Effects Of Epichlo(?) Endophyte And Environmental Factors On Root And Rhizosphere Soil Bacteria Of Achnatherum Inebrians

Rhizosphere soil bacterial are commonly distributed in terrestrial ecosystems,and play pivotal roles in sustaining stability of ecosystems,facilitating nutrients uptake and improving fitness of their host plant under stresses.In our present study,the seeds of Achnatherum inebrians were obtained from the plants infected by Epichlo(?) endophyte(endophyte-infected,EI)and not infected by Epichlo(?) endophyte(endophyte-free,EF)in Yuzhong as materials.The effects including the endophyte on the diversity of culturable bacterial in the rhizosphere soil,the endophyte and plant growth promoting rhizobacteria under different salt stress on the germination and other indicators of A.inebrians seeds and the effects of Epichlo(?) gansuensis endophyte on root and rhizosphere soil bacterial of A.inebrians under different soil moistures were studied.The main results were:(1)Set up the wild and artificial cultivation two habitat conditions,isolated the culturable bacteria strains from the rhizosphere soil of A.inebrians.A total of 990 bacterial clones were isolated and assigned to 65 species within 18 genera and 4 phyla.The richness of bacteria species in rhizosphere soil of A.inebrians was significantly(P<0.05)higher in wild than in cultivated condition.Additionally,Principal component analysis(PCA)showed that both foliar E.gansuensis and soil disturbance altered the composition of rhizosphere soil cultured bacterial community.Redundancy analysis(RDA)showed that soil properties mainly affected rhizosphere soil bacterial communities of wild A.inebrians,while,slightly affected rhizosphere soil bacteria communities of cultivated A.inebrians.Our findings suggested that both soil disturbance and foliar endophyte resulted in changes to A.inebrians rhizosphere soil bacterial biodiversity.(2)The present study was conducted to investigate the effects of E.gansuensis endophye and plant growth promoting rhizobacteria on salt resistance of A.inebrians.Plants seed were experimentaly exposed to NaCl concentrations 0?50?100?200 mmol/L.The results showed that E.gansuensis endophye,growth promoting rhizobacteria and salt stress had significant(P<0.05)effects on the germination rate and seedling growth of the seeds of A.inebrians.In addition,E.gansuensis endophye,growth promoting rhizobacteria and salt stress had significant(P<0.05)effects on Superoxide dismutase(SOD),Peroxidase(POD)and Catalase(CAT).Meanwhile,E.gansuensis endophye,growth promoting rhizobacteria and salt stress had significant(P<0.05)effects on the activities of Polyphenol oxidase(PPO)and the contents of Malondialdehyde(MDA)of seedlings of A.inebrians.In addition,with the increase of NaCl concentration,the seedling length gradually decreased,while,the contents of MDA gradually increased.However,with the increase of NaCl concentration,all the remaining indexes showed a trend of increasing first and then decreasing,reaching the highest level at 50 mmol/L.Among them,Arthrobacter sp.had a significant(P<0.05)promoting effect on germination rate and germination index;Bacillus licheniformis had a significant(P<0.05)promoting effect on germination rate,root length,SOD,POD and MDA;Pseudomonas aeruginosa had a significant(P<0.05)promoting effect on germination rate and seedling length and cat and PPO enzyme activity.Meantime,with the increase of NaCl concentration,inoculation of different rhizosphere growth promoting bacteria can significantly increase or maintain seed germination,and Bacillus licheniformis,Pseudomonas aeruginosa and Arthrobacter sp.all or part play a leading role in promoting seed germination.E.gansuensis endophyte significantly(P<0.05)promoted the germination rate,seedling length,SOD,POD,CAT and PPO activities of the seedlings.(3)Through high-throughput(16S)sequencing,the effects of endophytes and soil moisture on the bacterial diversity of A.inebrians root-associated and rhizosphere soil were studied.A total of 4371379 16 S rRNA gene sequences were obtained and assigned to 5025 operational taxonomic units(OTUs).These OUTs in roots and rhizosphere soil were divided into 13 and 17 phyla respectively,and the Actinobacteria and Proteobacteria were the most abundant phyla both in roots and rhizosphere soil.Shannon diversity and Chao1 richness index of bacterial in rhizosphere soil was significantly(P<0.05)higher than in roots.E.gansuensis decreased the Shannon diversity of root-associated bacterial community,increased Shannon diversity and Chao1 richness index of rhizosphere soil bacterial of A.inebrians.Meanwhile,Chao1 richness of the rhizosphere soil bacterial community of A.inebrians increased with the increase the soil moisture level.Structural equation modeling(SEM)also showed that E.gansuensis decreased the diversity of root-associated bacterial community and increased the diversity of rhizosphere soil bacterial community through decreasing soil available N.Additionally,soil moisture increased the diversity of rhizosphere soil bacterial community through increased soil pH,C/N,NN and decreased soil AP.The E.gansuensis endophyte and soil moisture effects on root and rhizosphere soil bacterial diversity were likely to be from responses to modifications of the rhizosphere soil properties.