Wild Potato Species Research Articles

Cell ultrastructure and physiological changes of potato during cold acclimation

Potato cultivars are sensitive to frost; thus, freezing damage often results in heavy loss of potato yield. In this study, two wild potato species, Solanum acaule W3, which is frost-resistant and has cold-acclimation ability, and Solanum cardiophyllum Cph12, which is frost-sensitive and cannot be cold-acclimated, were used to research the cell structure and physiological changes that occur during cold acclimation. The results showed that the frost resistance of W3 was enhanced by cold acclimation, while the frost resistance of Cph12 did not change. The subcellular characteristics related to the enhancement of freezing resistance mainly include a decrease in the proportion of the vacuole to total cell volume, integrity of the biomembrane, and orderly arrangement of grana lamellae. At the physiological level, the W3 damage index was correlated with membrane lipid peroxidation system indices (including chlorophyll, malondialdehyde, and the difference between relative conductivity before and after freezing treatment in W3), the activity of the antioxidant enzymes superoxide dismutase and catalase, the contents of the osmotic regulators proline and soluble protein, and the contents of the endogenous hormones salicylic acid (SA), indole acetic acid/abscisic acid (IAA/ABA), and SA/ABA, which indicated that cold acclimation enhanced the freezing resistance of wild potato species W3 by enhancing its original cold-tolerance characteristics. The results could be useful to clarify the cold resistance mechanism of plants, and to provide a theoretical basis for cold-resistance breeding.

Pathways to defense metabolites and evading fruit bitterness in genus Solanum evolved through 2-oxoglutarate-dependent dioxygenases

The genus Solanum comprises three food crops (potato, tomato, and eggplant), which are consumed on daily basis worldwide and also producers of notorious anti-nutritional steroidal glycoalkaloids (SGAs). Hydroxylated SGAs (i.e. leptinines) serve as precursors for leptines that act as defenses against Colorado Potato Beetle (Leptinotarsa decemlineata Say), an important pest of potato worldwide. However, SGA hydroxylating enzymes remain unknown. Here, we discover that 2-OXOGLUTARATE-DEPENDENT-DIOXYGENASE (2-ODD) enzymes catalyze SGA-hydroxylation across various Solanum species. In contrast to cultivated potato, Solanum chacoense, a widespread wild potato species, has evolved a 2-ODD enzyme leading to the formation of leptinines. Furthermore, we find a related 2-ODD in tomato that catalyzes the hydroxylation of the bitter α-tomatine to hydroxytomatine, the first committed step in the chemical shift towards downstream ripening-associated non-bitter SGAs (e.g. esculeoside A). This 2-ODD enzyme prevents bitterness in ripe tomato fruit consumed today which otherwise would remain unpleasant in taste and more toxic.

Genetic Diversity of Solanum pinnatisectum Dun. and Solanum chacoense Bitt. by Resistance to Potato Virus Y and Results of DNA Analysis

