Screening of potato varieties for multiple resistance to Synchytrium endobioticum in the western region of Ukraine

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 %).