Screening Of Plant Growth Promoting And Anti-drought Bacteria Isolated From Populus Euphratica Forest Soils And The Study Of Their Mechanisms

Populus euphratica is the only kind of arbor which can grow in arid area of desert in our country and it has strong resistance to abiotic stresses like drought,saline,sodic,high and low temperature,wind and sand,etc.Microbes colonized in the rhizospheric of Populus euphratica should contribute a lot to the plant resistance appearance,but related study is deficient.This study collected the rhizosphere soil of wild Populus euphratica forest located in Tarim river basin,and isolated 232 rhizospheric microbe strains from the samples by traditional culture methods.52 strains having plant growth related metabolic capacity have been selected in preliminary screening.These plant growth related metabolic capacity included ACC daminase,IAA,acetoin,siderophore and phosphate solubilizing ability.Then 10 bacteria strains with high growth-promoting effect were selected by biological assay using wheat seedlings under drought stress.By 16S rDNA sequences identification,these strains belonged to Pseudomonas sp.,Bacillus sp.,Stenotrophomonas sp.,etc.Comparing the effects of the dry weight,root developments and plant relevant defense enzymes of wheat seedlings under drought stress,the 10 strains played a significant role in promoting the wheat growth.In particular,the performance of strain 1-9 is of the most significant,making shoot dry weight of wheat seedlings increased by 34.4%,and the roots developed most vigorous as the root surface area tripled to control group.What's more,the promoting effect of this strain on the relevant plant defense enzyme activity is also the most obvious.Other strains also increased the dry weight of wheat shoot from 0.49%to 17.6%,and had different levels to improve the plant root area and defense enzyme activity.In different metabolites indicators,the strains with IAA synthetic ability possessed the most outstanding effects of promoting wheat seedlings growth and drought resistance,but IAA synthesis ability of the strains and their effects was not a positive correlation.Acetoin and siderophores substantially present a positive correlation.The strain 1-9 has the ability of producting IAA,and the IAA concentration is about 10?g/ml when cultured in IAA medium,which is inferred to be the most possible mechanism of its plant growth promoting and anti-drought effect.