www.julius-kuehn.de

Managing the soil microbiome –key for plant health and growth

Kornelia Smalla

Julius Kühn-Institute, Braunschweigkornelia.smalla@julius-kuehn.de

The rhizosphere is the zone of soil influenced/altered by roots.

www.julius-kuehn.de

How agricultural management influences the soilmicrobiome?

How to manage the soil microbiome throughOrganic amendmentsCover cropsTillageCrop rotationInoculants

Exploration of plant-microbe-interactions forimproving agricultural productivity andsustainability

www.julius-kuehn.de

INIA-JKI workshop 14-16 November 2019, Montevideo-Las Brujas, Uruguay„Towards a more sustainable agriculture through managing the soil microbiome“

www.julius-kuehn.de

Impact of long-term agricultural management practices on the soil and rhizosphere

microbiome and on plant health

Doreen Babin, Soumitra Paul Chowdhury, Michael Rothballer, Loreen Sommermann, Jörg Geistlinger, Saskia Windisch, Narges Moradtalab, Günther Neumann, Martin Sandmann, Rita Grosch and Kornelia Smalla

www.julius-kuehn.de

Objective

… soil suppressivenessagainst plant pathogens?

How do long-term farming practicesaffect…

How can socio-economic constellation and understanding be improved?

… establishment andcomposition of the bulk soiland rhizosphere microbiota?

… root exudationpatterns?

… plant performanceand health?

5

www.julius-kuehn.de

Do long-term farming strategies shapethe soil microbiota?

6

WW1 Winter wheat after maize

WW2 Winter wheat after rapeseed

P Plough

CT Cultivator

Int Standard N-fertilization + fungicide use

Ext 50% N-fertilization

Long-term field trial in Bernburg(est. 1992, AUAS)

Field soil samples of WW1 & WW2 (0-20 cm)

Total communityDNA extraction

ITS1 and ITS2 fragments

used as fungal marker

16S rRNAgenes used as

bacterial marker

Illumina Amplicon Sequencing

www.julius-kuehn.de

7

Bacteria Fungi

.

Babin et al. 2019, SBB Sommermann et al. 2018, PlosOne

Plough

Cultivator

WW2

WW1

WW2

WW1

Pre-crop and tillage practices influencedsignificantly bacterial and fungal

communities in field soils

www.julius-kuehn.de

Soil microbial communities are shaped bylong-term agricultural management practices

www.julius-kuehn.de

Babin et al. 2019, SBB

Is the effect transmitted to rhizospheremicrobiome of the preceeding crop?Does the effect influence plant performanceand health?

8

Sommermann et al. 2018, PlosOne

www.julius-kuehn.dewww.julius-kuehn.dewww.julius-kuehn.de

9

Mendes et al.2013, FEMS MR

Hypothesis: soil memory effectThe effect of long-term agricultural management on the soil microbiome is conveyed via rhizosphere microorganisms to the next plant generation affecting plant performance and health

www.julius-kuehn.de

Growth conditions

10 weeks growth period

20/15 °C day-/night-temperature

60/80 % relative humidity

420 µmol m-2 s-1 PAR

100 hPa water potential

0.32 g available N per pot

Material Soil from LTE-1 Bernburg (AUAS, 1992):

• Soil management:

Plough [P] vs. Cultivator Tillage [CT]

• N-Fertilization intensity:

Intensive [Int] vs. Extensive [Ext]

• Last standing field crop:

Wheat [W] vs. Rapeseed [R]

Lettuce Lactuca sativa L. cv. ‘Tizian’

Growth chamber experiment: Effect of soil management, fertilization intensity and last standing crop

10

Sampling

www.julius-kuehn.de

Explained Variance Bacteria (Rh) Fungi (RS)

Soil management 13% * 10% *

Fertilization intensity 9%* 16% *

Field crop 15%* 37% *

11

PERMANOVA analysis based on Bray-Curtis dissimilarities, 10,000 permutations (p<0.05)Rh = RhizosphereRS = Root-associated Soil

