Screening Of Functional Endophytic Bacteria And Effects On The Growth Of Rice Seedlings

In southern China,rice has always been an important food crop for people’s livelihood.In order to solve the problems of people’s food and clothing,it is necessary to increase the yield of rice as much as possible and achieve a bumper harvest.It is often blind that simply relying on the excessive use of chemical fertilizers and pesticides to increase the unit yield blindly and may not cause all kinds of damages in the short term.But with the passage of time,the malpractices caused by chemical fertilizers will become more and more prominent.Soil structure is destroyed and the quality of agricultural products and seed setting rate decrease.At the same time,rice would breed various diseases in the process of planting,which seriously affected the yield of rice.Microbial fertilizers can reduce the risk of chemical fertilizer and pesticide to a certain extent.In addition,it promote the growth of rice and improve the quality of rice.In this study,the culture medium TSA,YMA and R₂A were used to activate 46reservoir bacteria by inclined plane and plate streak method.The 16S rRNA gene sequence analysis were used to identify the activated bacterias.Some strains of growth promotion and disease-resistance and safety were screened by a series of functional experiments and hemolysis experiments.Finally,the fermentation experiment was carried out and the fermentation conditions were optimized.The conclusions of the study are as follows:（1）The strains for rice growth were screened out by functional test.There were 21strains with the function of iron production vector,2 strains with pHospHorus dissolving function,12 strains with antagonistic function against tomato wilt,4 strains with antagonistic effect on Pseudomonas clove,18 strains had antagonistic effect on rice blast pathogen,2 strains had antagonistic effect against phytophthora tabacum,24 strains with the ability to secrete IAA and 7 strains with ACC deaminase activity.（2）The safety evaluation test of the selected rice-promoting functional strains was carried out by blood plate test.Among them,15 strains had hemolysis,which would affect the safety of animals.The 32 strains were free of hemolysis and safe during rice production.（3）10 strains with better comprehensive functions were tested in pot experiments.The four strains numbered ACCC11025,HMC50,YC37 and YC41 were superior to the blank control in root length,stem length,root weight and total fresh weight of rice seedlings.The indexes had significant differences between the inoculated rice and the blank.（4）The fermentation conditions of the selected 4 strains were carried out,and the optimal conditions for the fermentation were determined.The optimum salt concentration of YC41 was 1.0%,the optimum pH was 6,and the optimum growth temperature was30℃.The optimum salt concentration of ACCC11025 was 0.5%,the optimum pH is 8,the optimum growth temperature is 25℃.The optimum salt concentration of HMC50 is 0.2%,the optimum pH is 8 and the optimum growth temperature is 35℃.The optimum salt concentration of YC37 is 0%,the optimum pH is 9 and the optimum growth temperature is 30℃.（5）The prepared microbial inoculum were applied to the field breeding experiments.The measurement of root length,stem length,root weight and individual plant weight showed that the microbial inoculum promoted the growth of rice seedlings.Especially the root weights of rice seedlings had a significant differences between treatments with microbial inoculum and treatments without application of microbial inoculum.Additionally,there were more fibrous roots in treatments with application of microbial inoculum.In this paper,after functional evaluation and safety evaluation of 46 strains in the seed preservation center,a total of 10 strains were selected for pot test.The final results showed that ACCC11025、YC37、YC41 and HMC50 had better growth promotion effect.The fermentation conditions of the four strains were optimized,including temperature,pH value and salt concentration.After these four strains were made into fungicides and applied to the experimental base of Harbin academy of agricultural sciences,heilongjiang province,it was found that the growth condition of rice seedlings in terms of root weight and fibrous roots was significantly better than that of rice seedlings only using the fungicides.