Preliminary Study On Screening And Promoting Effects Of ACC Deaminase Bacteria From Halostachys Caspica Rhizosphere

Halostachys caspica belongs to the family Chenopodiaceae and the genus Salicornia.It is the dominant plant species in the saline-alkali land of Xinjiang and grows in the poor soil with high degree of salinization.Plant Growth Promoting Rhizobacteria?PGPR?is a kind of beneficial fungi that can promote plant growth and vegetation to digest and absorb mineral elements,and inhibit harmful microbial reproduction.ACC deaminase can degrade the direct synthesis of ethylene in vegetation.The precursor material-ACC is a-butanone acid and ammonia,which in turn reduces the ethylene content.The researchers found that some bacteria in PGPR can secrete ACC deaminase,and bacteria producing ACC deaminase activity can decompose ACC produced by plants under adverse conditions,reduce barriers to vegetation growth,and improve vegetation survival.In this study,the rhizosphere soil of Halostachys caspica in Xinjiang was used as a sample to isolate and screen ACC deaminase-producing growth-promoting bacteria by directional enrichment method,and the screened strains were identified;the growth characteristics were studied;the activity of ACC deaminase-producing bacteria and the characteristics of salt and alkali tolerance were studied;at the same time,the growth-promoting potential of the screened strains was determined;the growth-promoting effects of different concentrations of bacterial solution on wheat and maize were also studied.The effects of strains screened under Salt Stress on the growth of wheat and maize were as follows:?1?Separation from the rhizosphere soil of the salt-eared wood,screening 1#,3#,5#,three strains producing ACC deaminase activity.?2?Three strains were observed and analyzed from three levels of morphological,physiological and biochemical characteristics,Biolog Gen III and 16 S r DNA molecular biology.The results of the three strains were: 1# strain was Klebsiella pneumoniae;3# strain is Klebsiella pneumoniae;5# strain is Klebsiella oxytoca.?3?The growth curves of the three strains showed that the growth rate was slowin the 0-2 h strain adapting to the environment;the bacterial growth rate was accelerated due to the abundant substances between 2 and 8 h,and the bacteria multiplied;the strain grew at 10 h.The speed is slowed down and the growth reaches equilibrium;it initially conforms to the law of bacterial growth.?4?1#,3#,5#,the ACC deaminase activities of the three strains were different;the activity of ACC deaminase produced by 5# strain was the strongest,and the difference of enzyme activity between 1# and 3# was not significant.The difference in enzyme activity between 1# and 5#;3# and 5# was significant?p<0.05?,and the order of ACC deaminase activity of the three strains was 5#>1# =3#.?5?The characteristics of salt and alkali tolerance of the three strains are as follows: when the mass concentration of Na Cl is 6%,the biomass of the three strains reaches the maximum,and decreases with the increase of salt concentration;the alkali tolerance of the three strains is better,and the microbial content of OD₆₀₀ is above2.0 when the p H is 7-10.?6?Growth-promoting potential of the three strains: all three strains have IAA-producing capacity,but there are differences,1 # and 3 # have significant differences?P < 0.001?,1 # and 5 # have significant differences?P < 0.001?;all three strains have potassium-soluble capacity,phosphorus-soluble capacity,nitrogen-fixing capacity;all have the potential of iron-producing carrier,but the amount of iron-producing carrier is not significant difference,iron-producing capacity is "++".?7?The different concentration of 1 # strain,3 # strain and 5 # strain could promote the growth of wheat and maize seed roots,hypocotyl growth and root branching number,but there were differences in different degrees.After comprehensive analysis,when the suspension concentration of three strains was 1.0 of OD₆₀₀,the overall effect of promoting root length,hypocotyl length and root branching number of wheat and maize was better.?8?The relative germination rate,hypocotyl length,root branching number,fresh weight and dry weight of wheat and maize seeds treated with 1 and 5 OD₆₀₀ bacterial solution at different concentrations of salt stress?0,50,100,150,200,300,350 mmol/L?were affected to varying degrees.It was found that the stress of salt solution on seeds could be alleviated and the germination rate of seeds could be increased in varying degrees after treated with bacterial solution.The growth of hypocotyl length and root branching number could be significantly promoted under low concentration of salt solution,but the fresh and dry weight of wheat and maize did not have much effect.Seeds treated with 1 # and 5 # bacterial liquor with ACC deaminase activity can promote plant growth and alleviate the damage of salt stress to them.