Effects Of PGPR Microbial Agents On Improving The Quality And Yield Of Flue-cured Tobacco And Its Effects On Soil Quality

The isolation and screening of bacteria resources for growth promoting effect from the quality tobacco rhizosphere soil in Pingdi tobacco planting area of Renhe District of Panzhihua,which have the functions of producing indole-3-acetic acid(IAA)、phosphate solubilizing and potassium solution.Through the pot experiment of flue-cured tobacco,the strains which showed significantly promoting effect on the growth of flue-cured tobacco were mixed into multifunction PGPR mixed agents.Through field test and analyze the impact of mixed agents on the growth and quality of flue-cured tobacco,yield,quality and yield verified the effect of multi-functional PGPR mixed agents on improving yield and quality of flue-cured tobacco,explored the best combination method of the mixed agents and organic fertilizer,and clarified the effect of mixed agents in reducing fertilizer and increasing efficiency;At the same time,the indexs of soil nutrients,microbial biomass carbon and nitrogen,soil enzyme activity of the rhizosphere of flue-cured tobacco at different growth stages were measured,combined with PCR-DGGE method,the effect of multifunctional PGPR mixed agents on the microbial community structure was analyzed,describes the function of multi-functional PGPR mixed agents active role in improving the quality of tobacco soil.The main results are as follows:(1)In this study,54 strains of bacteria were isolated from flue-cured tobacco rhizosphere soil,and 24 strains of IAA producting bacteria,22 strains of phosphate solubiling bacteria and14 strains of potassium releasing bacteria were screened out by the ability of promoting test.The 9 strains of strong growth promoting bacteria through molecular identification were attributable to the Bacillus,Ochrobacterum,Acinetobacter and Enterobacter.The antagonistic test showed that bacteria YCG1,YCG2 and YCG3 had no inhibitory effect on each other.They were mixed into multifunctional PGPR mixed agents according to 1:1:1 ratio.Further,the growth promoting effect of the mixed agents on flue-cured tobacco was verified by pot experiments.(2)Multifunctional PGPR mixed agents was applied to the field test of flue-cured tobacco in two ways,as root water irrigated root and mixed with organic fertilizer as base fertilizer,the results show that the best way is root water application;based on the results of the optimal method of application,we continue to study the effects of multifunctional PGPR mixed agents in less nitrogen fertilizer,the results show that the multi functional PGPR mixed agents as root water irrigation can make inorganic fertilizer less nitrogen 10%,and can significantly improve the agronomic traits of flue-cured tobacco,the tobacco black shank,reduce the incidence and disease index of Alternaria alternata,tobacco mosaic virus,increase the contents of total nitrogen and nicotine,it can make the tobacco leaf potassium content increased significantly,the chemical composition of tobacco leaves for more coordination,promote the proportion of medium and superior tobacco leaves,increase the economic value.(3)After application of multifunctional PGPR mixed agents,soil organic matter,available N,P and K content and soil microbial biomass C、N increased,and activities of urease,sucrase,alkaline phosphatase and catalase increased significantly.Multifunctional PGPR mixed agents can effectively change the microbial community structure of tobacco rhizosphere soil,mainly in the vigorous growing stage and mature stage of flue-cured tobacco rhizosphere soil microbial richness(S)and Shannon-Wiener(H’)index increased;With the increase of inorganic fertilizer application amount,S and H’ showed an increasing trend.Therefore,the application of multifunctional PGPR mixed agents in rhizosphere of flue-cured tobacco and 10% reduction of inorganic fertilizer had the best effect on improving yield and quality of tobacco planting soil effectively.