Soil management, fertilization intensity and field cropaffected the lettuce rhizosphere microbiota

www.julius-kuehn.de

12

Management-dependent prokaryoticcommunity composition and enrichment of

genera in the lettuce rhizosphere

CT (except Ext-W):PseudomonasMethylophilus

www.julius-kuehn.de

Tillage practice and N-fertilization intensity affected significantly lettuce growth

13

• Effect independent of the last standing field crop (wheat [W] and rapeseed [R]) and vegetation period (2015, 2016, 2017)

Shoot fresh mass [g/plant]

Different letters indicate significant difference (Tukey-Test, p<0.05)

www.julius-kuehn.de

Expression of plant defense-associated genes was by N-fertilization intensity and soil management

Significantly higher expression of plant defense-associated genes in CT-Ext compared to P-Ext suggests an induced physiological status

Reproducible effects in two independent experiments (2015, 2016)

14

Fold Change CT-Ext vs. P-Ext (Wheat)

Expression analysis of selected plant genes clustered depending on fertilization intensity

www.julius-kuehn.de

Summary & Outlook

www.julius-kuehn.de

15

Soil/rhizomicrobiota

Root exudation

Lettuce growth Lettuce health

Soil suppressiveness

Long-term field experiment Growth chamber experiment

Better understanding of belowgroundplant-microbe-soil interactions needed

www.julius-kuehn.de

Use of bacterial endophytes with in vitro antagonistic activity towards Ralstonia solanacearum for biocontrolof bacterial wilt

Tarek Elsayed1, Samuel Jacquiod2, Søren J. Sørensen2, and Kornelia Smalla1

1 Institute for Epidemiology and Pathogen Diagnostics, Julius Kühn-Institut - Federal ResearchCentre for Cultivated Plants (JKI), Braunschweig, Germany2Section of Microbiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark

www.julius-kuehn.de

Ralstonia solanacearum is a soil-borne pathogen that naturally infectsroots and invades and multiplies in the xylem vessels and has a verywide host range (more than 200 different plants)

Cell density-dependent expression of virulence genes

The pathogen: Ralstonia solanacearum

Pathogenicity mechanisms: secretion of virulence factors (Type III effectors), enzymatic degradation of host-produced substrates, EPS production

Host colonization and disease requires motility, chemotaxis and aerotaxis

Salicylic acid (SA) inhibits growth of R. solanacearum and induces generalstress response that includes repression of multiple bacterial wilt virulencefactors. The ability to degrade SA reduces the pathogen’s sensitivity toSA toxicity and increases its virulence on tobacco.

www.julius-kuehn.de

Bacillus velezensis B63Genome size = 4,001,023 bp

Proteins with functional assignments (3,333) Hypothetical proteins (789)

Biological control related secondary metabolites Bacilysin_biosynthetic_gene_cluster Macrolactin_biosynthetic_gene_cluster Bacillaene_biosynthetic_gene_cluster Bacillibactin_biosynthetic_gene_cluster Surfactin_biosynthetic_gene_cluster Fengycin_biosynthetic_gene_cluster

Genome size = 6,538,533 bpProteins with functional assignments (4,630)Hypothetical proteins (1,729)

Biological control related secondary metabolites 2,4-Diacetylphloroglucinol_biosynthetic_gene_clusterSiderophore biosynthesis genePhenazine biosynthesis genePhloroglucinol biosynthesis geneHydrogen cyanide synthase gene

Pseudomonas fluorescens P142

www.julius-kuehn.de

Transfer to soil infested with 106 B3B CFUs/g

Drenching with antagonists

Seed treatment 

Tomato roots

Greenhouse testing of in vitro antagonists towards R. solanacearum in tomato rhizosphere

Greenhouse testing of in vitro antagonists towards R. solanacearum in tomato rhizosphere

