Winter Sporangia Research Articles

Efficiency of detecting resting spores of Synchytrium endobioticum (potato wart disease) in infested sites of Ukraine and Georgia

Aim. To determine the occurrence and persistence of Synchytrium endobioticum, resting spore contamination in a small survey of (known infested) potato plots in Ukraine and Georgia; to compare the detection efficiency for resting spores (winter sporangia) of S. endobioticum using an extraction method, routinely applied in Ukraine, based on the use of sodium iodide (NaI) and an extraction method largely based on EPPO Standard PM 7/28(2) (2017), using kaolin and calcium chloride (CaCl2) for extraction. Methods. The examination of fields, aimed at detecting of S. endobioticum in 22 infested plots in Georgia, was conducted following the standard European Plant Protection Organisation (EPPO) phytosanitary procedure PM 3/59(3) (2017), and in Ukraine in 11 plots according to the Ukrainian Standard ‘Methodological recommendations on sampling during quarantine inspection and evaluation’ (Omeluta V P et al, 1996). Resting spores were extracted using kaolin and CaCl2 (following largely EPPO Standard PM 7/28(2) 2017), and floatation in a solution of NaI (Zelya et al, 2005), respectively. The content of soil organic matter (SOM), collected in potato wart infested plots in Ukraine and Georgia, was determined according to the ‘Method of laboratory determination of the content of organic matter’, largely following the method of Tyurin to determine total soil organic carbon (Jankauskas B et al, 2006). The persistence or decline of potato wart in infested plots was evaluated, based on our own observations and the data of the national phytosanitary services (https://dpss.gov.ua; http://agr.georgia.gov). The results of the study were subjected to statistical analysis, using Statistica 5 software. Results. It was found that under a low up to high level of organic matter in soil samples (2.0–2.7 and 3.1–3.9 %, respectively) and a moderate to high level of inoculum in soil (3–15 up to 41–65 resting spores/g soil, respectively) there were no significant differences in the efficiency of two extraction methods under consideration: the floatation in a solution of NaI and the application of kaolin and CaCl2. However, at a low number of resting spores present in soil (1–2 resting spores/g soil), the efficiency of the method using NaI decreased statistically significant by 20–30 % as opposed to the method using kaolin/CaCl2. A relatively high level of soil contamination with resting spores was found in 11 investigated plots of 4 Ukrainian regions: 41–46 resting spores/g soil in the Ivano-Frankivsk Region, 49 in the Lviv Region, 40–65 in the Zakarpattia and 52–65 Chernivtsi Regions. The majority of the 22 investigated Georgian plots showed a low inoculum level (1–7 resting spores/g soil) and only in one village their level amounted to 15 resting spores/g soil (Uchguli village, Mestia municipality). Conclusions. The method applying sodium iodide was found to be comparable to the method applying kaolin and CaCl2 under conditions of moderate to high inoculum levels (15–65 resting spores/g soil) but the latter method was more efficient under conditions of high content of organic matter and very low inoculum level (

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

Abstract 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.

PM 7/28 (2) Synchytrium endobioticum

Specific scopeThis Standard describes a diagnostic protocol for Synchytrium endobioticum.This Standard should be used in conjunction with PM 7/76 Use of EPPO diagnostic protocols.Specific approval and amendmentApproved in 2003‐09. Revision approved in 2017‐06.

First Report of New Pathotype 39(P1) of Synchytrium endobioticum Causing Potato Wart Disease in Poland.

Potato wart disease, caused by Synchytrium endobioticum (Schilb.) Perc., is one of the most dangerous diseases of cultivated potato. S. endobioticum is an obligate soil-borne fungus. The pathogen originated in the Andean zones of South America, from which it spread to North America and Europe at the end of the nineteenth century. The typical symptoms of cauliflower-like galls can develop on all meristematic tissues of potato except roots. The pathogen is on the European and Mediterranean Plant Protection Organization (EPPO) A2 list of quarantine pests. Since the discovery of pathotype 2(G1) in Germany, more than 40 pathotypes have been reported in Europe (1). In 2009, warted tubers were collected from Lesser Poland. Direct microscopic examination confirmed the presence of summer and winter sporangia in galls. The galls were multiplied on cv. Eersteling using the Glynne-Lemmerzahl method (GL), according to EPPO standard PM 7/28 (3). To identify the pathotype of S. endobioticum, 10 differential potato cultivars were inoculated with fresh galls following the GL method. The reaction types were evaluated 4 weeks after incubation in sand in a growth chamber. Cultivars Combi, Delcora, Deodara, Eersteling, Miriam, Producent, and Tomensa were extremely susceptible (predominant tumor formation); cv. Karolin was slightly susceptible (small galls with numerous winter sporangia); and cvs. Saphir and Ulme were resistant (early and late defense necrosis). This virulence profile was different from patterns of known European (1), Turkish (2), and Polish local pathotypes (4,5). The virulence of the pathogen to cv. Karolin was unique. Winter sporangia were isolated from galls formed on cv. Karolin and used in a modified Potoček's tube test (5) to obtain fresh galls with summer sporangia that were necessary to reconfirm the virulence profile of the pathotype. The reaction of all cultivars to the new pathotype was the same after the GL was performed. In accordance with the summation of known pathotypes, it is proposed to encode this new pathotype as pathotype 39(P1), using an Arabic number to designate the subsequent pathotype (the last one, 38 [Nevşehir], was identified in Turkey) (2) and the first letter of the locality where it was found (Piekielnik). The presence of pathotype 39(P1) was confirmed in four out of six districts where the Polish local pathotype 2(Ch1) was prevalent. The virulence profiles of both pathotypes were compared using differential set and cv. Asche Sämling, which is differential only for pathotype 2(Ch1). In contrast to all other pathotypes (big galls), no galls were observed on A. Sämling inoculated with pathotype 2(Ch1) and 39(P1). From this observation it appears that the new pathotype probably has been selected from the Polish local pathotype 2(Ch1). Pathotype 39(P1) was detected in small garden potato plots in the rainy mountainous area, a non-economically important potato-growing region where the old traditional cultivars of potato are cultivated without crop rotations. It seems, therefore, that where climatic conditions are suitable for S. endobioticum and the growing of slightly susceptible cultivars is possible, development of the new pathotype is favored.

