Impact of biocontrol plants on bacterial wilt and

non-targeted soil microbial communities

on a naturally infested soil

Sire Diedhiou-Sall, Paula Fernandes, Peninna Deberdt, Sonia Minatchi,

Régine Coranson-Beaudu, Benjamin Perrin, Eric Gozé, Alain Ratnadass

and Richard P Dick

GRDC

-

EUROSOIL Congress, 2 6 July 2012, Bari, Italy

Bacterial wilt is a serious tomato disease caused by Ralstonia solanacearum • A soilborne and vascular

disease caused by a β-proteobacteria, Gram –

• Worldwide distribution, tropical , subtropical and warm­temperate regions

• More than 250 host species including many economically important crops

• Quarantine organism

Bacterial wilt in Martinique

• Great economical importance

• Host plants • Solanaceous • Cucurbits • Anthurium (ornamental)

• Genetic characterization (Wicker et al., 2007; 2009)

• Historical population • Emerging population (Phyl II/seq4NP strains)

Effective methods for controlling bacterial wilt have not been developed for Rsol emerging population

The breeding of wilt-resistant cultivars is difficult owing to the complexity of host resistance characteristics

Management practices based on ecological intensification are urgently needed

Increasing demand for environmentally-friendly practices in agriculture

Introduction of service plants having biocontrol capacities

EUROSOIL Congress, 2-6 July 2012, Bari, Italy�

Conservation / facilitation of action of aerial natural enemies

Provision of alternate food resources

Provision of refugia/shelter

Microclimate alteration

Physical obstruction

Stimulant diversion

Deterrent diversion

Resource dilution

Disruption of the spatial cycle

Disruption of the temporal cycle

Allelopathy

Physiological resistance

Specific soil suppressiveness

General soil suppressiveness

Enhancement of diversity / activity of soil biota

Major pathways for reducing the impact of pests & diseases via the introduction of plant

species diversity in agroecosystems

from Ratnadass, Fernandes, Avelino and Habib, 2012 with courtesy of Agronomy for

Sustainable Development, open access

Veg

etat

iona

l div

ersi

ficat

ion

Ind

ire

ct

Dir

ect

Reduced im

pact of pests & diseases

Integrated approach set up�Farmers inquiry all over the island

Establishment of acceptance criteria and

selection of functional traits expected

Multisite evaluation of

agronomical behaviour Host status of candidate plants Evaluation of biocidal effect

Evaluation of sanitizing Fields

potential

Multicriteria selection

Evaluation under greenhouse : determination of active

phase and impact on BWI, soil communities and

functions

2006

Climatic

chamber

+ Laboratory 2009

2007

2008

2010

2010

2011

2012

2013

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EUROSOIL Congress, 2 6 July 2012, Bari, Italy

Selecting candidate plants

• Farmers’ requirements • Expected functional traits

Short cycle lenght

Seeds easy to find

and cheap

Hability to control weeds

Non host status

Bactericidal coumpounds

Easy to manage

and destroy

Not suitable for snakes

Rusticity

No negative impact on

soil functions and

communities

Stimulation of soil

suppressiveness

6 plants tested under greenhouse on a

naturally infested soil�

- Allium fistulosum

- Tagetes patula

- Raphanus sativus cv. Melody

- Mucuna deeringiana « Singapour»

- Crotalaria spectabilis

- Crotalaria juncea cv. IAC-1

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EUROSOIL Congress, 2 6 July 2012, Bari, Italy

Management of experiments and methods

Day 0

S0

S0 S2 S3

Pot A Pot B Pot C

Exp 1 : Long cycle (70 days)

Exp 2 : Short cycle (42 days)

Day 70Day 80

Day 42 Day 52

Maintaining R. solanacearum with

tomato plants

Field collected soil

Day 0

Pot D

Pot A Pot B Pot C Pot D

S1

S1

Day 21

Day 35 1 container

1 container

A

B

C

D

Following bacterial

wilt incidence

Quantifying enzymes

activity Following PLFAs Quantifying mineral N

Root and shoot biomass

Effect of biocontrol plants on BWI�a a

0

20

40

60

80

100

% D

isea

se in

cid

ence

End of plant life cycle 10 days after soil amendment

d

cd

b

bc

b

bc

bc

cd

bcd

bcd

bcd

bcd

cd

dcd

d

b

Initial

disease

level

(44,44%) cd

Control Mucuna Mucuna Crotalaria Crotalaria Crotalaria Crotalaria Allium Allium Tomato (bare soil) deeringiana deeringiana juncea FD juncea DD spectabilis spectabilis fistulosum fistulosum

FD DD FD DD FD DD

• 61 % with C spectabilis End of plant cycle

• 51% with C juncea

10 j after incorporation A • 58% avec C juncea

Effect of biocontrol plants on BWI�End ofplant life cycle 10 days after soil amendment

