Stability of agronomic traits in interspecific hybrid potato clones in the Central Region of European Russia

Background. Yield stability is a necessary trait for sustainable potato production under climate change. Potato breeding is based on crosses between parental lines selected for a set of important traits: productivity, structural yield components, and resistance to abiotic and biotic stresses. Data on plant responses to environmental conditions allows breeders to conduct informed selection of plant forms for crossing. The objective of this work was to characterize interspecific potato hybrids in terms of their productivity, yield plasticity and stability in the Central Region of European Russia.Materials and methods. For seven years (2014–2020), 19 hybrids and cv. ‘Favorit’ (reference) were assessed for productivity, number of tubers per plant, mean tuber weight, marketability, and resistance to late blight. Growing conditions were characterized using the hydrothermal coefficient. Environmental sustainability was determined by calculating the parameters of plasticity (bI) and stability (σ2) according to N. P. Sklyarova and V. A. Zharova.Results. Positive and negative anomalies in heat or moisture supply were observed during the test years. The maximum productivity was obtained in 2016, with heavy rainfall and higher temperatures; the minimum, in the hot and dry 2018. For productivity, the effect sizes of the factors “variety” and “year” were 29% and 38%, respectively. Hybrids with yield levels close to cv. ‘Favorit’ were identified: 117-2, 122-29, 99-6-5, 99-1-3, 99-6-6, and 34-5-2003. ‘Favorit’ is an intensive-type cultivar, with low yield stability. Hybrid 135-2-2006, also of the intensive type, had a stable yield, but developed medium-sized tubers and was less productive than other accessions. Hybrid 117-2 is of the extensive type, with medium stability, while hybrids 8-3-2004 and 135-5-2005 demonstrated high environmental plasticity and yield stability

Image-based analysis of quantitative morphological characteristics of wild potato tubers using the desktop application SeedСounter

The development of quantitative digital phenotyping methods for evaluation of wild potato (section Petota Dumort., genus Solanum L.) tuberization is required for annotation of genebank collections and selection of the suitable donor material for potato breeding. There are no available methods specifically designed for the quantitative analysis of wild potato tuber morphology. The current study is devoted to evaluation of wild potato tubers’ morphological characteristics using a digital image processing technique. For this purpose, the mobile application SeedSounter developed previously for grain analysis was specifically adapted for tuber phenotyping. The application estimates the number and shape of objects scattered on a standard sheet of white paper (i. e. A3 or A4). Twelve accessions from the VIR genebank collection belonging to nine Petota species were grown in pots protected with garden fabric during the growing season of cultivated potato (Novosibirsk region). Tubers were collected form plants of nine genotypes. Three genotypes did not produce tubers. The weight of tubers collected from each plant was measured. The tuber yield from each plant was analyzed using SeedCounter (http://wheatdb.org/seedcounter). The number of tubers per plant was counted; the following characteristics were extracted from the images of individual tubers: length, width, projected area, length to width ratio, сircularity, roundness, rugosity and solidity. One-way ANOVA showed a significant effect of genotype on all measured characteristics. A pairwise comparison of nine Petota accessions using all measured parameters revealed statistically significant differences between 86 % of pairs. The overall tuber yield volume for each plant was  calculated as a sum of volumes of individual tubers; tuber volume was calculated from its length to width ratio and projected area. A strong correlation between the evaluated tuber yield volume and yield weight was shown. We propose tuber yield volume as a characteristic for a general evaluation of tuberization for wild potato, implementing the four-step scale from 0 to 3. According to this characteristic, the twelve wild potato accessions studied could be divided into four groups with different tuberization abilities. The evaluated tuberization ability is partially in accordance with previously obtained VIR data. The results presented demonstrate the possibility to use SeedCounter for  wild potato  collections phenotyping

Late blight resistant potato hybrid clones in the VIR collection of plant genetic resources

Background. Late blight (LB) causes serious damage to potato crop. The genetic diversity of potato and their wild relatives in the VIR collection served as the basis for creating interspecific hybrids.Objective of the study. Selection of hybrid potato clones with high and long-term resistance to LB and identification of genotypes that can serve as the most promising sources of new LB resistance genes or new alleles of the already known resistance genes.Materials and methods. In 2015-2017, 45 hybrid clones with genetic material from two to nine species of Solanum L. section Petota Dumort. and six potato varieties were assessed in field conditions in the Northwestern and Central regions of Russia. The index of plant damage by P. infestans (rAUDPC), relative resistance to LB (Sx) and damage to plants at the end of growth period were determined. Thirty-six genotypes were evaluated in the lab for resistance to highly aggressive P. infestans isolates from the collection of VNIIF (All-Russian Research Institute of Phytopathology). In parallel, DNA markers were used to reveal three genes that confer broad-spectrum resistance to P. infestance (Rpi).Results and conclusions. The initial period of infection, the rate of pathogen development and the degree of potato crop damage by LB differed significantly in 2015, 2016 and 2017. The relationship between rAUDPC values in different years of study was statistically significant for hybrids and potato varieties (r = 0.87-0.94). Each year, var. 'Sarpo Mira', clones 10 / 05-09 and 50/1 KBA were highly resistant to LB (Sx = 7-8 points). As to other potato genotypes, the values of the Sx index varied between the years of the study. 'Sarpo Mira' and 12 clones, namely 38 KVA, 24-1, 24-2, 16/27-09, 4-1-2012, 118-5-2011, 39-1-2005, 50/1 KBA, 12/1-09, 171-3, 134-2-2006 and 15/13-09 were highly resistant to artificial infection with P. infestans. The average degree of consistency of potato resistance assessments in the field and laboratory experiments was established: the Spearman correlation coefficient r was 0.45-0.50 (p <0.05). In the cluster analysis, 36 potato genotypes were divided into three groups, which differed significantly in their resistance to LB under various environmental conditions. High resistance to LB correlated with the presence of resistance genes that confer broad-spectrum resistance (R8 = Rpi-smira2 in 'Sarpo Mira' and Rpi-blb1, Rpi-blb2 and Rpi-vnt1 in interspecific hybrids)