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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| Affiliation: | 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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