Aim. To evaluate potato breeding material for resistance to pathotypes of Synchytrium endobioticum (Schilbersky) Percival (1909) known to be present in Ukraine (pathotypes 1(D 1 ), 11, 13, 18 and 22); to identify resistant registered and potential varieties for the usage in the national wart disease eradication programs and to recommend these se- lected (potential and registered) potato varieties for the breeding program targeted on the development of multiple resistance against pathotypes of S. endobioticum present in Ukraine. Methods. Evaluation of the potato breeding material and registered potato varieties for the resistance against common pathotype 1 (D 1 ) and four aggressive pa- thotypes of S. endobioticum (pathotypes 11, 13, 18 and 22) in climatic chamber and greenhouse tests of Ukrainian Scientifi c Research Plant Quarantine Station of Institute of Plant Protection NAAS (Boyany, Ukraine) following the Spieckermann and Glynne-Lemmerzahl methods (EPPO Standard PM7/28(2)). Field trials on naturally infected soils were conducted according to standard methods adapted to national requirements in the area of Chernivtsi, Zakarpattia and Ivano-Frankivsk regions. Results. 3,736 samples of potato breeding material from six breeding institutions of Ukraine were tested for resistance against S. endobioticum during 2011–2017 in the western region of the country. Among all samples tested, 3,389 were identifi ed as resistant to the widely spread pathotype 1 in the preliminary climatic chamber and greenhouse tests, and 130 of them proved to be resistant under fi eld conditions. Five out of 41 Ukrainian registered potato varieties (Bazys, Hlazurna, Solokha, Bozhedar and Santarka) were found to be resistant to all 5 pathotypes tested (1 (D 1 ), 11, 13, 18 and 22). Conclusions. The 130 samples of potato breed- ing material (which were found to be resistant against the common pathotype 1 of S. endobioticum in the laboratory, greenhouse as well as in the fi eld trials) were recommended for the state variety registration and further usage in an eradication program to localize potato wart outbreaks of the western part of Ukraine. The screening tests revealed that the national breeding program targeted on resistance against S. endobioticum pathotype 11 was the most effec- tive (49 % of samples tested proved to be resistant against this pathotype), whereas it was the least effective against pathotype 18, namely only 30 % of samples resistant. It was speculated that such a dissimilarity may be related to the differences in the genetic material used in the breeding process at various institutions, and which may be the subject of further analysis in order to improve the results of breeding programs. The already registered potato variet- ies Bazys, Hlazurna, Solokha, Bozhedar and Santarka which were found to have a multiple resistance to common pathotype 1 and four local aggressive pathotypes of S. endobioticum (11, 13, 18 and 22) were recommended for use in the breeding process as sources of resistance and also for the eradication programs in the western region of Ukraine, where S. endobioticum is mostly distributed (2409 hectares or 98 %).

We have extended previously published sets of simple sequence repeat markers for Synchytrium endobioticum, selected to be polymorphic for the German-standard isolates of pathotypes P1, P2, P6, P8, and P18. These markers also complement the extensive published information on DNA polymorphisms for the mitogenomes of Synchytrium endobioticum. This extended set of 35 markers representing 73 alleles differentiated 51 isolates from Europe and North America into three large, well-separated clusters and subclusters using dendrogram analysis, principal coordinates analysis (PCoA), and population substructure analysis using STRUCTURE 2.3.4 software. This suggests a limited number of introgressions of the wart disease pathogen into current potato growing areas, followed by recombination and admixture of populations through human activities. The new markers extend the published marker sets and are useful tools for future analyses of population structure and dynamics in Synchytrium endobioticum, which are necessary to understand the biology of the interaction between the pathogen and its potato host and to develop future control strategies.

Six potato cultivars developed in Lithuania, ‘VB Venta’, ‘Goda’, ‘VB Liepa’, ‘VB Meda’, ‘VB Rasa’ and ‘VB Aista’, were selected based on the results of trials in the Ukrainian climatic zone from 2020-—2021. Three of the cultivars, ‘VB Goda’, ‘VB Liepa’, and ‘VB Meda’, presented elevated levels of resistance to Synchytrium endobioticum (Schilbersky) Percival and Phytophthora infestans (Mont) de Bary. These cultivars are recommended for use as parental lines for crossing and as sources of disease-resistant potatoes. Simple sequence repeat (SSR) markers are frequently employed in breeding and genetic studies because of their prevalence, repetition, and extensive genome coverage. These results indicate that Lithuanian potato cultivars exhibit significant genetic differences, which also translate into distinct agromorphological characteristics.

Goal. To evaluate and to choose potato varieties breeding material resistant to wart and search resistance sources to causative agent of potato wart Synchytrium endobioticum (Schilbersky) Percival. Methods. The study involved 739 samples breeding of potatoes varieties Institute for potato study NAAS and its’ Polissian division in 2020—2022. The samples were received by different parents forms crossings. Evaluation of breeding material for resistance to common 1(D1) and aggressive pathotypes of potato wart was performed in the laboratory conditions of the Ukrainian Science Research Plant Quarantine Station IPP NAAS on an artificial infectious background according to EPPO Standard PM 7/28/1 and EPPO Standard PM 7/28/2 and «Techniques or evaluation and choice of potato breeding material resistant to wart Synchytrium endobioticum (Schilb.) Perc harmonized as per EU requirements» and in field conditions of pathogen spread. Results. A 699 potato samples (94.6%) from 739 hybrids from 2022-through 2022 received resistant value to common pathotype of wart causative agent. 40 (5.4%) samples were defeated by disease causative agent and they were rejected by us. The researches results showed that 21 outlet potato parents forms had the highest resistance degree (1.2—2.0 points). They recommended for the following usage in in breeding process as a resistance source to potato wart. Hybridological analysis for potato resistance inheritance provided on the following variants of parents forms crossing F09.209-3/P14.3/12, Svitana / Mezhzyrichka, Vyhoda / Svitana, Radmysl / Svitana,Vzirets / Svitana, P10.10/35/Svitana. 81.13.9/1/Svitana, P12.14-8/Partner, Zvizdal/P10.109/35, Mezhyrichka/Sncedar, Levada /Rostovytsya, Svitana Rostovytsya, Nagoroda Rostovytsya / Rostovytsya, ВМ12.24-15 /Vygoda, Floatka/Rostovytsya, Mezhyrichka/Dorogyn, Agave/Aria, 08.102/4/Miranda, Ivankivska rannya/Alliance, Vectar/Radmysl; Charunka/Alliance; Tyras/89.715с88. The potato resistant inheritance showed 100% to wart. The crossing variant F 09.209-3 / P10.9-3, P09.26-2/Alliance gave 50.0% resistant inheritance. The crossing variant Myroslava/Н.07.162-1 gave 88.9% resistant inheritance. Conclusions. There were chosen 699 (94,6%) among 739 potato samples in 2020—2022 resistant to common pathotype. Hybridological analysis for potato resistance inheritance to wart showed that variant resistant (♀) × resistant (♂) give 100% resistance to wart potato inheritants. The most resultative resistant potato samples choice was resistant to D1 (common) and 22 (Bystrysia) agressive pathotype during potato breeding studies with complex resistance to wart pathotypes in 2021—2022. The most virulent was 18 (Yasynnia) aggressive pathotype. There were only 5 (21.7%) resistant to this wart pathotype. Chosen samples with complex resistance to wart pathotypes recommended for the following usage in breeding. They recommended for improve in disease sources and for the following usage in breeding process as potato resistance sources to disease causative agent and for the improving in disease sources.

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 (