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Knowledge regarding genetic diversity and population structure of breeding materials is essential for crop improvement. The Texas A&M University Potato Breeding Program has a collection of advanced clones selected and maintained in-vitro over a 40-year period. Little is known about its genetic makeup and usefulness for the current breeding program. In this study, 214 potato clones were genotyped with the Infinium Illumina 22 K V3 Potato Array. After filtering, a total of 10,106 single nucleotide polymorphic (SNP) markers were used for analysis. Heterozygosity varied by SNP, with an overall average of 0.59. Three groups of tetraploid clones primarily based on potato market classes, were detected using STRUCTURE software and confirmed by discriminant analysis of principal components. The highest coefficient of differentiation observed between the groups was 0.14. Signatures of selection were uncovered in genes controlling potato flesh and skin color, length of plant cycle and tuberization, and carbohydrate metabolism. A core set of 43 clones was obtained using Core Hunter 3 to develop a sub-collection that retains similar genetic diversity as the whole population, minimize redundancies, and facilitates long-term conservation of genetic resources. The comprehensive molecular characterization of our breeding clone bank collection contributes to understanding the genetic diversity of existing potato resources. This analysis could be applied to other breeding programs and assist in the selection of parents, fingerprinting, protection, and management of the breeding collections. [ABSTRACT FROM AUTHOR]

In the past, the potato plant microbiota and rhizosphere have been studied in detail to improve plant growth and fitness. However, less is known about the postharvest potato tuber microbiome and its role in storage stability. The storage stability of potatoes depends on genotype and storage conditions, but the soil in which tubers were grown could also play a role. To understand the ecology and functional role of the postharvest potato microbiota, we planted four potato varieties in five soil types and monitored them until the tubers started sprouting. During storage, the bacterial community of tubers was analysed by next-generation sequencing of the 16S rRNA gene amplicons. The potato tubers exhibited soil-dependent differences in sprouting behaviour. The statistical analysis revealed a strong shift of the tuber-associated bacterial community from harvest to dormancy break. By combining indicator species analysis and a correlation matrix, we predicted associations between members of the bacterial community and tuber sprouting behaviour. Based on this, we identified Flavobacterium sp. isolates, which were able to influence sprouting behaviour by inhibiting potato bud outgrowth. [ABSTRACT FROM AUTHOR]

Chipping potatoes are bred for their ability to produce light-colored, defect-free chips. Chips with stem-end chip defect (SECD) have dark blemishes and are undesirable to consumers and chip processors. The heritability of SECD is not known and genetic loci linked to defect formation have not been identified. Chip processing varieties 'Wauseon' and 'Lenape' were crossed and tubers from parents and 191 progeny were evaluated over four years for chip color descriptors L*, a*, and b* and SECD score in January, March, and May. Broad sense heritability for SECD was 0.64 or greater at each sampling time. Genotype data were used to construct a 1282 cM linkage map. Nine quantitative trait loci (QTL) for SECD were detected, and seven overlapped QTL for chip color traits. The QTL identified are starting points for developing molecular markers that are used to select genotypes that produce light-colored chips and have resistance to SECD formation. [ABSTRACT FROM AUTHOR]

Abstract: Key message Sen2gene for potato wart resistance, located on chromosome XI in a locus distinct fromSen1, provides resistance against eight wart pathotypes, including the virulent ones important in Europe.Abstract: Synchytrium endobioticum causes potato wart disease imposing severe losses in potato production, and as a quarantine pathogen in many countries, it results in lost trade markets and land for potato cultivation. The resistance to S. endobioticum pathotype 1(D1) is widespread in potato cultivars but new virulent pathotypes appear and the problem re-emerges. To characterize and map a new gene for resistance to potato wart, we used diploid F1 potato population from a cross of potato clone resistant to S. endobioticum pathotype 1(D1) and virulent pathotypes: 2(G1), 6(O1), 8(F1), 18(T1), 2(Ch1), 3(M1) and 39(P1) with a potato clone resistant to pathotype 1(D1) only. The 176 progeny clones were tested for resistance to eight wart pathotypes with a modified Glynne-Lemmerzahl method. Bimodal distributions and co-segregation of resistance in the population show that a single resistance gene, Sen2, underlies the resistance to eight pathotypes. Resistance to pathotype 1(D1) was additionally conferred by the locus Sen1 inherited from both parents. Sen2 was mapped to chromosome XI using DArTseq markers. The genetic and physical distances between Sen1 and Sen2 loci were indirectly estimated at 63 cM and 32 Mbp, respectively. We developed PCR markers co-segregating with the Sen2 locus that can be applied in marker-assisted selection of potatoes resistant to eight important pathotypes of S. endobioticum. Wide spectrum of the Sen2 resistance may be an indication of durability which can be enhanced by the pyramiding of the Sen2 and Sen1 loci as in 61 clones selected within this study. [ABSTRACT FROM AUTHOR]

To develop an in vitro assay method for bacterial wilt resistance in potato, resistant and susceptible standard genotypes were grown in vitro, and different conditions of inoculation with Ralstonia solanacearum phylotype I/biovar 4 were examined. The optimal condition was the inoculation of 6-8 leaf stage plants with a bacterial concentration of 102 CFU ml−1 and an incubation temperature of 28 °C. Evaluation of stem wilting was more reliable than that of leaf wilting. Using this method, nine genotypes with different resistance levels in the field were evaluated. Lower disease indices were obtained for genotypes with high resistance levels in the field, suggesting that this assay is useful for evaluating bacterial wilt resistance in a controlled environment. [ABSTRACT FROM AUTHOR]

Greening is a major cause of quality loss in potato tubers. As underground stems, potato tubers are non-photosynthetic plant organs that lack photosynthetic machinery. However, after light exposure, amyloplasts convert to chloroplasts in tuber peripheral cell layers, which cause the accumulation of the green photosynthetic pigment, chlorophyll. Tuber greening can be impacted by genetic, cultural, physiological and environmental factors including planting depth, tuber physiological age, temperature, atmospheric oxygen levels, and lighting conditions. Numerous studies have been devoted to understand and control this costly defect for the potato industry. This review brings together the available knowledge on light-induced greening, from causes to solutions and suggestions on further research with a focus on identifying the underlying mechanisms of tuber greening. [ABSTRACT FROM AUTHOR]

Andean Potato is a major crop for farmers in the Andes and represents an important gene pool for potato improvement. We present the population structure and genetic diversity of 88 Andigena accessions collected in Northwestern Argentina based on functional markers (25 SSR) distributed along 12 chromosomes. Polymorphic information content ranged from 0.40 to 0.87. A Bayesian approach, a Principal Coordinate Analysis and a Cluster Analysis revealed the presence of: I) a major group containing most of the Andean accessions and II) a smaller group including the out-group cv. Spunta and the sequenced genotype DM. Several group specific alleles were detected. AMOVA showed that 81% of the variability was within each group. Eleven of the SSRs analyzed are linked or within genes reported to regulate traits of nutritional and industrial interest. Additionally, the allelic variant of a photoperiod dependent tuberization regulator gene, StCDF1.2, was exclusively detected in accessions clustered in group II. [ABSTRACT FROM AUTHOR]

Potato tubers must be cold-stored to extend their shelf life and maintain an uninterrupted supply chain for food processors. However, a side-effect of low-temperature storage is manifested in terms of cold-induced sweetening (CIS) of potato tubers, which reduces the processing quality and the commercial value of the end-products. RNA interference (RNAi) technology, whereby transgene-derived small interfering RNAs can trigger the homology-based knockdown of cognate host genes and can initiate gene silencing, has been successfully applied in crop improvement through targeted gene knockout in host plants. In the current study, transgenic potato plants (Solanum tuberosum cv. Désirée) were generated, expressing a 300 bp hairpin loop nucleotide sequence targeting the potato vacuolar invertase gene (VInv), under the constitutive Cauliflower mosaic virus 35S promoter. Tubers collected from transgenic lines showed a significant reduction in reducing sugar content after 180 days of cold storage, without showing any measurable off-target effects on plant morphology and tuberization compared to non-transformed control plants. The cold-stored tubers were further assayed for chip color, which showed a fairly light colored quality in the samples originating from RNAi lines. Together with similar effects seen in previously published experiments involving other potato varieties, the Désirée results described here establish the efficacy of using RNAi for the successful reduction of CIS in potato tubers. [ABSTRACT FROM AUTHOR]

