Suggestions for changes in the Polish scale used to evaluate the resistance of potato cultivars to potato wart disease according to the EPPO Diagnostic Protocol PM 7/28

W Polsce, od ponad 30 lat oceny odporności laboratoryjnej metodą Glynne-Lemmerzahla na raka ziemniaka następowały zmiany skali oceny do postaci akceptowanej przez Państwa Członkowskie Unii Europejskiej (UE). W roku 1980 (Malec, 1980) podstawą pierwszej skali oceny było występowanie sorusów, co pozwalało na selekcję podatnych i pozostawianie rodów odpornych. Zastosowanie tej skali nie pozwalało wyszczególnić rodów krańcowo odpornych, odpornych i słabo odpornych. W roku 2008 nowa skala pozwalała na taki podział, który wykonywano na podstawie reakcji nekrotycznych gospodarza (Przetakiewicz, 2008). Zastosowana skala oceny nie była jednak zrozumiała dla innych Państw Członkowskich UE i nie pokrywała się ze skalą Protokołu Diagnostycznego EPPO PM 7/28 (OEPP/EPPO, 2004). W Polsce skala rozpoczynała się od stopnia 0 (krańcowo odporne) poprzez IV, III, II/III, II do I (krańcowo podatne). Natomiast w skali Protokołu Diagnostycznego EPPO PM 7/28 (OEPP/EPPO, 2004) stopień 1 oznaczał krańcowo odporne poprzez 2, 3, 4 do stopnia 5 oznaczającego krańcową podatność. W roku 2009 podjęto decyzję o ujednoliceniu polskiej oceny odporności na raka ziemniaka zgodnie z Protokołem Diagnostycznym EPPO PM 7/28 (OEPP/EPPO, 2004) z podziałem na pięć stopni: 1 — krańcowo odporne, 2 — odporne, 3 — słabo odporne, 4 — słabo podatne i 5 — krańcowo podatne. Odmiany uznawane za odporne w warunkach laboratoryjnych (testowane metodą Glynne-Lemmerzahla) mieszczą się w przedziale od 1 do 3 stopnia.Over 30 years of evaluating in Poland the resistance of potato to Synchytrium endobioticum by the Glynne-Lemmerzahl method, the resistance scale pattern has evolved to its final version that is acceptable to other Members of EU. In 1980, the first scale focused on the occurrence of sori. This approach allowed to eliminate susceptible breeding lines and recognize resistant lines. However, there was no possibility to discriminate between extremely resistant, resistant and weakly resistant lines. Such a discrimination was possible after developing in 2008 a new scale, based on the necrotic response of the host. This scale however was not understandable for other Members of EU. Moreover, it greatly differed from the scale accepted in the EPPO Diagnostic Protocol PM 7/28. In the Polish scale, 0 (extremely resistant) was followed by IV, III, II/III, II and I, the latter degree meaning extremely susceptible. In the EPPO scale, I (extremely resistant) is followed by 2, 3, 4 and 5, the latter degree indicating extremely susceptible. In 2009, the decision was made on adjusting the Polish scale to the EPPO standards. The modified scale has five degrees: 1 — extremely resistant, 2 — resistant, 3 — weakly resistant, 4 — slightly susceptible, and 5 — extremely susceptible. The cultivars considered as resistant to S. endobioticum under laboratory conditions based on the Glynne-Lemmerzahl method are given 1–3 points

Sampling, Maintenance and Pathotype Identification of Synchytrium Endobioticum (Schilb.) Perc

Plant Breeding and Acclimatization Institute - National Research Institute (IHAR-PIB) is responsible for pathotype identification of Synchytrium endobioticum isolates collecting from Poland. Pathogenicity tests are carried out using the Glynne-Lemmerzahl method, according to EPPO Standard PM 7/28. Pathotypes are defined based on their reaction to a range of well-characterized differential cultivars of potato. Assessment of one isolate of the fungus requires more than 20 differential cultivars. All pathotypes of S. endobioticum from Polish reference collection are multiplied and maintained (fresh warts) on tubers of extremely susceptible cultivars continuously. For all references pathotypes and isolates of S. endobioticum, the compost with winter sporangia are prepared for long-term of maintenance

