Evaluation of potato varieties and hybrids on the resistance against black scab under conditions of Ukraine’s polissia

Abstract

To estimate the potato cultivars and hybrids on their resistance against black scab as well as to select the highly resistant cultivar-forms. On the European level there is no standard method as to estimating and selecting of both starting and selection materials of potato on their resistance against black scab. However, the main principle of the existing methodology resolves itself to testing the cultivars, hybrids and varieties of potato on the natural or artificial infection backgrounds when using pure culture of fungus Rhizoctonia solani Kuhn. The culture, which was grown in a double-dish, was introduced into soil when the potatoes were planted out. The degree of tuber and stem infection was estimated on the basis of the affection of underground organs of plants and potato yield, further the cultivar samples were assessed according to susceptivity, tolerance and resistance to infection. When estimating the cultivars and hybrids of potato on their resistance against the disease agent Rhizoctonia solani Kuhn, a nine-grading scale was used, where grade 9 means that there is no affection of tubers and stems, grade 7 means that disease affection equals 10 % (high resistance), grade 5 – the disease affection equals 11–25 % (medium resistance), grade 3 – the disease affection equals 26–50 % (low resistance). On the basis of testing the potato cultivars and hybrids on their resistance against black scab, relatively resistant are considered 19 or 12.3 % (Dubravka, Vesta, Lugovska, Obriy, Serpanok, Yavir, Scarbnytsia, Tyras and the hybrids П.207.407 (Polisska Rozheva); 205.17-24 (Аdretta х 23- 16с/73) and others, 85 cultivar samples or 54.8 % belong to mid-resistant (5grades), in particular – Chervona Ruta, Povin, Vodogray, Horlytsia, Zov, Cupava, Nadiyna, Belarossa, Olivia, Svitanok Kyivskyi, Ukrainska Rozheva, Beregynia, Charunka, Okolytsia, Slutch and the hybrids П.210.14- 23 (Аdretta х Posvit); 211.20-31 (Prolisok х Lugovska) and 51, or 32.9 % belong to susceptive ones. We have proved that mid-early ripening and early ripening cultivars as well as selection hybrids are more infected with black scab than mid-ripening, mid-late ripeningand and late ripening cultivars. These relatively resistant potato cultivars and hybrids are expedient to use in the selection on the resistance against black scab.