Two antagonists were selected

30 dps 14 days after infection

DNA extraction 

qPCR targetingRs and gfp‐tagged 

antagonists 

CFU counts KB, PCA, SMSA 

Transfer to non-infested soil

Illumina amplicon sequencing

fliC gene: PCR‐Southern blot hybridization

www.julius-kuehn.de

Wilting symptoms on tomato plants 14 dpi compared to the control

www.julius-kuehn.de

CFU counts Real-time PCR

PCR-Southern blot hybridization of fliC gene specific for R. solanacearum in tomato rhizosphere total community DNA samples, two week after transplanting into B3B infested soil

Monitoring inoculant strain and R. solanacearum

www.julius-kuehn.de

Proteobacteria was the most dominant phylum in control samples (TC) followed by   Actinobacteria, Bacteroidetes and Firmicutes. 

Relative abundance of Actinobacteria increased in response to antagonist inoculation

Amplicon sequencing of 16S rRNA gene amplified fromTC‐DNA of tomato rhizosphere

www.julius-kuehn.de

Samples Ralstonia solanacearum OTU_1 Total number of seq. Rs relative % Rs qPCR/g

TC1  ‐ 24395 ‐ ‐TC2 ‐ 19236 ‐ ‐TC3 ‐ 15303 ‐ ‐TC4 ‐ 37015 ‐ ‐TCR1 7386 37458 19.72 8.52TCR2 7547 30359 24.86 8.210TCR3 11258 23683 47.54 8.61TCR4 16426 32675 50.27 8.43

TC‐B63/1 ‐ 29036 ‐ ‐TC‐B63/2 ‐ 38854 ‐ ‐TC‐B63/3 ‐ 35139 ‐ ‐TC‐B63/4 ‐ 25421 ‐ ‐TCR‐B63/1  8 36714 0.02 5.04TCR‐B63/2 57 26975 0.21 5.01TCR‐B63/3 11 23238 0.05 5.16TCR‐B63/4 5 24536 0.02 5.16TC‐142 /1 ‐ 30737 ‐ ‐TC‐142 /2 ‐ 29462 ‐ ‐TC‐142 /3 ‐ 4461 ‐ ‐TC‐142 /4 ‐ 20023 ‐ ‐TCR‐142/1 79 22953 0.34 6.69TCR‐142/2 20 27600 0.07 6.05TCR‐142/3 1 12465 0.01 5.19TCR‐142/4 16 22281 0.07 5.99

Detection of OTU affiliated to R. solanacearum

Lower Rs OTUs in the rhizosphere of tomato plants treated with antagonists 

www.julius-kuehn.de

Shifts of the prokaryotic community compositions inthe tomato rhizosphere in response to the treatments

Dynamic taxaTC-B63: 85 OTUs increased while 31 OTUs decreasedTC-AL2YTEN-142:52 OTUs were increased while 16 OTUs decreased

www.julius-kuehn.de

Relative abundance of dominant responding genera (Relative abundance ≥ 0.5%)Class Genus OTUs TC TCR TC-B63 TCR-B63 TC-142 TCR-142Actinobacteria Aciditerrimonas OTU_574 0.1 + 0b 0.1 + 0a 0.6 + 0.1d 0.3 + 0c 0.3 + 0.1c 0.2 + 0bc

Curtobacterium OTU_45 0.7 + 0.2b 0.2 + 0.1a 0.5 + 0.2b 0.6 + 0.2b 0.6 + 0.2b 0.7 + 0.1b

Salinibacterium OTU_1281 0.7 + 0.3b 0.2 + 0.1a 0.6 + 0.2b 0.8 + 0.1b 0.7 + 0.2b 0.8 + 0.2b

Arthrobacter OTU_37 4.2 + 1.3b 1 + 0.7a 6.5 + 1.3bc 9 + 1.1c 6.2 + 2.9bc 11 + 1.3c