The potato Solanum tuberosum L. has the greatest diversity of cultivated and wild relatives, whose genetic nature has been studied insufficiently. The aim of the present study was to examine the resistance to PVY in S. chacoense Bitt. and S. pinnatisectum Dun. and to search for DNA markers linked to resistance genes. For the first time, representative populations of two diploid tuber-bearing Solanum species were evaluated by the resistance to PVY and the presence of DNA markers linked to the Ry (extreme resistance) or Ny (hypersensitivity) genes localized on the long arm of chromosome 9. Nine accessions of S. chacoense and six accessions of S. pinnatisectum represented by 168 and 170 genotypes, respectively, from the VIR collection were assessed by resistance to artificial infection with PVY. The differences in segregation of two wild potato species into phenotypic classes with response to PVY infection have been established. The diversity of visible reactions of S. chacoense plants after PVY infection differs from the uniform type of symptoms observed in S. pinnatisectum. DNA analysis was performed in 170 S. chacoense genotypes and 44 S. pinnatisectum genotypes using the Ry186, S1d11, and CT220 markers linked to genes determining viral resistance in potato varieties, breeding clones, or species of the genus Solanum L. Most genotypes of S. chacoense and S. pinnatisectum have amplified CT220 marker linked to the Nxphu gene and the Sw-5 gene in the IvP35 line of the species S. phureja Juz. et Buk. and tomato, respectively. The STS Ry186 marker linked to the Rychc gene in Japanese varieties created on the basis of S. chacoense was identified in a small number of S. chacoense genotypes; however, no association between the DNA marker and resistance phenotype was detected. The CAPS S1d11/AcsI marker, which distinguishes between the PVY resistant and susceptible genotypes of both wild potato species, was developed. The plants of two wild-growing tuber-bearing species of Solanum L. were first examined for the presence of the GBSS gene-specific PCR marker (the gene encoding granules-bound starch synthase). A significant part of the genotypes (15% in S. pinnatisectum and 25% in S. chacoense) did not reveal the genetic marker regulating amylose biosynthesis in the forming starch granules. No significant differences in the ability to form tubers depending on the genotypes with or without GBSS marker, indicating the possible presence of an alternative allelic variant of the GBSSI gene in S. chacoense and S. pinnatisectum species, were detected.

Inheritance of steroidal glycoalkaloids in potato tuber flesh

Potato (Solanum tuberosum L.) is the third most important food crop worldwide after wheat and rice in terms of human consumption. A critical domestication trait for potato was the decrease of toxic steroidal glycoalkaloids (SGAs) in tuber flesh. Here, we used a diploid F2 segregating population derived from a cross between S. tuberosum and the wild potato species Solanum chacoense to map the quantitative trait loci (QTLs) associated with the regulation of SGAs content in tuber flesh. In a three-year study, we identified two QTLs on chromosomes 2 and 8 affecting SGAs content in tuber flesh. The QTL on chromosome 8 harbors 38 genes that are co-expressed with the GLYCOALKALOID METABOLISM genes. These findings lay the foundation for exploiting the genes controlling SGAs content in tuber flesh and they provide a theoretical basis for the use of wild germplasm in potato breeding.

Extreme resistance to late blight disease by transferring 3 R genes from wild relatives into African farmer-preferred potato varieties

Three late blight resistance (R) genes from wild potato species were transferred as a stack into the farmer-preferred varieties ‘Tigoni’ and ‘Shangi’. Transgenic events were tested by detached-leaf assays (DLA) and whole-plant assays (WPA) with isolates of Phytophthora infestans using 20,000 sporangia / mL inoculum. For the first DLA, 9 out of 13 ‘Tigoni’ and 10 out of 12 ‘Shangi’ transgenic events had scores below 3% of leaf affected area. 17 of the 19 transgenic events with low scores were subjected to a second DLA using two different P. infestans isolates. 8 of them exhibited extreme LB resistance while the remaining 9 transgenic events showed hypersensitive response (HR). 6 transgenic events (2 ‘Tigoni’ and 4 ‘Shangi’) with extreme resistance by DLA were subjected to WPA and they all exhibited extreme resistance to LB. Hence, this study demonstrates that a simple DLA predicts high level of resistance to late blight. R gene expression analysis in 18 transgenic events showed different transgenic events exhibiting different levels of expression in the three genes. However, that pathogen induction and / or high R gene expression are necessary for extreme resistance when transgenic events bear a stack of three R genes was not observed. Key words: Detached-leaf assay, late blight, Phytophthora infestans, resistance.

Pollination Type Recognition from a Distance by the Ovary Is Revealed Through a Global Transcriptomic Analysis.

