The Growth-promoting Of Plant Growth Promoting Rhizobacteria On Pepper And Preliminary Study Of Its Machanism

In order to screen the Plant Growth Promoting Rhizobacteria(PGPR)strains,This study collect root and soil samples of different healthy plants in different place of Henan province,such as Xinyang,Pingdingshan,Xuchang,Yuanyang,Songshan,Mao zhuang etc.We Separate the Rhizobacteria with Gradient dilution method,and preliminarily screen the PGPR strains According to the ability of Phosphate-solubilizing,Indole-3-Acetic Acid(IAA)and Siderophores-producing with lab screening.Then the target PGPR strains A21-4,R2-1,G2-1 were screened out after the trails of pepper seedlings promoting.The morphological and physiological characteristics and 16S rDNA sequence analysis were used to identify the strains.We measured their colonization density in root and rhizosphere soil of pepper,studying the effect of soil physical and chemical properties and soil enzyme activity and analysing their mechanism of promoting growth preliminarily.Laying the foundation of using promoting rhizosphere microorganism to promote plant growth,enhancingdisease resistance and yelt of plants and researching biological Pesticide.1.According to the test of lab screening and pepper seedlings promoting screening,A21-4,R2-1,G2-1 three PGPR strains were screened.All three PGPR strains can significantly increase the aboveground and roots morphological indexes of pepper and significantly increasing the chlorophyll content and root activity.2.Based on the morphological characters,physiological-biochemical characters and 16S rDNA sequence analysis,the strain R2-1 was identified as Bacillus velezensis;G2-1 was identified as Pseudomonas brassicacearum.A21-4 was identified as Serratia plymuthica by our laboratory before.Three PGPR strains all can solubilze phosphate,procucing Siderophores and Indole-3-Acetic Acid.In addition A21-4 can produce cellulase and chitinase,R2-1 can produce cellulase,protease,amylase and chitinase.A21-4 and R2-1 have different antagonistic activity against the selected pathogens.And G2-1 has no antagonistic activity against the selected plant pathogens.3.A21-4,R2-1 and G2-1 are all have a strong colonization in pepper roots and rhizosphere soil.28d after the treament,the colonization density in pepper roots and rhizosphere soil of A21-4 were still 1.52 × 104 cfu.g-1 and 1.80 × 104 cfu.g-1;R2-1 were 3.08 × 105 cfu.g-1 and 1.34 × 105 cfu.g-1;G2-1 were 1.00 × 105 cfu.g-1 and 1.70× 105 cfu.g-1.4.There is no a significant effect on the pH and electrical conductivity of pepper rhizosphere soil after the treatment of A21-4,R2-1 and G2-1,but a significant increasing of the organic content and available phosphorus content of pepper rhizosphere soil.organic content of pepper rhizosphere soil were increased 58.44%?64.36%and 34.55%after the treatment of A21-4,R2-1 and G2-1,and the available phosphorus content of pepper rhizosphere soil were increased 31.94%?146.42%and 99.28%.At the same time,the treatment of A21-4,R2-1 and G2-1 also can significantly increase the urease activity and phosphatase activity of pepper rhizosphere soil.64.99%?109.21%and 29.48%were increased of urease activity and 32.59%?151.11%and 78.52%were increased of phosphatase activity after the treatment of A21-4,R2-1 and G2-1.5.The promoting activity under the condition of not using phosphorus were significantly higher than the promoting activity under the condition of using phosphorus after the treatment by three PGPR strains.