John B. Bamberg

Assessing changes in the genetic diversity of potato gene banks. 1. Effects of seed increase

Abstract Effects of gene bank seed-increases on the genetic integrity of potato germ plasm is a major concern of gene bank managers. Thus the Association of Potato Inter-gene-bank Collaborators (APIC), a consortium of world potato gene bank leaders, initiated this joint research project using RAPD markers to determine genetic relationships between increased generations within accessions. Solanum jamesii (2n=2x=24) and S. fendleri (2n=4x=48), two wild potato species native to North America, were used as plant material. These species represented two major breeding systems found among Solanum species: outcrossing diploids and inbreeding disomic tetraploids, respectively. Comparisons were made between populations one generation apart and between sister populations generated from a common source. Fourteen such comparisons within S. jamesii accessions had an average similarity of 96.3%, and 21 such comparisons within S. fendleri accessions had an average similarity of 96.0%. No pairs of populations were significantly different, despite the fact that RAPD markers easily separated all of these very similar accessions within their respective species. Only one of six S. jamesii accessions analyzed showed a significant change in gene frequencies among generations. These findings indicate that there has been minimal loss or change of genetic diversity in ex situ germplasm using the gene bank techniques standard at NRSP-6 and other world potato gene banks.

Potato genetic resources: Sources of resistance and systematics

The major potato of commerce,Solanum tuberosum L., is the fourth most important food crop in the world after rice, wheat and corn. Fortunately, the potato has many primitive cultivars and wild species relatives useful to reduce our reliance on chemical controls. These include resistances against diseases, pests, and traits for useful agronomic characters such as yield, specific gravity, chipping qualities, and suppression of enzymatic browning. This paper summarizes some of these qualities, and provides an overview of germplasm availability and taxonomy of the wild species.The major potato of commerce,Solanum tuberosum L., is the fourth most important food crop in the world after rice, wheat and maize. It is grown in more countries than any other crop but maize, and forms the staple crop of many societies. Over 280 million metric tons were grown worldwide in 1989, with Eastern Europe growing 46%, Asia 22%, Western Europe 17%, North America 7%, Latin America 5%, and Africa 3% (2). It is the leading vegetable crop in acreage and farm value in the United States, with 1.2 million acres planted in 1991, with a value of sales almost two and one-half billion dollars (53).Solanum tuberosum is one species of a group of seven cultivated and 216 additional tuber-bearing, and nine non-tuber-bearing wild relatives, all classified by Hawkes (41) in the genusSolanum, sectionPetota DumortThe purposes of this paper are threefold: 1) to provide examples of the proven and potential utility of wild and cultivated landrace members of sect.Petota for reducing our reliance on chemical controls for many pests and diseases that affect commercial cultivars, 2) to provide an overview of the status of germplasm availability of these species, and 3) to highlight the benefits for continuing germplasm collections and systematic studies of the group.CompendioSolanum tuberosum L., la principal papa en el mercado, es el cuarto cultivo alimenticio más importante en el mundo, después del arroz, del trigo y del maíz. Afortunadamente, la papa tiene muchos cultivares primitivos y especies silvestres relacionadas útiles para reducir nuestra dependencia en los controles químicos. Estos incluyen resistencias contra enfermedades y plagas, así como también útiles características agronómicas tales como rendimiento, gravedad específica, calidades para fritura a la inglesa y supresión del pardeamiento enzimático. Este artículo resume algunas de estas cualidades y provee una vision del germoplasma disponible y de la taxonomía de las especies silvestres.