Sexual reproduction in flowering plants involves intimate contact and continuous interactions between the growing pollen tube and the female reproductive structures. These interactions can trigger responses in distal regions of the flower well ahead of fertilization. While pollination-induced petal senescence has been studied extensively, less is known about how pollination is perceived at a distance in the ovary, and how specific this response is to various pollen genotypes. To address this question, we performed a global transcriptomic analysis in the ovary of a wild potato species, Solanum chacoense, at various time points following compatible, incompatible, and heterospecific pollinations. In all cases, pollen tube penetration in the stigma was initially perceived as a wounding aggression. Then, as the pollen tubes grew in the style, a growing number of genes became specific to each pollen genotype. Functional classification analyses revealed sharp differences in the response to compatible and heterospecific pollinations. For instance, the former induced reactive oxygen species (ROS)-related genes while the latter affected genes associated to ethylene signaling. In contrast, incompatible pollination remained more akin to a wound response. Our analysis reveals that every pollination type produces a specific molecular signature generating diversified and specific responses at a distance in the ovary in preparation for fertilization.

Analysis of allelic variation in wild potato (Solanum) species by simple sequence repeat (SSR) markers.

Allelic variation in wild potato (Solanum) species was analysed using 14 simple sequence repeat (SSR) markers. SSR allelic profiles showed high polymorphism and distinctness among the wild species. A total of 109 alleles of 14 polymorphic SSR markers were scored in 82 accessions belonging to 22 wild potato species. Allele size ranged from a minimum of 104bp (STI0030) to a maximum of 304bp (STM5114). Number of SSR alleles per marker ranged from 4 (STM5127/STM1053) to 13 (STM0019), whereas PIC value varied between 0.66 (STM1053) and 0.91 (STM0019). Cluster analysis using SSR allelic profiles of 82 accessions grouped showed 5 major clusters (I-V) based on the Dice similarity coefficient using neighbour-joining clustering method. Distinct allelic variations were observed among the accessions irrespective of the origin country, series and species. Our study suggests that SSR-based molecular characterization of wild potato species is accession specific and development of an allelic dataset for all the accessions would strengthen their utilization in potato research in future.

Production of male fertile interspecific hybrides between cultivated potatoes and valuable for breeding allotetraploid species Solanum stoloniferum

The germplasm of valuable for breeding wild allotetraploid potato species Solanum stoloniferumis rarely used because of pre- and postzygotic reproductive barriers with cultivated potatoes. One of the factors that complicate crosses between S. stoloniferum and S. tuberosumis unilateral incompatibility (UI).Here, we present the results of application of original SvSv-lines for overcoming UI in crosses with S. stoloniferum and of generating male fertile hybrids derived from this species. SvSv-lines are F2 S. tuberosum dihaploid× S. verrucosum that are male fertile and have D/γ-type cytoplasm. Since they are hybrids on homozygous for Svgene from S. verrucosum, they do not form SvSv-lines and have the same ability for elimination of prezygotic incompatibility as this species.As a result of pollination seven SvSv-lines were pollinated by 26 accessions of S. stoloniferum and a lot of hybrid seeds have been produced.In spite of low percentage of germination (1.9 %), formed 40 seedlings of interspecific hybrids. The experiment on hybridization between SvSv-lines and S. stoloniferum has been reproduced with the accession PI205522 of the wild species, which had DNA markers of PVY and LB resistance genes and “sterile” type cytoplasm W/γ: 950 hybrid seeds and 12 viable seedlings were produced. The genome of the seedlings was doubled by colchicine treatment, which generated hexaploids (F1) that formed highly fertile pollen and set seeds from self-pollination. We were able to cross them as females with the variety Katahdin. Produced pentaploid hybrids (BC1) were readily backcrossed by potato variety Quarta. Seedlings of BC2 were then backcrossed by potato varieties as female and, some of them, as male parents. The substantial part of F1, BC1 and BC2 plants of interspecific hybrids were male fertile (produced a lot functionally fertile pollen).

