Research On The Effects Of Streptomyces JD211on Rice Growth Promotion And Disease Prevention Mechanism

Streptomyces JD211is separated and screened from Davidia involucrata plants bodyat the Bioengineering Training Base Laboratory in Jiangxi Agricultural University. Itsactive ingredient components have a strong inhibitory effect on a variety of plantpathogenic fungi. Through the optimization of fermentation conditions of JD211Streptomyces solid bacterium, research on drug resistance marker and colonization rule,By observing the effect of Streptomyces JD211on rice seedling quality and soil microbialcommunities, its physiological and biochemical mechanisms of crop growth promotionand disease resistance are explored in this paper. Results in this thesis are drawn asfollows.(1) Single factor and orthogonal experiments are employed to determine the optimalsolid-state fermentation conditions of Streptomyces JD211. The results were as follows:the optimum fermentation substrate was rice; inoculum was8%; solid-liquid ratio of1:0.6;fermentation temperature28℃; bottling capacity50g (triangular flask volume250ml).(2) By employing investigation on seedling quality, disease control efficiency andmeasuring chlorophyll, root activity and soluble sugar content in different growth stages,to study the effect of Streptomyces JD211on the rice seedlings. the results are shown asfollows: JD211solid agents with a suitable concentration (10g Kg-1) have played asignificant role in promoting the growth of rice seedlings. They help accelerate the growthrate of rice seedlings, while improve their various physiological qualities. Compared withthe Control Group, the seedling height, leaf age, pseudo-stem width, leaf width, the totalnumber of roots, white roots, root length, main root length, fresh weight, dry weight, haverespectively improved25.71%,32.42%,54.95%,49.53%,49.28%,50.84%,14.84%,28.42%,157.06%,145.54%, obviously the difference was significant. Compared with CK,when Streptomyces JD211was added a dosage of10g Kg-1, chlorophyll, root activity andsoluble sugar content of rice seedling were increased respectively by50.00%,19.07%,29.75%. Both the10g Kg-1JD211solid fertilizer and the50%JD211broth had significantinhibitory effect on rice blast, and their control efficiency reached respectively61.27%and91.47%.(3) Determine the quantity of Streptomyces JD211in the soil and plants with the useof antibiotic marker experiment, and make clear that the optimal antibiotic marker ofStreptomyces JD211is cephalosporin500μg·mL-1and chloramphenicol50μg·mL-1.Streptomyces JD211is able to colonize in the rice rhizosphere soil, but not in the riceplants. Streptomyces JD211has a significant impact on plant endophyte content of riceseedlings, and with the increase of the concentration of agents, endophyte content ofseedlings shows a decreasing trend.(4) Through plant, soil and mineral nutrients change measuring experiment and enzyme activity assay in rhizosphere soil, it is found that, compared with CK, the totalnitrogen, total phosphorus, dry soil available nitrogen and phosphorus of StreptomycesJD211with a dosage of10g Kg-1were significantly increased. Plant total nitrogen, totalphosphorus were increased by90.10%and58.51%respectively, and soil availablenitrogen and phosphorus were increased by37.49%,40.62%. JD211solid Streptomycesbacterium can significantly improve the rice rhizosphere soil enzyme activities, amongwhich the urease, dehydrogenase and invertase activity were respectively0.95±0.02mg/(g·24h),1.98±0.12μg/(g·24h), and8.7±0.26mg/(g·24h). Compared with the control,they have increased by28.38%,108.42%, and56.76%respectively. With the increasingconcentration of JD211agents, the organic matter content in the soil increased to someextent. The available N, P and K also increased significantly. Urease is involved inNitrogen cycle, and alkaline phosphatase is involved in phosphorus cycle; Dehydrogenaseactivity represents the overall activity characterization of the soil microbial, and invertaseactivity is sensitive to changes in organic matter. Increase of soil mineral nutrients andenzyme activity to some extent improved the rhizosphere soil environment, enhancingfertilizing and supplying capacities of the soil. Therefore, they have provided rich nutritionfor the rhizosphere microbial activity, and promoted growth of the plants.(5) Through MPN determination of microbial function and T-RFLP analysis, a clearchange is shown in the composition of rhizosphere microbial community structure. Theresults were as follows: Through inhibition of the number of pathogenic microorganismsin soil, Streptomyces JD211prompts the growth of the bacteria with weak ecologicalpotential, for example, the beneficial fungi, actinomycetes, primitive animals, Bacillus andStreptomyces bacteria and other functions, so that some can be involved in soil nutrientcycling, degrading soil allelochemicals and improving soil texture. Probiotics andfunctional bacteria with the control of plant diseases can multiply rapidly and continue toaccumulate, becoming the dominant flora. Mutually beneficial collaboration betweenvarious microorganisms helps improve the resistance level of roots, and the soil fertilityand supply capacity. Soil microbial community tends to be a dynamic equilibrium inconstant competition. It regulates the soil micro environment and promotes thetransformation and dissemination of soil nutrients. Its functions promote the growth of rice,thus increasing its yield and quality.In summary, Streptomyces JD211has a significant growth-promoting anddisease-resisting effect on rice, which displays itself as a biocontrol actinomycete of greatprospects for further development.