Akey tosustainable managementofgrapevine resistance :acase

study with downy mildew

FrançoisDelmotte,ChloéDelmas,YannDussert,IsabelleDemeaux,SylvieRichart-Cervera,CaroleCouture,FrédéricFabre,LaurentDelièreINRABordeaux,France

• Decreasingsignificantly(>50%)thegrapevinedependencyuponfungicidesnecessarilyinvolvesa“breakthrough”.

• Inthisline,theuseofnaturalgrapevineresistance againstpathogensiscertainlythemostpromising“innovation”toreducefungicidetreatments.

Resistances arepresent innorth america whereVitisspecies havecoevolved with thepathogens

AmericanVitis spp

AsiaticVitis spp

V.vinifera

• New grapevine varieties showing low to high level ofresistance to powdery and downy mildew are nowregistrated in Europe.

• Contrary to « old interspecific hybrids », these newlybred varieties present good cultural and oenologicalfeatures.

INRAresistantcultivar(blanc) INRAcultivar (noir)V.vinifera(Merlot)

Chemicalcontrol

Moving ontowards amorebalancedcropping system

Plantmanipulation

Biological methods

Chemicalcontrol

Plantdiseaseresistance

LONG-TERM AGRONOMICAL AND ECONOMICAL PERFORMANCESOF LOW INPUT WINE-GROWING SYSTEMS

System cultivar strategy

RES Resistant variety Low-input

INT Merlot IPM

BIO Merlot ORGANIC

100m

N PlantationDensityTotalareaDesignAssesmment

20116580ceps/ha1,8ha3replicates of0,2ha• Yield• Disease prevalence• Labourtime• Costs• Wine quality• Pesticide residus

TOWARDS LOW INPUT WINE-GROWING SYSTEMS

-90%

-20%

0

2

4

6

8

10

12

14

16

Reference Organic Resistant

TreatmentFrequencyIndex

Bordeaux,2015

INRA-IJ134

• However,weneedtomakesurethattheresistanceemployednotonlyiseffective,butalsopersistsintime,despitetheconstantevolutionofpathogens.

• Thedurabilityofresistanceisespeciallyimportantinperennialspecieslikegrapevinewhicharemeanttostayinthefieldforatleast20years.

• We knowfrom results obtained inmany otherpathosystems that plantR-genes arenot« everlastings »…

Theother side ofthecoin:R-genes durability

Plantresistance genes arenot« everlastings »

What makes aresistance durable?• Thenatureofresistance genes andthe

interactionwith pathogen effectors isimportant(totalvspartialresistance)

• Theevolutionnary constrains related thethemodificationofthecorresponding avrgene inthepathogen =>theso-called‘Cost ofvirulence’

• Theevolutionnary potential ofpathogenpopulations

ü Genetic diversity,reproductivesystem,populationeffectivesizes,gene flow,etc.

❸Sporulation

❶Germination

❷Latency

25 American Vitis spp.

XIXthGrape

pathogens

Grapevine downymildew is anoomycete,Stramenopiles

Plasmoparaviticolais anativespecies fromNorth America

P.viticola attacks alargerangeofVitisspp.innorthAmerica

Rouxel etal.,Phytopathology2014

Inits nativerange,P.viticola is acomplexofseveral crytic species that arehostspecialized onwild andcultivated vitis spp.

AC

BD

Vitis spp.

1878

99

99100

P.viticolaf.sp.riparia

P.viticolaf.sp.vinifera

P.viticola f.sp.aestivalis

β-tubulin gene83haplotypes

P.viticola f.sp.quinquefolia

ØVery low geneticdifferentiation

ØFST=0,020*

Ø low butsignificant IBDatthecontinentalscale

• Ariskrelatedtore-introductionsofthepathogenintoEurope

• Efficientsexualreproduction• Largepopulationeffectivesizeandimportantgeneflowatlargegeographicalscales

Highevolutionarypotential

Bianca • Villard Blanc x Bouvier : Bianca

• Cultivated in Hongaria (<1000 ha)

• One strain of P. viticola breaks down the Rpv3 resistance…

P.viticola is evolving evolveinresponsetoplantresistancedeployment

Inoculationofhostplantswith

pathogenisolates

Pathogenlife-cyclequantitative

traitsassessment

LargescalesamplingofP.viticola isolates

Testingforpathogenadaptationtopartialresistance

Alsace-Baden

Zurich

Vaud-ValaisTessino

Sampling design--- [n=103]20locations,>20grapevine varieties

Susceptible host (V. vinifera)

…

Inoculated

ho

sts

Bronner Prior Regent Cab. sauvignon

Resistant host (n=11)

Pathogen

po

pulatio

ns

o 103 isolates * 4 plantso 412 interactions o 1545 leaf discs

o Sporangial productiono Sporangia sizeo Latent periodo Sporulation dynamicso Number of zoospore

QuantitativetraitsofpathogenicityAuniquebioassay

Diminution de l’efficacité de la résistance de la vigne contre le mildiou

-26%

-26%

-7% Naïve population49isolates from V.vinifera

Adapted population54isolates from resistantvarieties

Efficacy ofresistance (%)

Anundergoing erosion ofgrapevine partialresistance

Rpv3 Rpv3 Rpv10

Cultivarspecificity?Ageneralincreaseofaggressiveness

50

100

150

200

250

300

350

400

450

500

Bronner Prior Regent

Spor

angi

a nu

mbe

r / m

m2

(a)

10

10.5

11

11.5

12

12.5

Bronner Prior Regent Sp

oran

gium

size

(µm

)

(b) Local Foreign

2.8

2.9

3

3.1

3.2

3.3

3.4

3.5

Bronner Prior Regent

Late

nt p

erio

d (d

pi)

(c)

foreignlocal

-2

-1

0

1

2

-2 -1 0 1 2

PCA2

PCA1

from resistant host

from susceptible host

Pathogen isolates

FST =-0.0012ns

AllP.viticola isolatesweredistincts andwefoundnogeneticdifferentiationbetween

naïveandadaptedisolates

What arethegenes responsibleintheerosion ofresistance ?

• 2016 : Release of the P. viticolagenome sequence (INRA-Pv221)

• Population genomics approach by resequencing P. viticolaisolates

• Design molecular tools

Achievedurable

managementofresistantvarieties

MODELLING- Howtodeployresistance ?:Howdopathogen THVimpacttheerosion ofresistance?

- Howtheconnectivity ofthelandscape affecterosion ofresistance ?Comparestrategies :stacking,cvmixture?

CROPPINGSYSTEM– Combinepractices(fungicides,agronomical)to:§ limit theadaptationofpathogen popscomplete resistance efficacy inorder tosecure theproduction

§ controlthepathogens that arenottargetedbyresistance (i.e.blackrot)

• Plantresistance is apromising solutiontodecreasethedependancy tofungicides.

• R-genes constitute afinite ressource(11locusforPM/14locusforDM).

• Thisressourceis acommon goodthat havetobepreserved since it is limited.

• The« community »hastomanagethis ressourceinanon-selfish manner,ifwe want toavoid thecollapseofthesystem.

Thiswork hasbeenfunded by: