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

Potato mosaic viruses which infect plants of tuber-bearing Solanum spp. growing in the VIR field gene bank

Potato crop is particularly affected by virus diseases, and potato virus Y (PVY) currently considered the most important pathogen distributed worldwide as a diversity of strains. Wild and cultivated tuber-bearing species of the genus Solanum L., stored in the VIR collection, are used as the initial material in creation domestic potato varieties (Solanum tuberosum L.) resistant to virus diseases. The preservation and rational utilization of the potato collection is based on regular phytosanitary monitoring, including quarantine objects, foremost PSTVd (potato spindle tuber viroid). The aim of the work is to examine plants of tuber-bearing Solanum species in the field gene bank of VIR for the presence of PSTVd and PVX (potato virus X), PVS (potato virus S), PVM (potato virus M) and PVY, which are the most common viruses on potatoes in the North-West District of Russia. We examined clonal plants of 137 genotypes representing 31 species of the section Petota of the genus Solanum L. A diagnostic was carried out using ELISA, RT-PCR and indicator plants. No PSTVd was found in the studied plants, but a plural infestation by mosaic viruses was detected, more than half of the tested clones are infected with two or more viruses. In the studied samples, only 17 genotypes (12 %) are not infected by PVX, PVS, PVM and PVY according to the ELISA test. There are statistically significant differences in the virus infestation of Solanum species with different origins, according to Pearson’s chi-squared test. Among the studied genotypes of wild relatives of potatoes, the proportion of those affected by PVY was significantly higher in the South American than in the North American species (χ2 = 4.56, p = 0.03); the proportion of genotypes affected by PVХ was significantly higher in the North American species (χ2 = 8.81, p = 0.003), the critical value was χ2 = 3.841. PVY strains were identified by multiplex RT-PCR in 37 genotypes of Solanum spp. We found that 27 genotypes are infected by a common PVYO strain, two genotypes are infected by PVYNW (A) and PVYNW (B) strains, respectively, seven genotypes are infected by a mixture of PVYO +PVYNW (A) strains, and one is infected by a mixture of PVYO +PVYNTN-NW (SYRI)+SYRIII strains. The recombinant strains of PVY are detected in the North-West District of Russia for the first time. Coherency of the results of PVY strains detection by various (immunological, molecular and biological) methods is discussed

Wild relatives and interspecific hybrids of potato as source materials in breeding for resistance to golden nematode

Background. Predominant use of the H1 and Gro1-4 genes of resistance to golden nematode (PGN) in potato breeding requires widening the gene pool of resistance to this pathogen.Materials and methods. Thirty-four genotypes of wild potatoes from North and South Americas, 14 interspecific hybrids, and 10 Russian potato cultivars were studied for PGN resistance. Screening for resistance to PGN pathotype Ro1 and molecular screening for the presence of H1 and Gro1-4 gene markers were performed. Amplification products of the Gro1-4 gene marker were sequenced.Results. Only seven among the studied 34 potato genotypes (two of S. brachystotrichum (Bitt.) Rydb., four of S. lesteri Hawkes et Hjerting, and one of S. kurtzianum Bitt. et Wittm.) were susceptible to PGN, while the rest demonstrated high or medium resistance. Molecular screening for the presence of H1 and Gro1-4 gene markers allowed us to identify Gro1-4 in 13 South American genotypes of S. alandiae Cárd., S. × doddsii Corr., S. kurtzianum, S. leptophyes Bitt., and S. yungasense Hawkes. The remaining 14 genotypes may supposedly contain resistance genes non-identical to H1 or Gro1-4. Hybrids of S. tuberosum L. with medium-resistant wild accessions of S. kurtzianum, S. leptophyes, S. sparsipilum (Bitt.) Juz. et Buk., S. alandiae, and S. × doddsii inherited PGN resistance determined either by the Gro1-4 gene or genes non-identical to H1 or Gro1-4. Sequencing a fragment of the Gro1-4 gene showed that changes in the structure of this fragment in orthologous genes did not affect the feature of resistance to PGN pathotype Ro1.Conclusion. For the first time, sources of resistance to PGN were found among the North American species S. brachystotrichum (k-23201) and S. lesteri (k-24475). Among the wild South American Solanum spp., sources of resistance determined by genes different from H1 or Gro1-4 were identified. Resistant interspecific hybrids can serve as donors of the Gro1-4 resistance gene or new resistance genes

