Zósimo Huamán

Reclassification of landrace populations of cultivated potatoes (Solanum sect. Petota)

Cultivated potatoes have been classified as species under the International Code of Botanical Nomenclature (ICBN) and as cultivar-groups under the International Code of Nomenclature of Cultivated Plants (ICNCP); both classifications are still widely used. This study examines morphological support for the classification of landrace populations of cultivated potatoes, using representatives of all seven species and most subspecies as outlined in the latest taxonomic treatment. These taxa are S. ajanhuiri, S. chaucha, S. curtilobum, S. juzepczukii, S. phureja subsp. phureja, S. stenotomum subsp. stenotomum, S. stenotomum subsp. goniocalyx, S. tuberosum subsp. andigenum, and S. tuberosum subsp. tuberosum. The results show some phenetic support for S. ajanhuiri, S. chaucha, S. curtilobum, S. juzepczukii, and S. tuberosum subsp. tuberosum, but little support for the other taxa. Most morphological support is by using a suite of characters, all of which are shared with other taxa (polythetic support). These results, combined with their likely hybrid origins, multiple origins, evolutionary dynamics of continuing hybridization, and our classification philosophy, leads us to recognize all landrace populations of cultivated potatoes as a single species, S. tuberosum, with the eight cultivar-groups: Ajanhuiri Group, Andigenum Group, Chaucha Group, Chilotanum Group, Curtilobum Group, Juzepczukii Group, Phureja Group, and Stenotomum Group. We defer classification of modern cultivars, traditionally classified in Tuberosum Group, to a later study.

Marker-assisted sampling of the cultivated Andean potato Solanum phureja collection using RAPD markers

The potato crop originated in the Andean highlands where numerous farmers varieties and non-cultivated wild species exist. An Andean potato collection is held in trust at the International Potato Center (CIP) to preserve the biodiversity of this crop and ensure the supply of germplasm for potato improvement worldwide. A core collection representing the biodiversity of the Andean potato germplasm is under construction using morphological, molecular, and geographic data. One of the eight cultivated potato species, Solanum phureja, has been genotyped using the RAPD technique. A protocol suitable for large germplasm collection genotyping has been developed to process numerous samples at reasonable costs. From 106 RAPD primers evaluated, we have selected 12 primers yielding 102 polymorphic markers, which unambiguously discriminated all 128 accessions but 2 that are possible duplicates. The S. phureja germplasm collected throughout the Andean countries appears to have a homogeneous genetic constitution. There was no clear geographic pattern as indicated by cluster analysis of the RAPD data. A sub-group of 20 accessions has been identified on the basis of the marker data and selected to maximize molecular (RAPD) variance and polymorphism. The probability of capturing equal amounts of marker polymorphism in this sub-group of 20 accessions by random sampling is less than 40%. This set accessions represents our first group of accessions that may constitute a core of the S. phureja collection. This tentative core will be challenged for diversity content by alternate markers and agronomic traits. Hence, the methodology for sampling less than 10% of the base collection, proposed for core collections by Brown (1989), can be based on molecular marker data provided cost-efficient fingerprints are developed.

Assessing genetic diversity of sweet potato (Ipomoea batatas (L.) Lam.) cultivars from tropical America using AFLP.

The sweet potato genebank at the International Potato Center (CIP) maintains 5,526 cultivated I. batatas accessions from 57 countries. Knowledge of the genetic structure in this collection is essential for rational germplasm conservation and utilization. Sixty-nine sweet potato cultivars from 4 geographical regions (including 13 countries) of Latin America were randomly sampled and fingerprinted using AFLP markers. A total of 210 polymorphic and clearly scorable fragments were generated. A geographic pattern of diversity distribution was revealed by mean similarity, multidimensional scaling (MDS), and analysis of molecular variance (AMOVA). The highest genetic diversity was found in Central America, whereas the lowest was in Peru-Ecuador. The within-region variation was the major source of molecular variance. The between-regions variation, although it only explains 10.0% of the total diversity, is statistically significant. Cultivars from Peru-Ecuador, with the lowest level of within region diversity, made the most significant contribution to the between region differentiation. These results support the hypothesis that Central America is the primary center of diversity and most likely the center of origin of sweet potato. Peru-Ecuador should be considered as a secondary center of sweet potato diversity.

Updated listing of potato species names, abbreviations and taxonomic status

Tuber-bearingSolanum species described since 1753 are listed alphabetically. A three-letter abbreviation for numerous species not included in Simmonds (1963) are proposed. Some pertinent taxonomic notes are provided for all species names. The systems of classification proposed by S.M. Bukasov, D.S. Correll, J.G. Hawkes, and C.M. Ochoa have been used to determine the current taxonomic status of each species.ResumenLas especies tuberiferas deSolanum descritas desde 1753 son listadas en orden alfabético. Para numerosos nombres especificos no incluidos en Simmonds (1963) se proponen sus abreviaciones en tres letras. También se proporcionan otras notas taxonómicas pertinentes para todas las especies. Los sistemas de clasificación propuestos por S.M. Bukasov, D.S. Correll, J.G. Hawkes, y C.M. Ochoa han sido utilizados para determinar el estado taxonómico actual de cada especie.

RAPD variation in sweetpotato (Ipomoea batatas (L.) Lam) cultivars from South America and Papua New Guinea

The island of New Guinea is considered a secondary center on diversity for sweetpotato, because of its range of isolated ecological niches and large number of cultivars found within a small area. Information of genetic diversity in Papua New Guinea (PNG) sweetpotato is essential for rationalizing the global sweetpotato germplasm collection. Using random amplified polymorphic DNA (RAPD), we compared the genetic variation and genetic diversity in 18 PNG cultivars versus 18 cultivars from South America. The analysis of molecular variance revealed large genetic diversity in both groups of cultivars. The within-group (among individuals) variation accounted for 90.6% of the total molecular variance. However, the difference between PNG and South American groups is statistically significant, although it explained only 9.4% of the total molecular variance. The PNG cultivars are also less divergent than their South American ancestors as the mean genetic distance in PNG group is significantly smaller than that of South American group. The lower level of genetic diversity in PNG cultivars was also reflected by multidimensional scaling. This study shows that PNG cultivars, after many years of isolated evolution in an unique agro-ecological environment are substantially divergent from their ancestors in South America. The genetic diversity level in PNG cultivars is significantly lower than that in South American cultivars. It thus provides a baseline for continuing studies of genetic diversity in different sweetpotato gene pools.

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.

Selecting a Solanum tuberosum subsp. andigena core collection using morphological, geographical, disease and pest descriptors.

One of the largest and most diverse clonally propagated potato collections of cultivated potato species is maintained at the International Potato Center (CIP). Almost 75% of this collection isS. tuberosum subsp.andigena (hereafterandigena) cultivars. The first step to select a core collection of this subspecies was to identify duplicate accessions of the same cultivar using comparisons of morphological characters and electrophoretic banding patterns of total proteins and esterases. This reduced the number of accessions in the collection from 10,722 to 2,379. The number of accessions of the same cultivar in the original collection ranged from 1 to 276. This is a report on the selection of a core from the 2,379 morphologically different cultivars using morphological, geographical, and evaluation data. A total of 25 morphological descriptors were scored from all 2,379andigena cultivars. A phenogram was constructed from these data using a simple matching coefficient and the unweighted pair group method using arithmetic averages. We decided to include in the core a proportional sample consisting of approximately the square root of the number of accessions from each first geographical division (state, department, or province) of countries whereandigena was collected. Accessions were chosen first to represent the widest morphological diversity and to maximize geographical representation of the clusters distributed on the main branches of the morphological phenogram. Second, the representative accession of each cluster was also chosen considering data on resistance to diseases and pests, dry matter content, and number of duplicate accessions identified in the original collection. The resulting core has 306 accessions (12.86%) from eight countries from Mexico to Argentina. The full breeding potential of Andean farmerselected potato cultivars that have been maintained for centuries in their center of diversity remains unknown. A thorough evaluation of their reaction to diseases and pests and other desirable traits is now feasible because the selectedandigena core set covers the broadest genetic base that is available in ex situ conservation.ResumenUna de las más grandes y diversas colecciones de especies cultivadas de papa se conserva clonalmente en el Centro Internacional de la Papa (CIP). Casi el 75% de esta colección son cultivares deS. tuberosum subsp.andigena (en adelanteandigena). El primer paso para seleccionar una colección representativa de esta subspecie fue identificar las accesiones duplicadas del mismo cultivar utilizando comparaciones de caracteristicas morfológicas y de sus patrones de bandas electroforéticas de proteínas y esterasas totales. Esto redujo el número de entradas en la colección de 10,722 a 2,379. El número de entradas del mismo cultivar fluctuó entre 1 y 276. Este es un reporte sobre la selección de una colección representativa de los 2,379 cultivares morfológicamente diferentes, usando datos morfológicos, geográficos y de evaluatión. De los 2,379 cultivaresandigena, se registraron datos de un total de 25 descriptores morfológicos. Con estos datos se construyó un dendograma utilizando el coeficiente de correspondencia simple y el método de comparación de promedios aritméticos simple. Nosotros decidimos incluir en la colección representativa, una muestra proporcional que fuera aproximadamente igual a la raíz cuadrada del número de entradas de la primera división geográfica (estado, departamento o provincia) de los países donde se hicieron colectas deandigena. Las entradas seleccionadas deberían representar la más amplia diversidad morfologica y maximizar la representatión geográfica de acuerdo a la distribución de los conglomerados principales del dendograma morfológico. Segundo, las entradas representativas de cada conglomerado también se escogieron considerando los datos sobre la resistencia a las enfermedades y plagas, el contenido de materia seca y el número de entradas duplicadas identificadas en la colección original. La colección representativa resultante tiene 306 cultivares (12,86%) de ocho países desde Mexico a Argentina. El potential de mejoramiento de los cultivares de papa seleccionados por agricultores que se han conservado durante siglos en su centro de diversidad, permanece aún casi desconocido. Una evaluación minuciosa de sus reacciones a las enfermedades, plagas y otras características deseables para el mejoramiento del cultivo de la papa es ahora factible, porque la colección representativa deandigena que se ha seleccionado abarca la base genética más amplia que está conservada ex situ.

