The mechanism of potato resistance to Globodera rostochiensis: comparison of root transcriptomes of resistant and susceptible Solanum phureja genotypes.

BACKGROUND: Globodera rostochiensis belongs to major potato pathogens with a sophisticated mechanism of interaction with roots of the host plants. Resistance of commercial varieties is commonly based on specific R genes introgressed from natural populations of related wild species and from native potato varieties grown in the Andean highlands. Investigation of molecular resistance mechanisms and screening the natural populations for novel R genes are important for both fundamental knowledge on plant pathogen interactions and breeding for durable resistance. Here we exploited the Solanum phureja accessions collected in South America with contrasting resistance to G. rostochiensis. RESULTS: The infestation of S. phureja with G. rostochiensis juveniles resulted in wounding stress followed by activation of cell division and tissue regeneration processes. Unlike the susceptible S. phureja genotype, the resistant accession reacted by rapid induction of variety of stress response related genes. This chain of molecular events accompanies the hypersensitive response at the juveniles' invasion sites and provides high-level resistance. Transcriptomic analysis also revealed considerable differences between the analyzed S. phureja genotypes and the reference genome. CONCLUSION: The molecular processes in plant roots associated with changes in gene expression patterns in response to G. rostochiensis infestation and establishment of either resistant or susceptible phenotypes are discussed. De novo transcriptome assembling is considered as an important tool for discovery of novel resistance traits in S. phureja accessions.

Differential expression of NBS-LRR-encoding genes in the root transcriptomes of two Solanum phureja genotypes with contrasting resistance to Globodera rostochiensis.

BACKGROUND: The characterization of major resistance genes (R genes) in the potato remains an important task for molecular breeding. However, R genes are rapidly evolving and frequently occur in genomes as clusters with complex structures, and their precise mapping and identification are complicated and time consuming. RESULTS: Comparative analysis of root transcriptomes of Solanum phureja genotypes with contrasting resistance to Globodera rostochiensis revealed a number of differentially expressed genes. However, compiling a list of candidate R genes for further segregation analysis was hampered by their scarce annotation. Nevertheless, combination of transcriptomic analysis with data on predicted potato NBS-LRR-encoding genes considerably improved the quality of the results and provided a reasonable number of candidate genes that provide S. phureja with strong resistance to the potato golden cyst nematode. CONCLUSION: Combination of comparative analyses of tissue-specific transcriptomes in resistant and susceptible genotypes may be used as an approach for the rapid identification of candidate potato R genes for co-segregation analysis and may be used in parallel with more sophisticated studies based on genome resequencing.

Genome sequence of a divergent Colombian isolate of potato virus V (PVV) infecting Solanum phureja.

Deep sequencing analysis of the transcriptome of a Solanum phureja cv. Criolla Colombia plant with symptoms typical of a virus disease revealed an infection with potato virus V (PVV). The PVV-phureja genome comprises 9904 nt, exhibits 83% nucleotide identity with currently fully sequenced PVV isolates and contains one large ORF that codes for a polyprotein of 3065 residues flanked by 5' and 3' UTR of 217 and 448 nt, respectively. Phylogenetic analysis of the PVV-phureja polyprotein indicates that it is divergent with respect to most PVV isolates. This is the first complete PVV genome of an isolate infecting a host different to S. tuberosum and, to this date, the only one from the South American Andes.

Multiple QTLs Linked to Agro-Morphological and Physiological Traits Related to Drought Tolerance in Potato.

Dissection of the genetic architecture of adaptation and abiotic stress-related traits is highly desirable for developing drought-tolerant potatoes and enhancing the resilience of existing cultivars, particularly as agricultural production in rain-fed areas may be reduced by up to 50 % by 2020. The "DMDD" potato progeny was developed at International Potato Center (CIP) by crossing the sequenced double monoploid line DM and a diploid cultivar of the Solanum tuberosum diploid Andigenum Goniocalyx group. Recently, a high-density integrated genetic map based on single nucleotide polymorphism (SNP), diversity array technology (DArT), simple sequence repeats (SSRs), and amplified fragment length polymorphism (AFLP) markers was also made available for this population. Two trials were conducted, in greenhouse and field, for drought tolerance with two treatments each, well-watered and terminal drought, in which watering was suspended 60 days after planting. The DMDD population was evaluated for agro-morphological and physiological traits before and after initiation of stress, at multiple time points. Two dense parental genetic maps were constructed using published genotypic data, and quantitative trait locus (QTL) analysis identified 45 genomic regions associated with nine traits in well-watered and terminal drought treatments and 26 potentially associated with drought stress. In this study, the strong influence of environmental factors besides water shortage on the expression of traits and QTLs reflects the multigenic control of traits related to drought tolerance. This is the first study to our knowledge in potato identifying QTLs for drought-related traits in field and greenhouse trials, giving new insights into genetic architecture of drought-related traits. Many of the QTLs identified have the potential to be used in potato breeding programs for enhanced drought tolerance.

In silico search for and analysis of R gene variation in primitive cultivated potato species.

Pathogen recognition receptors encoded by R genes play a key role in plant protection. Nowadays, R genes are a basis for breeding many crops, including potato. Many potato R genes have been discovered and found suitable for breeding thanks to the studies of a wide variety of wild potato species. The use of primitive cultivated potato species (PCPS) as representatives of the primary gene pool can also be promising in this respect. PCPS are the closest to the early domesticated forms of potato; therefore, their investigation could help understand the evolution of R genes. The present study was aimed at identifying and analyzing R genes in PCPS listed in the open database of NCBI and Solomics DB. In total, the study involved 27 accessions belonging to three species: Solanum phureja Juz. & Bukasov, S. stenotomum Juz. & Bukasov and S. goniocalyx Juz. & Bukasov Materials for the analysis were the sequencing data for the said three species from the PRJNA394943 and PRJCA006011 projects. An in silico search was carried out for sequences homologous to 26 R genes identified in potato species differing in phylogenetic distance from PCPS, namely nightshade (S. americanum), North- (S. bulbocastanum, S. demissum) and South-American (S. venturii, S. berthaultii) wild potato species, as well as the cultivated potato species S. tuberosum and S. andigenum. Homologs of all investigated protein-coding sequences were discovered in PCPS with a relatively high degree of similarity (85-100 %). Homologs of the Rpi-R3b, Rpi-amr3 and Rpi-ber1 genes have been identified in PCPS for the first time. An analysis of polymorphism of nucleotide and amino acid sequences has been carried out for 15 R genes. The differences in frequencies of substitutions in PCPS have been demonstrated by analysis of R genes, the reference sequences of which have been identified in different species. For all the studied NBS-LRR genes, the proportion of substituted amino acids in the LRR domain exceeds this figure for the NBS domain. The potential prospects of using PCPS as sources of resistance to Verticillium wilt have been shown.

Potato root-associated microbiomes adapt to combined water and nutrient limitation and have a plant genotype-specific role for plant stress mitigation.

BACKGROUND: Due to climate change and reduced use of fertilizers combined stress scenarios are becoming increasingly frequent in crop production. In a field experiment we tested the effect of combined water and phosphorus limitation on the growth performance and plant traits of eight tetraploid and two diploid potato varieties as well as on root-associated microbiome diversity and functional potential. Microbiome and metagenome analysis targeted the diversity and potential functions of prokaryotes, fungi, plasmids, and bacteriophages and was linked to plant traits like tuber yield or timing of canopy closure. RESULTS: The different potato genotypes responded differently to the combined stress and hosted distinct microbiota in the rhizosphere and the root endosphere. Proximity to the root, stress and potato genotype had significant effects on bacteria, whereas fungi were only mildly affected. To address the involvement of microbial functions, we investigated well and poorly performing potato genotypes (Stirling and Desirée, respectively) under stress conditions and executed a metagenome analysis of rhizosphere microbiomes subjected to stress and no stress conditions. Functions like ROS detoxification, aromatic amino acid and terpene metabolism were enriched and in synchrony with the metabolism of stressed plants. In Desirée, Pseudonocardiales had the genetic potential to take up assimilates produced in the fast-growing canopy and to reduce plant stress-sensing by degrading ethylene, but overall yield losses were high. In Stirling, Xanthomonadales had the genetic potential to reduce oxidative stress and to produce biofilms, potentially around roots. Biofilm formation could be involved in drought resilience and nutrient accessibility of Stirling and explain the recorded low yield losses. In the rhizosphere exposed to combined stress, the relative abundance of plasmids was reduced, and the diversity of phages was enriched. Moreover, mobile elements like plasmids and phages were affected by combined stresses in a genotype-specific manner. CONCLUSION: Our study gives new insights into the interconnectedness of root-associated microbiota and plant stress responses in the field. Functional genes in the metagenome, phylogenetic composition and mobile elements play a role in potato stress adaption. In a poor and a well performing potato genotype grown under stress conditions, distinct functional genes pinpoint to a distinct stress sensing, water availability and compounds in the rhizospheres.

Maximization of Markers Linked in Coupling for Tetraploid Potatoes via Monoparental Haploids.

Haploid potato populations derived from a single tetraploid donor constitute an efficient strategy to analyze markers segregating from a single donor genotype. Analysis of marker segregation in populations derived from crosses between polysomic tetraploids is complicated by a maximum of eight segregating alleles, multiple dosages of the markers and problems related to linkage analysis of marker segregation in repulsion. Here, we present data on two monoparental haploid populations generated by prickle pollination of two tetraploid cultivars with Solanum phureja and genotyped with the 12.8 k SolCAP single nucleotide polymorphism (SNP) array. We show that in a population of monoparental haploids, the number of biallelic SNP markers segregating in linkage to loci from the tetraploid donor genotype is much larger than in putative crosses of this genotype to a diverse selection of 125 tetraploid cultivars. Although this strategy is more laborious than conventional breeding, the generation of haploid progeny for efficient marker analysis is straightforward if morphological markers and flow cytometry are utilized to select true haploid progeny. The level of introgressed fragments from S. phureja, the haploid inducer, is very low, supporting its suitability for genetic analysis. Mapping with single-dose markers allowed the analysis of quantitative trait loci (QTL) for four phenotypic traits.

Comparison of Compatible and Incompatible Response of Potato to Meloidogyne incognita.

One susceptible (D6) and two resistant (E2 and N4) clones of Solanum sparsipilum x (S. phureja x haploid of S. tuberosum) were used to study the responses of potato roots and tubers to race 1 of Meloidogyne incognita (Kofoid &White) Chitwood. The compatible response was characterized by rapid penetration of large numbers of second-stage juveniles (J2) into roots, cessation of root growth, and occasional curving of root tips. The life cycle of M. incognita in the susceptible clone was completed in 25 days at 23-28 C. The incompatible response was characterized by penetration of fewer J2 into roots, necrosis of feeding sites within 2-7 days, and lack of nematode development. There were no differences in response of tubers from resistant and susceptible clones to nematode infection. Small numbers of J2 were detected in tubers, but they did not develop.

Extracción de glicoalcaloides de papa nativa (Solanumphureja) variedad ratona morada con líquidos presurizados / Extraction of glycoalkaloids of native potato (Solanum phureja) ratona morada variety with pressurized liquids

RESUMEN La cáscara de papa es un residuo originado por su procesamiento agroindustrial, que genera un gran impacto ambiental debido a su inadecuado manejo o eliminación. No obstante, la cáscara de papa es una buena fuente de ingredientes funcionales como los glicoalcaloides (GA). Este estudio investigó la extracción de dos GA (α-solanina y α-chaconina) de cáscara de papa nativa (Solanum phureja) variedad ratona morada del departamento de Nariño-Colombia, utilizando la tecnología de extracción con líquidos presurizados (ELP), mediante un diseño experimental central compuesto, con el fin de determinar el efecto de la presión (P) y la temperatura (T), sobre el rendimiento y la composición de GA. Los extractos se analizaron por cromatografía líquida HPLC. Los resultados obtenidos permitieron establecer que la temperatura ejerció un efecto significativo (p <0,05) sobre el rendimiento, α-solanina y α-chaconina. El rendimiento óptimo fue de 5,62 % p/p. Los GA, α-solanina y α-chaconina, aumentaron su concentración al disminuir la temperatura. La extracción con líquidos presu-rizados promete ser una buena alternativa al uso de solventes orgánicos para obtener compuestos bioactivos de cáscara de papa.

SUMMARY Potato peel is a waste originated by its agro-industrial processing, generating an environmental impact due to its inadequate handling or elimination. However, potato peel is a good source of functional ingredients such as glycoalkaloids (GA). This study investigated the extraction of two GA (α-solanine and α-chaconine) from native potato rind (Solanum phureja) ratona morada variety from the department of Nariño-Colombia, using the technology of extraction with pressurized liquids (PLE), through a experimental central composite design, in order to determine the effect of pressure (P) and temperature (T), on the performance and composition of GA. The extracts were analyzed by liquid chromatography HPLC. The results obtained allowed us to establish that the temperature exerted a significant effect (p <0.05) on the yield, α-solanine and α-chaconine. For the yield an optimum value of 5.62 % w/w was reached. α-solanine and α-chaconine increased their concentration as the temperature decreased. The extraction with pressurized liquids promises to be a good alternative in the use of organic solvents to obtain bioactive compounds of potato husk.

Molecular Identification of Potyviruses Infecting Potato Plots in Eastern Antioquia (Colombia) / Identificación molecular de potyvirus infectando cultivos de papa en el oriente de antioquia (colombia)

RESUMEN Los potyvirus son uno de los grupos de virus más limitantes en los cultivos de papa (Solanum tuberosum y S. phureja) en el mundo, siendo PVY, PVV y PVA las especies más prevalentes. En este trabajo se evaluó la presencia de estos potyvirus en cuatro lotes de S. tuberosum cv. Diacol-Capiro y cuatro lotes de S. phureja cv. Criolla-Colombia ubicados en el oriente de Antioquia, analizando la cápside viral mediante RT-PCR/secuenciación Sanger y secuenciación de nueva generación (NGS) para S. tuberosum. Los resultados indicaron la ocurrencia de los potyvirus PVY y PVV en las muestras de S. tuberosum y S. phureja, respectivamente; siendo detectadas mediante cebadores específicos la presencia de tres diferentes cepas de PVY (PVYN, PVYNTN y PVY°) en la región de estudio. Este hallazgo fue confirmado por NGS, obteniendo las secuencias completas de los genomas de estas tres cepas, lo que representa el primer reporte de PVYO en Colombia. Por su parte, los análisis de secuencias de la región CP de PVV indicaron niveles de identidad superiores a 99% con respecto a aislamientos del linaje PVVPhu reportado previamente en Antioquia. Estos hallazgos evidencian la necesidad de ajustar los sistemas de detección de virus en los programas de certificación de tubérculo-semilla de papa adelantados en el país.

ABSTRACT Potyviruses are one of the most limiting viruses for the potato (Solanum tuberosum and S. phureja) production worldwide, being PVY, PVV and PVA the most prevalent species. In this work, we tested the presence of these viruses in four commercial S. tuberosum cv. Diacol-Capiro and S. phureja cv. Criolla-Colombia plots in eastern Antioquia using RT-PCR and Sanger sequencing of the coat protein (CP) region, as well as next generation sequencing (NGS) for S. tuberosum samples. Our results revealed the presence of a PVV strain infecting S. phureja with high sequence identity (>99%) to lineage PVVPhu previously reported in Antioquia. Three strains of PVY (PVYN, PVYNTN and PVY°) were found to infect S. tuberosum. The presence of these three PVY strains was confirmed by NGS, allowing the assembly of their complete genomes. This is the first report of the full genome sequence of PVYo strain in Colombia. These findings highlight the need to adjust the tuber-seed certification programs currently implemented in the country.

EVALUACIÓN DE LA PRODUCCIÓN DE PAPA CRIOLLA Solanum phureja CLON PAISA EN CONTENEDORES DE POLIETILENO DE ALTA DENSIDAD BAJO EL MARCO DE AGRICULTURA URBANA / EVALUATION OF "PAPA CRIOLLA" Solanum phureja "CLONE PAISA" PRODUCTION IN HIGH DENSITY POLYETHYLENE CONTAINERS WITHIN THE FRAMEWROK OF URBAN AGRICULTURE

Con el fin de evaluar la producción de papa criolla Solanum phureja clon Paisa en el contexto urbano, se desarrolló una investigación pionera de tipo descriptiva en la cual se evaluaron las siguientes variables: incidencia de plagas, peso en fresco por contenedor, peso fresco total y peso por clasificación comercial. Se utilizaron contenedores de doble fondo de polietileno de alta densidad y técnicas agroecológicas de producción, de las cuales se destaca la fertilización utilizada con base en tres componentes: materia orgánica, minerales y microorganismos. A partir de los datos obtenidos se calculó media, mediana, moda, desviación estándar y se realizó un análisis de la dispersión por medio de cuartiles para el resumen de la información en cada una de las clasificaciones de la papa. También se analizó el rango intercuartílico y coeficientes de variación para establecer la normalidad en la distribución de los datos. Los resultados mostraron que la producción promedio de S. phureja en los contenedores fue de 528,36 g/planta, que al ser comparados con las medias de producción en Colombia y en el departamento de Cundinamarca, se convierten en una alternativa viable, que contribuye de forma directa con el fortalecimiento de la soberanía y seguridad alimentaria. Esta investigación resalta que la producción agroecológica de papa en contenedores bajo el marco de la agricultura urbana y diseñada desde el punto de vista agroecológico, no solo es una realidad para promover la suficiencia y soberanía y seguridad alimentaria por medio de la producción de alimentos saludables de forma autónoma por la comunidad, sino que además se constituye en una herramienta para los procesos de construcción del espacio urbano con beneficios socioculturales, ambientales y paisajísticos.

In order to evaluate the production of "papa criolla" Solanum phureja, Paisa clone in the urban context, a pioneer descriptive research was carried out in which the following variables were assessed: incidence of pests, fresh weight per container, total fresh weight and weight per trade classification. Fresh weight per container. High density polyethylene and ecological techniques double bottom containers were used in production, in which the fertilizer used was based on three components: organic matter, microorganisms and minerals was emphasized. From the data obtained the mean, median, mode, standard deviation and dispersion analysis were calculated by using quartiles for the summary of the information in each of the potato classifications. The interquartile range and coefficients of variation were also analyzed in order to establish normal data distribution. The results showed that the average production of S. phureja in containers was 528.36 g/plant, that, when compared to the media production in Colombia and in the Department of Cundinamarca, become a viable alternative which directly contributes to the strengthening of food security and sovereignty. This research highlights how agroecologic production of potato, in containers under the framework of urban agriculture and designed from an agroecology point of view, is not only a reality to promote food sufficiency, sovereignty and food security through the production of healthy food by the community in an autonomous way, but also becomes a tool in the construction processes of urban space with sociocultural, environmental and landscape benefits.

Composition andffunction of the microbial commuity related with the nitrogen ccycling on the potato rhizosphere / Composición y función de la comunidad microbiana relacionada con el ciclaje de nitrógeno en la rizosfera de Solanum tuberosum (BAHUIN) grupo phureja

In the S. tuberosum group phureja crops, mineral fertilizer and organic amendments are applied to meet the plants´ nutritional demands, however the effect of such practices on the associated rizospheric microbial communities are still unknown. Nitrogen plays an important role in agricultural production, and a great diversity of microorganisms regulates its transformation in the soil, affecting its availability for the plant. The aim of this study was to assess the structure of microbial communities related with the N cycle of S. tuberosum group phureja rizospheric soil samples, with contrasting physical-chemical properties and fertilization strategy. Few significant differences between the community composition at the phylum level were found, only Planctomycetes phylum was different between samples of different soil type and fertilization strategy. However, the analysis of nitrogen-associated functional groups made by ribotyping characterization, grouped soils in terms of such variables in a similar way to the physical-chemical properties. Major differences between soil samples were typified by higher percentages of the ribotypes from nitrite oxidation, nitrogen fixation and denitrification on organic amendment soils. Our results suggest that, the dominant rhizosphere microbial composition is very similar between soils, possibly as a result of population´s selection mediated by the rhizosphere effect. However, agricultural management practices in addition to edaphic properties of sampled areas, appear to affect some functional groups associated with the nitrogen cycling, due to differences found on soil´s physicalchemical properties, like the concentration of ammonium that seems to have an effect regulating the distribution and activity of nitrogen related functional groups in the S. tuberosum rhizosphere.

Fertilización mineral y enmiendas orgánicas son aplicadas para satisfacer las demandas nutricionales de los cultivos de S. tuberosum grupo phureja . Sin embargo, el efecto de esas prácticas sobre la comunidad microbiana asociada a la rizósfera aún no se conocen. El nitrógeno juega un papel importante en la producción agrícola y una gran diversidad de microorganismos regulan su transformación en el suelo, afectando su disponibilidad para la planta. El objeto de este estudio fue determinar la composición de la comunidad microbiana de la rizósfera de S. tuberosum grupo phureja , asociada con el ciclo del nitrógeno, en muestras de suelo contrastantes en sus propiedades fisicoquímicas y estrategia de fertilización. Pocas diferencias significativas entre la composición de la comunidad microbiana a nivel de phylum fueron encontradas, Í°nicamente el phylum Planctomycetes fue diferente entre las muestras de suelos con estrategias de fertilización diferentes. Sin embargo, el análisis de grupos funcionales asociados al nitrógeno llevado a cabo por la caracterización de ribotipificación, agrupó los suelos en términos de esas variables en una forma similar a las propiedades fisicoquímicas del suelo. Diferencias mayores entre las muestras de suelo fueron tipificadas por los altos porcentajes de ribotipos asociados a la oxidación de nitrito, fijación de nitrógeno y denitrificación sobre los suelos con enmiendas orgánicas. Nuestros resultados sugieren que la composición microbiana dominante es muy similar entre suelos, posiblemente como resultado de la selección de poblaciones mediada por el efecto rizosférico. Sin embargo, las prácticas del manejo agrícola en conjunto con las propiedades del suelo en las áreas muestreadas, parecen afectar algunos grupos funcionales asociados con el ciclo de nitrógeno, debido a las diferencias encontradas en las propiedades fisicoquímicas del suelo, como la concentración de amonio que parece tener un efecto regulando la distribución y actividad de los grupos funcionales relacionados con el ciclo del nitrógeno en la rizosfera de S. tuberosum.

DETECCIÓN Y CUANTIFICACIÓN DE Spongospora subterranea f. sp. subterranea EN PLANTAS SEÑUELO Y CULTIVOS DE PAPA EN COLOMBIA MEDIANTE qPCR / Detection and Quantification of Spongospora subterranea f. sp. subterranea in Bait Plants and Potato Fields in Colombia using qPCR

La sarna polvosa de la papa (Solanum tuberosum, S. phureja) causada por Spongospora f. sp. subterranea (Sss), es una de las enfermedades más limitantes de este cultivo. En Colombia, se han empleado diferentes métodos de detección asintomática de Sss, incluyendo bioensayos con plantas señuelo, PCR de ITS y pruebas de ELISA. Sin embargo, sus niveles de sensibilidad son bajos o requieren tiempos extensos. Una alternativa para complementar dichas herramientas es la PCR cuantitativa en tiempo real (qPCR). En este trabajo se evaluó dicha técnica utilizando los juegos de cebadores SsTQF1-SsTQR1; Spon421F-Spon494R y SscolF-SscolR (diseñados en este estudio), bajo la metodología de SYBR Green®; mientras que con Taqman® se evaluaron los cebadores SponFSponR y la sonda SponP. Una vez determinada la funcionalidad de los cebadores, se descartó por inespecificidad, el par Spon421F-Spon494R ; para los restantes se realizaron curvas estándar basadas en diluciones seriadas de quistosoros. Las pruebas de qPCR detectaron a Sss en las 20 muestras evaluadas de plantas señuelo de Nicotiana benthamiana y papa, utilizando los cebadores SsTQF1-SsTQR1 (Ct: 10,57-29,34) y SscolF-SscolR (Ct: 14,39-34,08); mientras que 19 de las muestras fueron positivas con SponF-SponR-SponP (Ct: 15,63-38,93). A partir de 20 muestras de raíces de papa de cultivos de La Unión (Antioquia, Colombia), fue posible detectar el patógeno en 17 de ellas con SscolF-SscolR, estimándose una concentración de 6470 a 1,39 x 10(10) quistorosos/mL. Estos resultados indican la ocurrencia de altos niveles de inóculo de Sss en esta región y enfatizan en la necesidad de fortalecer los programas de certificación de tubérculo-semilla en Colombia.

In recent years, potato crops (Solanum tuberosum, S. phureja) have been seriously affected by powdery scab; a disease caused by Spongospora subterranea f.sp. subterranea (Sss). In Colombia, asymptomatic detection of Sss has been achieved with bait plants, PCR of ITS regions and ELISA tests. Unfortunately, these techniques have low sensitivity and may require long processing times. In this work, Quantitative real time PCR (qPCR) was tested for detection of Sss using different sets of primers. Primers SsTQF1-SsTQR1, Spon421F-Spon494R and SscolF-SscolR (designed in this study), were tested using SYBR Green®, while primers SponFSponR were tested using the Taqman® probe SponP. Primers Spon421F-Spon494R were discarded due to lack of specificity. Standard curves were obtained from serial dilutions of cystosori. The 20 N. benthamiana and potato bait plants evaluated tested positive for Sss using primers SsTQF1-SsTQR1 (Ct: 10.57-29.34) and SscolF-SscolR (Ct: 14.39-34.08) and 19 samples were positive with primers SponF-SponR-SponP, with Ct values ranging between 15,63 and 38,93. Sss was detected in 17 out of 20 root samples from potato crops in La Unión (Antioquia) using primers SscolF-SscolR, with an estimated concentration of 6470 to 1,39x10(10) cystosori/ mL. These results suggest high levels of Sss in the potato fields from this region and recall the importance of strengthening seed-certification programs in Colombia.

EXPRESIÓN GUS EN EXPLANTES DE Solanum phureja (Juz. et. Buk) Var. Criolla Colombia , TRANSFORMADOS CON Agrobacterium tumefaciens / Gus Expression in Solanum phureja Explants (Juz. et. Buk) Cultivar Criolla Colombia , Transformed with Agrobacterium tumefaciens

La expresión transitoria y estable del gen gusA-intron en explantes internodales de papa criolla variedad Criolla Colombia cocultivados con Agrobacterium tumefaciens es reportada. Con el fin de determinar la susceptibilidad de esta variedad a la transformación mediada por A. tumefaciens, explantes internodales de Solanum phureja fueron infectados con la cepa LBA4404 de A. tumefaciens que contiene el plásmido pCAMBIA2301. Este plásmido contiene el gen ntpII que confiere resistencia a kanamicina y el gen reportero gusA-intron. La selección de los explantes potencialmente transgénicos fue realizada en medios con kanamicina. La eficiencia de transformación estable y transitoria fue calculada con base en la actividad GUS (ß-glucuronidasa), detectada por el ensayo histoquímico X-gluc. La expresión transitoria y estable del gen gusA-intron fue observada en células del explante más bien que en tejidos completos. Estos resultados demuestran que la papa criolla (S. phureja Juz. et. Buk) variedad Criolla Colombia es susceptible a la infección por A. tumefaciens.

The stable and transient expression of the gusA-intron reporter gene in internodal explants of "Papa Criolla" cultivar Criolla Colombia co-cultivated with Agrobacterium tumefaciens is reported. In order to determine the susceptibility of this cultivar to the A. tumefaciens-mediated transformation, internodal explants of Solanum phureja were infected by A. tumefaciens containing the vector pCAMBIA2301. This vector contains the kanamycin resistance gene ntpII and the reporter gene gusA-intron. The selection of potential transgenic explants was performed on kanamycin-containing media. The stable and transient transformation efficiency was calculated on the basis of the GUS (ß-glucuronidase) activity, detected by the histochemical X-Gluc essay. Transient and stable expression of the gusA-intron gene is observed in explants cells rather than in whole tissues. Nonetheless, these results demonstrated that "Papa Criolla" (Solanum phureja Juz. et. Buk) Cultivar Criolla Colombia is susceptible to the Agrobacterium tumefaciens infection.