Federal Department of Economic Affairs,Education and Research EAER

Agroscope

www.agroscope.ch I good food, healthy environment

19.07.2016

Susceptibility of potato cultivars to powdery scab (caused by Spongospora subterranea)

Brice Dupuis, Ruedi Schwaerzel, Jean-Marie Torche, Theo Ballmer, Thomas Hebeisen

2Powdery scab workshop | Einsiedeln: 17th July-20th July 2016Brice Dupuis, Ruedi Schwaerzel

Material and method

� Total number of field trials: 50� Locations: � La Fretaz (Bullet, VD) 1’202m a.s.l.� Wallestalden (Langnau, BE) 950m a.s.l� Reckenholz (Zürich, ZH) 443m a.s.l

� Years: 2004 to 2015� Cultivars:� 212 cultivars tested� Cv. Agria, Bintje, Lady Felicia and Lady Claire were used as

controls� Sampling at harvest� Nb. of tubers: 100/variety and trial

3Powdery scab workshop | Einsiedeln: 17th July-20th July 2016Brice Dupuis, Ruedi Schwaerzel

M&M: locations of trials

Wallestalden

Reckenholz

La Frêtaz

4Powdery scab workshop | Einsiedeln: 17th July-20th July 2016Brice Dupuis, Ruedi Schwaerzel

M&M: observations

� Percentage of tubers with scabs

� Assessment of the scabs on the tubers� 0 = non tumors� 1 = 1 or 2 tumors� 2 = 3 - 10 tumors� 3 = >10 tumors� 4 = >many tumors

� Calculation of the tubers infection index:� ��������� � ∑������ ∗ �. �������

5Powdery scab workshop | Einsiedeln: 17th July-20th July 2016Brice Dupuis, Ruedi Schwaerzel

M&M: selection of trials

� Tuber symptoms observed out of 50 field trials

� Rejection of the trials in which:� No tubers of Bintje are showing symptomsand/or� No tubers of Lady Claire are showing symptoms

� Rejection of control varieties presenting aberrant results(visual observation of the linerar regression)

6Powdery scab workshop | Einsiedeln: 17th July-20th July 2016Brice Dupuis, Ruedi Schwaerzel

M&M: resistance of the control cv.

� Classification following a 9 grades scale of resistance: very low (9); very low to low (8); low (7); low to medium (6); medium (5); medium to high (4); high (3); high to very high (2); very high (1)

� Calculation of the resistance of all control cultivars using the equation of the linear regression of the extreme values of symptoms expression (average of the maximum for all trials)

Observation Minimum Maximum

Percentage of infected tubers

0% 69%

Index 0 338

7Powdery scab workshop | Einsiedeln: 17th July-20th July 2016Brice Dupuis, Ruedi Schwaerzel

M&M: resistance of the control cv.

� The exemple of cv. Agria:

cv. Agria cv. Agria

8Powdery scab workshop | Einsiedeln: 17th July-20th July 2016Brice Dupuis, Ruedi Schwaerzel

M&M: resistance of the control cv.

Cultivar Observation Average values Resistance scale

Agria Index 259 7.1% 61 8.0

Bintje Index 117 3.8% 32 4.7

Lady Felicia Index 33 1.8% 11 2.3

Lady Claire Index 117 3.8% 34 4.9

Maximum Index 338 9.0% 69 9.0

9Powdery scab workshop | Einsiedeln: 17th July-20th July 2016Brice Dupuis, Ruedi Schwaerzel

M&M: resistance of the tested cv.

� Step 1: for each trial, use of the linear regression between the resistance scale and the symptoms expression (index and %) of the control cultivars� Exemple: trial in the location Reckenholz in the year 2012

10Powdery scab workshop | Einsiedeln: 17th July-20th July 2016Brice Dupuis, Ruedi Schwaerzel

M&M: resistance of the tested cv.

� Step 2: Calculation of the resistance of a tested cultivars (for example the cv. Georgina)� For this trial: (3.60+4.45)/2 = 4.03� For all trials (n=3): mean value of all trials

(9.92+5.85+4.03)/3=6.59

28

3.6

13

4.45

11Powdery scab workshop | Einsiedeln: 17th July-20th July 2016Brice Dupuis, Ruedi Schwaerzel

Results: loss of trials

� 29 trials (58%) were loss due to low disease pressure

� The risk of trial loss varies depending on the location:� 22% of loss for Wallestalden (2 out of 9 trials)� 39% of loss for La Frêtaz (7 out of 18 trials)� 87% of loss for Reckenholz (20 out of 23 trials)

12Powdery scab workshop | Einsiedeln: 17th July-20th July 2016Brice Dupuis, Ruedi Schwaerzel

Results: high variability

� High variability of response from one trial to the other

� A cultivar has to be tested several years� Only the cultivars tested for at least two years were

considered (116 out of 212)

13Powdery scab workshop | Einsiedeln: 17th July-20th July 2016Brice Dupuis, Ruedi Schwaerzel