Molecular markers as tools in breeding for resistance to Potato Virus Y

Potato virus Y (PVY) is an economically important pathogen of potato as a vegetatively propagated crop. High resistance to all strains of PVY is determined by Ry-genes, which are introgressed into modern potato varieties from a limited number of sources of resistance ‒ Solanum stoloniferum Schlechtd. et Bche., Solanum andigenum Juz. et Buk., Solanum chacoense Bitt. Use of new species Solanum and interspecific hybrids based on them provides for the expansion of existing potato gene pool in breeding for resistance to PVY. Traditional breeding for resistance to viruses has still a great potential, though, it is a long and laborious process. Molecular markers linked to Ry-genes are widely integrated in order to increase the effectiveness of practical breeding. Previous studies have revealed a number of shortcomings in using the molecular markers of Ry-genes. To assess the predictive abilities of molecular markers RYSC3, M45, M6 of the Ryadg gene and YES3-3A of the Rysto gene for resistance to PVY, the F1 generation of two potato populations was studied, in the creation of which inter-specific hybrids were used. The nature of segregation 5:3 obtained by phenotype showed that the original parental forms can be the sources of not only previously identified, but also unidentified Ry-genes and Ny-genes of hypersensitivity. Correlation coefficient between the presence of markers and resistance to PVY was 0.64 for the YES3-3 marker (79 % matching) and 0.54 for RYSC3, М45, М6 markers (76 % matching). There have been revealed the cases of “false positive” results of the study (the presence of a marker in susceptible genotypes), which indicate to the insufficient effectiveness of the markers used. The marker segregation observed in the populations was consistent with chromatid segregation, confirming the simplex nature of Ry-genes inheritance from resistant parents. The ratio of genotypes with the presence/absence of markers was 0.86:1

APPLICATION OF MOLECULAR MARKERS IN BREEDING FOR RESISTANCE TO POTATO CYST NEMATODE

The article presents the results of the application of molecular markers of the genes controlling resistance to potato cyst nematode in different stages of potato breeding - for screening genetic collections and promising hybrids of the All-Russian Institute of Potato Research and the Vavilov Institute of Plant Genetic Resources. It has been established that "pseudopositive" and "pseudonegative" results of a marker-mediated breeding process are associated not only with the specificity of the used markers, but with a lack of objectivity in phenotypic evaluation for resistance to the nematode

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

De Novo Domestication Concept for Potato Germplasm Enhancement

Wild potato germplasm serves as a natural pool of agronomically valuable traits for potato breeding, such as resistance to pathogens and abiotic stresses, quality, and consumer-oriented traits. The introgression of these traits into cultivated potato is hampered by the different kinds of incompatibility and linkages between desirable and undesirable features in hybrid progeny. The trait donor improvement via correction of negative characteristics prior to hybridization to domestic potato can be a solution to the linkage drag problem. The de novo domestication concept for developing new crops using gene editing technologies was previously proposed and performed for tomato and physalis. In this review, we collected information about donor properties of different wild potato species and developed a strategy for potato germplasm enhancement using the de novo domestication approach. The possible modifications of several candidate genes responsible for undesirable traits in wild potato, including high steroidal glycoalkaloid content, self-incompatibility, tuberization under short day conditions, and long stolons are proposed. The current challenges and future prospects of implementing the de novo domestication strategy for potato are discussed

De Novo Domestication Concept for Potato Germplasm Enhancement

Wild potato germplasm serves as a natural pool of agronomically valuable traits for potato breeding, such as resistance to pathogens and abiotic stresses, quality, and consumer-oriented traits. The introgression of these traits into cultivated potato is hampered by the different kinds of incompatibility and linkages between desirable and undesirable features in hybrid progeny. The trait donor improvement via correction of negative characteristics prior to hybridization to domestic potato can be a solution to the linkage drag problem. The de novo domestication concept for developing new crops using gene editing technologies was previously proposed and performed for tomato and physalis. In this review, we collected information about donor properties of different wild potato species and developed a strategy for potato germplasm enhancement using the de novo domestication approach. The possible modifications of several candidate genes responsible for undesirable traits in wild potato, including high steroidal glycoalkaloid content, self-incompatibility, tuberization under short day conditions, and long stolons are proposed. The current challenges and future prospects of implementing the de novo domestication strategy for potato are discussed