CHALLENGES FOR RESISTANCE BREEDING IN EUROPE

In Europe, high incidence of clubroot is noted in Central Europe, including Poland, Germany, France

and Czech Republic. Infection causes

yield reduction of 50 % and more.

Introduction of clubroot resistant

rapeseed cv. Mendel to the European

market in 2000 helped farmers to

cultivate rapeseed even on infested

fields. Today‘s new clubroot-resistant

varieties possess better seed yield and agronomic characteristics and demonstrate the potential of

plant breeding for a better control of the disease. Almost all commercial clubroot resistant

rapeseed varieties carry the Mendel-resistance.

P. brassicae possesses 8 different pathotypes (according to SOMÉ et al. 1996). Resistance of Mendel

is successful against P1, P2, P3 and P5. Cultivation of rising acreages of resistant varieties disclose

increasing resistance breaks in Europe (ZAMANI-NOOR 2015). For successful breeding, monitoring

and pathotype identification of P. brassicae is of high value.

RESULTS

Experiment 1: Monitoring of clubroot spreading

In this study occurrence of clubroot infection in commercial fields was mapped for Germany, Poland

and Czech Republic (Fig. 2). The map shows high clubroot infestation for North-East Germany, North

and South-West Poland and North and Central of Czech Republic. For France clubroot monitoring is

shown from the studies conducted by CETIOM.

Infection:

Fig. 2: Map of clubroot infected regions in Central Europe

Experiment 2: Pathotype identification

Example for presence of pathotype P3 according to SOMÉ et al. 1996 (Tab. 1): Cvs. Nevin and

Wilhelmsburger show no clubbed roots but roots of cv. Brutor are highly damaged by P. brassicae.

Fig. 3: Results of pathotype identification (Disease Index) Fig. 4: Pattern of damage on examined varieties

Example for presence of pathotype P3 that breaks Mendel-resistance: Also both control varieties

show damage on their roots. DI of these varieties are often higher than DI of cv. Brutor.

DISCUSSION & CONCLUSION Monitoring of clubroot disease spreading was carried out in Germany, Poland and Czech Republic.

These results add to existing monitorings (DIEDERICHSEN 2013, DIXON 2009, ZAMANI-NOOR 2015).

Knowledge on geographic dispersion of clubroot is important due to ongoing expansion of the

disease. Further studies will be necessary in the future.

Results of pathotype identification show, that plants were infected by P. brassicae pathotype P3.

Infection of variety with Mendel-resistance implies, that the pathogen was able to break resistance.

Today, we also find pathotypes which are declared as P1 or P3 but, however, can break Mendel-

resistance as well (ZAMANI-NOOR 2015). These pathotypes are not observed by the differential set of

SOMÉ et al. 1996. Integrating Mendel to this differential set would make future identification of

pathotypes more precise.

Today, it is the challenge for European breeders to detect new sources of resistance against

clubroot and to introduce them in new competitive rapeseed varieties. For better disease control,

monitoring of clubroot and identification of P. brassicae pathotypes is of high importance.

REFERENCES CETIOM (2015): http://www.terresinovia.fr/colza/cultiver-du-colza/maladies/hernie/

DIEDERICHSEN (2013): Clubroot in Germany and Europe. International Clubroot Workshop. Edmonton, Canada. June 2013.

DIXON (2009): The Occurrence and Economic Impact of Plasmodiophora brassicae and Clubroot Disease. J Plant Growth Regul 28, p. 194-202.

SOMÉ et al. (1996): Variation for virulence on Brassica napus amongst Plasmodiophora brassicae collections from France and derived single-spore isolates. Plant Pathol45 (3), p. 432-439.

ZAMANI-NOOR (2015): Verbesserung der Resistenz von Winterraps gegen Plasmodiophora brassicae unter Feldbedingungen.

DPG Arbeitskreis Raps. Braunschweig, Germany. February 2015.

CONTACT

Benedikt Flecke // benedikt.flecke@syngenta.com // Zum Knipkenbach 20, 32107 Bad Salzuflen, Germany

Clubroot Disease in Rapeseed – A Persistent Challenge thanks to Varying Pathotypes

Benedikt Flecke1, Johan De Dobbelaere2, Michaela Wille1, Becke Strehlow3, Stephan Pleines1

1Syngenta Seeds GmbH, Germany - 2Syngenta ICS Commercial Unit, Belgium – 3University of Rostock, Germany

10

15

20

25

30

35

40

Resistant varieties Susceptible varieties

Yie

ld (

in d

t/h

a)

CLUBROOT AT A GLANCE • Pathogen: Plasmodiophora brassicae

• Symptoms: Root thickening and subsequent gall formation

• Soil-borne disease of high importance for Brasssica crops

• Prevalent on every continent

• Virulence of pathotypes differs against varying host plants

• Resistance breeding is a strong option for disease control

Fig. 1: Seed yield of resistant and susceptible varieties on clubroot infested soil

Old

var

iety

New

var

iety

New

var

iety

New

var

iety

CETIOM 2015

low moderate high no low medium high no yes

ABSTRACT

Clubroot, caused by Plasmodiophora brassicae, is an important disease of Brassica crops in Europe.

