title: Soil type dependent rhizosphere competence and biocontrol of two bacterial inoculant strains and their effects on the rhizosphere microbial community of field-grown lettuce.
abstract: Rhizosphere competence of bacterial inoculants is assumed to be important for successful biocontrol. Knowledge of factors influencing rhizosphere competence under field conditions is largely lacking. The present study is aimed to unravel the effects of soil types on the rhizosphere competence and biocontrol activity of the two inoculant strains Pseudomonas jessenii RU47 and Serratia plymuthica 3Re4-18 in field-grown lettuce in soils inoculated with Rhizoctonia solani AG1-IB or not. Two independent experiments were carried out in 2011 on an experimental plot system with three soil types sharing the same cropping history and weather conditions for more than 10 years. Rifampicin resistant mutants of the inoculants were used to evaluate their colonization in the rhizosphere of lettuce. The rhizosphere bacterial community structure was analyzed by denaturing gradient gel electrophoresis of 16S rRNA gene fragments amplified from total community DNA to get insights into the effects of the inoculants and R. solani on the indigenous rhizosphere bacterial communities. Both inoculants showed a good colonization ability of the rhizosphere of lettuce with more than 10(6) colony forming units per g root dry mass two weeks after planting. An effect of the soil type on rhizosphere competence was observed for 3Re4-18 but not for RU47. In both experiments a comparable rhizosphere competence was observed and in the presence of the inoculants disease symptoms were either significantly reduced, or at least a non-significant trend was shown. Disease severity was highest in diluvial sand followed by alluvial loam and loess loam suggesting that the soil types differed in their conduciveness for bottom rot disease. Compared to effect of the soil type of the rhizosphere bacterial communities, the effects of the pathogen and the inoculants were less pronounced. The soil types had a surprisingly low influence on rhizosphere competence and biocontrol activity while they significantly affected the bottom rot disease severity.
authors.affiliation: Julius Kühn-Institut - Federal Research Centre for Cultivated Plants (JKI), Institute for Epidemiology and Pathogen Diagnostics, Braunschweig, Germany; Leibniz Institute of Vegetable and Ornamental Crops Großbeeren/Erfurt e.V., Department Plant Health, Großbeeren, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Schreiter
authors.affiliation: Leibniz Institute of Vegetable and Ornamental Crops Großbeeren/Erfurt e.V., Department Plant Health, Großbeeren, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Sandmann
authors.affiliation: Julius Kühn-Institut - Federal Research Centre for Cultivated Plants (JKI), Institute for Epidemiology and Pathogen Diagnostics, Braunschweig, Germany.
authors.forename: Kornelia
authors.initials: K
authors.lastname: Smalla
authors.affiliation: Leibniz Institute of Vegetable and Ornamental Crops Großbeeren/Erfurt e.V., Department Plant Health, Großbeeren, Germany.
authors.forename: Rita
authors.initials: R
authors.lastname: Grosch
mesh_terms: D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D018545:Lactuca / Q000254:growth & development*; D059013:Microbial Consortia / Q000502:physiology*; D011549:Pseudomonas / Q000502:physiology*; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism; D012336:RNA, Ribosomal, 16S / Q000235:genetics / Q000378:metabolism; D058441:Rhizosphere; D012705:Serratia / Q000502:physiology*; D012988:Soil Microbiology
chemical_list: D004269:DNA, Bacterial; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S
references.citation: FEMS Microbiol Ecol. 2000 Jul 1;33(1):41-49
references.pmid: 10922502
references.citation: FEMS Microbiol Ecol. 2006 May;56(2):167-77
references.pmid: 16629747
references.citation: Appl Environ Microbiol. 2001 Apr;67(4):1945-8
references.pmid: 11282653
references.citation: Front Microbiol. 2014 Jan 24;5:2
references.pmid: 24478764
references.citation: Appl Environ Microbiol. 2009 Jun;75(12):3859-65
references.pmid: 19376893
references.citation: Appl Environ Microbiol. 1997 Aug;63(8):3233-41
references.pmid: 9251210
references.citation: Microbiology (Reading). 2004 Nov;150(Pt 11):3889-3897
references.pmid: 15528673
references.citation: Ecotoxicol Environ Saf. 2004 Sep;59(1):127-32
references.pmid: 15261734
references.citation: FEMS Microbiol Ecol. 2008 Apr;64(1):106-16
references.pmid: 18248441
references.citation: Appl Environ Microbiol. 2002 Dec;68(12):6371-82
references.pmid: 12450862
references.citation: Annu Rev Phytopathol. 2002;40:309-48
references.pmid: 12147763
references.citation: FEMS Microbiol Lett. 2007 Jul;272(2):127-36
references.pmid: 17521360
references.citation: Nat Rev Microbiol. 2005 Apr;3(4):307-19
references.pmid: 15759041
references.citation: FEMS Microbiol Ecol. 2006 May;56(2):207-18
references.pmid: 16629751
references.citation: PLoS Genet. 2012 Jul;8(7):e1002784
references.pmid: 22792073
references.citation: FEMS Microbiol Ecol. 2005 Jan 1;51(2):215-29
references.pmid: 16329870
references.citation: PLoS One. 2013 Jul 23;8(7):e68818
references.pmid: 23935892
references.citation: Front Microbiol. 2014 Apr 08;5:144
references.pmid: 24782839
references.citation: Curr Opin Plant Biol. 2001 Aug;4(4):343-50
references.pmid: 11418345
references.citation: Appl Environ Microbiol. 2001 Jun;67(6):2545-54
references.pmid: 11375162
references.citation: Environ Microbiol. 2008 Nov;10(11):3082-92
references.pmid: 18393993
references.citation: J Environ Sci Health B. 2004 Jan;39(1):1-17
references.pmid: 15022737
references.citation: Annu Rev Phytopathol. 2012;50:403-24
references.pmid: 22681451
references.citation: New Phytol. 2007;173(3):600-610
references.pmid: 17244055
references.citation: J Biotechnol. 2013 Aug 20;167(2):142-55
references.pmid: 23280342
references.citation: J Bacteriol. 1995 Sep;177(18):5387-92
references.pmid: 7665535
references.citation: FEMS Microbiol Ecol. 2005 Sep 1;54(1):21-33
references.pmid: 16329969
references.citation: Annu Rev Phytopathol. 2001;39:461-90
references.pmid: 11701873
references.citation: FEMS Microbiol Ecol. 2009 Jul;69(1):62-74
references.pmid: 19486156
references.citation: J Bacteriol. 2011 Jan;193(1):177-89
references.pmid: 20971913
references.citation: Can J Microbiol. 2005 Apr;51(4):345-53
references.pmid: 15980897
references.citation: Microb Ecol. 2012 Oct;64(3):725-37
references.pmid: 22576821
references.citation: Mol Plant Microbe Interact. 2000 Nov;13(11):1177-83
references.pmid: 11059484
references.citation: J Microbiol Methods. 2004 May;57(2):187-95
references.pmid: 15063059
references.citation: Appl Environ Microbiol. 2002 Aug;68(8):3795-801
references.pmid: 12147474