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Title: Cucumber rhizosphere microbial community response to biocontrol agent Bacillus subtilis B068150

Author
item LI, LIHUA - China Agricultural University
item MA, JINCAI - Jilin University
item Ibekwe, Abasiofiok - Mark
item WANG, QI - China Agricultural University
item YANG, CHING-HONG - University Of Wisconsin

Submitted to: Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/16/2015
Publication Date: 12/29/2015
Citation: Li, L., Ma, J., Ibekwe, A.M., Wang, Q., Yang, C. 2015. Cucumber rhizosphere microbial community response to biocontrol agent Bacillus subtilis B068150. Agriculture. 6(2):1-15. doi: 10.3390/agriculture6010002.

Interpretive Summary: Biological control may be a potential alternative approach to controlling soilborne plant diseases, since chemical methods may have some adverse effects on the environment and food safety. At present, the acceptability of biocontrol agents, and the predicted rate of growth of this method is about 10% annually. However, an introduced biocontrol agent will interact not only with the pathogen to be controlled but also with all the biotic components of the soil. In this study, we assess the ecological fitness of B. subtilis strain B068150 by using nucleic acid technique to explore the influence of soil types on the rhizosphere competence and biocontrol activity of strain B068150 and its effects on the indigenous soil bacteria and fungi. During our study, no significant differences were found between native microbial communities with strain B068150 except in bacterial community in clay. There were also no significant differences in microbial diversity between the control and cucumber rhizosphere inoculated with B subtilis B068150. The results of this research will be used by growers, researchers, FDA, and different state agencies that are involved in crop production.

Technical Abstract: Gram-positive bacteria Bacillus subtilis B068150 has been used as a biocontrol agent against the pathogen Fusarium oxysporum f. sp. Cucumerinum. However, their survival ability in cucumber rhizosphere and non-rhizosphere as well as their influence on native microbial communities has not been fully investigated. In this study, cucumber was grown in three soils with strain B068150 inoculated in a greenhouse for 90 days, and the colonization ability of strain B068150 in cucumber rhizosphere and non-rhizosphere soils was determined. Changes in total bacteria and fungi community composition and structures using denaturing gradient gel electrophoresis (DGGE) and sequencing were determined. Colony counts showed that B068150 colonization in the rhizosphere was significantly higher (P<0.05) than in non-rhizosphere soils. Strain B068150 impacts on the diversity of the cucumber rhizosphere microbial populations were assessed in 0, 10 and 32 days after inoculation. Results distinguished between bacterial communities in the three soils and the controls inoculated with strain B068150, but not with fungal population where Ascomycota phylum was the largest community in cucumber rhizosphere. Based on our data, the introduction of B. bacillus B068150 did not change the diversity of microbial communities significantly in the rhizosphere of three soils although the abundance of B. subtilis B068150 in rhizosphere was significantly higher than in non-rhizosphere. Furthermore, our data showed that the inoculation of B068150 in clay soil had a significant negative correlation on bacterial diversity in cucumber rhizosphere in comparison to loam and sandy soils, suggesting that the impact of B068150 might be soil specific.