Evaluation of Tuber-Bearing Solanum Species for Nitrogen Use Efficiency and Biomass Partitioning

Modern potato cultivars (Solanum tuberosum L.) require high rates of fertilizer nitrogen (N). This practice is costly and can pose a serious threat to surface and groundwater. Previous evaluation of wild potato germplasm demonstrated the existence of species capable of producing high total biomass under low N conditions, with the ability to make maximum use of added N. Therefore, a two-year field experiment was conducted in 1994 and 1995 to investigate the response of selected wild potato accessions and their hybrids with the haploid USW551 (USW) to low and high N environments. The haploid USW and cultivars Russet Burbank, Red Norland, and Russet Norkotah were also included in the study. Uniform propagules and seedlings from the variousSolanum species were transplanted to a Hubbard loamy sand (Udic Haploboroll) at Becker, Minn. and were subjected to two N treatments: 0 and 225 kg N ha-1. At harvest, total dry biomass of wild and hybrid potato germplasm was equal to or higher than that of the cultivars. However, cultivar biomass partitioning was 1% to roots, 15% to shoots, 0% to fruits, and 84% to tubers, whereas wild potato species partitioned 18% to roots plus nontuberized stolons, 52% to shoots, 23% to fruits, and only 7% to tubers. Hybrids were intermediate, allocating 9% of their biomass to roots plus nontuberized stolons, 39% to shoots, 14% to fruits, and 38% to tubers. Nitrogen use efficiencies for many of the species and crosses were comparable to that for Russet Burbank and greater than those for Red Norland and Russet Norkotah. Of the wild species tested,S. chacoense accessions had the highest biomass accumulation and N uptake efficiencies and may be the best source of germplasm for improving NUE in a potato breeding program.

Assessing changes in the genetic diversity of potato gene banks. 2. In situ vs ex situ

Abstract An important question in the conservation of potato germ plasm is whether germ plasm in the gene bank, although stable, still represents the in situ populations from which it was collected, sometimes many decades ago. The answer would direct objective decisions regarding the value of re-collections and in situ preservation. The present study was undertaken as a project of the Association of Potato Inter-gene-bank Collaborators (APIC). It measured genetic differentiation between potato germ plasm maintained in the US gene bank for many years and current in situ populations re-collected from the same original sites in the wild. Solanum jamesii and Solanum  fendleri from the United States were used as representatives of potato germ plasm. Re-collections were carried out in 1992 at the same locations at which gene bank-conserved accessions had been collected in 1958 and 1978. RAPD markers revealed significant genetic differences between gene bank-conserved and re-collected in situ populations for all seven comparisons of S. jamesii (diploid outcrosser), and 12 of 16 comparisons within S.  fendleri (tetraploid inbreeder). The average genetic similarities were 65.2% for S.  jamesii and 80.4% for S.  fendleri. Possible explanations and consequences of these unexpectedly large differences are discussed.

Frost tolerance in wild potato species: Assessing the predictivity of taxonomic, geographic, and ecological factors

AbstractThe use of genetic resources could be more effective and efficient if we were able to predict the presence or absence of useful traits in different populations or accessions. We analyzed the extent to which taxonomic, geographic and ecological factors can predict the presence of frost tolerance in wild potatoes. We used screening data for 1646 samples from 87 species that had been collected in 12 countries in the Americas. There was a strong association of frost tolerance with species and to a lesser extent with taxonomic series. There was significant geographic clustering of areas with wild potatoes with similar levels of frost tolerance. Areas with a high level of frost tolerance are the central and southern Peruvian Andes, the lowlands of Argentina and adjacent areas, and a small area in the central Chilean Andes. There is a greater chance of finding wild potatoes with high levels of frost tolerance in areas with a yearly mean minimum temperature below 3 °C than there is in warmer areas. However, temperature is only a weak predictor of frost tolerance. Temperature data alone did not predict observed frost tolerance in eastern Argentina/Uruguay and falsely predicted it in the southwestern United States. Because many wild potato species occur over small areas, taxonomic, ecological, and geographical factors are difficult to disentangle.

