.12 %)than in September(32.78 %)in different seasons.6.Shannon Wiener index and evenness index were the highest in Wuhai.The results of variance partitioning showed that time scale,spatial scale and soil factors all affected the diversity of DSE fungi,and soil factors accounted for 61.4%(different years)and 90.6%(different seasons)of DSE diversity,which were the main influencing factors.