First Report of Synchytrium endobioticum (Potato Wart Disease) Pathotype 18(T1) in Poland.

Synchytrium endobioticum (Schilb.) Perc. is a soil-borne biotrophic fungus causing potato wart disease (PWD) of cultivated potato, one of the most important crops in Poland. S. endobioticum infects epidermal cells of young potato organs, such as eyes, sprouts, young tubers, stolons, stems, leaves, and even flowers, but never roots. S. endobioticum survives in the soil as winter (resting) spores, which germinate, infect the plant, and produce secondary sporangia (summer spores); infection results in galls on the stolons and tubers, in which the pathogen multiplies. Its long persistence in soil and the severe losses it inflicts to potato crops have prompted its inclusion into the A2 quarantine list. The fungus originates from the Andean zones of South America, from where it spread to North America and Europe at the end of the 19th century. S. endobioticum was first reported in the United Kingdom in 1876. This pathogen is quite variable. The first discovery of a new pathotype in Europe occurred in former East Germany in 1941, and there have been 38 S. endobioticum pathotypes identified so far. Pathotypes 1(D1), 2(G1), 6(O1), 8(F1), and 18(T1) are of greatest relevance in Europe. In 2008, the Polish Inspectorate of Plant Health and Seed Inspection (PIORiN) collected soil samples from Mazowieckie Region in Central Poland. Microscopic examinations revealed the presence of viable resting spores of S. endobioticum in a soil sample collected from a crop plantation of ornamentals intended for export. One kilogram of soil contained an average of 300 viable spores. A bioassay (pot tests), recommended by the EPPO standard PM 3/59 (1), showed no wart symptoms because of the very low sporangium density of S. endobioticum. However, concentrating S. endobioticum inoculum by centrifugation and using for a bioassay modified Potocek's tube test (1) allowed us to obtain fresh galls with summer sporangia. The first symptoms of PWD were visible on sprouts of extremely susceptible potato genotypes 7 weeks after inoculation. To identify the pathotype of S. endobioticum, 10 differential potato cultivars (Deodara, Tomensa, Eersteling, Producent, Combi, Saphir, Delcora, Miriam, Karolin, and Ulme) were inoculated with fresh galls of S. endobioticum using the Glynne-Lemmerzahl method (2), according to EPPO standard PM 7/28. Galls were formed on all cultivars except Saphir, Karolin, and Ulme (resistant cultivars). This virulence profile was identical to that of European pathotype 18(T1) of S. endobioticum. This is the first detection in Poland of pathotype 18(T1), which is one of the most virulent pathotypes of this fungus. It should be noted that in 2004, prior to planting, the field was investigated by PIORiN and found to be free of S. endobioticum. The winter sporangia were found on the field with ornamental plants originating from Western Europe, where pathotype 18(T1) is still occurring. S. endobioticum is a classic example of the distribution of plant pathogens by man. Although an infection source has not been determined, the field was probably infested by soil connected with roots of the plantlets. This is an example of alternative ways for S. endobioticum spreading without potato as a main host.

Assessment of the resistance of potato cultivars toSynchytrium endobioticum(Schilb.) Per. in Poland

In Poland the Plant Breeding and Acclimatization Institute is responsible for officially assessing the resistance toSynchytrium endobioticumof domestic potato breeding lines and cultivars from other countries. Cultivation of potato cultivars in Poland requires confirmation of resistance to potato wart disease. The official assessment uses the modified Glynne‐Lemmerzahl method (laboratory tests) and pot tests. The full cycle of assessment of resistance to wart disease requires 52 seed potatoes per variety/breeding line. Forty two tubers are used in laboratory tests. To complete the laboratory tests the next 10 tubers are grown in pot tests (in soil with winter sporangia) during the vegetation season. The final results for domestic breeding lines of potato are available after 3 years of investigation. For cultivars from other countries the authorization of resistance toS. endobioticumtakes approximately one year. The Polish breeders (breeding lines) or the breeder's representative (cultivars from other countries) receive the certificate only for lines/cultivars with laboratory and field resistance toS. endobioticum.

Infectivity of Summer Sporangia of Potato Wart Disease in Incipient Infections on Varieties Immune in the Field

IT is known that a number of potato varieties which appear immune to wart disease (Synchytrium endobioticum) in the field develop incipient and transitory infections under the more intensive infection conditions in the laboratory. Investigation has shown that summer sporangia, and less often winter sporangia, are developed apparently normally until necrotic areas produced in the host interfere with the nutrition of the fungal parasite and cause it to be sloughed off, so that signs of infection disappear within a few weeks.