Nocardioides OTU_371 0 + 0a 0 + 0a 0.6 + 0.2b 0.7 + 0.1b 0.1 + 0a 0.1 + 0a

Gaiella OTU_466 1.1 + 0.2b 0.8 + 0.2a 2.9 + 0.3d 2.2 + 0.3cd 1.8 + 0.4c 1.6 + 0.2c

Rubrobacter OTU_0 3.1 + 1.8bc 0.5 + 0.6a 5.2 + 1.5c 1.3 + 0.8ab 7.7 + 3.3c 2.8 + 0.7bc

Sphingobacteriia Chitinophaga OTU_201 1.4 + 0.8c 0.4 + 0.2ac 0.4 + 0.3ab 1 + 0.5bc 0.5 + 0.5ac 0.2 + 0.2a

Ferruginibacter OTU_827 2.9 + 1.2c 1.8 + 0.7c 0.9 + 0.3ab 0.7 + 0a 1.9 + 0.5c 1.6 + 0.3bc

Niastella OTU_624 0.2 + 0a 0.5 + 0.3b 1.1 + 0.3d 0.9 + 0.3cd 0.5 + 0.1bc 0.6 + 0.2bd

Terrimonas OTU_444 0 + 0a 0 + 0a 0.6 + 0.3c 0.1 + 0ab 0.4 + 0.1c 0.2 + 0.1b

Haliscomenobacter OTU_1954 1.8 + 0.8c 2.2 + 1.7c 0.3 + 0.1a 0.2 + 0a 1.3 + 0.6bc 0.6 + 0.1ab

Pedobacter OTU_183 1.1 + 0.6c 1.1 + 1.2bc 0.1 + 0.1a 0.2 + 0.1ab 0.3 + 0.2ab 0.3 + 0.1ac

Bacilli Bacillus OTU_32 0.9 + 0.5c 0 + 0a 0.2 + 0.1b 0.2 + 0b 0.3 + 0.1b 0.2 + 0.1b

Clostridia Unclass_Lachnospiraceae OTU_199 2.9 + 0.7c 1.3 + 0.4a 3.1 + 0.6c 1.6 + 0.3ab 3.5 + 0.8c 2.4 + 0.4bc

Unclass_Ruminococcaceae OTU_364 1.2 + 0.1b 0.6 + 0.2a 1.3 + 0.1b 1.5 + 0.3b 1.9 + 0.6b 1.3 + 0.4b

Gemmatimonadetes Gemmatimonas OTU_265 0.5 + 0.2ab 0.4 + 0.1a 1.3 + 0.2d 0.7 + 0.1bc 1 + 0.3cd 0.7 + 0.1bc

Alphaproteobacteria Asticcacaulis OTU_12 3.1 + 0.5b 5.5 + 5.2b 0.7 + 0.5a 0.8 + 0.2a 2 + 1.4ab 1.7 + 0.6ab

Brevundimonas OTU_590 0.2 + 0.1ab 0.2 + 0.1a 0.4 + 0.1bc 0.5 + 0.1c 0.8 + 0.4c 0.6 + 0.1c

Bradyrhizobium OTU_10 2.1 + 0.6bc 1 + 0.3a 2.3 + 0.4c 2.4 + 0.2c 1.7 + 0.6bc 1.4 + 0.2ab

Ochrobactrum OTU_669 0.3 + 0.1a 0.3 + 0.1a 0.7 + 0.1b 0.8 + 0bc 0.9 + 0.2bc 1 + 0.2c

Devosia OTU_93 1.5 + 0.2ab 1.2 + 0.4a 2.6 + 0.5c 2.4 + 0.3c 2.3 + 0.3bc 2.3 + 0.5bc

OTU_255 1.5 + 0.2c 0.9 + 0.1b 0.7 + 0.1b 0.4 + 0a 1.5 + 0.2c 1.2 + 0.3c

OTU_244 0.3 + 0.1a 0.4 + 0.2a 0.7 + 0.3bc 0.4 + 0.1a 1.1 + 0.1c 0.5 + 0ab

Rhizobium OTU_173 2 + 0.7c 1.1 + 0.5bc 0.3 + 0.1a 1.1 + 0.4bc 0.6 + 0.2ab 0.8 + 0.2b