The Solanum chacoense Fertilization-Related Kinase 3 (ScFRK3) is involved in male and female gametophyte development

BackgroundThe Fertilization-related kinases (FRK) form a class that belongs to the MEKK subfamily of plant MAPKKKs. It was recently shown that FRK class kinases expanded during angiosperm evolution, reaching their maximum numbers in the lineage leading to solanaceous species and culminating in the Solanum genus where they account for more than 40% of the total MEKKs. The first members studied, ScFRK1 and ScFRK2 were shown to play a pivotal role in gametophyte development in the wild potato species Solanum chacoense.ResultsScFRK3 is also involved in gametophyte development. ScFRK3 is expressed in developing pollen and young ovules, reaching its highest level immediately after meiosis and during the mitosis steps in both gametophytes. Hence, three independent lines of ScFRK3 RNAi mutant plants showed decreased number of seeds per fruit. We also observed an important number of degenerated embryo sac in mature ovary. Analysis of ovule development showed that most embryo sac did not enter mitosis I in ScFRK3 RNAi mutant plants. Severe lethality was also observed during male gametophyte development, pollen being arrested before mitosis I, as observed in the female gametophyte. Obvious defects in vegetative organs were not observed, emphasizing the reproductive roles of the FRK class kinases. To isolate MAP kinases acting downstream of ScFRK3, a de novo S. chacoense transcriptome from male and female reproductive organs was assembled. Of the five ScMKKs and 16 ScMPKs retrieved, only the ScMKK3 interacted with ScFRK3, while only the ScMPK13 interacted with ScMKK3, leading to an apparent single three-tiered canonical MAP kinase cascade combination involving ScFRK3-ScMKK3-ScMPK13.ConclusionsThe ScFRK3 MAPKKK is involved in a signaling cascade that regulates both male and female gamete development, and most probably act upstream of ScMKK3 and ScMPK13.

Heat Tolerance in Diploid Wild Potato Species In Vitro

Potatoes are a cool season crop. Yet, with growth in the world population and rising temperatures, more heat tolerant cultivars are going to be needed. The objectives of this work were to identify heat tolerance in diploid wild Solanum species, as measured by the ability to form microtubers in tissue culture, and to compare four different methods of evaluating heat tolerance. In each of five experiments conducted over time, four nodal cuttings from up to 20 genotypes from each of ten diploid wild potato species were grown in MS medium supplemented with 8% sucrose and cultured at 19 °C (cool) and 25 °C (warm) in the dark. Four methods were used to evaluate heat tolerance: percent microtuberization under warm conditions, difference in percent microtuberization between cool and warm conditions, microtuber yield under warm conditions, and the difference in microtuber yield between cool and warm conditions. Species were ranked for each of these four methods (with rank = 1 being most heat tolerant) and ranks were summed across the four methods to identify the most heat tolerant. There were significant differences among species and the species x temperature interaction was significant for percent microtuberization and microtuber yield. Percent microtuberization in five of the species was similar under cool and warm temperatures; greater under cool temperatures for three species; and, greater under warm temperatures for two species. Microtuber yield in four of the species was similar under cool and warm temperatures; greater under cool temperatures for six species; and, greater under warm temperatures for one species. Rankings of heat tolerance among the species varied by the method used, but S. kurtzianum and S. sogarandinum were the most heat tolerant.

Phytotoxic potential of cultivated and wild potato species (Solanum sp.): role of glycoalkaloids, phenolics and flavonoids in phytotoxicity against mustard (Sinapis alba L.)

The phytotoxic abilities of potato (Solanum tuberosum L.), in a population consisting of wild species, potato diploid hybrids and potato cultivars, against mustard (Sinapis alba L.) were investigated. Measurements of total glycoalkaloid, phenolic and flavonoid concentrations in potato leaf extracts and their role in phytotoxicity were performed. Extracts prepared from wild potato species, particularly Solanum maglia and Solanum chacoense, had the strongest inhibitory effect on mustard growth. Most extracts significantly extended the germination time, as determined by Piepper’s index, but extracts prepared from potato cultivars did not affect seedling growth/development. However, only S. maglia and S. chacoense prolonged the time of germination, corresponding to inhibition of mustard growth. The Pearson’s correlation coefficient of concentrations of total glycoalkaloids, phenolics and flavonoids in potato leaf extracts and length of mustard seedlings showed a significant negative correlation for glycoalkaloids (r = − 0.51), with the strongest effect for root length of potato wild species (r = − 0.79) and potato diploid hybrids (r = − 0.86). Our data indicated that glycoalkaloids are the major phytotoxic compounds responsible for potato phytotoxicity against mustard. However, we observed phenolics and flavonoids may influence the strength of the phytotoxic effects caused by glycoalkaloids.