Screening tuber-bearingSolanum (potato) germplasm for efficient accumulation of tuber calcium

Resistance to several pathological and physiological tuber defects has been correlated with calcium level in the peel. In this study, a representative sample of potato species (including cultivated), was grown in the greenhouse. Plants were watered with low and high calcium solutions, and the resulting tubers analyzed. Thus, potato germplasm was screened for ability to accumulate tuber calcium when a control level of calcium is available, and ability to respond when higher levels are supplied. Some wild species significantly exceeded cultivated materials in one or both of these measures. Such species may provide a resource for breeding varieties which are more efficient calcium accumulators.CompendioLa resistencia a varios defectos patológicos y fisiológicos de los tubérculos han sido correlacionados con el nivel de calcio en la piel. En este estudio, una muestra representativa de especies de papa (incluyendo a las cultivadas), se mantuvo en el invernadero. Las plantas fueron regadas con soluciones de baja y alta concentración de calcio y se analizaron los tubérculos obtenidos. Así, el germoplasma de papa fue evaluado y selecionado para capacidad de acumulación de calcio en los tubérculos cuando se dispone de un nivel de control del calcio y capacidad para responder cuando se proveen nivelés más altos. Algunas especies silvestres excedieron significativamente a los materiales cultivados en una o ambas de estas medidas. Tales especies pueden proporcionar un recurso para el mejoramiento de variedades que son acumuladoras más eficientes de calcio.

The Inter-genebank potato database and the dimensions of available wild potato germplasm

The Association of Potato Inter-genebank Collaborators (APIC) constructed a database of all wild potato holdings of the most important potato genebanks in Europe, the United States, Peru, and Argentina. The Inter-genebank Potato Database (IPD) now contains data of 11,819 wild potato accessions conserved in seven potato genebanks. The collector’s number is the key identifier used to merge all databases into the IPD. A total of 7,112 different wild potato accessions were identified, which comprise 5,306 accessions with known collector’s numbers. The IPD passport database showed that almost 30% of accessions held in APIC genebanks are from Argentina, a country that comprises less species diversity than Peru and Bolivia. These latter countries are represented by 24% and 20% of accessions, respectively. APIC genebanks maintain 188Solarium taxa out of more than 230 recognized by the latest comprehensive treatment of potatoes(Solarium sect.Petota) by Hawkes (1990). About 60% of the accessions comprise only 20 taxa represented by 785 to 92 accessions each. Conversely, 2% of the accessions comprise 72 taxa and are represented by five or fewer accessions each. About 70 taxa are not available in any genebank. The IPD evaluation database comprises 5,603 records with data from more than 33,000 evaluations of wild potato accessions. Fifty-five traits are summarized, including the reactions of the accessions to 12 pathotypes or races or strains of 12 fungi, four bacteria, 12 viruses, one viroid, 13 nematodes, and seven insects; response to heat and cold stress; and content of dry matter, starch, vitamin C, amylase, reducing sugars, and glycoalkaloids. About 30% of the wild potato populations screened showed various levels of resistance to most of the diseases and pests evaluated. The IPD database is available on the Internet at www.potgenebank.org.ResumenLa Associatión para la Colaboración entre Bancos Genéticos de Papa (APIC) ha ensamblado una base de datos de todas las especies silvestres de papa conservada en los bancos genéticos más importantes de Europa, E.E.U.U., Perú y Argentina. La Base de Datos de Papa de los Banco Genéticos (IPD) contiene datos de 11,819 entradas de papas silvestres conservada en siete bancos genéticos. Se utilizó el número de colector como el identificador clave para unir todas las bases de datos de cada banco genético. Se identificó un total de 7,112 entradas diferentes de papas silvestres que comprenden 5,306 entradas con número de colector conocido. La base de datos IPD muestra que las papas silvestres de la Argentina representan casi el 30% de las entradas conservadas en los bancos genéticos de la APIC. Argentina tiene menos diversidad de especies que Perú y Bolivia, que están representados por 24% y 20% de entradas respectivamente. Los bancos genéticos en APIC conservan 188 especies silvestres de papa de más de 230 que son reconocidas por Hawkes (1990). Alrededor de un 60% de las entradas en APIC comprenden solamente 20 especies representadas por 785 a 92 entradas cada una. En el otro extremo, 2% de las entradas comprenden 72 especies que están representadas por 5 o menos entradas cada una. Cerca de 70 especies de papas silvestres no están disponibles en los bancos genáticos. La base de datos IPD con datos de evaluación de especies silvestres comprenden 5,603 registros con más de 33,000 evaluaciones. El número de características evaluadas es de 55 incluyendo las reacciones a patotipos, razas o strains de 12 hongos, 4 bacterias, 12 virus, 1 viroide, 13 nematodes, y 7 insectos; reacción al calor y la sequía, y contenido de materia seca, almidón, vitamina C, amilasa, azúcares reductores y glicoalkaloides. Alrededor del 30% de las poblaciones de especies silvestres tamizadas mostraron varios niveles de resistencia a la mayoria de enfermedades y plagas evaluadas. Esta base de datos esta disponible en Internet www.potgenebank.org.