Assessment of Potato Resistance to Synchytrium Endobioticum

In Poland the Plant Breeding and Acclimatization Institute - National Research Institute (IHAR-PIB) is responsible for officially assessing the resistance of potato breeding lines and cultivars to Synchytrium endobioticum. In the official assessment of wart resistance the modified Glynne-Lemmerzahl method is used. A full cycle of assessment of the wart disease resistance requires 42 - 45 tubers per cultivar/breeding line. Forty two tubers are used in laboratory tests. To complete the laboratory tests, another 10 tubers are inoculated with winter sporangia of the fungus, using ring test. The final results are available after 3 years of investigation. If necessary, the full cycle of resistance tests to S. endobioticum can be performed during one year on 15 tubers in each of the 3 replications (45 tubers in total). Molecular verification of potato genotypes resistance to pathotype 1(D1) is possible with the use of SCAR marker Nl25-1400. Nevertheless, an official phenotypical assessment of advanced breeding lines, as the final verification of their resistance, is required

Resistance of Polish cultivars of potato to virulent pathotypes of Synchytrium endobioticum (Schilb.) Per.: 2(Ch1) and 3(M1)

Od roku 2008 w Procowni Organizmów Kwarantannowych oceniana była odporność na wirulentne patotypy S. endobioticum 2(Ch1) i 3(M1) 69 polskich odmian ziemniaka. Dziesięć z nich: Ikar, Wist, Cekin, Adam, Ibis, Bzura, Gandawa, Kuba, Zagłoba i Ślęza było odpornych na patotyp 2(Ch1): a jedenaście: Ikar, Wist, Cekin, Adam, Ibis, Bzura, Gandawa, Kuba, Zagłoba, Ślęza i Rudawa uznano za odporne na patotyp 3(M1). Kolejne 7 odmian: Harpun, Neptun, Pasja, Sonda, Hinga, Miłek i Ruta oceniono jako słabo podatne na obydwa testowane patotypy. Odmiana Rudawa wykazała słabą podatność tylko na patotyp 2(Ch1) była natomiast odporna na patotyp 3(M1). Za odmiany odporne na dany patotyp grzyba uznano tylko takie, które wykazały pełną odporność zarówno w warunkach laboratoryjnych jak i w testach doniczkowych. Odmiany, które charakteryzowały się słabą lub krańcową podatnością w testach laboratoryjnych były dyskwalifikowane. Każda z odmian, która została ostatecznie uznana za odporną była oceniana w ciągu 2–3 lat w co najmniej 3 niezależnych doświadczeniach.The resistance of 69 Polish cultivars of potato to virulent pathotypes of S. endobioticum 2(Ch1) and 3(M1) has been evaluated since 2008 at the Laboratory of Quarantine Organisms. Ten of them: Ikar, Wist, Cekin, Adam, Ibis, Bzura, Gandawa, Kuba, Zagłoba and Ślęza were found to be resistant to pathotype 2(Ch1). The same cultivars as well as cv. Rudawa appeared to be resistant to pathotype 3(M1). Another 7 cultivars: Harpun, Neptun, Pasja, Sonda, Hinga, Miłek and Ruta have been assessed as weakly susceptible to both pathotypes, whereas cv. Rudawa was found to be weakly susceptible to the 2(Ch1) but resistant to the 3(M1). The group of resistant cultivars included only those which have been classified as resistant both in laboratory and in pot tests. The cultivars assessed as weakly or extremely susceptible under laboratory conditions have been declassified. All the resistant cultivars were tested using the Glynne-Lemmerzahl method in at least 3 independent replications during a period of 2 or 3 years

Diploid potato hybrids — a source of resistance to potato wart disease (Synchytrium endobioticum (Schilb.) Perc.)

