Identification Of Plant Growth Promoting Rhizosphere Bacteria (PGPR) And Its Effect On Plant Growth

Many countries in the world are committed to the research of microbial fertilizers.The research and development of the plant growth promoting rhizobacteria(PGPR)has become a research focus of microbial fertilizers.The interaction of PGPR is very important not only for the growth and productivity of plants,but also for the health and function of our planet.The ten PGPR were isolated from purple soil in Beibei,Chongqing,and cultured in selective medium,identified by morphology and physiological and biochemical characteristics and named as Bacillus sp.GN01,Bacillus sp.GN02 and Bacillus sp.GN03;Bacillus sp.RP01,Bacillus sp.RP02 and Bacillus sp.RP03;Bacillus sp.JK01?Bacillus sp.JK02?Bacillus sp.JK03 and Bacillus sp.JK04 in the research.The K326 tobacco seeds were used as experimental materials,and the growth status of tobacco seedlings and the number of microbes in tobacco rhizosphere in unsterilized and sterilized substrates were investigated by floating seedlings with inoculation of PGPR.This research laid the foundation for the development and utilization of PGPR and the utilization of tobacco production.(1)Among 3 nitrogen fixing bacteria,the colony of GN02 and GN03 was larger.GN01 was positive only in the hydrolysis of starch,while GN02 was positive in contact enzyme test,oxidase test and sugar fermentation test;And GN03 was positive in the contact enzyme test and the starch hydrolysis test.GN01's bacterial liquid pH is the smallest.In 3 phosphate-solubilizing bacteria,the contact enzyme tests of RP01,RP02and RP03 were positive;RP01 was positive in the sugar fermentation test;And RP03was positive in both oxidase test and sugar fermentation test.The pH value of RP03 was the smallest.4 potassium-solubilizing bacteria in the contact enzyme test and sugar fermentation tests were positive;JK01,JK03 and JK04 in the hydrolysis of starch was also positive;And JK02 was positive in the oxidase test.The pH value of JK01 is the smallest and the change amplitude is the smallest,followed by JK02,and the pH of JK03 is the largest.(2)The effect of PGPR on the growth of K326 tobacco seedlings showed that GN01,RP01 and JK03 had the best growth promoting effect on tobacco seedlings inoculated with 10~6cfu/mL,compared with those without inoculants.The effect of RP01,RP02,JK02 and JK04 on the growth of tobacco seedlings was the best,and the effect of JK04 was the most significant in the tobacco seedlings with 10~3 cfu/mL.The promotion effect of 10~6concentration is better than 10~3.The biological effects of PGPR on tobacco seedlings showed that,GN02,RP01 and JK02 had better effects on tobacco growth in PGPR strain inoculated with 10~6 cfu/mL compared with the treatment without bacteria.Good growth in tobacco seedlings inoculated at 10~3cfu/mL was mainly concentrated on GN02,JK02 and JK03.Considering comprehensively,the growth of tobacco with potassium-solubilizing bacteria is better than nitrogen-fixing bacteria and phosphate-solubilizing bacteria,and the tobacco growth of 10~3concentration was better than 10~6.(3)In the non-sterile matrix and the sterilized matrix,from the rhizosphere microorganisms of tobacco,inoculation of ten PGPR significantly increased the number of target bacteria in tobacco rhizosphere.The number of nitrogen-fixing bacteria in rhizosphere was generally less than that of phosphate-solubilizing bacteria and potassium-solubilizing bacteria.For the culturable bacteria,the number in the non-sterile matrix began to be relatively less and then increased;The bacteria count in the rhizosphere of the 10~6 concentration of the sterilization matrix showed a tendency to decrease gradually,and the number inoculated with 10~3concentration increased first and then decreased.From the endorhizosphere microbes,the count of target bacteria and culturable bacteria is generally less than that of tobacco rhizosphere.In the non-sterile matrix,the number of nitrogen-fixing bacteria entering the endorhizosphere is far less than the number of phosphate-solubilizing bacteria and potassium-solubilizing bacteria;In the sterilization matrix,the number of target bacteria and culturable bacteria inoculated with four strains of JK01,JK02,JK03,and JK04 was generally more than 6other strains.In addition,the ten strains inoculated with 10~6 and 10~3 concentration were able to reduce the pH of the rhizosphere soil compared with the uninoculated control,and the inoculation of 10~6soil pH values was less than 10~3concentration.(4)Compared with non-sterile substrates,the growth of tobacco in the sterile matrix was not as good as that of the non-sterile substrate,and the tobacco index measured at the same time decreased by more than 50%.Moreover,the number of bacteria in the matrix is significantly reduced.