Diversity And Potential Functions Of Seed Endophyte Of Grassland Species Growing In The Qinghai Tibet Plateau

The microbiome of seeds contains a variety of bacteria and fungi,which can affect the structure and function of plant microbial communities.Seed endophytes provide beneficial effects to their host plants.The aim of this study was to characterize and investigate the potential functions of the seed microbiome of plants growing on the alpine meadows of the Qinghai-Tibet Plateau(QTP).In September 2017,seeds of eight plant species in Maqu and seeds of Elymus nutans from four different regions of the QTP were collected.And Illumina Miseq DNA sequencing technology was used to characterize the seed endophytic bacterial and fungal community.The results showed that there were significant differences in endophytic bacterial and fungal communities between 8 plant species growing in alpine meadow in the QTP.It is shown that plant identity was an important determinant of seed microbiome.The endophytic bacterial community in Elymus nutans seeds was not affected by plant growth environment,but the fungal composition of Elymus nutans seeds was significantly different in the four plant growth areas,indicating that the environment has a strong effect on selection of seed endophytic fungi.In order to explore the effect of seed endophytes on the host plant,the isolation,purification and identification of endophytic bacteria and fungi from the seeds of 8 plants were carried out.A total of 28 strains of bacteria and 19 strains of fungi were obtained with diverse morphology and growth characteristics.Some endophytic bacteria were repeated in the seeds of eight plants,especially Pseudomonas and Bacillus,the number is 7,with a strong adaptability and a wide range of life.Usally,the isolatable endophytic fungi have strong specificity and the same endophytic fungi species were not repeated in different plant seeds.Among the fungal isolations,the number of Penicillium and Cladosporium is largest,4.The isolation results showed that the seeds of alpine meadow plants in the QTP contained their own unique endophytic bacteria.To study the effect of seeds endophyte on plants,the isolated endophytes were tested for potential functions;nitrogen fixation,ACC deaminase activity,mineral phosphate solubilization,auxin production,siderophores production,pectinase activity and cellulase activity.The results showed that many endophytic bacteria had most functional characteristics.For example,11 bacteria had ACC deaminase activity,13 bacteria could produce siderophores,12 bacteria had pectinase activity and 11 bacteria had cellulase activity.And Bacillus had six functional properties besides dissolving mineral phosphates,Pseudomonas had six functional properties besides potential nitrogen fixation.In addition,endophytic fungi also have rich functional diversity,for example: 12 fungi with auxin production,11 fungi with siderophores production,11 fungi with pectinase activity and cellulase activity.All these in vitro functional properties indicate that these endophytes have the potential to promote the growth of host plants and enhance their stress resistance and disease resistance.In summary,the results of this study provide a rich resource for determining the functional characteristics of endophytic bacteria in seeds.Meanwhile it will be helpful to regulate seed microorganisms,improve grassland productivity and maintain grassland health in the future and provide scientific basis for the research and utilization of microbial resources in alpine meadow.