W latach 2006–2012 w IHAR — PIB w Radzikowie, w Pracowni Organizmów Kwarantan-nowych, oceniano diploidalne klony ziemniaka pod względem odporności na Synchytrium endobioticum (Schilb.) Perc. Klony te, wyselekcjonowane w IHAR — PIB w Młochowie, w Pracowni Genetyki, są mieszańcami międzygatunkowymi ziemniaka Solanum tuberosum powstałymi z udziałem dzikich i uprawnych gatunków Solanum. Klony testowano pod względem odporności na patotypy: 1(D1), 2(G1), 2(Ch1), 3(M1), 6(O1), 8(F1), 18(T1) i 39(P1) S. endobioticum, pochodzące z kolekcji Pracowni Organizmów Kwarantannowych. Testy oceny odporności na patotypy S. endobioticum wykonano zmodyfikowaną metodą Glynne-Lemmerzahla. Z 288 badanych klonów wyselekcjonowano 101 odpornych na patotyp 1(D1). Grupę 70 klonów testowano pod względem odporności na pięć patotypów 2(G1), 2(Ch1), 6(O1), 8(F1) i 18(T1) S. endobioticum, 44 z nich dodatkowo na patotyp 3(M1), a 22 klony dodatkowo na patotypy 3(M1) oraz 39(P1). W wyniku testów wyselekcjonowano siedem diploidalnych klonów ziemniaka jednocześnie odpornych na siedem wirulentnych patotypów S. endobioticum: 2(G1), 2(Ch1), 3(M1), 6(O1), 8(F1), 18(T1) i 39(P1). Są to wyjątkowo złożone rekombinanty pod względem odporności na patotypy S. endobioticum, jakich dotychczas nie opisano w innych pracach. Mieszańce te są materiałem do poszukiwania i lokalizacji na mapie genetycznej ziemniaka markerów sprzężonych z odpornością na poszczególne patotypy S. endobioticum. Odporne klony diploidalne charakteryzują się dobrym poziomem cech jakościowych i odpornościowych. Pięć z nich wytwarza męskie gamety o niezredukowanej liczbie chromosomów (gamety 2n), dzięki którym allele odporności na patotypy S. endobioticum można przekazać na poziom tetraploidalny w krzyżowaniach 4x × 2x.In 2006–2012 in IHAR — PIB Radzików, in Laboratory of Quarantine Organisms, diploid potato clones were tested for resistance to Synchytrium endobioticum (Schilb.) Perc. The diploid clones selected in IHAR — PIB Młochów, in Laboratory of Genetics, were interspecific hybrids of Solanum tuberosum possessing in their pedigree wild and primitively cultivated Solanum species. Clones were tested for resistance to following pathotypes of S. endobioticum: 1(D1), 2(G1), 2(Ch1), 3(M1), 6(O1), 8(F1), 18(T1), and 39(P1), from the collection of Laboratory of Quarantine Organisms. Modified method of Glynne-Lemmerzahl was used for evaluation of their resistance. From 288 tested clones 101 were found resistant to pathotype 1(D1). The group of 70 clones was tested for resistance to 5 pathotypes of S. endobioticum: 2(G1), 2(Ch1), 6(O1), 8(F1), and 18(T1); 44 clones from that group were evaluated additionally for the pathotype 3(M1) and 22 clones were assessed for 2 additional pathotypes 3(M1) and 39(P1). Selection resulted with 7 diploid clones simultaneously resistant to 7 virulent pathotypes of S. endobioticum: 2(G1), 2(Ch1), 3(M1), 6(O1), 8(F1), 18(T1), and 39(P1). They are complex recombinants combining resistance to wart disease agent pathotypes that have not been described in other studies, so far. Selected resistant hybrids are excellent material for identification and localization on potato genetic map of genetic markers linked to the resistance to particular pathotypes of S. endobioticum. These diploid clones exhibit a good level of quality and resistance traits. Five of them produce male 2n gametes which can be used in 4x × 2x crosses for transfer of alleles of resistance to wart disease agent pathotypes to tetraploid level

Molecular characterization and comparisons of potato wart (Synchytrium endobioticum) in historic collections to recent findings in Canada and the Netherlands

Synchytrium endobioticum (Schilb.) Perc. is a chytrid fungus causing potato wart disease and is one of the most important quarantine diseases on cultivated potato. Infected host tissues develop warts rendering the crop unmarketable. Resting spores, that can remain viable and infectious for decades, are formed in warted tissues and are released into the surrounding soil when host tissue decays. To better understand the pathogen’s diversity and to potentially uncover pathways of migrations and introduction events, molecular characterization was performed on the historical S. endobioticum resting spore collection of the Dutch National Plant Protection Organization. Mitochondrial genomes were assembled and annotated, and four novel structural variants were identified from these materials with intronic presence-absence variation in cox1 or cob genes and structural variation in the dpoB – TIR region. Several fungal isolates were shown to contain mixtures of structural variants. We analyzed the mitogenomic sequences obtained from recent potato wart disease findings in Canada and the Netherlands in the context of the historical materials and found that fungal isolates from the new Dutch outbreak contained a specific mixture of mitogenomic variants previously not observed in the Netherlands. Based on the mitogenomic profile, pathotype 38(Nevşehir) was suspected which was later verified with the Spieckermann bioassay. To further facilitate dissemination of data and interactive visual analytics we created a public Nextstrain webpage with S. endobioticum mitogenomic sequences and associated metadata on their geographic origin, pathotype identity and (mixture) of mitogenomic variants (https://nextstrain.nrcnvwa.nl/Sendo)