Pseudolabrys OTU_118 0.3 + 0ab 0.2 + 0.1a 0.8 + 0.1c 0.8 + 0.1c 0.4 + 0.2b 0.4 + 0.1b

OTU_1424 0.3 + 0.2b 0.2 + 0a 0.9 + 0.1d 0.6 + 0.1cd 0.4 + 0.1bc 0.4 + 0.1b

Unclass_Rhodospirillaceae OTU_108 0.4 + 0.1b 0.1 + 0.1a 1.6 + 0.3c 2.1 + 0.2c 0.3 + 0.1b 0.3 + 0b

Sphingobium OTU_1976 0.2 + 0.2a 0.9 + 0.9b 0.2 + 0ab 0.3 + 0.1ab 0.2 + 0.1a 0.4 + 0.1ab

Sphingomonas OTU_107 1.2 + 0.2b 0.5 + 0.1a 2.5 + 0.6c 2.4 + 0.2c 1.6 + 0.5b 1.5 + 0.3b

OTU_33 1 + 0.1b 0.4 + 0.2a 2.3 + 0.2d 1.3 + 0.2bc 2.2 + 0.4cd 1.4 + 0.2bc

OTU_2099 1.1 + 0.3b 0.4 + 0.1a 1.4 + 0.3bc 2 + 0.2c 0.9 + 0.1b 1.3 + 0bc

Betaproteobacteria Ralstonia OTU_1 0 + 0a 35.8 + 15.7b 0 + 0a 0.1 + 0.1a 0 + 0a 0.1 + 0.2a

Acidovorax OTU_296 0.2 + 0.1a 0.2 + 0.2a 0.8 + 0.1b 0.8 + 0.1b 1 + 1b 0.5 + 0.2ab

Massilia OTU_100 4 + 2.1b 3.5 + 4.3ab 1 + 0.1a 2.4 + 1ab 1.2 + 0.5ab 2.9 + 1.6ab

Shinella OTU_16 5.1 + 1.7b 4.1 + 0.5b 2.5 + 0.5a 8.6 + 1.6c 2.4 + 0.4a 4.7 + 0.9b

GammaproteobacteriaUnclass_Enterobacteriaceae OTU_2015 3.2 + 1.2c 0.5 + 0.4a 3.2 + 0.6c 1.2 + 0.5b 4.1 + 1.2c 1.7 + 0.2bc

Dyella OTU_968 1.1 + 0.7b 0.2 + 0.1a 0.3 + 0.1a 0.2 + 0.1a 0.1 + 0a 0.1 + 0.1a

OTU_1223 0.5 + 0.1b 0.1 + 0a 0 + 0a 0.1 + 0a 0.1 + 0.1a 0.1 + 0.1a

Rhodanobacter OTU_282 9 + 2.7c 2.2 + 0.6b 0.7 + 0a 1.2 + 0.2ab 1.3 + 0.6ab 1.6 + 0.5b

Rudaea OTU_278 0.7 + 0.2bc 0.5 + 0.2b 0 + 0a 0 + 0a 1 + 0.5c 0.7 + 0.2bc

Verrucomicrobiae Luteolibacter OTU_168 0.1 + 0a 0 + 0a 0.5 + 0.2bc 0.3 + 0.1b 0.6 + 0.3c 0.3 + 0.1bc

www.julius-kuehn.de

R. solanacearum and antagonists CFU counts 14 days post infection. Samples sharing the same letter had no significant differences in the B3B counts.

