Resistance of potato cultivars to Synchytrium endobioticum in field and laboratory tests, risk of secondary infection, and implications for phytosanitary regulations |
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| Authors: | R P Baayen H Bonthuis J C M Withagen J G N Wander J L Lamers J P Meffert G Cochius G C M van Leeuwen H Hendriks B G J Heerink P H J F van den Boogert P van de Griend R A Bosch |
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| Institution: | Plant Protection Service, PO Box 9102, 6700 HC Wageningen (Netherlands);email:; Centre for Genetic Resources, PO Box 16, 6700 AA Wageningen (Netherlands); Applied Plant Research, Arable Farming, Field production of Vegetables and Multifunctional Agriculture, PO Box 430, 8200 AK Lelystad (Netherlands); Plant Research International, PO Box 16, 6700 AA Wageningen (Netherlands); HLB Research, Kampsweg 27, 9418 PD Wijster (Netherlands) |
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| Abstract: | Laboratory (Spieckermann) tests, pot tests and field tests provided concordant evidence for the partial nature of resistance of potatoes to pathotypes 1 (D1) and 6 (O1) of Synchytrium endobioticum . Susceptible potato cultivars produced large warts (> 16 mm in diameter) in Spieckermann tests and had low field resistance levels (1–6). Field-resistant cultivars (levels 7–9) produced small warts or no warts at all in Spieckermann and field tests. In pot tests, at low inoculum levels (1 sporangium per 25 g soil) susceptible cultivars still developed warts, whereas field-resistant ones did not develop any warts below 25 sporangia per g soil. Above 35 sporangia per g soil, 100% disease incidence was observed in susceptible cultivars but only minimal wart development in field-resistant ones. Tests with continuous cultivation of potato cultivars in infected soil during three consecutive years showed that field-resistant cultivars will not support build-up of inoculum in soil. It is concluded that field-resistant cultivars do not create a risk of secondary infection, the criterion given for resistance in EU Directive 69/464/EC. |
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