The mechanisms of potato (Solanum tuberosum L.) plants’ tolerance to chloride salinity were investigated in cv. Lugovskoi regionalized in Russia. Regenerated plants were produced in vitro from apical meristem and grown on half-strength Murashige and Skoog medium (0.5 MS) using a hydroponic unit in controlled-climate conditions. At the age of six weeks, the plants were exposed to salt stress (50-150 mM NaCl, 7 days). Plant response to salt stress was estimated by growth parameters (fresh and dry biomass of the aboveground and underground parts of plants, linear dimensions of shoot and root, area of leaf surface, and number of stolons) and physiological characteristics (level of photosynthetic pigments, accumulation of sodium, potassium, and calcium ions in the aboveground and underground parts of plants, content of proline, activity of antioxidant enzymes, plant tissue hydration, osmotic potential, and POL). It was found that, in response to salinity, the plants of potato, cv. Lugovskoi, showed a considerable inhibition of growth processes, reduction in chlorophyll a content, and suppression of stolon formation, which points to a rather low salinity tolerance of the cultivar. At the same time, under weak or moderate salt stress, the plants preserved water homeostasis owing to effective osmoregulation, actively accumulated proline that acted as a stress protector, and showed hardly any signs of oxidative stress. It was assumed that low salt tolerance of this cultivar depends on the inability of its root system to retain sodium ions and ensure selective ion transport to the aboveground part of the plant and on inefficiency of the system of sodium ions’ removal from the cytoplasm of leaf cells and their compartmentalization in the central vacuole with the purpose of reducing their toxic effect. The obtained results may be useful for working out a technique of improving salt tolerance of this cultivar by the methods of molecular genetics. [ABSTRACT FROM AUTHOR]

In a remote mountainous region of the Philippines, farmers selected their own clones from hybrid True Potato Seed (TPS) populations and have maintained them for 30 years without public support. In 1985, the International Potato Center (CIP) initiated on-farm TPS research in the Mount Kanlaon area to help farmers control or reduce the rates of bacterial wilt caused by Ralstonia solanacearum. Seedlings were either grown in nursery beds or as transplants in the field. At harvest, farmers not only harvested their crop for either food or for sale but also selected their preferred clones. A survey conducted in 2016 showed that farmers are still growing potato clones selected from TPS and that these clones had spread to numerous areas within and around Mount Kanlaon. Farmers kept these clones because it was profitable because they required minimum inputs and their resistance to various pests and diseases and adverse weather conditions. ELISA tests showed that these clones have excellent virus resistance which partially explains why these clones have been growing for 30 years without a formal seed production program or any government support. Parents used to develop the TPS hybrids included those with virus and R. solanacearum resistance. [ABSTRACT FROM AUTHOR]

The golden cyst nematode (Globodera rostochiensis) is a serious pest that can dramatically reduce potato crop yield. Pathotype Ro1 of G. rostochiensis was first detected in the United States in 1941 and is still present on several farms in New York State. The H1 gene confers high levels of resistance to pathotype Ro1 but screening for it with a bioassay is time consuming and expensive. In this study two known molecular markers, 57R and TG689, were evaluated for their ability to identify resistant clones among 38 global cultivars and 350 New York breeding clones. The ability of either marker to predict resistance was high - 99.7% and 98.3% for 57R and TG689, respectively - but the ability to predict susceptibility was much lower, 47% and 41%, respectively. As resistance is the trait of interest, either of these markers is sufficient to make selection decisions in a practical breeding program. Cases exhibiting discordance between presence/absence of diagnostic markers and bioassay results were investigated further. Recombination, inflow of other resistance genes, and occasional failure of marker- and/or bio-assays are discussed as potential causes. [ABSTRACT FROM AUTHOR]

Common scab caused by the soil-borne bacterium Streptomyces scabies is a serious disease for the potato industry. We have identified a strong source of resistance in the diploid wild relative Solanum chacoense. This resistance has been introgressed into tetraploid cultivated potato via unilateral sexual polyploidization. This paper describes three hybrid clones (M8, M16, M17) for use by potato breeding programs to enhance resistance to common scab. They were created by crossing a diploid clone (50% S. tuberosum, 50% S. chacoense) to tetraploid cultivars, producing hybrids with 75% cultivated and 25% wild germplasm. The clones are male and female fertile, and are adapted to temperate zone production environments. [ABSTRACT FROM AUTHOR]

Key message: Cd is a toxic metal, whilst Zn is an essential for plant and human health. Both can accumulate in potato tubers. We examine the genetic control of this process.Abstract: The aim of this study was to map quantitative trait loci (QTLs) influencing tuber concentrations of cadmium (Cd) and zinc (Zn). We developed a segregating population comprising 188 F1 progeny derived from crossing two tetraploid cultivars exhibiting divergent tuber-Cd-accumulation phenotypes. These progeny were genotyped using the SolCap 8303 SNP array, and evaluated for Cd, Zn, and maturity-related traits. Linkage and QTL mapping were performed using TetraploidSNPMap software, which incorporates all allele dosage information. The final genetic map comprised 3755 SNP markers with average marker density of 2.94 per cM. Tuber-Cd and Zn concentrations were measured in the segregating population over 2 years. QTL mapping identified four loci for tuber-Cd concentration on chromosomes 3, 5, 6, and 7, which explained genetic variance ranging from 5 to 33%, and five loci for tuber-Zn concentration on chromosome 1, 3, 5, and, 6 explaining from 5 to 38% of genetic variance. Among the QTL identified for tuber-Cd concentration, three loci coincided with tuber-Zn concentration. The largest effect QTL for both tuber-Cd and Zn concentration coincided with the maturity locus on chromosome 5 where earliness was associated with increased tuber concentration of both metals. Coincident minor-effect QTL for Cd and Zn sharing the same direction of effect was also found on chromosomes 3 and 6, and these were unrelated to maturity The results indicate partially overlapping genetic control of tuber-Cd and Zn concentration in the cross, involving both maturity-related and non-maturity-related mechanisms. [ABSTRACT FROM AUTHOR]

Studying phenotypic and genomic modifications associated with pathogen adaptation to resistance is a crucial step to better understand and anticipate resistance breakdown. This short review summarizes recent results obtained using experimentally evolved populations of the potato cyst nematode Globodera pallida. In a first step, the variability of resistance durability was explored in four different potato genotypes carrying the resistance quantitative trait loci (QTL) GpaVvrn originating from Solanum vernei but differing by their genetic background. The consequences of the adaptation to resistance in terms of local adaptation, cross-virulence and virulence cost were then investigated. Finally, a genome scan approach was performed in order to identify the genomic regions involved in this adaptation. Results showed that nematode populations were able to adapt to the QTL GpaVvrn, and that the plant genetic background has a strong impact on resistance durability. A trade-off between the adaptations to different resistant potato genotypes was detected, and we also showed that adaptation to the resistance QTL GpaVvrn from S. vernei did not allow adaptation to the colinear locus from S. sparsipilum (GpaVspl). Unexpectedly, the adaptation to resistance led to an increase of virulent individual’s fitness on a susceptible host. Moreover, the genome scan approach allowed the highlighting of candidate genomic regions involved in adaptation to host plant resistance. This review shows that experimental evolution is an interesting tool to anticipate the adaptation of pathogen populations and could be very useful for identifying durable strategies for resistance deployment. [ABSTRACT FROM AUTHOR]

