核桃根际耐旱促生菌的分离筛选及其促生作用研究OA北大核心CSTPCD

In order to solve the problem of soil quality degradation caused by blind application of chemical fertilizer in walnut production,high-efficient and growth-promoting strains of walnut rhizosphere were screened out for the development of biofertilizer to improve soil fertility,to promote plant growth and de-velopment,and to lay theoretical foundation for improving walnut quality.By using the rhizosphere soils from walnut plantations as the materials,plant growth promoting rhizobacteria(PGPR)with the abilities to fix nitrogen,dissolve phosphorus,secrete growth hormone(IAA)and produce exopolysaccharides(EPS)were isolated and screened out.The strains were identified by 16S rDNA sequences analysis.Ac-cording to the principle of functional superposition and synergism,compound flora were constructed artifi-cially and the growth promoting effect of compound flora on walnut seedlings was verified by pot experi-ment.The results showed that a total of 9 drought-tolerant PGPR were screened out.Among them,5 strains showed the effect of solubilizing phosphorus(2.28-61.63 μg·mL-1),4 strains had the ability to secrete IAA(2.32-9.44 μg·mL-1),and 4 strains had the ability to produce EPS(37.69-112.84 μg· mL-1).They were identified as the genera of Arthrobacter,Enterobacter,Ensifer,Sinorhizobium,Pseudo-monas,and Sphingobacterium,respectively.The pot experiment showed that the four compound flora could significantly promote the growth of walnut seedlings,and significantly increase the plant height,bio-mass and net photosynthetic rate(Pn)of walnut seedlings(P＜0.05).Compared with the control group,the plant height increased by 32.3％-64.2％,the biomass increased by 37.6％-52.6％,and Pn increased by 47.4％-68.5％.In addition,the application of compound flora also affected the nutrient level of walnut rhizosphere soil,significantly increased the enzymatic activities of β-glucosidase(BG),β-N-acetylglu-cosaminidase(NAG)and alkaline phosphate,and increased the contents of available phosphorus,nitrate ni-trogen and ammonium nitrogen(P＜0.05),among which T4 had the best effect.The results of this study can pro-vide bacterium resources for the development of microbial fertilizer suitable for arid and semi-arid areas.