Isolation And Identification Of Endophytic Bacteria From Sweet Potato

China contributes to more than half of global production of sweet potatoes.In Fujian Province,sweet potato is the second largest crop and it is essential for food security of Fujian.Sweet potato,as we all know,has wider adaptability and higher stress resistance compare with other crop.Those advantages might owe to endophytes,a group of bacteria which benefit plant a lot.Because endophytes can promote plant growth,improve plant stress resistance,fix nitrogen and enhanced plant immunity.However,so far,there is rare report related to separation and function study of endophytic bacteria of sweet potato.In this study,17 endophytic bacteria of sweet potato isolate from sweet potato stems or roots by tissue dicing method.Furthermore,sweet potato endophytic bacteria were classified and functionally identified.By doing those,endophytic bacteria which has antagonistic effect on sweet potato vine disease and has phosphorus-dissolving ability had been identified.After this,biological characteristics of endophytes was carried out.The detail results are as follows:(1)Totally,17 strains(SP-01 to SP-17)of endophytic bacteria of sweet potato were isolated: 12 strains from stem and 5 strains from roots.Among those strains,12 are Gram-positive and 5 strains are Gram-negative.(2)16S rDNA Sequencing and alignment analysis prove that isolated endophytes belong to 10 genus: Lelliottia nimipressuralis,Enterobacter tabaci,Pseudomonas oryzihabitans,Lelliottia amnigena,Bacillus aryabhattai,Bacillus megaterium,Curtobacterium herbarum,Serratia rubidaea,Pantoea dispersa and Atlantibacter hermannii.(3)The time period of 17 isolated strains to reach stable growth phase are different: SP-01 needs 12 h,SP-09 needs 16 h,SP-13 needs 24 h,SP-07 needs 32 h,three strains(SP-03,SP-08,SP-10)need 36 h,SP-11 needs 48 h,three strains(SP-04,SP-05,SP-12)need 60 h and six strains(SP-02,SP-06,SP-14,SP-15,SP-16,SP-17)need 84 h.(4)By measuring the phosphorus-dissolving circle,three strains(SP-14,SP-15,SP-16)with strong phosphorus solubilization were identified.(5)By performing endophytic plate sputum test,SP-13 regards as the strain which has strongest antibacterial activity with 47.62% of bacteriostatic rate to Fusarium wilt of sweet potato.In detail,SP-13 molecularly identifies as Serratia marcescens.(Serratia rubidaea),which play a role in mycelium autolysis promoting.Disease resistance test shows that the inoculation of endophytic SP-13 to sweet potato enhanced the plant resistance to sweet potato vine disease,the rate of inhibitory effect is 65.18%.Through growth characteristics test,the optimum culture pH range of SP-13 from 7.5 to 9,the optimal temperature ranged from 28 °C to 30 °C and the shortest time to reach stable growth phase is 24 h.