Identification And Co-culture Of Salt Tolerant Promoting Growth Bacteria And Biological Control Bacteria

Xinjiang is an arid and semi-arid areas.The existing 31.1 percent of arable land in the area was hazarded by salinity,and 80% of the salinization of arable land is secondary salinization. It seriously affected the cotton and tomato's seed germination and emergence. It had become a main limiting factor of development of cotton and tomato. Based on preparatory work about action of microoganisms on growth promotion and disease control for cotton and tomato,this paper studied on co-culture between five bacteria in order to solve this regional problem,providing theoretical basis for the large-scale production of compound agents and application of the provision of scientific. Among them,two bacteria known as salt solutions and growth-promoting bacteria,can increase crop in the salinity tolerance of the soil environment.Three bacteria known as biocontrol bacteria,can control crop seedling diseases. Experiments mainly include the following:1.Strain identification and study on the symbiotic antagonism:Based on the morphological characteristics,physiological and biochemical characteristics,16S rDNA sequence homology,the strains Rs-198,SL-13,SL -14 and SL-44 used in this paper were identified. The results of tentative identifacation showed that Rs-198 was identified as Pseudomonas fluorescens. SL-13,SL-14 and SL-44 were identified as Bacillus atrophaeus. Combinations of any two from Rs-5,Rs-198,SL-13,SL-14 and SL-44 bacteria strains disclosed the interactions between five bacteria. The results showed that strain Rs-5 could inhibit SL-13,strain Rs-198 could inhibit SL-13,SL-14,strain SL-13 could inhibit SL-14;strain SL-44 could inhibit SL-13,SL-14,other combinations could co-culture。2. Co-culture conditions research: Symbiotic halotolerant and promoting growth bacteria Rs-198 and Rs-5 were selected for studying on co-culture. First of all,Rs-5 and Rs-198 were cultured under different temperatures and different initial pH,it was determined that the initial temperature 28℃and pH 6.5 for co-culture; Secondly,through analysising the residual glucose,cell optical density and pH change in different mixed mode of Rs-198 and Rs-5,synergy was revealed and the best mixed concentration ratio was determined as 106:106 each milliliter。3. Medium optimization:Co-culture of Rs-198 and Rs-5 mixed in certain ratio of viable number 106:106 each milliliter,the optimal medium composition of co-culture was determined by orthogonal method experiment. The results were glucose 5 g/L,protein 35 g /L,yeast extract 15 g/L,Na2 HPO4·12H2O 10g/L,MgSO4·7H2O 1.2g/L and KH2PO4 3.63g/L.4. Control effect experiment:A pot experiment showed that mixed microbial agent can improve the emergence rate 22.1 percent. Field experiments showed that the mixed microbial agents can improve the yield 10.05 percent,and verified that the mixed microbial agent had the mixed-effect role.5. Shelf life experiment:The agent made of a different cell by distilled water was preserved at dark place at room temperature and a viable testing every one months between storage.After 5 months,the number of live bacteria of the agent Rs-5,SL-14,BCL-8 could increase respectively by 1.63,1.72,1.20log.The number of live bacteria of the agent Rs-198,SL-13,SL-44 could reduce respectively by 0.56,0.55,0.28log.