Comparison of Two Strategies to Introgress Genes for Resistance to Common Scab from Diploid Solanum chacoense into Tetraploid Cultivated Potato

Wild potato relatives are important sources of novel genes useful for potato improvement. Since most wild potato species are diploid and most cultivars are tetraploid, it is typically necessary to employ ploidy manipulations to access wild potato germplasm. A common strategy is unilateral sexual polyploidization (USP), in which a tetraploid cultivated clone is crossed with a diploid that produces 2n gametes. The diploid parent may be a wild plant selected for a trait of interest. Alternatively, the wild plant may be crossed to a cultivated diploid and, after selection, the diploid hybrid is then crossed to the tetraploid parent. This study was designed to compare these two strategies for the introgression of common scab resistance from wild diploid Solanum chacoense (chc) into cultivated potato. Progeny were evaluated in naturally scab-infested soil in Maine and Michigan. There were no differences between introgression methods for tuber surface area covered by scab. Scab lesions were significantly more severe when a hybrid was used as the diploid parent, but this difference is likely not large enough to be important in a breeding program. Reciprocal cross differences were not significant. However, location x clone interactions were detected for both surface area and lesion type. This study revealed that, while hybridization strategy did not play a major role in developing this scab resistant germplasm, it is critical to consider production environment when screening for resistance.

MЕКСИКАНСКИЙ ВИД КАРТОФЕЛЯ SOLANUM NEOANTIPOVICZII BUK. (= S. STOLONIFERUM SCHLECHTD.) ИЗ ТАКСОНОМИЧЕСКОЙ СЕРИИ LONGIPEDICELLATA BUK. ДЛЯ ИСПОЛЬЗОВАНИЯ В МЕЖВИДОВОЙ ГИБРИДИЗАЦИИ

Background . There are more than 200 tuber-bearing species in the genus Solanum L. Many of them possess valuable traits able to improve some characteristics in present-day potato cultivars. Wild potato species have formed an entire ploidy series ranging from diploid to hexaploid. Many wild species have not yet been used in potato breeding. A barrier exists in crosses due to differences in chromosome numbers and EBN of parental species. In our previous evaluation of the accession S. neoantipoviczii Buk. VIR k-8505 was found to be highly resistant to Phytophthora infestans and to tree strains of Potato Virus Y (PVY) conferring resistance through the gene Rysto. In J. Hawkes's monography this species is mentioned as synonymous to S. stoloniferum Schlechtd. Russian taxonomist S. M. Bukasov recognized it as an independent species. At the same time D. Correll hypothesized that this species is the hybrid between tetraploid S. stoloniferum and diploid S. verrucosum Schlechtd. We counted the chromosome number in thirty seedlings of the accession S. neoantipoviczii k-8505 and studied the crossability of this accession in combinations with several other species. Material and methods. The plants of the species: S. neoantipoviczii Buk (female parent), original hybrid S. microdontum Bitt. x S. tarijense Hawk., S. berthaultii Hawk., S. ruiz-ceballosii Card., S. kurtzianum Bitt. et Wittm., S. papita Rydb., S. phureja Juz. et Buk. and S. tuberosum L. (male parents) differing in chromosome numbers and previously studied for useful traits were included in hybridization. The chromosome counting was performed in meristem root cells, extracted from in vitro plants. Hybridization was performed using cut branches of female parents after bud decapitation. Results and conclusions . Plants of the accession S. neoantipoviczii k-8505 were basically found tetraploid. In the crosses of S. neoantipoviczii used as the female parent, seeds were obtained in combinations with the accessions of wild (S. berthaultii, S. kurtzianum, S. papita, S. ruiz-ceballosii, hybrid S. microdontum x S. tarijense) and cultivated (S. phureja, S. tuberosum) potato species. Low seed numbers were recorded in the crosses with S. kurtzianum and S. berthaultii. In crosses with the other species, the seed number varied from 50.4 to 106.6.