The activity of the pool of sgRNA molecules designed for different regions of potato coilin and phytoene desaturase genes was compared in vitro. Due to the presence of nucleotides unpaired with DNA, sgRNA is able not only to inhibit but also to stimulate the activity of the Cas9-sgRNA complex in vitro. Although the first six nucleotides located in the DNA substrate proximally to the PAM site at the 3' end are the binding sites for cas9, they had no significant effect on the activity of the Cas9-sgRNA complex. [ABSTRACT FROM AUTHOR]

Steroidal glycoalkaloids (SGAs), while found in many solanaceous plants, can accumulate to unacceptably high levels in potato tubers. The two primary SGAs that occur in potatoes are the tri-glycosylated alkaloids, α-solanine and α-chaconine. The first glycosylation steps in their biosynthetic pathways are performed by the regulated enzymes SGT1, the UDP-galactose:solanidine galactosyltransferase, and SGT2, the UDP-glucose:solanidine glucosyltransferase, respectively. Using fragments of the Sgt1 and Sgt2 genes to produce small inhibitory RNAs (siRNA), we have been able to down-regulate each branch of the pathway. The use of the siRNA approach increases the efficiency of producing transgenic plant lines with reductions in individual SGAs but further research is required to achieve reductions in levels of total SGA accumulation. [ABSTRACT FROM AUTHOR]

Six hundred untrained panelists evaluated the baked sensory appeal of up to six varieties, three clones, and two Russet Norkotah (RN) strains. Panelists consumed small samples of plain baked potato and recorded their preference for aroma, flavor, texture, aftertaste and acceptance. After viewing photographs of two unidentified baked potatoes (RN and Classic Russet) sliced in half, they selected the photo that best described their visual preference of a baked potato; each potato was stored at 6.7 °C for 6 months prior to cooking. Eighty percent of panelists shown the photographs of the unidentified baked potatoes preferred the visual appearance of Classic R (white/cream - colored flesh) to that of RN (yellow/Gy - colored flesh). Mean scores for all culinary traits averaged > 5.0 on the 1-9 scale, which indicated that panelists generally liked the culinary attributes of all trialed varieties, however, panelists were able to detect differences among varieties. Flavor and texture were addressed in written comments from panelists more frequently than other attributes. On a texture scale of 1-7, with 1 = moist/dense and 7 = dry/crumbly, most panelists preferred baked potatoes with a texture of 3 (creamy/smooth). [ABSTRACT FROM AUTHOR]

Potato ( Solanum tuberosum L.) is a major crop worldwide and its productivity is severely reduced by high soil salinity. The aim of the current study was to gain insights into the response and regulation of the antioxidant system in the transgenic potato, overexpressing two genes viz. thermostable CuZn-superoxide dismutase ( PaSOD) gene from polyextremophile high-altitude plant Potentilla atrosanguinea and ascorbate peroxide ( RaAPX) gene from Rheum australe under salinity stress. Transgenic lines and wild type (WT) were assessed under 50, 100, and 150 mM concentrations of NaCl treatment at the anatomical, transcriptional and metabolic levels. Although superoxide dismutase (SOD) and ascorbate peroxide (APX) activities in transgenic lines were significantly higher than WT under salt stress, the secondary cell wall lignification was profoundly affected by the modulated antioxidant enzymes activities and the corresponding HO levels in transgenic. Expression profiles showed that the several genes and transcription factors directly involved in lignin biosynthesis were profoundly induced in transgenic lines as compared to WT. In addition, transgenic plants harbored increased starch accumulation, improved growth attributes, and reduced accumulation of reactive oxygen species than WT plants. Together, these results indicated that the expression of SOD and APX genes in transgenic potato may function as a positive set of physiological, anatomical, and molecular adjustments in the HO regulated lignin biosynthesis signaling pathway, enabling the plants to withstand severe saline conditions. [ABSTRACT FROM AUTHOR]

Key message: A tetraploid potato population was mapped for internal heat necrosis (IHN) using the Infinium 8303 potato SNP array, and QTL for IHN were identified on chromosomes 1, 5, 9 and 12 that explained 28.21% of the variation for incidence and 25.3% of the variation for severity. This research represents a significant step forward in our understanding of IHN, and sets the stage for future research focused on testing the utility of these markers in additional breeding populations. Abstract: Internal heat necrosis (IHN) is a significant non-pathogenic disorder of potato tubers and previous studies have identified AFLP markers linked to IHN susceptibility in the tetraploid, B2721 potato mapping population. B2721 consists of an IHN susceptible×resistant cross: Atlantic×B1829-5. We developed a next-generation SNP-based linkage map of this cross using the Infinium 8303 SNP array and conducted additional QTL analyses of IHN susceptibility in the B2721 population. Using SNP dosage sensitive markers, linkage maps for both parents were simultaneously analyzed. The linkage map contained 3427 SNPs and totaled 1397.68 cM. QTL were detected for IHN on chromosomes 1, 5, 9, and 12 using LOD permutation thresholds and colocation of high LOD scores across multiple years. Genetic effects were modeled for each putative QTL. Markers associated with a QTL were regressed in models of effects for IHN incidence and severity for all years. In the full model, the SNP markers were shown to have significant effects for IHN ( p < 0.0001), and explained 28.21% of the variation for incidence and 25.3% of the variation for severity. We were able to utilize SNP dosage information to identify and model the effects of putative QTL, and identify SNP loci associated with IHN resistance that need to be confirmed. This research represents a significant step forward in our understanding of IHN, and sets the stage for future research focused on testing the utility of these markers in additional breeding populations. [ABSTRACT FROM AUTHOR]

The expression of insecticidal genes must be induced at appropriate time and in sufficient amount to confer protection against targeted pests. However, the increased scientific reports of resistance development in insect pest against insecticidal delta-endotoxins, produced by Bacillus thuringiensis, provide impetus for the development of alternative insect management strategies. The present study was conducted to investigate the importance of targeted expression of a hybrid insecticidal gene (SN19) in potatoes. For this purpose, two plant expression vectors were constructed by cloning hybrid SN19 gene ( cry1Ba-domain I-III and cry1Ia-domain II) under the control of a wound-inducible promoter isolated from Asparagus officinalis (AoPR1) and CaMV 35S promoter, and were transferred to Agrobacterium tumefaciens strain EHA 105. Four potato genotypes (Marabel, Innovator, Tokat 10/1 and Tokat 6/24) were transformed with EHA 105 strain harboring pTF101.1 35S-SN19 and pTF101.1 AoPR1-SN19 constructs. Phosphinothricin (PPT) was used at concentration of 1 mg/l for selection of primary transformants. PCR results showed the presence of both introduced SN19 and bar genes in 43 plants out of total 154 putative transgenics. Expression of SN19 protein in primary transformants was confirmed by Western blot assays. The mechanical wounding of transgenic plants exhibited more accumulated levels of SN19 proteins during post wounding period. Leaf biotoxicity assays with Colorado potato beetle (Coleoptera) and tomato leafminer (Lepidoptera) exhibited 100% mortality of the pests in primary transformants. Based on our mortality results with both constructs, we concluded that the potato transgenic lines exhibited targeted expression of insecticidal gene under the control of AoPR1 promoter upon insect wounding with eliminated toxicity of Cry protein and hence can be further used effectively in potato breeding programme. [ABSTRACT FROM AUTHOR]

Genome editing (also known as targeted mutation) has promise for molecular breeding. Compared with the CRISPR/Cas9 system, the transcription activator-like effector nucleases (TALENs) have likely a lesser off-target rate in genome editing. Both a rapid test system for the functionality of designed TALENs and an effective delivery system for introducing the TALENs to plants are critical for successful target mutation. TALENs have usually been tested in protoplasts or introduced to plants with viral vectors. However, plant regeneration from protoplast culture can generate extensive somatic variation. Viral vectors are not always available, and plants edited by these vectors usually require virus elimination. Here, we used a non-viral, Agrobacterium-mediated transient expression approach, to serve both rapid test and effective delivery of TALENs into two vegetatively propagated potato cultivars, Solanum tuberosum Russet Burbank and Shepody. Two TALENs with different molecular weights (22 and 27 aa-repeat modules) were expressed to target two endogenous genes (starch branching enzyme and an acid invertase) by Agrobacterium-mediated infiltration (agroinfiltration) into leaves of potato plants. The infiltrated leaf DNA was analyzed using restriction site loss assay and subsequent DNA sequencing. Deep sequencing of these tetraploid cultivars was also conducted to determine the zygosity at the targeted chromosomal loci. TALENs, with different molecular weights, successfully agroinfiltrated and induced mutations at both targeted loci. [ABSTRACT FROM AUTHOR]

Key message: Transient 5-azacytidine treatment of leaf explants from potato plants with transcriptionally silenced transgenes allows de novo regeneration of plants with restored transgene expression at the whole plant level. Abstract: Transgenes introduced into plant genomes frequently become silenced either at the transcriptional or the posttranscriptional level. Transcriptional silencing is usually associated with DNA methylation in the promoter region. Treatments with inhibitors of maintenance DNA methylation were previously shown to allow reactivation of transcriptionally silenced transgenes in single cells or tissues, but not at the whole plant level. Here we analyzed the effect of DNA methylation inhibitor 5-azacytidine (AzaC) on the expression of two silenced reporter genes encoding green fluorescent protein (GFP) and neomycin phosphotransferase (NPTII) in potato plants. Whereas no obvious reactivation was observed in AzaC-treated stem cuttings, transient treatment of leaf segments with 10 μM AzaC and subsequent de novo regeneration of shoots on the selective medium with kanamycin resulted in the production of whole plants with clearly reactivated expression of previously silenced transgenes. Reactivation of nptII expression was accompanied by a decrease in cytosine methylation in the promoter region of the gene. Using the plants with reactivated GFP expression, we found that re-silencing of this transgene can be accidentally triggered by de novo regeneration. Thus, testing the incidence of transgene silencing during de novo regeneration could be a suitable procedure for negative selection of transgenic lines (insertion events) which have an inclination to be silenced. Based on our analysis of non-specific inhibitory effects of AzaC on growth of potato shoots in vitro, we estimated that AzaC half-life in the culture media is approximately 2 days. [ABSTRACT FROM AUTHOR]

Tuber formation of potato is a complex biological process and is regulated by many factors including phytochrome, hormones, transcription factors, RNAs, microRNAs, etc. In our previous study, CYP707A1, an ABA 8′-hydroxylase gene, was down-regulated in the StCOL antisense transgenic potato stolons, but its relation with potato tuberization has not been studied yet. In this study, to investigate the role of this gene in potato tuberization, we cloned a CYP707A1 gene from potato cultivar Désirée and constructed the StCYP707A1 over-expression and anti-sense potato lines by Agrobacterium-mediated transformation. In total, four over-expression transgenic lines and nine anti-sense transgenic lines were confirmed by PCR analysis. Semi-quantitative RT-PCR and qRT-PCR analysis showed that the level of StCYP707A1 transcripts was significantly higher in the over-expression lines (A7 and A9) and lower in the anti-sense lines (F2 and F8), compared to the wild-type control. We further analyzed tuber formation in the transgenic lines and the wild-type control. The result showed that tuber yield per plant and average tuber weight were decreased in A7 and A9 and increased in F2. We also measured the content of ABA and GA in transgenic lines. ABA level was reduced in A7 and A9 and increased in F2. Contrariwise, the concentration of GA was higher in A7 and A9, and lower in F2 than in wild-type control. These results indicate that StCYP707A1 negatively affects potato tuberization through ABA regulation on gibberellic acid concentration. [ABSTRACT FROM AUTHOR]

Key message : Ectopic auxin overproduction in transgenic potato leads to enhanced productivity accompanied with concerted and occasional changes in hormonal status, and causing altered response of transformants to exogenous auxin or cytokinin. Abstract: Previously, we generated potato transformants expressing Agrobacterium-derived auxin synthesis gene tms1 driven by tuber-specific patatin gene promoter (B33-promoter). Here, we studied the endogenous hormonal status and the response to exogenous phytohormones in tms1 transformants cultured in vitro. Adding indole-3-acetic acid (IAA) or kinetin to culture medium affected differently tuberization of tms1-transformed and control plants, depending also on sucrose content in the medium. Exogenous phytohormones ceased to stimulate the tuber initiation in transformants at high (5-8%) sucrose concentration, while in control plants the stimulation was observed in all experimental settings. Furthermore, exogenous auxin partly inhibited the tuber initiation, and exogenous cytokinin reduced the average tuber weight in most transformants at high sucrose content. The elevated auxin level in tubers of the transformants was accompanied with a decrease in content of cytokinin bases and their ribosides in tubers and most shoots. No concerted changes in contents of abscisic, jasmonic, salicylic acids and gibberellins in tubers were detected. The data on hormonal status indicated that the enhanced productivity of tms1 transformants was due to auxin and not mediated by other phytohormones. In addition, exogenous cytokinin was shown to upregulate the expression of genes encoding orthologs of auxin receptors. Overall, the results showed that tms1 expression and local increase in IAA level in transformants affect both the balance of endogenous cytokinins and the dynamics of tuberization in response to exogenous hormones (auxin, cytokinin), the latter reaction depending also on the carbohydrate supply. We introduce a basic model for the hormonal network controlling tuberization. [ABSTRACT FROM AUTHOR]

Key message : The method of graphical genotyping is applied to a panel of tetraploid potato cultivars to visualize haplotype sharing. The method allowed to map genes involved in virus and nematode resistance. The physical coordinates of the amount of linkage drag surrounding these genes are easily interpretable. Abstract: Graphical genotyping is a visually attractive and easily interpretable method to represent genetic marker data. In this paper, the method is extended from diploids to a panel of tetraploid potato cultivars. Application of filters to select a subset of SNPs allows one to visualize haplotype sharing between individuals that also share a specific locus. The method is illustrated with cultivars resistant to Potato virus Y (PVY), while simultaneously selecting for the absence of the SNPs in susceptible clones. SNP data will then merge into an image which displays the coordinates of a distal genomic region on the northern arm of chromosome 11 where a specific haplotype is introgressed from the wild potato species S. stoloniferum (CPC 2093) carrying a gene ( Ny ) conferring resistance to two PVY strains, PVY and PVY. Graphical genotyping was also successful in showing the haplotypes on chromosome 12 carrying Ry- f , another resistance gene derived from S. stoloniferum conferring broad-spectrum resistance to PVY, as well as chromosome 5 haplotypes from S. vernei, with the Gpa5 locus involved in resistance against Globodera pallida cyst nematodes. The image also shows shortening of linkage drag by meiotic recombination of the introgression segment in more recent breeding material. Identity-by-descent was found to be a requirement for using graphical genotyping, which is proposed as a non-statistical alternative method for gene discovery, as compared with genome-wide association studies. The potential and limitations of the method are discussed. [ABSTRACT FROM AUTHOR]

Main conclusion : Tolerance to heat stress for retention of low-temperature sweetening-resistant phenotype in potato is conferred by insensitivity of acid invertase activity to cold induction. Heat stress exacerbated cold sweetening (buildup of reducing sugars) of the LTS (low-temperature sweetening)-susceptible potato ( Solanum tuberosum L.) cultivars, Ranger Russet and Russet Burbank, and completely abolished the resistance to cold sweetening in the LTS-resistant cultivars/clones, Sage Russet, GemStar Russet, POR06V12-3 and A02138-2. Payette Russet and EGA09702-2, however, demonstrated considerable tolerance to heat stress for retention of their LTS-resistant phenotype. Heat-primed Payette Russet and EGA09702-2 tubers accumulated fourfold more sucrose when subsequently stored at 4 °C, while reducing sugar concentrations also increased marginally but remained low relative to the non-heat-tolerant LTS-resistant clones, resulting in light-colored fries. By contrast, sucrose concentrations in heat-primed tubers of the non-heat-tolerant clones remained unchanged during LTS, but reducing sugars increased fivefold, resulting in darkening of processed fries. Acid invertase activity increased in the LTS-susceptible and non-heat-tolerant LTS-resistant cultivars/clones during cold storage. However, Payette Russet tubers maintained very low invertase activity regardless of heat stress and cold storage treatments, as was the case for Innate Russet Burbank (W8) tubers, where silenced invertase conferred robust tolerance to heat stress for retention of LTS-resistant phenotype. Importantly, heat-stressed tubers of Payette Russet, EGA09702-2 and Innate Russet Burbank (W8) demonstrated similar low reducing sugar and high sucrose-accumulating phenotypes when stored at 4 °C. Tolerance to heat stress for retention of LTS-resistant phenotype in Payette Russet and likely its maternal parent, EGA09702-2, is, therefore, conferred by the ability to maintain low invertase activity during cold storage of heat-stressed tubers. [ABSTRACT FROM AUTHOR]

The Northwest Potato Variety Development (NWPVD) Program has released 45 improved potato varieties since 1985. Thirty-four potato varieties, four breeding clones and two advanced selections from NWPVD Program, and six commonly-grown potato varieties were fingerprinted using 32 simple sequence repeat (SSR) markers and 12,808 single nucleotide polymorphism (SNP) markers. Of 32 SSR markers, 29 exhibited significant polymorphism across all the 46 potato clones studied. A total of 143 alleles were observed with an average of 4.6 alleles per SSR marker. These markers span all 12 chromosomes of potato, with a maximum of five markers from chromosome VIII and minimum of one marker from chromosome VI. The polymorphic information content (PIC) and expected heterozygosity (H) of the SSR markers ranges between 0.18 to 0.75 and 0.20 to 0.78, respectively. Based on PIC, H, and ease of scoring, we recommend a set of eight SSR markers: STG0016, STI0004, STI0012, STI0023, STI0030, STI0033, STM1016 and STM1104 for fingerprinting NWPVD varieties. Out of 12,808 SNPs, 88.8% resulted in reliable three cluster diploid calling of which 87.8% were polymorphic. Tetraploid calling resulted in 44.2% of SNPs of which 94.5% were polymorphic. Our study provided fingerprinting resources for the NWPVD varieties and can be used in issues related to intellectual property rights, ownership, trademark and diversity analysis. [ABSTRACT FROM AUTHOR]

Potato processing is becoming particularly popular in developing countries and French fries are the main product being developed. This paper describes the South African frozen French fry industry, identifying aspects for improvements for further growth. Although South Africa produces over two million tonnes of potatoes per year, only 17 to 20% are processed, mainly as frozen French fries. While this is a larger production achievement than in the past, trends in consumption show that the frozen French fry industry has potential for further growth. Industry expansion is limited by the shortage of suitable raw potato stock linked to cultivar and potato production capacity constraints for frozen French fry processing. The country relies mainly on two processing cultivars produced in localized areas, for which yields are also threatened by unpredictably detrimental weather conditions. Produce shortages often lead to subsequent importation of products from other countries. The lack of cultivar-specific information on the amount of land used, production tonnages and yield achievements restricts diagnosis of specific factors contributing to this shortage. Based on the overall crop performance, a region-based approach is suggested to improve yield achievements of the few cultivars used for frozen French fry processing in the country. This could be achieved by optimizing natural resource management, particularly irrigation, fertilizer and land use, in the four agro-climatic regions contributing to the processing industry. Furthermore, the number of French fry processing cultivars can be increased by increasing financial investment on local breeding efforts to develop new cultivars and by focusing foreign cultivar adoption on processing needs to increase the genetic diversity and safeguard against the effects of climate change. [ABSTRACT FROM AUTHOR]

Background and aims: The diets of many people lack sufficient zinc (Zn). This article investigates the production of potato ( Solanum tuberosum L.) crops with greater tuber Zn concentrations to increase dietary Zn intakes. Methods: Field experiments were undertaken to increase Zn concentrations in potato tubers using foliar Zn fertilisers. Results: Foliar Zn fertilisers increased tuber Zn concentrations but excessive applications reduced tuber yield in all four potato genotypes studied. Zinc oxide and zinc sulphate were more effective than zinc nitrate as foliar fertilisers for increasing tuber Zn concentrations whilst maintaining yields. Foliar Zn-fertilisers increased Zn concentrations in both flesh and skin of tubers. Although Zn-biofortification had no effect on the concentrations of iron, manganese, copper, calcium, magnesium or potassium in tubers, it increased tuber phytate concentrations. Cooking reduced Zn concentrations in Zn-biofortified tubers and this effect was exacerbated by peeling. After cooking, the quotient of Zn concentrations in Zn-biofortified/non-biofortified tubers ranged from 2.36 to 3.58. Applying foliar Zn fertilisers to a preceding potato crop increased Zn concentrations in grain of a following barley crop significantly in only one out of 3 years. Conclusion: Foliar Zn fertilisers can increase Zn concentrations in potato tubers and, potentially, dietary Zn intakes. [ABSTRACT FROM AUTHOR]

Key message: Altered starch quality with full knockout of GBSS gene function in potato was achieved using CRISPR-Cas9 technology, through transient transfection and regeneration from isolated protoplasts. Abstract: Site-directed mutagenesis (SDM) has shown great progress in introducing precisely targeted mutations. Engineered CRISPR-Cas9 has received increased focus compared to other SDM techniques, since the method is easily adapted to different targets. Here, we demonstrate that transient application of CRISPR-Cas9-mediated genome editing in protoplasts of tetraploid potato ( Solanum tuberosum) yielded mutations in all four alleles in a single transfection, in up to 2 % of regenerated lines. Three different regions of the gene encoding granule-bound starch synthase ( GBSS) were targeted under different experimental setups, resulting in mutations in at least one allele in 2-12 % of regenerated shoots, with multiple alleles mutated in up to 67 % of confirmed mutated lines. Most mutations resulted in small indels of 1-10 bp, but also vector DNA inserts of 34-236 bp were found in 10 % of analysed lines. No mutations were found in an allele diverging one bp from a used guide sequence, verifying similar results found in other plants that high homology between guide sequence and target region near the protospacer adjacent motif (PAM) site is essential. To meet the challenge of screening large numbers of lines, a PCR-based high-resolution fragment analysis method (HRFA) was used, enabling identification of multiple mutated alleles with a resolution limit of 1 bp. Full knockout of GBSS enzyme activity was confirmed in four-allele mutated lines by phenotypic studies of starch. One remaining wild-type (WT) allele was shown sufficient to maintain enough GBSS enzyme activity to produce significant amounts of amylose. [ABSTRACT FROM AUTHOR]

Potato production in Uganda is being affected by rainfall fluctuations in both timing and amount, resulting into inadequate soil moisture availability and low productivity. Also, potato production is expanding into locations at lower altitudes, where drought is more common. Therefore, drought stress mitigation measures and coping mechanisms need to be devised to face future challenges of climate change, particularly in developing countries to ensure steady supply of adequate quantities of quality food. This study thus, aimed at characterizing new potato clones from CIP (International Potato Center) for tolerance to drought under Ugandan conditions. Consequently a screen house experiment was conducted twice at Kachwekano Zonal Agricultural Research and Development Institute (KAZARDI) from October 2011 to February 2012 and April to July 2012 to evaluate and characterize eight potato genotypes; five of which were obtained from CIP's breeding collection for drought tolerance and low altitude areas, and three locally released varieties from Uganda. These clones were tested for drought tolerance at three levels of simulated moisture deficit; 25 % field capacity, 50 % and 100 % field capacity (FC). Data were collected on leaf chlorophyll content, relative leaf water content, number of days to 50 % flowering, percent ground cover, leaf area, plant height, number of stems per plant, stem diameter, stress score, increment in plant height after imposing stress, tuber dry matter content and yield components. Of all the traits evaluated, yield and number of days to 50 % flowering contributed most to drought tolerance among the potato genotypes evaluated. There were significant ( P ≤ 0.05) differences among genotypes for all evaluated traits. Results from both growth, physiological and yield parameters revealed that the new potato clones were less affected by drought stress compared to adapted varieties. Total tuber yield was 23 tons per hectare, 11.4 and 8.1 in plots at full field capacity, 50 % and 25 % moisture stressed plots respectively in the first experiment. A similar trend was obtained in the second experiment with 19 tons per hectare, 13.7 and 11.3 respectively. The new clones at highest moisture stress had significantly ( P ≤ 0.05) higher yields than adapted varieties providing a promise for possible new varieties and breeding stock in extreme conditions of moisture deficit. [ABSTRACT FROM AUTHOR]

Potato is an increasingly important crop in Ethiopia, but the origin of local cultivars grown throughout the country is unknown. To evaluate the genetic diversity of Ethiopian potato cultivars, and to assess their relationship with germplasm from North America, Europe and the International Potato Center (CIP), 8303 SNP markers were used to characterize 44 local Ethiopian cultivars, as well as 26 CIP, 22 American and 17 European potato cultivars and advanced breeding clones. The marker data revealed that most of the local cultivars were duplicates; among the 44 cultivars tested, only 15 unique genotypes were observed. Principal component and neighbor-joining dendrogram analyses showed that American, European and CIP germplasm form three distinct clusters, with older Ethiopian cultivars overlapping the European cultivars, suggesting that the oldest local cultivars are of European descent. Local cultivars overall separated into two distinct clusters, suggesting that at least two distinct introductions gave rise to current local cultivars in Ethiopia. Ethiopian germplasm harbors comparable levels of genetic diversity to American, European, and CIP germplasm and could provide the foundation for a national potato breeding program. [ABSTRACT FROM AUTHOR]

This study presents the development of a core collection capturing the genetic diversity of a collection of 350 tetraploid cultivated potato varieties ( Solanum tuberosum L.). The core collection was established by using simple sequence repeats (SSR) data and the M strategy, which aims at maximizing the allelic diversity. A 48-core collection was defined which captured 99.5% of the SSR alleles used to establish it, and 96.9% of the SSR alleles which belonged to an independent set of markers. The defined core collection was further validated by analysing 35 agro-morphological traits. The class coverage value and the estimates of the Shannon-Weaver diversity index indicated a good representation of the phenotypic diversity in the core collection. Furthermore, the core set included accessions having the most desirable status for several agronomic traits. A linkage disequilibrium (LD) analysis, using data obtained with the SolCAP SNP array on the defined core collection, was performed. The population structure analysis showed that the core collection did not present a clear genetic structure. The linkage disequilibrium analysis carried out between markers located on the same pseudomolecule within 10,000 bp concluded that 41.3% of these pairs of SNP markers have a significant LD. We conclude that this core collection, representative of the genetic diversity of cultivated potato varieties, is a relevant tool for a first screening for genetic variation regarding novel traits of interest. [ABSTRACT FROM AUTHOR]

Main conclusion : Solanum tuberosum genome analysis revealed 12 StSULTR genes encoding 18 transcripts. Among genes annotated at group level ( StSULTR I-IV), group III members formed the largest SULTRs-cluster and were potentially involved in biotic/abiotic stress responses via various regulatory factors, and stress and signaling proteins. Employing bioinformatics tools, this study performed genome-wide identification and expression analysis of SULTR ( StSULTR) genes in potato ( Solanum tuberosum L.). Very strict homology search and subsequent domain verification with Hidden Markov Model revealed 12 StSULTR genes encoding 18 transcripts. StSULTR genes were mapped on seven S. tuberosum chromosomes. Annotation of StSULTR genes was also done as StSULTR I- IV at group level based mainly on the phylogenetic distribution with Arabidopsis SULTRs. Several tandem and segmental duplications were identified between StSULTR genes. Among these duplications, Ka/Ks ratios indicated neutral nature of mutations that might not be causing any selection. Two segmental and one-tandem duplications were calculated to occur around 147.69, 180.80 and 191.00 million years ago (MYA), approximately corresponding to the time of monocot/dicot divergence. Two other segmental duplications were found to occur around 61.23 and 67.83 MYA, which is very close to the origination of monocotyledons. Most cis-regulatory elements in StSULTRs were found associated with major hormones (such as abscisic acid and methyl jasmonate), and defense and stress responsiveness. The cis-element distribution in duplicated gene pairs indicated the contribution of duplication events in conferring the neofunctionalization/s in StSULTR genes. Notably, RNAseq data analyses unveiled expression profiles of StSULTR genes under different stress conditions. In particular, expression profiles of StSULTR III members suggested their involvement in plant stress responses. Additionally, gene co-expression networks of these group members included various regulatory factors, stress and signaling proteins, and housekeeping and some other proteins with unknown functions. [ABSTRACT FROM AUTHOR]

Key message : The paper proposes and validates a robust method for rapid construction of high-density linkage maps suitable for autotetraploid species. Abstract: Modern genotyping techniques are producing increasingly high numbers of genetic markers that can be scored in experimental populations of plants and animals. Ordering these markers to form a reliable linkage map is computationally challenging. There is a wide literature on this topic, but most has focussed on populations derived from diploid, homozygous parents. The challenge of ordering markers in an autotetraploid population has received little attention, and there is currently no method that runs sufficiently rapidly to investigate the effects of omitting problematic markers on map order in larger datasets. Here, we have explored the use of multidimensional scaling (MDS) to order markers from a cross between autotetraploid parents, using simulated data with 74-152 markers on a linkage group and also experimental data from a potato population. We compared different functions of the recombination fraction and LOD score to form the MDS stress function and found that an LOD weighting generally performed well, including when missing values and genotyping errors are present. We conclude that an initial analysis using unconstrained MDS gives a rapid method to detect and remove problematic markers, and that a subsequent analysis using either constrained MDS or principal curve analysis gives reliable marker orders. The latter approach is also particularly rapid, taking less than 10 s on a set of 258 markers compared to 6 days for the JoinMap software. This MDS approach could also be applied to experimental populations of diploid species. [ABSTRACT FROM AUTHOR]

Key message : Linkage mapping can help unravel the complexities of polyploid genomes. Here, we integrate haplotype-specific linkage maps in autotetraploid potato and explore the possibilities for mapping in other polyploid species. Abstract: High-density linkage mapping in autopolyploid species has become possible in recent years given the increasing number of molecular markers now available through modern genotyping platforms. Such maps along with larger experimental populations are needed before we can obtain sufficient accuracy to make marker-trait association studies useful in practice. Here, we describe a method to create genetic linkage maps for an autotetraploid species with large numbers of markers and apply it to an F1 population of tetraploid potato ( Solanum tuberosum L.) of 235 individuals genotyped using a 20K SNP array. SNP intensity values were converted to allele dosages after which we calculated pairwise maximum likelihood estimates of recombination frequencies between all marker segregation types under the assumption of random bivalent pairing. These estimates were used in the clustering of markers into linkage groups and their subsequent ordering into 96 homologue maps. The homologue maps were integrated per chromosome, resulting in a total map length of 1061 cM from 6910 markers covering all 12 potato chromosomes. We examined the questions of marker phasing and binning and propose optimal strategies for both. We also investigated the effect of quadrivalent formation and preferential pairing on recombination frequency estimation and marker phasing, which is of great relevance not only for potato but also for genetic studies in other tetraploid species for which the meiotic pairing behaviour is less well understood. [ABSTRACT FROM AUTHOR]

Russet Burbank is the predominant potato ( Solanum tuberosum L.) cultivar grown and stored for fresh market and frozen processing (French fry) use in North America. Multi-year assessments of potato tuber quality under different storage regimes can provide information about a cultivar's ability to retain process quality when challenged with seasonal variations across multiple years. The objective of a 15-year study initiated in 1999 was to evaluate the quality of Russet Burbank tubers grown and stored at the Kimberly Research and Extension Center. Potatoes were measured for specific gravity at harvest and stored for eight months under three temperatures (5.6, 7.2 and 8.9 °C) and periodically sampled throughout the storage season to determine dormancy length, sugar content, fry color and mottling severity (a quality issue), and weight loss. The year in which the crop was grown significantly ( p < 0.001) affected all quality characteristics except specific gravity (average ranged between 1.071 and 1.081). Tubers held during the 2011-2012 and 2013-2014 storage seasons exhibited generally higher glucose, darker fry color, more severe mottling, and higher weight loss. Average sucrose content at 7.2 °C and 8.9 °C across the 15 years significantly decreased over the eight-month storage while average glucose content remained consistent after first month of storage. Average percent weight loss across the 15 years was 6.1 % after eight months in storage. This 15-year study emphasized that variation of post-harvest storage quality from year to year was likely a result of variable seasonal growing conditions. Storage temperatures between 7.2 and 8.9 °C were the optimum range for storing fry processing Russet Burbank potatoes and the warmer temperature of 8.9 °C appears to ameliorate the seasonal effects on glucose content and fry color to maintain better processing quality throughout storage. [ABSTRACT FROM AUTHOR]

Spongospora subterranea causes root galls and powdery scab on potato tubers ( Solanum tuberosum L.). Host resistance represents an economically suitable and long term approach for the management of the disease; however, the relationship between root and tuber symptoms may vary across potato genotypes. To assess susceptibility differences among genotypes, 30 potato cultivars and 83 advanced clones with varying skin type (market class) were evaluated for powdery scab and root gall formation. Five field experiments were conducted during 2011 and 2012 on naturally infested soils in Minnesota and North Dakota. Differences among genotypes in the degree of susceptibility to tuber and root symptoms were observed ( P < 0.001, n = 33 to 80). Higher powdery scab pressure ( P < 0.001, n = 90) was observed in North Dakota locations across years. Environmental conditions influenced the formation of root galls and the expression of powdery scab, with greatest variability among white- and red-skinned genotypes. Under high disease pressure, the estimates of broad-sense heritability for powdery scab incidence and severity were 0.76 and 0.63, respectively. Across environments, russet-skinned genotypes resulted in less disease on tubers, but yielded similar levels of root galls as red-skinned genotypes. Tuber scab and root gall formation indices were significantly associated (r = 0.42, P < 0.001, n = 80); however, high levels of disease in roots were observed in genotypes ranked resistant to powdery scab. Cultivars Dakota Trailblazer, Dakota Russet and Karu ranked highly resistant, whereas Shepody, Kennebec and Red LaSoda were highly susceptible to both phases of the disease. Cultivar selection is highly recommended for disease management. [ABSTRACT FROM AUTHOR]

Plant subtilisin-like serine proteases or subtilases constitute a large expanded gene subfamily in potato. We identified 82 potato subtilases encoded by 74 genes. All subtilases present a characteristic S08 domain, and the majority of them have an association protein domain, an inhibition_I9 domain and a signal peptide that consists of a signal sequence for targeting to the secretory pathway. Phylogenetic studies revealed five subtilase groups named StSBT1 to StSBT5. A genome expansion of potato subtilase subfamily was reflected in two phylogenetic clusters, StSBT1 and StSBT4 both characterized by intronless genes in tandem arrays mainly in chromosome I and VIII. Twenty nine of the identified subtilases co-localize with six out of 24 metaQTLs related to late blight resistance previously described in potato. These metaQTLs includes subtilase genes up regulated in detached potato leaves inoculated with P. infestans, some of which are homologous to p69 subtilases genes from tomato. [ABSTRACT FROM AUTHOR]

Growing potato conventionally for dehydration is not economically feasible. The key cost would be seed under organic farming. The objective is to identify seed-piece sizes and spacings producing a profitable return for potato dehydration in western Nebraska. Atlantic potatoes were grown under dryland conditions using organic practices. Rain was 205, 270, and 360 mm in 2013, 2014, and 2015. Seed-pieces were hand-cut into five weights from 42.5 to 85.0 g and planted in five spacings from 15.2 to 45.7 cm. Seeding rates were 1.02 to 6.1 Mg/ha. Yield was highest at the spacing of 15.2 cm (16.1 Mg/ha) and decreased to 12.4 Mg/ha when seed-pieces were planted at 38.1 and 45.7 cm apart. Seed-piece size had little effect except that yield was lowest with 42.5 g pieces at 13.2 Mg/ha and increased to 14.2 Mg/ha with 63.8 g and larger. Specific gravity decreased slightly when pieces were spaced 30.5 cm (1.092) compared to 15.2 cm (1.094). Seed size had no effect. The size and spacing combinations with the highest yield were not found to be economical due to higher seed cost. Planting seed-pieces weighing 56.7 g, and planted 38.1 and 45.7 cm apart in 91 cm rows were economically feasible for dry matter production. The net returns, taking into account seed cost, transportation, and operations, for this combination was $326/ha, greater than for dryland winter wheat and millet. This study showed that western Nebraska would be a good location to grow dryland potatoes for organic dry matter production. [ABSTRACT FROM AUTHOR]

The first impact of the potato on society was the intimate relationship between the domestication of the potato and the evolution of Andean civilization which affected Andean culture and religion. In addition to food potatoes were used for several non-food purposes. In the Inca Empire the freeze-dried chuño was collected as taxes from the peasants and disbursed from imperial storehouses to labor gangs for building roads, waging war, and erecting monuments. After the Spanish conquest chuño was used to feed the slaves in the Andean silver and gold mines. This in turn set the stage for flooding the Spanish and eventually the global market with these precious metals and subsequent world-wide inflation of consumer goods. The potato became the major contributor to the European population explosion of 1750-1850 which in turn resulted in increased urbanization and contributed to the underpinning of the Industrial Revolution in England in the nineteenth century. By feeding rapidly growing populations the potato permitted a small number of nations in northern Europe to assert dominion over much of the world between 1750 and 1950. The failure of the potato crop in Ireland in the 1840s led Britain to repeal the protectionist Corn Laws and set the country on a path of free trade. At least one million Irish refugees emigrated, mostly to North America where they left a great legacy. The past 50 years have seen a major global shift in potato production towards many developing countries in Asia, including China and India. Throughout its history the potato has provided bread for the poor. Today it contributes to food security on a global scale. The potato's depiction on postage stamps demonstrates the esteem in which it is held worldwide and the many references to the potato in art, literature and folklore worldwide are evidence how it has become interwoven in the cultures of many societies today. [ABSTRACT FROM AUTHOR]

Efficient assessment of genetic diversity in a potato genebank includes understanding how much of the available genetic diversity has been captured in the genebank (from the wild or from other ex situ sources). We used existing datasets from three of the genebank's 93 species to model the increase of diversity over time, as measured by the addition of AFLP bands. DNA samples of a total of 411 populations of S. microdontum (mcd), S. jamesii (jam), and S. fendleri (fen) were analyzed . Assuming the first (oldest) populations as the baseline, the number of AFLP markers have increased by 128 % (mcd), 154 % (jam) and 111 % (fen) with addition of populations to the genebank. The pattern of actual observed chronological gain in diversity was similar to that which one would expect from random additions of populations except for fen, suggesting recent additions were somewhat redundant. All species continued to accumulate new loci at least up to 100 populations, jam particularly so. Much effort has been made over many years to thoroughly collect jam, so its 125 populations could serve as a model for the number of samples one might practically hope to acquire for the average species. Since 100 jam populations captured 95 % of its polymorphic loci, 100 populations might be set as an optimal benchmark. The average species in the genebank now has about 54 populations, so the size of the genebank would need to roughly double its capacity to optimize diversity according to the jam model. That would be a challenge, but probably not as limiting as the great time and resources needed to collect the germplasm. [ABSTRACT FROM AUTHOR]