Resistance breeding is a powerful tool to control the disease. Due to ongoing spreading, monitoring

of clubroot occurrence becomes very important. During the last years, increasing incidence for

resistance breaks were determined. Adapting differential sets for pathotypes will enable for more

precise identification.

MATERIALS & METHOD

Experiment 1: Monitoring of clubroot spreading

Farmers in Germany, Poland and Czech Republic took soil sample from their fields. At University of

Rostock the bioassay was conducted under greenhouse conditions on 35 seedlings of susceptible B.

napus (cv. Visby) used for each soil sample. Control plants were transplanted into pots filled with

soil mix without resting spores. Symptoms were assessed after 6 weeks. Disease rating was

recorded on a scale from 0 to 3, with 0 = no disease and 3 = main root heavily clubbed.

Experiment 2: Pathotype identification

Due to specific host-pathogen interaction it is possible to classify pathotypes. For pathotype

identification, clubs of a resistant variety collected in South Germany were examined. From each

club one pathogen suspension was produced. According to SOMÉ et al. 1996, B. napus cvs. Nevin,

Wilhelmsburger and Brutor were infected to identify the prevalent pathotype.

resistant susceptible

Tab. 1: Pathotype identification according to SOMÉ et al. 1996

For control pathotype identification with Mendel-resistance and susceptible cv. Visby was also

conducted. Disease rating was recorded on a scale from 0 to 5, with 0 = no disease and 5 = main

root heavily clubbed. Disease Index (DI) was determined by:

DI (%) = Σ(n∗0+n*1+n*2+n*3+n*4+n*5)*100 / N*5

Per definition a DI of > 25 % detects varieties as susceptible.

Variety P1 P2 P3 P4 P5 P6 P7 P8

Nevin

Wilhelmsburger

Brutor

0

10

20

30

40

50

60

70

80

DI (

in %

)

Undersowing oilseed rape with various crop mixtures: what benefits for farmers?

A. Baux

1, S. Breitenmoser

1, N. Courtois

2

1Agroscope, Route de Duillier 50, 1260 Nyon, Switzerland 2Agrigenève, Rue des Sablières 15, 1242 Satigny, Switzerland

Oilseed rape (OSR) is the first oilseed produced in Switzerland. It is well adapted to the Swiss climate and is

considered as an important crop. Its production is intensive with high fertilization and crop protection. However,

in Switzerland, nitrogen fertilization is limited within the farm and the will to reduce phytosanitary treatment led

to new subsidies for crop management without herbicides, insecticides or fungicides.

Intercropping OSR with various living mulches was tested as a solution to reduce fertilization and pesticides.

Various mixtures, consisting of frost-sensitive or frost-tolerant, legumes or non-legume species, were tested on

farm since 2011. Weed cover and yield were registered during 6 years. An additional experiment in a split plot

design was set up to assess the impact of these associations on pest damages and nitrogen nutrition. The plants

were grown with no insecticide and only the control plots were treated with herbicide. Fertilization level were

either “normal”, calculated with the “réglette azote”, or reduced.

The variability among years was large for all the measured parameter, and the differences among treatments

were seldom significant. Competition between OSR and additional species resulted in lower OSR biomass in

winter, but this was compensated in spring, and did not lead to any yield reduction. Adult flea beetles caused

slightly more damages on the cotyledons and the first leaves of sole OSR, but no significant difference could be

found among treatments for the amount of larvae per plant, more related to the total OSR biomass in autumn.

Finally, the reduction of nitrogen fertilization did not result in significant yield loss in most years. However, our

data showed that the yield gap between high and low fertilization was generally reduced when OSR was sown

with companion plants, especially when the mixture consist of a majority of legumes.

Growing OSR as a sole crop or with companion plants led to very similar yields. In most years, undersowing

allowed OSR to reach satisfactory grain yield in spite of pesticides and fertilization reduction. In the practice,

this technique is booming in Switzerland, promoted by the agricultural policy. Nevertheless, more knowledge is

still needed to define long term benefits of undersowing, and propose a better adapted management system.

Keywords: oilseed rape, intercropping, living mulches, nitrogen fertilization, flea beetle, low-input cropping

systems