Finding RB/Rpi-blb1/Rpi-sto1-like sequences in conventionally bred potato varieties

The main objectives in potato breeding are increasing yield abilities and improving resistance to numerous pathogens and pests. Among them, the late blight caused by the Phytophthora infestans oomycete is one of the most destructive potato diseases both in Russia and worldwide. Wild relatives of cultivated potato are traditionally used in breeding as the source of valuable R genes conferring resistance to pathogens. Of particular interest are Mexican wild species because Mexico is the centre of origin and diversity of P. infestans and at the same time, it is the centre of potato species diversity. Mexican wild potato species S. bulbocastanum and S. stoloniferum are an important source of the R genes conferring broad-spec trum resistance against various isolates of P. infestans (Rpi-blb1, Rpi-blb2, Rpi-sto1). Recently these genes have been transferred into cultivated potato gene pool using the cisgene approach. At the same time there is a high probability of finding geno types with the Rpi-sto1 gene (functional homologues of Rpi-blb1) among conventionally bred varieties because for about 40 years S. stoloniferum has been used in breeding as a source of the Rysto and Ry-fsto genes of the extreme resistance to the most important viral pathogen PVY. In this study 188 potato varieties bred in Russia and in near-abroad countries were screened for the presence of six gene-specific markers of the RB/Rpi-blb1 = Rpi-sto1 and Rpi-blb2 genes conferring broad-spectrum resistance against P. infestans, and for the markers linked to the Rysto and Ry-fsto genes conferring extreme resistance to PVY. In addition, a marker for detecting male sterile mitochondrial DNA type gamma derived from S. stoloniferum was used. The genotypes selected through the molecular markers were divided into four groups: (A) 13 PVY resistant varieties carrying diagnostic markers of the Rysto, Ry-fsto genes and having sterile mt-type gamma; (B) four varieties possessing mt-type gamma and not having the markers of the R genes introgressed from S. stoloniferum; (C) eight genotypes carrying five gene-specific markers for the RB/Rpi-blb1/= Rpi-sto1; (D) the rest 166 (86.9 %) varieties not possessing any of the diagnostic markers associated with the S. stoloniferum genetic material. The sequences of the Rpi-sto1- and BLB1 F/R-amplicons were identical in all the genotypes of group ‘C’ and showed respective 99 % and 100 % similarity to the corresponding fragments of the Rpi-sto1 and Rpi-blb1 genes from the GenBank database. Among the genotypes of group ‘C’ various mt-types were detected, and some of them were male fertile.

Resistance to Meloidogyne chitwoodi Identified in Wild Potato Species

Meloidogyne chitwoodi (Columbia root-knot nematode, CRKN) can cause serious damage in potato production systems, decreasing tuber value in the fresh market and processing industries. Genetic resistance to CRKN was first identified from the wild diploid potato species Solanum bulbocastanum accession SB22 and was successfully introgressed into tetraploid potato breeding material. To expand the base of genetic resistance, 40 plant accessions representing nine wild potato species were screened for their resistance to M. chitwoodi. Greenhouse screening identified fifteen clones from S. hougasii, one clone from S. bulbocastanum, and one clone from S. stenophyllidium with moderate to high levels of resistance against three isolates of M. chitwoodi. Geographical mapping showed that the resistance sources identified in this and previous studies primarily originated in the states of Jalisco and Michoacan in west-central Mexico. These new sources of resistance will be introgressed into elite potato populations to facilitate the development of potato cultivars with durable resistance to M. chitwoodi.