Evidence for the up-regulation of stearoyl-ACP (Δ9) desaturase gene expression during cold acclimation

Our previous studies demonstrated that an increase in 18:2 (linoleate) in the purified plasma membrane fraction during cold acclimation is associated with genetic variations in cold acclimation capacity. This increase was found only in genotypes that are able to cold acclimate and was reversible on deacclimation suggesting a link between the accumulation of 18:2 and acquisition of freezing tolerance. The present study was aimed at understanding the association between the induction of stearoyl-ACP (acyl carrier protein) (Δ9) desaturase and the ability to cold acclimate. Our approach was to study the induction of Δ9 desaturase at the transcript level using potato Δ9 desaturase gene-specific primers and reverse transcription polymerase chain reaction (RT-PCR). For this purpose, total RNA fromSolanum tuberosum (cold sensitive, unable to acclimate) andSolanum commersonii (cold tolerant, able to cold acclimate) was extracted before and after cold acclimation. RT-PCR produced a single band and sequence analysis confirmed that the amplified band was Δ9 desaturase. While the cold acclimating species,Solanum commersonii, exhibited an increase in Δ9 desaturase transcript levels after cold acclimation, the cold non-acclimating species,Solanum tuberosum, exhibited no change. Our results show that the increase in Δ9 desaturase gene transcripts during cold acclimation is associated with the cold acclimation response in potato.ResumenEstudios realizados en nuestro laboratorio han demostrado que durante la acclimatación a bajas temperaturas existe un incremento del ácido linoleico (18:2) en la membrana plasmática. Dicho incremento está asociado con la variación genética observada en la capacidad de aclimatación en papa. Este incremento fue encontrado únicamente en los genotipos capaces de aclimatarse y fue reversible durante la deaclimatacion sugiriendo que existe una relacion entre acumulación de 18:2 y adquisición de resistencia a bajas temperaturas. El presente trabajo tuvo como objetivo estudiar la asociación entre la inducción de la desaturasa stearoyl-ACP (proteina portadora de acyl) (Δ9) y la habilidad de aclimatarse a bajas temperaturas. Para ello se estudió la inducción de la desaturasa Δ9 a nivel the transcripción utilizando primers especificos para el gen de desaturasa de papa mediante reacción de polimerasa en cadena de transcripción reversa (RT-PCR). Se extrajo el ARN total deSolanum tuberosum (sensible a heladas, incapaz de aclimatarse a bajas temperaturas) ySolanum commersonii (resistente a heladas, capaz de aclimatarse a bajas temperaturas) antes y después del proceso de aclimatación. RT-PCR produjo una sohl banda y el análisis de la secuencia confirmó que la banda amplificada era desaturasa Δ9. Mientras que la especie capaz de aclimatarse,Solanum commersonii, exhibió un incremento en los niveles de transcripción de la desaturasa Δ9 después de la aclimatación, la especie incapaz de aclimatarse,Solanum tuberosum, no exhibió ningún cambio. Nuestros resultados demuestran que el incremento en la transcripción del gen de desaturasa Δ9 durante la aclimatación a bajas temperaturas está asociado con la capacidad de aclimatación a bajas temperaturas en papa.

