Study On The Disease Prevention And Growth Promotion Functions Of A Strain Of Bacillus Cereus DW019

A strain with various proliferation and stress tolerance properties was isolated from the inter-rhizosphere soil of an ionic rare earth mineral plant in Gannan,and was identified as Bacillus cereus DW019 by 16S r RNA gene sequence analysis.Thanatephorus cucumeris,Fusarium moniliforme Sheldon（CGMCC3.2879）and Alternaria alternata（Fries）Keissler（CGMCC3.4255）showed antagonistic effects.The results of pot experiments showed that the inoculation of B.cereus DW019 had significant effects on the biomass,photosynthetic capacity,plant antioxidant enzyme activity and inter-root soil microbial community of lettuce and cherry tomato plants.The main findings were as follows:1.B.cereus DW019 had strong salt and alkali resistance.The strain isolated from the inter-rhizosphere soil of ionic rare earth mineral plants in Gannan had Indole-3-acetic acid（IAA）and iron carrier producing ability,where the IAA production was 16.06 mg·L^-1 and the iron carrier activity was 33.68%.The strain was identified as Bacillus cereus by 16S r RNA gene sequence analysis,named as Bacillus cereus DW019.Salinity tolerance test results showed that the strain could grow normally in 10%Na Cl at p H 10.0.2.B.cereus DW019 had a strong growth-promoting effect on lettuce and cherry tomato.The short-term pot experiment of lettuce and virgin fruit was conducted in five treatment groups(uninoculated cells（CK）,10⁸ CFU/m L inactivated cells（DC8）,10⁸ CFU/m L active cells（VC8）,10⁹ CFU/m L active cells（VC9）,and 2×10⁹ CFU/m L active cells（DVC9）.The experimental results showed that the DC8-DVC9 group had effects on vegetable biomass,photosynthetic capacity,nutritional quality of edible parts,antioxidant enzyme activity and malondialdehyde（MDA）.Compared with the control group,the above-ground biomass of lettuce increased by5.42%,50.64%,155.15%and 229.30%,and the below-ground biomass increased by 17.10%,62.16%,124.32%and 174.43%,respectively.The biomass of aboveground part of cherry tomato increased by 45.83%,87.50%,400.00%and 462.50%,and the biomass of belowground part increased by 43.96%,81.22%,193.22%and 344.96%,respectively.Meanwhile,inoculation of the strain increased the nutritional quality and antioxidant enzyme activity of the edible fractions.In addition,the relative conductivity,MDA content in the leaves and the damage of vegetable cell membranes in DC8-DVC9 groups could be significantly reduced.3.B.cereus DW019 had effective control of a variety of soil-borne diseases causing bacteria.The results of the antibanterial experiments showed that the strain had good antagonistic effects against Thanatephorus cucumeris,Fusarium moniliforme Sheldon（CGMCC3.2879）and Alternaria alternata（Fries）Keissler（CGMCC3.4255）.The inhibition rates were 53.57%,57.32%and 42.62%,respectively.The results of the pot experiment showed that lettuce and cherry tomatto inoculated with the pathogenic bacteria and strain DW019 in the experimental group grew well,and the leaves did not get wilt and yellow significantly compared with those inoculated with the pathogenic strain only,and the control was effective.4.A total of 36 bacterial phyla were found in the rhizosphere soil of cherry tomato,among which Proteobacteria,Actinobacteria,Bacteroidetes,Gemmatimonadota and Acidobacteria were the dominant groups in the soil groups of bacteria.Proteobacteria was the largest taxon in all samples,accounting for more than 50%of the total bacteria.Inoculation of inactivated and active bacterial cell suspensions reduced the Alpha diversity and affected the Beta diversity of rhizosphere soil microorganisms.Correlation analysis between physiological and biochemical indicators and bacterial community diversity of cherry tomato showed that the inoculation of the inter-rhizosphere promoting strain led to an increase in the proportion of Proteobacteria and Actinobacteria in the inter-rhizosphere soil microbial community.