Monitoring B3B and antagonist´s CFU countsin the rhizosphere

The development of wilting symptoms recorded 14 dpi showed that 19 out of 32

TCR plants (59%) were collapsed

Only 6 out of 32 plants (18.8%) were collapsed in treated plants

www.julius-kuehn.de

R. solanacearum gene copy numbers determined in total community DNA from tomato rhizosphere and shoot samples by qPCR

www.julius-kuehn.de

Colonization patterns of P. fluorescens P142Micro-colonies could be observed along the root surface while the endophytic life style of P-142 isolate was observed as the ability to colonize and invade the epiphytic root cells as well as xylem vessels

www.julius-kuehn.de

Summary

Different soil types and plant spheres harbor different proportions and diversity of antagonists

Plants select bacteria with potential biocontrol activity and the highest proportionof antagonists was observed in the endophytic compartments

Strong reduction of wilting symptoms and B3B abundance in the rhizosphere of tomato plants inoculated with the antagonists revealed byplating, qPCR, Southern blot hybridization and amplicon sequencing

Gfp-positive P-142 were detected in lateral roots, root hairs and epidermal cells and within xylem vessels

Amplicon sequencing of 16S rRNA gene fragments amplified from total community DNA revealed pronounced treatment dependent shifts in bacterial communities in the tomato rhizosphere and numerous dynamictaxa in response to B3B or the inoculants were identified

However, B3B was detected in low numbers in the stem of healthy lookingtomato plants inoculated with P142 indicating latent infections

www.julius-kuehn.de

Enhanced plant growth in soil under reduced P supply through microbial inoculants and microbiome shifts

Namis Eltlbany1,2,3, Mohamed Baklawa2,3, Ding Guochun4, Nino Weber5, Günter Neumann5, Samuel Jacquiod6 and Kornelia Smalla2

1Abitep GmbH, Glienicker Weg 185, 12489 Berlin, Germany.2Julius Kühn-Institut, Federal Research Centre for Cultivated Plants (JKI), Institute for Epidemiology and Pathogen Diagnostics, 38104 Braunschweig, Germany3Suez Canal University, Faculty of Agriculture, Ismailia, Egypt.4College of Resources and Environmental Science, China Agricultural University, Beijing 100193, People's Republic of China.5Agroécologie, UMR1347, INRA Centre Dijon, Dijon, France

www.julius-kuehn.de

Aims of the experiments

Monitoring biostimulants in rhizosphere and bulk soil

• Development and establishment of methods to detect BEs(qPCR, CLSM, selective plating)

• Determination of the ability to colonize the rhizosphere ofinoculated tomato and maize plants (rhizocompetence)

Effect of different biostimulants applications on:

• Plant performance• The accumulation of the nutrients in maize and tomato plants.• Plant-associated microbial communities in rhizosphere and

bulk soil.

www.julius-kuehn.de

B1: Trianum PB2: ProradixB3: Bacillus amyloliquefaciens FZB42 (FB01 mut1)B4: Pseudomonas sp. RU47

1

2

3

4

5

6

7

8

2 Weeks 3 Weeks 4 Weeks 6 Weeks

Log

CFU

/ g fr

esh

root

s

Sampling time

Best rhizosphere competence observed for BE3 (FZB42) and BE4 (RU47) was observed in the rhizosphere of tomato and maize plants

1

2

3

4

5

6

7

8

2 weeks 3 weeks 4 weeks 6 weeks

Log

CFU

/g fr

esh

root

s

Sampling time

Tomato Maize

Rhizocompetence of inoculants followed by selective plating

Effect of microbial biostimulants on the plant growth andindigenous rhizosphere communities of maize andtomato plants grown in soil with reduced P-fertilization

www.julius-kuehn.deBacillus amyloliquefaciens FZB42 (FB01 mut1)

Confocal laser scanning microscopy

Pseudomonas sp. RU47

Root colonization patterns of inoculants followed by

www.julius-kuehn.de

B0: controlB1: Trianum PB2: ProradixB3: B. amyloliquefaciens FZB42(FB01)B4: Pseudomonas sp. RU47

B0

B1

B2

B3

B4

B0

0

1

2

3

4

B0 B1 B2 B3 B4

Plan

t dry

wei

ght (

g)

BEs application

Tomato

0

2

4

6

8

10

12

B0 B1 B2 B3 B4Pl

ant d

ry w

eigh

t (g)

BEs application

Maize

a aa

b bcc

c cd

B4 (RU47) and B3 (FZB42) increased significantly the growth oftomato and maize.