Plant Resistance to Colorado Potato Beetle (Coleoptera: Chrysomelidae) in Diploid F2 Families Derived From Crosses Between Cultivated and Wild Potato.

Colorado potato beetle, Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae), is a serious global pest of potato, Solanum tuberosum L. Management of L. decemlineata has relied heavily on insecticides, but repeated evolution of insecticide resistance has motivated the exploration and development of alternative strategies, such as plant resistance. The recent development of two diploid potato families derived from crosses between cultivated and wild potato species (S. chacoense and S. berthaultii) has provided a unique opportunity to reexamine plant traits for resistance breeding. In this 2-yr study, we surveyed select F2 clones for the induction of L. decemlineata mortality and a reduction in defoliation in no-choice feeding assays when challenged with adults and larvae from three sites in Wisconsin. We tested for an association with glandular trichome density and foliar levels of the glycoalkaloids chaconine and solanine. Several potato clones demonstrated resistance in specific feeding assays, but none excelled consistently across experiments. Mortality and defoliation generally differed significantly among L. decemlineata populations, which could be indicative of heritable variation in beetle responses to plant defenses or variation in the physiological status of the beetle populations tested. Contrary to expectations, higher trichome density increased mortality or decreased defoliation in only a few cases, and levels of mortality and defoliation were unrelated to foliar glycoalkaloid content, warranting further investigation of the defense mechanisms of resistant clones. In addition to identifying several potential L. decemlineata resistance sources, this study underscores the need to include multiple insect populations in surveys of plant resistance to this diverse pest.

EVALUATION OF CYTOPLASMIC GENETIC DIVERSITY OF WILD ALLOTETRAPLOID POTATO SPECIES SOLANUM STOLONIFERUM IN CONNECTION WITH THE PROBLEM OF MALE STERILITY OF INTERSPECIFIC HYBRIDS

Valuable for breeding wild allotetraploid potato species S. stoloniferum can be only used as a female in crosses with cultivated potatoes. However, male sterility of potato varieties is associated with W/γ cytoplasm of the wild species that limits their use in breeding. The collection of 26 accessions of S. stoloniferum was studied to evaluate the cytoplasmic genetic diversity. It has been revealed that W/α, D/α, D/γ cytoplasms as well as rare type of cytoplasm that does not fit to existing nomenclature are present in genic pool of the species along with W/γ cytoplasm. It is believed that discovery of S. stoloniferum accessions with cytoplasm different from W/γ makes it possible to produce interspecific hybrids that can be used for breeding male fertile potato varieties.

Genome sequence of M6, a diploid inbred clone of the high-glycoalkaloid-producing tuber-bearing potato species Solanum chacoense, reveals residual heterozygosity.

Cultivated potato (Solanum tuberosum L.) is a highly heterozygous autotetraploid that presents challenges in genome analyses and breeding. Wild potato species serve as a resource for the introgression of important agronomic traits into cultivated potato. One key species is Solanum chacoense and the diploid, inbred clone M6, which is self-compatible and has desirable tuber market quality and disease resistance traits. Sequencing and assembly of the genome of the M6 clone of S.chacoense generated an assembly of 825767562bp in 8260 scaffolds with an N50 scaffold size of 713602bp. Pseudomolecule construction anchored 508Mb of the genome assembly into 12 chromosomes. Genome annotation yielded 49124 high-confidence gene models representing 37740 genes. Comparative analyses of the M6 genome with six other Solanaceae species revealed a core set of 158367 Solanaceae genes and 1897 genes unique to three potato species. Analysis of single nucleotide polymorphisms across the M6 genome revealed enhanced residual heterozygosity on chromosomes 4, 8 and 9 relative to the other chromosomes. Access to the M6 genome provides a resource for identification of key genes for important agronomic traits and aids in genome-enabled development of inbred diploid potatoes with the potential to accelerate potato breeding.