A a aAab

0

20

40

60

80

100

% D

isea

se in

cid

ence

A

A

A A

bc

bc c

Initial

disease level

(82.22 %)

No significant effect on reduction of BWI in 42D plants B

BCP impact of enzymes and N – 70D

Treatment Arylsulfatase Chitinase FDA NH4 + Plant biomass

S2 S3 S2 S3 S2 S3 S2 S3 above-

ground

below-

ground

μg pNP h-1g-1 μg FDA h-1g-1 μg N g-1 mg dw

M. deeringiana

FD 31.9c 48.5abc 23.7abc 32.7cd 49.7ab 254.7cd 4.6bc 0.9d 197.9ab 30.7ab

DD 42.4ab 49.6abc 30a 53.5ab 79.3ab 418.5ab 1.7cde 0.2d 292.9a 44.8a

C. juncea

FD 34.5c 38.7abc 23.7abc 37bcd 86.9ab 287.5bcd 4.3bc 9.5abc 46.7e 10.3d

DD 34.8bc 55.9abc 22.5abc 55.5a 59.8ab 432.3ab 5.3bc 11.1ab 71.9de 18.8c

C. spectabilis

FD 34.1c 51.6abc 25.5ab 63.5a 44.6b 495.5a 2.4de 1.5d 84.8cd 18.7c

DD 45.8a 52.4ab 29.8a 57.3a 43.5b 444.4a 2.2e 5.1bc 125.5bc 25.9bc

A. fistulosum

FD 44.3a 45.6bdc 16.9c 26.7d 102.9a 207.7de 6b 18.2a 14.3f 1.3f

DD 39.6abc 42.8dc 20.4bc 20.9d 64.7ab 163.8e 3.8bcde 4c 19.2f 3.4e

Tomato 44.5a 46.1bcd 18.6bc 46.8abc 83.2ab 363.4abc 5.2bcd 10.3abc 1.5g 0.5g

Control 35.6bc 37.4dc 18.9bc 36.1cd 108.1a 281.7cd 11.5a 24.5a 0h 0g

Values in the same column with the same letters are not significantly different (LSD, p<0.05)

BCP impact of enzymes and N – 42D

Treatment Arylsulfatase Chitinase FDA NH4

+ Plant biomass

S2 S3 S2 S3 S2 S3 S2 S3 above-

ground

below-

ground

μg pNP h-1g-1 μg FDA h-1g-1 μg N g-1 mg dw

T. patula

FD 35.6a 36.3ab 13.2bc 19.9ab 71.5bc 154.8ab 15abc 9.7bc 7.8b 1.2bc

DD 39.9a 38.7ab 14.5abc 18.9b 76.7abc 145.8ab 11.3bc 4.9d 13a 2.5a

R. sativus

FD 38.8a 38.8ab 16.3ab 18.8b 96.6ab 146.5b 9.9bc 9.3bc 11.7ab 0.8cd

DD 40.8a 39.8ab 15.1ab 31.7a 82.6ab 245.4a 6.1c 5.1cd 14a 1.5b

Tomato 39.2a 41.7a 11.7c 27.4ab 81.8c 213.8ab 36.5a 14.1ab 2.3c 0.5d

Control 39.6a 31.3b 16.7a 22.7ab 94.1a 175.7ab 26ab 22.6a 0d 0e

Evolution of PLFA on 70D cycle�Actino Fungi Gram+ Gram-

b b b b

b

a a

a a

bc

cd d

abc

cd

bc

ab

cde cde

de

e

S2 : end of growing phase

S3 : 10 days after incorporation

PLFA with plant biomass

(G+, G- and tot PLFA)

Fungi (M deeringiana and

C spectabilis)

• After decomposition�• Highest G+, G-, actino,

fungi, tot PLFA : M

deeringiana and C

spectabilis

• G-, actino and totPLFA :

C juncea

• G+ pour A fistulosum�

PLF

A (

nm

ol/

g s

ol

sec)

20

18

16

14

12

10

8

6

4

2

0

0

2

4

6

8

10

12

14

16

18

20

PLF

A (

nm

ol/

g s

ol

sec)

Actino

Fungi

Gram+

Gram-

S2 : end of growing phase S3 : 10 days after incorporation

bc c

c

c

a

bc

a a a

a

ab

Evolution of PLFA on 42D cycle

Higher G+, G,

actino and tot

PLFA : R sativus

After

decomposition

:

• Higher G+,

G-, actino

and totPLFA

: R sativus

and control

Links between BWI, microbial communities and�soil enzymes at S2

Observations (axes F1 et F2 : 54,33 %) Bact/Fungi

6

4

2

T1

T1

T1

T2

T2

T2

T3

T3

T3

T4

T4

T4

T5

T5

T5T6

T6

T6

T7

T7

T7

T8

T8

C spectabilis

T8

T9

T9

T9

T10

T16 T10T10T11

T16 T11T11

T12T15T12

T12

B-glucosidase T13

T13

T13T14

T14

T14

T15

T15

T16

-10 -8 -6 -4 -2 0 2 4 6 8 10

A fistulosum

C juncea

M deeringiana

BWI

NO3

Non wilted tomato

BWI

G-

G+

Fungi 0

Actino

Chitinase

Biomass -2

-4

-6

F2

(1

6,4

4 %

)�

F1 (37,88 %)�

Links between BWI, microbial communities and�soil enzymes at S2�

Observations (axes F1 et F2 : 54,33 %) Bact/Fungi

6

4

2

T1

T1

T1

T2

T2

T2

T3

T3

T3

T4

T4

T4

T5

T5

T5T6

T6

T6

T7

T7

T7

T8

T8T8

T9

T9

T9

T10

T16

C spectabilis

T10T10T11

T16 T11T11

T12T15T12

T12

B-glucosidase T13

T13

T13T14

T14

T14

T15

T15

T16

-10 -8 -6 -4 -2 0 2 4 6 8 10

A fistulosum

C juncea

M deeringiana

BWI

NO3

Non wilted tomato

BWI

G-

G+

Fungi 0

Actino

Chitinase

Biomass -2

-4

-6

F1 (37,88 %)

F2

(1

6,4

4 %

)�

Links between BWI, microbial communities and�soil enzymes at S3�

Observations (axes F1 et F2 : 56,82 %)

4

2

T1

T1

T1

T2

T2

T2

T3

T3

T3

T4

T4

T4

T5

T5

T5

T6

T6

C juncea

T6

T7

T7 T7

T8 T9

T8

T8

T9

T9

T10

T10 T10

T14 T14

T11

T11T11 T12

T12

T12

T13 T13

T13 T14

T15 T15 T16T16

T15 T16

-8 -6 -4 -2 0 2 4 6 8

F2

(1

5,1

5 %

)

A fistulosum

C spectabilis

M deeringiana

BWI

NO3

BWI

Fungi

Bact/Fungi

G-0 Actino

Chitinase

B-glucos.

FDA -2

Biomass

NH4

-4

-6

F1 (41,67 %)

Factors associated with stimulation or reduction of BWI�

End of plant cycle�Variables BWI

Moisture 0,412

N_NH4 0,048

N_NO3 0,449

Above ground biomass -0,104

Below ground biomass -0,153

N tomato -0,879

W tomato -0,810

ifb 1

Aryl 0,242

Bgluc 0,419

Chitin -0,281

FDA 0,202

Gram­ -0,406

Gram+ -0,454

Fungi -0,192

Actino -0,352

Bact/Fun -0,044

Sat/Mono 0,410

Cy/18:1w7c -0,332

Stimulation of BWI :

high moisture,

nitrate, easily

decomposable C,

Sat/Mono

Reduction of BWI : Higher

Gram Negative and Actinos

NH4, Gram+ and root

biomass

After 10 days of

decomposition�Variables BWI

Moisture -0,042 N_NH4 -0,478 N_NO3 -0,019

Above ground biomass -0,240

Below ground biomass -0,326

N tomato -0,757

W tomato -0,688 ifb 1 Aryl -0,259 Bgluc -0,279 Chitin -0,189

FDA -0,190 Gram­ -0,386 Gram+ -0,230 Fungi 0,045 Actino -0,369 Bact/Fun -0,352 Sat/Mono -0,177

Cy/18:1w7c 0,023

Summary�

• Main BWI control occured during vegetation phase

• Rhizospheric processes involved

• Deceiving impact of plant biomass incorporation

• Mechanical operation to incorporate OM (= soil tillage)

might had a negative impact on previously built equilibrium

• PLFA were more accurate variables than enzymes

• Gram- and actinomycetes, NH4, Bact/Fun ratio

• Improvement of spatial arrangement

Perspectives • In field evaluation of BC plants efficiency

• On going experiments where mulching replaces incorporation • Research station

• Farmers’s fields on other soil types

• Optimization of the cropping system • Seeding density and agencement to maximize soil volume colonized by roots

• Plants associations

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EUROSOIL Congress, 2 6 July 2012, Bari, Italy

ACKNOWLEDGEMENTS

Thanks :

• to all my co-workers

• technicians :Alain Pelage, Jerome

Carbety, Joel Daniel, having a tough

work to run experiments

• Master students who participated

since 2006 in our project (Johan

Crance, Felix Mathurin, Marie-Ange

Lebas, Celine Caillard, Florian

Carlet…..)

Please vote for France for Eurosoil 2016

Hope to meet you there again !!

THANKS FOR YOUR ATTENTION !