Molecular identification of extreme resistance genes to PVY among breeding lines and potato varieties of Ukrainian origin

Aim. Molecular identification of two genes responsible for extreme resistance (ER) to potato virus Y (PVY), viz. Ryadg and Rychc. in potato lines and varieties bred in Ukraine. Methods. In total 78 potato samples (40 breed- ing lines and 38 varieties) were studied. To identify the Ryadg and Rychc genes, the molecular markers RYSC3 and Rу186, respectively, were used. The silica-based technique was used to isolate DNA from potato leaves or tubers. Amplified products were analysed with agarose gel-electrophoresis. Results. Molecular markers were used to evaluate 40 breeding lines produced by the Polissia Experimental Department of the Institute for Potato Research, the NAAS, the harvest of 2022, and 38 cultivars, registered in the period of 1981–2015, from the collection of the Ustymivka experimental station of the Institute of Plant Production n.a. V.Ya. Yuriev, the NAAS. Five varieties, Oksamyt, Horlytsia, Lybid, Ivankivska rannia, and Ikar, and 19 lines contained the marker for Rychc. The gene Ryadg marker was detected in one cultivar (Obriy) and eight breeding lines. Six lines carried both genes Ryadg and Rychc. Field evaluation against the natural PVY infection background indicated false-positive results of the presence of ER genes in Obriy and Lybid. The frequencies of the ER genes to PVY Ryadg and Rychc were considerably higher in the group of breeding lines than in the sample of varieties, 47.5 and 10.5 % for Rychc, and 20 and 0 % for Ryadg, respectively. Conclusions. Our study confirmed the possible presence of extreme resistance genes to PVY, Ryadg and Rychc, in 4 Ukrainian potato varieties and 21 breeding lines. A higher frequency of carriers of the resistance genes was present in the new breeding lines (52.5 %) than in the varieties already in production (10.5 %). The total frequency of both genes was fairly similar to the one detected in the earlier study. If the lines and varieties where the above-mentioned resistance genes were detected are truly resistant in the field and origin of these resistance genes in the Ukrainian potato material has still to be investigated.