Single Nucleotide Polymorphism (SNP) markers associated with high folate content in wild potato species.

Micronutrient deficiency, also known as the hidden hunger, affects over two billion people worldwide. Potato is the third most consumed food crops in the world, and is therefore a fundamental element of food security for millions of people. Increasing the amount of micronutrients in food crop could help alleviate worldwide micronutrient malnutrition. In the present study, we report on the identification of single nucleotide polymorphism (SNP) markers associated with folate, an essential micronutrient in the human diet. A high folate diploid clone Fol 1.6 from the wild potato relative Solanum boliviense (PI 597736) was crossed with a low/medium folate diploid S. tuberosum clone USW4self#3. The resulting F1 progeny was intermated to generate an F2 population, and tubers from 94 F2 individuals were harvested for folate analysis and SNP genotyping using a SolCap 12K Potato SNP array. Folate content in the progeny ranged from 304 to 2,952 ng g-1 dry weight. 6,759 high quality SNPs containing 4,174 (62%) polymorphic and 2,585 (38%) monomorphic SNPs were used to investigate marker-trait association. Association analysis was performed using two different approaches: survey SNP-trait association (SSTA) and SNP-trait association (STA). A total of 497 significant SNPs were identified, 489 by SSTA analysis and 43 by STA analysis. Markers identified by SSTA were located on all twelve chromosomes while those identified by STA were confined to chromosomes 2, 4, and 6. Eighteen of the significant SNPs were located within or in close proximity to folate metabolism-related genes. Forty two SNPs were identical between SSTA and STA analyses. These SNPs have potential to be used in marker-assisted selection for breeding high folate potato varieties.

Моделювання природної еволюції видів роду Solanum L. cекції Petota Dumort. за фітофторостійкістю

<p>The article presents the theoretical substantiation and experimental data, confirming the natural evolution of potato species from the standpoint of the stability and effectiveness of genetic control of resistance to late blight. Resistant samples of wild potato species which were differ in the appearance of the trait were used as the initial material for research. Artificial infection of seedlings obtained from self-pollination of potato samples with the race of phytophthora (<em>Phytophtora infestans </em>(Mont.) De Bary) 1-11X, Y, Z (25-30 conidia in the view of the microscope, 120 x), which made it possible to identify various types of resistance to fungus. The evolutionary changes of the species, relating their response to the changing of phytopathological situation in their areas have been experimentally proven. The intraspecific variety of <em>S. demissum </em>Lindl and <em>S. stoloniferum </em>Schlechtd. samples by resistance to phytophthora, which manifested both among I1 and among I2, has been identified. Depending on the evolution of the samples, differences in the genetic control of resistance to the pathogen were found, which was manifested in the frequency of appearance of offspring with high resistance, hypersensitivity, high, medium and low field resistance, as well as complete damage of seedlings. In the species of <em>S. demissum</em> the sample was found, in its progeny the seedlings with extremely high resistance to the pathogen were not isolated, but in the case of the UK sample No 27-19 the part of such material was 94.2%. The lower level of genetic control in this species was characterized by the type of supersensitive resistance. Variation in the offspring samples by this type of resistance was observed in the range of 0-78.4%, and the splitting of seedlings with high field stability was even smaller and was within 0-45%. Similar data were obtained for the species of <em>S. stoloniferum</em>. A similar type of conjugate evolution of phytophthora resistance in the testing species has been experimentally proved. There were no differences in the manifestation of hypersensitive resistance or they were very insignificant. The maximum differences between species were 4% in the class with the offspring frequency of 81-100%. Based on the results of the phytophthora resistance evaluation of various samples of potato species in I2, it was assumed that under epiphytotic conditions in the area of species growth, samples with effective genetic control of the trait, i.e., with an extremely high degree of resistance, will be evolutionally promising. </p>