Isolation, Identification And Preliminary Application Of Rape PGPR

In Rape planting areas in Xinjiang, rape yield has been affected due to perennial continuous cropping, disease(Sclerotinia) and pest, basically behaving in soil fertility decline, seedling damage, slow growth and so on. In the agricultural production process, the plant rhizosphere promoting bacteria(PGPR) can provide a variety mineral nutrition and produce antibiotics for plants, and therefore promote the growth of crop root system,enhance plant growth and disease resistance.This study isolates beneficial plant rhizosphere promoting bacteria strains from rape seedlings rhizosphere soil,determines promoting effect and sclerotinia resistance of the strains, and optimizes fermentation medium and conditions of one promoting strain. Promoting strains have been isolated from rape seedlings rhizosphere soil by dilution coating method, screened by rape seed germination,seeding growth potential and biomass and data analysis with SPSS17.0 statistical analysis software.Antagonistic strains have been screened by flat confrontation test against Sclerotinia sclerotiorum from promoting strains. Screened strains therefore have been identified by morphological and 16 S rDNA amplification and analysis sequences. Fermentation medium and conditions of strain QZB24-6 has been optimized with index of viable count,spore count and spore-forming rate.1. Bacteria strains of QZB24-6, QZB24-7 and XYB173-8 with significant growth-promoting effect on rape seedlings has been screened through primary screening and re-screening from 68 bacteria strains isolated initially, and then identified as Bacillus cereus(QZB24-6), and Bacillus megaterium(QZB24-7,XYB173-8) based on morphology and 16 S rDNA sequence alignment analysis.2. Results of promoting effect test on rape seedling shows that, compared with the control group,treatment of QZB24-6, QZB24-7 and XYB173-8 increased 23.9%,18.09% and 23.11%on stem length, 83.15%, 78.80% and 86.68%on leaf expand,significantly 2 times above on stem fresh weight and root fresh weight.3. Antagonistic bacteria QZB22-5 andXYB174-72 have been screened by flat confrontation method against Sclerotinia sclerotiorum from promoting strains isolated,and then identified as Bacillus simplex and Bacillus atrophaeus based on morphology and 16 S rDNA sequence alignment analysis. Inhibition rate against Sclerotinia sclerotiorum of the two strains reached 57.8% and 77.1% respectively.4. For QZB24-6 as the research object,optimization of fermentation medium results shows that the optimal culture medium formula for growth and spore production as follows: 2% lactose, 1.5% yeast extract, 0.07% manganese sulfate,0.4% disodium hydrogen phosphate, 0.2%sodium dihydrogen phosphate.Optimization of spore producing fermentation condition results in the optimum fermentation temperature 35 ℃,pH value 7.0, inoculum 4%, liquid volume100 mL,speed is under 180 rpm fermentation 72 h.From the view of economic point,the fermentation period of 60 h is better.