Results: distribution of resistance

� Very low resistance: 0.9% of the cultivars (n=1)� Very low to low resistance: 0.9% of the cultivars (n=1)� Low resistance: 3.4% of the cultivars (n=4)� Low to medium resistance: 5.2% of the cultivars (n=6)� Medium resistance: 8.6% of the cultivars (n=10)� Medium to high resistance: 12.1% of the cultivars (n=14)� High resistance: 21.6% of the cultivars (n=25)� High to very high resistance: 20.7% of the cultivars (n=24)� Very high resistance: 25.9% of the cultivars (n=30)

� Mean of all cultivars: high resistance (n=116)

14Powdery scab workshop | Einsiedeln: 17th July-20th July 2016Brice Dupuis, Ruedi Schwaerzel

Results by class

Very low Low to medium MediumAllians (n=3) Agnes (n=2) Caruso (n=2)

Clairette (n=3) Crisper (n=3)Very low to low Fabiana (n=3) Dolce Vita (n=3)

Amany (n=3) Merida (n=2) Doris (n=2)Oriana (n=2) Erntestolz (n=3)

Low Rosa Gold (n=2) Mustang (n=3)Agria (n=21) Novella (n=3)Eurostar (n=3) Pepite (n=2)Georgina (n=3) Printaline (n=2)Sonate (n=3) Talent (n=2)

15Powdery scab workshop | Einsiedeln: 17th July-20th July 2016Brice Dupuis, Ruedi Schwaerzel

Results by class

Medium to highAntoinet (n=3) Opaline (n=3)Bintje (n=20) Pirol (n=3)Challenger (n=3) Pomqueen (n=3)Crispy (n=3) Toscana (n=3)Elfe (n=3)Grandeur (n=2)Lady Claire (n=18)Mozart (n=3)Musica (n=3)Naviga (n=3)

16Powdery scab workshop | Einsiedeln: 17th July-20th July 2016Brice Dupuis, Ruedi Schwaerzel

Results by class

HighAlbata (n=3) Esmeralda (n=3) Puccini (n=3)Apolline (n=3) Forza (n=3) Red Fantasy (n=2)Arietis (n=2) Granada (n=3) Roncalla (n=3)Ballerina (n=3) Gwenne (n=2) Salome (n=2)Canelle (n=3) Kiebitz (n=3) Umatilla Russet (n=3)Clarina (n=3) Krone (n=2)Corsa (n=3) Lanorma (n=2)Delianne (n=3) Maria Sarah (n=3)Dinky (n=3) Omega (n=3)Erika (n=2) Ottawa (n=3)

17Powdery scab workshop | Einsiedeln: 17th July-20th July 2016Brice Dupuis, Ruedi Schwaerzel

Results by class

High to very highAlert (n=2) Fabiola (n=3) Soraya (n=2)Anoe (n=3) Fridor (n=3) Toluca (n=4)Antonia (n=2) Gala (n=2) Venezia (n=2)Anuschka (n=3) Lady Felicia (n=18) Vivi (n=3)Biogold (n=3) Lady Lenora (n=3)Bridget (n=3) Lady Valora (n=2)Citadelle (n=3) Lolita (n=3)Colomba (n=3) Lucie (n=3)Daniela (n=3) Magnum (n=2)Destiny (n=2) Rumba (n=3)

18Powdery scab workshop | Einsiedeln: 17th July-20th July 2016Brice Dupuis, Ruedi Schwaerzel

Results by class

Very highAction (n=3) Kiwi (n=3) Red Lady (n=3)Ambrine (n=2) Lady Amarilla (n=3) Red Scarlett (n=2)Cecile (n=3) Lady Blanca (n=2) Rodriga (n=3)Celtiane (n=3) Leontine (n=3) Romanze (n=2)Diego (n=3) Malou (n=2) Satellite (n=3)Endeavour (n=2) Mariska (n=2) Sirtema (n=3)Galante (n=2) Miss Malina (n=3) Sissi (n=2)Golf (n=3) Pandora (n=2) Susanne (n=3)Gourmetta (n=3) Performer (n=2) Taurus (n=3)Gredine (n=3) Poupette (n=2) Triplo (n=2)

19Powdery scab workshop | Einsiedeln: 17th July-20th July 2016Brice Dupuis, Ruedi Schwaerzel

Conclusions

� The soil of the locations used for variety trials has to be highly infected by the pathogen in order the minimize the risk of trial loss

� Not all the years of trial can be used to asses the susceptibility of the cultivars, a minimum of disease pressure is needed

� The variability of response is high among trials, thus the trials needs to be repeated several times (years)

� A minimum of 3 to 4 control cultivars are needed to have reliable results

� New cultivars are overall tolerant to the disease

20Powdery scab workshop | Einsiedeln: 17th July-20th July 2016Brice Dupuis, Ruedi Schwaerzel

Acknowledgments

� Roger Wütrich� Christian Vetterli� Walter Herren� and many others…

21Powdery scab workshop | Einsiedeln: 17th July-20th July 2016Brice Dupuis, Ruedi Schwaerzel

Thank you for your attention

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