The use of colored tubers of Solanum tuberosum L. is growing worldwide due to their health benefits and attractive color. The positive health effects of purple-fleshed tubers are a result of anthocyanins and various phenolic compounds. The aim of this study was to evaluate and compare variety Blue Congo and its cross-breeds of Desiree and Granola to yellow-fleshed tubers. The concentration of total phenols, anthocyanins, sugars, and mineral elements were evaluated in all tubers. The results showed differences between all tested materials, with largest differences in sugar content. Moreover, the results confirmed the preservation of health improving compounds of Blue Congo when cross-bred with yellow-fleshed tubers. The total phenolic content and anthocyanin concentrations of all analyzed tubers were above the comparison yellow ones.

A plant-multiplication technique developed at the Department of Plant Biotechnology EVIKA of the Estonian Research Institute of Agriculture involves multiplying plantlets in plastic rolls on peat before transplanting them onto the field, where the first generation of seed tubers will be grown. Four possible multiplication methods of potato meristem plants were compared from the aspect of obtaining optimal-sized, disease-free seed tubers. The plants grown from tip- and stem-cuttings and truncated plants were considered in relation to the plants multiplied by the in vitro micro-plant cultivation in plastic rolls. The main objective of this paper is to analyse how the tubers' mass per plant and their size distribution depend on the multiplication method, experimental year, and potato variety. Two local late-maturing potato varieties, Ants and Vigri, were used in the study, carried out in 2005–2007. A significant influence of multiplication method and experimental year on tuber weight and tuber-size distribution throughout the growing period was found. While plants multiplied by in vitro micro-cuttings produced substantially lower tuber mass per plant, also their tuber-size distribution was considerably inclined towards smaller dimensions – more tubers with 60 mm diameter were formed. Compared with plants multiplied by the in vitro micro-plants method, significantly fewer tubers within the most proper seed-tuber size range (Ø 30–60 mm) were received for plants multiplied from tip- and stem-cuttings, while the plants grown from truncated seedlings provided about the same yield as micro-plants in this size interval. All stated differences were magnified by unfavourable growing years, whereas in favourable conditions the differences were almost non-existent. The influence of potato variety on tuber mass and their size distribution was not proved. All described EVIKA multiplication methods achieve quite similar tuber yields and seed-production potential, comparable to those obtained by in vitro methods.

Regardless of variable environmental conditions and changing pathogen populations, the Estonian potato cultivar (cv.) Ando has shown elevated field resistance to Phytophthora infestans for over 40 years. One of cv. Ando’s parents, the Latvian cultivar Agra, is considered a cultivar of medium to low resistance, the other parent, line 382-48, has a well-known source of resistance, Solanum demissum, in its pedigree. Segregation of late blight disease severity in a population of 95 hybrid plants from cv. Ando’s backcross to cv. Agra (cv. Ando x cv. Agra BC1) in field trials of three consecutive years (2013−2015) and in a test of a single pathogen isolate fits a model of additive action of multiple unlinked race-specific resistance genes responsible for the field resistance of cv. Ando. At least some of the resistance genes in cv. Ando’s genome do not function in juvenile plants and are developmentally upregulated.