Screening of exotic potato germplasm for nitrogen uptake and biomass production

Exotic potato germplasm may contain useful traits for improving nitrogen (N) use efficiency in cultivated potatoes (Solanum tuberosum L.). The objective of this study was to evaluate a “mini” core collection of wild germplasm for biomass production, N uptake, and N use efficiency. A field study was conducted during the 1993 growing season on a loamy sand soil at Becker, Minnesota. Uniform transplants for 39 wild accessions and 3 varieties were grown under greenhouse conditions, and after 40 days, they were transplanted to the field. Plants were subjected to two N treatments, 0 and 225 kg N ha1, replicated three times in a split-plot design. Plant parts were collected separately 111 days after transplanting, dried, weighed, and analyzed for N concentration. Nitrogen rate and potato species had significant effects on total dry weight, N content, and tissue N concentration. The regression coefficient of N concentration on total dry weight was very low (r=0.22, NS), whereas the regression coefficient of total N content on total dry weight was high (r=0.94, P>0.001). At both low and high N environments, Russet Burbank had greater dry weight than all the accessions. Several wild accessions, especiallyS. chacoense, S. commersonii, S. kurtzianum, S. microdontum, andS.phureja, had equal to or greater dry weights than Russet Norkotah or Red Norland. For N uptake efficiency, 2,7, and 20 accessions were ranked better than Russet Burbank, Russet Norkotah, and Red Norland, respectively. Recovery of soil applied N by the varieties ranged from 16 to 36%; the top seven wild accessions recovered between 27 and 49%. Based on plant growth without added N fertilizer and relative response to N fertilizer, the species were categorized into four relative N use efficiency groups: good foragers with good response to N, poor foragers with good response to N, good foragers with poor response to N, and poor foragers with poor response to N.ResumenEl germoplasma exótica de la papa podría contener caracteres útiles para mejorar la eficiencia del uso del nitrógeno en papas cultivadas(Solanum tuberosum L.). El objetivo de este estudio fue evaluar una “muestra” de la coleccion del germoplasma silvestre para analizar la produccion de biomasa, absorción de nitrógeno y eficiencia del uso del N. Durante la estación de crecimiento de 1993 se llevó a cabo un estudio de campo en un suelo franco-arenoso en Becker, Minnesota. Plantulas uniformes de 39 entradas silvestres y 3 variedades se desarrollaron bajo condiciones de invernadero y, después de 40 días, fueron trasplantadas al campo. Las plantas fueron sometidas a dos tratamientos de N, 0 y 225 kg N ha1, en un diseno de parcela dividida con tres replicaciones. Diferentes partes de las plantas se cosecharon en forma separada 111 días después de haber sido trasplantadas, secadas, pesadas y analizadas por su concentración de N. La tasa de nitrógeno y la especie de papa tuvieron efectos significativos sobre el peso seco total, contenido de N y concentración de N en el tejido. El coeficiente de regresión de la concentración de N sobre el peso seco total fue muy bajo (r=0.22, NS), mientras que el coeficiente de regresión del contenido total de N sobre el peso seco total fue alto (r=0.94, P>0.001). En ambos tratamientos, de bajo y alto contenido de N, Russet Burbank tuvo en mayor peso seco que todas las entradas. Varias entradas silvestres, especialmenteS. chacoense, S. commersonnii, S. kurtzianum, S. microdontum yS. phureja tuvieron un peso seco igual o mayor que Russet Norkotah o Red Norland. En el análisis de la eficiencia de la absorción del N, 2, 7 y 20 entradas fueron clasificadas mejor que Russet Burbank, Russet Norkotah y Red Norland, respectivamente. La recuperación del N aplicado al suelo por las variedades varié de 16% a 36%; las 7 entradas silvestres más altas recuperaron entre 27% y 49%. Basándose en el crecimiento de la planta sin añadir fertilizante de N y la respuesta relativa al fertilizante de N, las especies fueron clasificadas en cuatro grupos relativos para la eficiencia del uso del N: buena producción de follaje con buena respuesta al N, pobre producción de follaje con buena respuesta al N, buena producción de follaje con pobre respuesta al N y pobre producción de follaje con pobre respuesta de N.