Key message: The S-ribonuclease sequences of 16 S-alleles derived from diploid types of Solanum are presented. A phylogenetic analysis and partial phenotypic analysis support the conclusion that these are functional S-alleles. Abstract: S-Ribonucleases (S-RNases) control the pistil specificity of the self-incompatibility (SI) response in the genus Solanum and several other members of the Solanaceae. The nucleotide sequences of S-RNases corresponding to a large number of S-alleles or S-haplotypes have been characterised. However, surprisingly, few S-RNase sequences are available for potato species. The identification of new S-alleles in diploid potato species is desirable as these stocks are important sources of traits such as biotic and abiotic resistance. S-RNase sequences are reported here from three distinct diploid types of potato: cultivated Solanum tuberosum Group Phureja, S. tuberosum Group Stenotomum, and the wild species Solanum okadae. Partial S-RNase sequences were obtained from pistil RNA by RT-PCR or 3′RACE (Rapid Amplification of cDNA Ends) using a degenerate primer. Full-length sequences were obtained for two alleles by 5′RACE. Database searches with these sequences identified 16 S-RNases in total, all of which are novel. The sequence analysis revealed all the expected features of functional S-RNases. Phylogenetic analysis with selected published S-RNase and S-like-RNase sequences from the Solanaceae revealed extensive trans-generic evolution of the S-RNases and a clear distinction from S-like-RNases. Pollination tests were used to confirm the self-incompatibility status and cross-compatibility relationships of the S. okadae accessions. All the S. okadae accessions were found to be self-incompatible as expected with crosses amongst them exhibiting both cross-compatibility and semi-compatibility consistent with the S-genotypes determined from the S-RNase sequence data. The progeny analysis of four semi-compatible crosses examined by allele-specific PCR provided further confirmation that these are functional S-RNases. [ABSTRACT FROM AUTHOR]

Genome editing using sequence-specific nucleases (SSNs) is rapidly becoming a standard tool for genetic engineering in crop species. The implementation of zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs) and CRISPR/Cas (clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated systems (Cas)) for inducing double-strand breaks enables targeting of virtually any sequence for genetic modification. Targeted mutagenesis via nonhomologous end-joining (NHEJ) and gene targeting via homologous recombination (HR) have been demonstrated in a number of plant species but reports have been limited in vegetatively propagated crops, such as potato ( Solanum tuberosum Group Tuberosum L.). This review provides a historical overview of genetic engineering in agriculture, applications of SSN technologies for genome editing in plant species, and prospects of using SSNs for genetic improvement of potato. [ABSTRACT FROM AUTHOR]

Light quality and intensity have severe impact on Steroidal glycoalkaloid (SGA) biosynthesis, causing the quality degradation of potato by greening and accelerating SGA-induced toxicity. In this study, Atlantic and Haryoung cultivars responded differently when exposed to seven light qualities viz., purple, red, blue, green, yellow, UV and fluorescent lights. Haryoung tuber exhibited a 44 % lesser SGA accumulation in yellow light compared to fluorescent light. Further screening of selected light sources by investigating the expression pattern of key genes and SGA contents, showed lower transcript levels of key genes in yellow light which in-turn reflected in the least amount of SGA accumulation with a 22 % lesser SGA levels in yellow light compared to fluorescent light. This suppression in the SGA accumulation suggests that yellow light can be used as an alternative light source instead of fluorescent light which would help in minimizing the quality degradation and SGA- induced toxicity. [ABSTRACT FROM AUTHOR]

Current safety assessment of genetically modified crops requires detailed information about the insertion of the transgene and the effect of its expression on the biochemistry and physiology of the host plant. Whilst the intended effect of the transformation can be verified through phenotypic screening, molecular approaches are required to observe unintended effects. We investigated the molecular details of the integration of a polygalacturonase inhibiting protein 1 gene from Malus domestica ( Mdpgip1), overexpressed in Solanum tuberosum (cv BP1) for enhanced resistance against Verticillium wilt. Genome walking studies of the selected AppA6 transformant revealed that the T-DNA containing the Mdpgip1 transgene under control of the CaMV 35S promoter was inserted into the genome without any non-T-DNA sequences from the pCAMBIA2300 vector. Sequence data indicate that the insertion of the Mdpgip1 transgene was in a gene-rich region of chromosome 1, adjacent to the photosystem Q gene but without disruption of structural genes. Transcriptome-based cDNA-representational difference analysis revealed the distinctive expression of Mdpgip1 in the transgenic AppA6 line, verifying the intended effect. Protein extracts from the transgenic plants inhibited the activities of Verticillium dahliae polygalacturonases in in vitro studies, showing that the transgene is expressed to produce an active PGIP defense protein. cDNA-AFLP fingerprinting revealed genes that were differentially expressed, including genes encoding tryptophan/tyrosine permease, Ef-Tu domain and SKP1-like 1A proteins. qRT-PCR indicated that the Mdpgip1 transgene insertion resulted in increased expression in the AppA6 transgenic of the xyloglucan endotransglycosylase ( xth) gene and an endogenous Stpgip1 gene. These unintended changes were either caused by the constitutive expression of the Mdpgip1 transgene or transformation-related somaclonal variation. The results indicate that the stable, single copy integration of the Mdpgip1 gene in the AppA6 transgenic line did not disrupt any structural genes but caused unintended effects that affected gene expression compared to the parental counterpart under the non-stressed experimental conditions investigated. [ABSTRACT FROM AUTHOR]

Snakin/GASA proteins have been involved in different aspects of plant growth and development although their exact role is still intriguing. All of them maintain 12 cysteines of the C-terminus in highly conserved positions that are responsible for their structure and are essential for their biochemical activity as antioxidants. Two members were isolated from Solanum tuberosum to date (Snakin-1 and Snakin-2) and were shown to have antimicrobial activity. We have recently demonstrated that Snakin-1 has additional roles in plant growth and development. We carried out a genome-wide search for new Snakin/GASA family members in potato. 16 Snakin/GASA genes were isolated, sequenced and characterized. Interestingly, we found in Solanum tuberosum subsp. tuberosum cv. Kennebec that Snakin-1, Snakin-2 and Snakin-3 expression is affected by bacterial and/or fungal inoculation. These results strengthen the participation of Snakin-1 and Snakin-2 genes in biotic stress tolerance and suggest that Snakin-3 is also involved in plant defense. The data presented here could be a good starting point for more focused and deep investigations regarding the biological functions of potato Snakin/GASA genes during plant development and in response to environmental stress. [ABSTRACT FROM AUTHOR]

Access to genetic and genomic resources can greatly facilitate biological understanding of plant species leading to improved crop varieties. While model plant species such as Arabidopsis have had nearly two decades of genetic and genomic resource development, many major crop species have seen limited development of these resources due to the large, complex nature of their genomes. Cultivated potato is among the ranks of crop species that, despite substantial worldwide acreage, have seen limited genetic and genomic tool development. As technologies advance, this paradigm is shifting and a number of tools are being developed for important crop species such as potato. This review article highlights numerous tools that have been developed for the potato community with a specific focus on the reference de novo genome assembly and annotation, genetic markers, transcriptomics resources, and newly emerging resources that extend beyond a single reference individual. [ABSTRACT FROM AUTHOR]

Potato is the world's most important vegetable crop, with nearly 400 million tons produced worldwide every year, lending to stability in food supply and socioeconomic impact. In general, potato is an intensively managed crop, requiring irrigation, fertilization, and frequent pesticide applications in order to obtain the highest yields possible. Important traits are easy to find in wild relatives of potato, but their introduction using traditional breeding can take 15-20 years. This is due to sexual incompatibility between some wild and cultivated species, a desire to remove undesirable wild species traits from adapted germplasm, and difficulty in identifying broadly applicable molecular markers. Fortunately, potato is amenable to propagation via tissue culture and it is relatively easy to introduce new traits using currently available biotech transformation techniques. For these reasons, potato is arguably the crop that can benefit most by modern biotechnology. The benefits of biotech potato, such as limited gene flow to conventionally grown crops and weedy relatives, the opportunity for significant productivity and nutritional quality gains, and reductions in production cost and environmental impact, have the potential to influence the marketability of newly developed varieties. In this review we will discuss current and past efforts to develop biotech potato varieties, traits that could be impacted, and the potential effects that biotech potato could have on the industry. [ABSTRACT FROM AUTHOR]