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
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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 warm
temperate regions
• More than 250 host species
including many economically
important crops
Bacterial wilt in Martinique
•
Great economical
importance
•
Host plants
•
Solanaceous
•
Cucurbits
•
Anthurium (ornamental)
•
Genetic characterization
(Wicker et al., 2007; 2009)
•Historical population
•Emerging population
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
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
V e g e ta ti o n a l d iv e rs if ic a ti o n In d ir e ct D ir e ct R e d u c e d im p a c t o f p e s ts & d is e a s e s
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�
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Allium fistulosum
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Tagetes patula
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Raphanus sativus cv. Melody
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Mucuna deeringiana « Singapour»
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Crotalaria spectabilis
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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 a0 20 40 60 80 100 % D is e a s e in c id e n c e
End of plant life cycle 10 days after soil amendment
d cd b bc b bc bc cd bcd bcd bcd bcd cd d cd 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
Effect of biocontrol plants on BWI�
End ofplant life cycle 10 days after soil amendment
A a A a ab 0 20 40 60 80 100 % D is e a s e in c id e n c e A A A A bc bc c Initial disease level (82.22 %)
No significant effect on reduction of BWI in 42D plants
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
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� P LF A (n m o l/ g so l se c) 20 18 16 14 12 10 8 6 4 2 0
0 2 4 6 8 10 12 14 16 18 20 P LF A (n m o l/ g so l se c) Actino Fungi Gram+
Gram-S2 : end of growing phase S3 : 10 days after incorporation
b c 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 T5 T6 T6 T6 T7 T7 T7 T8 T8 C spectabilis T8 T9 T9 T9 T10 T16 T10T10 T11 T16 T11T11 T12 T15T12 T12 B-glucosidase T13 T13 T13 T14 T14 T14 T15 T15 T16 -10 -8 -6 -4 -2 0 2 4 6 8 10 A fistulosum C juncea M deeringiana BWI NO3Non wilted tomato
BWI G-G+ Fungi 0 Actino Chitinase Biomass -2 -4 -6 F 2 (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 T5 T6 T6 T6 T7 T7 T7 T8 T8 T8 T9 T9 T9 T10 T16 C spectabilis T10 T10 T11 T16 T11T11 T12 T15T12 T12 B-glucosidase T13 T13 T13 T14 T14 T14 T15 T15 T16 -10 -8 -6 -4 -2 0 2 4 6 8 10 A fistulosum C juncea M deeringiana BWI NO3Non wilted tomato
BWI G-G+ Fungi 0 Actino Chitinase Biomass -2 -4 -6 F1 (37,88 %) F 2 (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 F 2 (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
•
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
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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
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