(1) Background: Although resistance to pathogens and pests has been researched in many potato cultivars and breeding lines with DNA markers, there is scarce evidence as to the efficiency of the marker-assisted selection (MAS) for these traits when applied at the early stages of breeding. A goal of this study was to estimate the potential of affordable DNA markers to track resistance genes that are effective against the pathogen Phytophthora infestans (Rpi genes), as a practical breeding tool on a progeny of 68 clones derived from a cross between the cultivar Sudarynya and the hybrid 13/11-09. (2) Methods: this population was studied for four years to elucidate the distribution of late blight (LB) resistance and other agronomical desirable or simple to phenotype traits such as tuber and flower pigmentation, yield capacity and structure. LB resistance was phenotypically evaluated following natural and artificial infection and the presence/absence of nine Rpi genes was assessed with 11 sequence-characterized amplified region (SCAR) markers. To validate this analysis, the profile of Rpi genes in the 13/11-09 parent was established using diagnostic resistance gene enrichment sequencing (dRenSeq) as a gold standard. (3) Results: at the early stages of a breeding program, when screening the segregation of F1 offspring, MAS can halve the workload and selected SCAR markers for Rpi genes provide useful tools.

Late blight (LB) caused by the oomycete Phytophthora infestans (Mont.) de Bary is the greatest threat to potato production worldwide. Current potato breeding for LB resistance heavily depends on the introduction of new genes for resistance to P. infestans (Rpi genes). Such genes have been discovered in highly diverse wild, primitive, and cultivated species of tuber-bearing potatoes (Solanum L. section Petota Dumort.) and introgressed into the elite potato cultivars by hybridization and transgenic complementation. Unfortunately, even the most resistant potato varieties have been overcome by LB due to the arrival of new pathogen strains and their rapid evolution. Therefore, novel sources for germplasm enhancement comprising the broad-spectrum Rpi genes are in high demand with breeders who aim to provide durable LB resistance. The Genbank of the N.I. Vavilov Institute of Plant Genetic Resources (VIR) in St. Petersburg harbors one of the world’s largest collections of potato and potato relatives. In this study, LB resistance was evaluated in a core selection representing 20 species of seven Petota series according to the Hawkes (1990) classification: Bulbocastana (Rydb.) Hawkes, Demissa Buk., Longipedicellata Buk., Maglia Bitt., Pinnatisecta (Rydb.) Hawkes, Tuberosa (Rydb.) Hawkes (wild and cultivated species), and Yungasensa Corr. LB resistance was assessed in 96 accessions representing 18 species in the laboratory test with detached leaves using a highly virulent and aggressive isolate of P. infestans. The Petota species notably differed in their LB resistance: S. bulbocastanum Dun., S. demissum Lindl., S. cardiophyllum Lindl., and S. berthaultii Hawkes stood out at a high frequency of resistant accessions (7–9 points on a 9-point scale). Well-established specific SCAR markers of ten Rpi genes—Rpi-R1, Rpi-R2/Rpi-blb3, Rpi-R3a, Rpi-R3b, Rpi-R8, Rpi-blb1/Rpi-sto1, Rpi-blb2, and Rpi-vnt1—were used to mine 117 accessions representing 20 species from seven Petota series. In particular, our evidence confirmed the diverse Rpi gene location in two American continents. The structural homologs of the Rpi-R2, Rpi-R3a, Rpi-R3b, and Rpi-R8 genes were found in the North American species other than S. demissum, the species that was the original source of these genes for early potato breeding, and in some cases, in the South American Tuberosa species. The Rpi-blb1/Rpi-sto1 orthologs from S. bulbocastanum and S. stoloniferum Schlechtd et Bché were restricted to genome B in the Mesoamerican series Bulbocastana, Pinnatisecta, and Longipedicellata. The structural homologs of the Rpi-vnt1 gene that were initially identified in the South American species S. venturii Hawkes and Hjert. were reported, for the first time, in the North American series of Petota species.