Fine screeningSolanum (potato) germplasm accessions for resistance to Colorado potato beetle

This study was conducted to investigate the utility of systematic screening at the genotype level withinSolanum accessions highly resistant to the Colorado potato beetle. Evaluations of clonally replicated genotypes showed that most accessions reported to be uniform when screened as populations contained small but significant variation among genotypes for resistance to oviposition, larvae, and defoliation, differences for numbers of larvae being most common. Adult counts and percentage defoliation were not as useful in evaluating among-genotype variability in beetle resistance. Genotypes ofS. pinnatisectum WRF 343 andS. tarijense PI 473227 were the most uniformly and highly resistant to Colorado potato beetle. Genotypes of S.berthaultii PI 473331,S. chacoense PI 473405, andS. tarijense PI 473336 were moderately to highly resistant, and genotypes ofS. bukasovii PI 473494 andS. canasense PI 230511 were uniformly susceptible to Colorado potato beetle. Nonparametric correlation analyses indicated that number of egg masses, small larvae, large larvae, and defoliation scores were positively correlated, negatively correlated, or not correlated, depending on the species. One generation of selection attempting to segregate resistance and susceptibility in nearly uniform and highly resistantS. pinnatisectum WRF 343 resulted in “divergent” populations that could not be distinguished from each other or the base population. Thus, through genotype (“fine”) screening and selection, we showed that some existing populations are virtually pure for extreme resistance. Use of individuals from such families would make screening breeding populations more efficient, and reduce the risk of losing resistance genes that have non-dominant effects. Fine screening, recurrent selection, and maintenance of such elite populations is recommended as an extension of population-based evaluation usually done by genebanks.CompendioEl objetivo de este estudio fue investigar la utilidad de la evaluación sistemática a nivel de genotipo entre accesiones deSolanum con alta resistencia al gorgojo Colorado de la papa. A pesar que muchas de las accesiones analizadas a nivel poblacional habian sido reportadas como uniformes, la evaluación de genotipos reproducidos clonalmente demostró que existe una variación significativa en la resistencia a la postura de huevos, larvas y defoliación, siendo la diferencia en el número de larvas la más común. El conteo de adultos y el porcentaje de defoliación no fue tan útil en la evaluación de variabilidad entre genotipos con resitencia al gorgojo. Los genotipos de S.pinnatisectum WRF 343 yS. tarijense PI 473227 mostraron la mayor uniformidad y resistencia al gorgojo Colorado de la papa. Los genotipos deS. berthaultii PI 473331,S. chacoense PI 473405, yS. tarijense PI 473336 mostraron entre moderada y alta resistencia, y los genotipos deS. bukasovii PI 473494 yS. canasense PI 230511 fueron unformemente susceptibles al gorgojo. El análisis de correlación no paramétrica indicó que el número de masas de huevos, larvas pequeñas, larvas grandes y defoliación tienen una correlación positiva, negativa, o no tienen correlación, dependiendo de las especies. El intento de utilizar una generación de selección divergente para producir segregación de resistencia y susceptibilidad en una accesión de relativa uniformidad y con alta resistencia (S. pinnatisectum WRF 343) no fue exitoso. En consecuencia, este estudio demuestra la existencia de poblaciones esencialmente puras para la resistencia extrema y por ello no necesitan ser previamente mejoradas para ser utilizadas en los programas de mejoramiento de germoplasma. En conclusión, la evaluación de genotipos o evaluación “fina” y selección podrían ser útiles para la identificación o el establecimiento de poblaciones en las cuales la resistencia máxima es verdadera (homozygota). La evaluación fina, selección recurrente, y el mantenimiento de dichas poblaciones sería una útil extensión de las evaluaciones basadas en poblaciones, las cuales son usualmente hechas por los bancos de germoplasma.