B1

B2

B3

B4

All bacterial inoculants promoted the growth of tomato and maize.

What is the effect of different inoculants onplant growth six weeks after sowing?

www.julius-kuehn.de

Analysis of macro-nutrients (P, Mg, Ca and K)in maize plant shoots

0

5

10

15

20

25

30

35

40

45

50

B0 B1 B2 B3 B4

Mac

ro-n

utrie

nts

conc

entr

atio

ns in

mg

/ pla

nt

shoo

t dry

mat

ter

Treatments

PMgCa

0

50

100

150

200

250

300

350

400

450

B0 B1 B2 B3 B4

Mac

ro-n

utrie

nts

conc

entr

atio

ns in

mg

/ pla

nt

shoo

t dry

mat

ter

Treatments

K

B0: controlB1: Trianum PB2: ProradixB3: Bacillus amyloliquefaciensB4: Pseudomonas sp. RU47

aabbc

c

ab

cd

e

a

bbc

cd

a

abbcc

d

The accumulation of the macro-nutrients in the shoot dry matterincreased significantly in all biostimulants applicationP increased significantly only in the treatments with bacterialbiostimulant application.

www.julius-kuehn.de

B0: controlB1: Trianum PB2: ProradixB3: Bacillus amyloliquefaciensB4: Pseudomonas sp. RU47

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

B0 B1 B2 B3 B4

Mic

ro-n

utrie

nts

conc

entr

atio

ns in

mg

/ pla

nt s

hoot

dr

y m

atte

r

Treatments

MnFeZn

Analysis of micro-nutrients in maize plant shoot

a ab bcc

a

a

a

aa

aab

bc cd

The accumulation of the Zn in the shoot dry matter increased significantly

by inoculation of biostimulants

The application of all bacterial biostimulans tended to increase Fe accumulation

The application of B3, B4 and B1 increased significantly the accumulation of Mn.

www.julius-kuehn.de

Significantly higher relative abundance of Gammaproteobacteria, Alphaproteobacteria and Bacteroidetes (Cytophagia and Sphingobacteria) in maize rhizosphere microbiomes was observed

The relative abundance of Actinobacteria, Firmicutes (Clostridia and Bacilli), Gemmatimonadetes, Planctomycetes and Nitrospira was higher in the bulk soil.

Principal component analysis (PCA) of the prokaryotic communities in maize rhizosphere and bulk soil

www.julius-kuehn.de

Taxonomic distribution of the sequences belonging to OTUs significantly promoted by each BEs at each week.

www.julius-kuehn.de

Summary

High rhizosphere competence correlated with plant growth promotion

Biostimulants increased plant growth and nutrient accumulation

Time dependent changes of the rhizosphere microbiome composition farmore pronounced than the microbiome shifts caused by the inoculatedbiostimulants

Complex and dynamic rhizosphere microbiome shifts were biostimulantstrain and growth stage dependent

High application potential for a bio-based agriculture in particular in soilwith reduced P-fertilization

www.julius-kuehn.de

Soil type, plant species, plant growth stage; the cultivar might influence the plant microbiome but also the ecology of the inoculants and pathogens

The plant and its microbiome in the rhizosphere

PGPR/antagonist Pathogen

The mode of action of microbial inoculants

Inoculants act through several modes of action

Inoculants interact with the plant, its microbiome and the pathopogens through: phytohormons, nutrients; induced resistance but they cause also shifts of the indigenous microbiome through antibiotics, QS, VOCs or enzymes

www.julius-kuehn.deAG Smalla & guests 21 June 2017

www.julius-kuehn.de

Control ARD

The soil and itsmicrobiome matter!!!

Thanks to the teams involvedin the projects!

Thanks you for your attention!