Fourteen Russian potato cultivars (cvs.) grown for three years in the field plots of VIR (North-Western region of the Russian Federation) were evaluated annually for productivity and 12 biochemical parameters of tubers one month after harvesting and after cold storage (at 2–4 °C). The aim of this study was to quantify the level of biochemical components in tubers and to determine the influence of the environment on their content. The results indicated a substantial variation in different nutrients in potatoes during cultivation for three consecutive years. The nutritional value of tubers (the content of dry matter, sugars, starch and protein) was determined to a greater extent (38–49%) by varietal characteristics, rather than by meteorological conditions in the vegetation period. The content of vitamin C, carotenoids, protein and anthocyanins varied depending on the year. Of the cultivars, ‘Kumach’ has the highest productivity, but the nutritional value of tubers is lower than that of standard ‘Nayada’. Cv. ‘Fioletovyi’ is suitable for consumption as part of a low-calorie diet because of a low amount of starch (11.8–12.7%) and a higher anthocyanins content (102.0–103.9 mg/100 g). Cv. ‘Sokur’ is distinguished by its high nutrition because of its high content of dry matter (24.3%) and protein (more than 2.0%). Cv. ‘Plamya’ is remarkable for the lowest content of reducing sugars (0.24–0.47%) in tubers during the post-harvest and post-storage analysis.

Fourteen Russian potato cultivars (cvs.) grown for three years in field plots of VIR (Northwestern region of the Russian Federation) were evaluated for productivity and a number of biochemical parameters of tubers. The 12 parameters that have been evaluated in tubers annually one month after harvesting and after cold storage (at 2 - 4°C) include the content of dry matter, starch, protein, ascorbic acid, carotenoids and β-carotene, anthocyanins, total sugars and monosaccharides (reducing sugars), phenolic compounds, as well as total acidity, and antioxidant activity. The cultivars differed significantly in productivity and biochemical composition of tubers. Dry matter content ranged from 16.40% in cv. ʻKumachʼ to 27.28% in ʻNayadaʼ, starch content ranged from 8.96 % in cvs. ʻFioletovyjʼ, ʻKumachʼ to 20.08% in ‘Sokur’, the total sugar content reached 2.46% in cv. ʻSiverskij’ whereas ‘Sokur’ has the smallest content of reducing sugars in post-harvest tubers. Protein content ranged from 1.02% to 2.77% with the highest accumulation in cv. ʻSokurʼ. Content of ascorbic acid (vitamin C) ranged from 6.3 mg/100 g FW in ʻKrasa Meŝeryʼ to 26.6 mg/100 g FW in cv. ʻKrasavchikʼ. Carotenoids content ranged from 0.157 mg/100 g FW in cv. ‘Nayada’ to 0.645 mg/100 g FW in cv. ʻGrandʼ. Content of anthocyanins in potato ranged from 1.04 mg/100g FW (not colored tubers of cv. ʻKrasa Meŝeryʼ) to 283.04 mg/100g FW (colored tubers of cv. ʻFioletovyiʼ). The nutritional value of tubers (content of dry matter, sugars, starch and protein) was determined to a greater extent (38-49%) by varietal characteristics, rather than by meteorological conditions in vegetation period. The content of vitamin C, carotenoids, protein and anthocyanins varied depending on the year. The highest content of dry matter, starch and carotenoids was noted in tubers harvested in 2019, marked by low temperatures and precipitation deficit in growing season. The conditions of 2020 with low temperatures and excess precipitation were the most favorable for anthocyanin’s accumulation in potato tubers while not for other biochemical parameters. Of the cultivars, ʻSokurʼ had the highest content of dry matter, protein and starch. Cv. ʻFioletovyiʼ had small starch content and high level of anthocyanins. Cv. ʻPlamyaʼ can be recommended for potato products manufacturing due to dry matter content above 20% and reducing sugars content 0.24%..