In vitro conservation of potato germplasm at the International Potato Center

The last decade has seen growing awareness of the value of germplasm conservation.In vitro maintenance of germplasm can offer many advantages as a complement to field maintenance. The International Potato Center (CIP) has actively researched a wide range of methods for effectivein vitro maintenance in its large potato germplasm collection. This review describes the methodology applied by CIP and discusses new research now being undertaken to study the genetic stability of these storage methods.

A decade of collecting and research on wild potatoes of the Southwest USA

Potato is an important world crop with an abundant diversity of wild relatives for research and breeding. About 200 tuber-bearingSolarium relatives of the cultivated potato are distributed from southern Chile to the southwest USA. Only five of these have been reported in the USA, and only two exist with certainty (S. fendleri andS. jamesii). This paper reviews the procedures and outcome of 12 expeditions by the authors to the Southwest USA from 1992 to 2001 that resulted in 132 new germplasm accessions. Previously published information allowed successful collection from many documented sites, and many new sites were discovered and sampled. Incomplete or inaccurate records were improved and refined, making it possible for others to easily find these sites. When assessed for genetic diversity, re-collections from the same site were found to be nearly as genetically different as samples from different sites, and genetic differences between sites could not be linked with any ecogeographic parameter, even physical distance of separation. In conclusion, wild potato germplasm from the USA and associated knowledge was greatly expanded, but reaching the goal of obtaining and keeping the most complete sample possible of the genetic diversity will involve additional collecting and continued research on the reproductive behavior of these plants.ResumenLa papa es un cultivo importante a nivel mundial; con una gran diversidad de formas silvestres que han sido importantes para realizar investigaciones y trabajos de majoramiento genético. Existen alrededor de 200 especies deSolanum que producen tubérculos, ellas estait distribuídas desde el sur de Chile hasta el sudoeste de EE UU. Cinco de estas especies han sido reportadas en EE UU pero, probablemente, solo existen dos de ellas (S. fendleri y S. jamesii). Este artículo es una revisión de los detalles y los resultados de 12 expediciones llevadas a cabo por los autores en el sudoeste de EE UU desde 1992 hasta el 2001, las cuales permitieron colectar 132 accesiones nuevas de germoplasma. Gracias a publicaciones hechas anteriormente, las colecciones en los lugares previamente descritos fueron exitosas, asimismo muchos lugares nuevos fueron encontrados y muestreados. Los registros de colección que estaban incompletos o equivocados fueron corregidos y mejorados, haciendo de ellos fácilmente ubicables para cualquiera. La evaluación de la diversidad genética determinó que las re-colecciones hechas en el mismo lugar eran genéticamente tan diferentes como las colecciones hechas en diferentes lugares, que diferencias genéticas entre lugares no estaban asociadas a ningún parámetro ecogeográfico, incluyendo separación física. En conclusión, el germoplasma silvestre de papa de EE UU asi como el conocimiento asociado a este ha sido expandido enormemente, sin embargo la meta de colectar y mantener la mayor cantidad de diversidad genética va a requerir de más colecciones e investigación contínua sobre el comportamiento reproductivo de estas plantas.

Genetic equivalence of putative duplicate germplasm collections held at CIP and US potato genebanks

A common effort among members of the Association of Potato Inter-Genebank Collaborators (APIC) has yielded a global inventory of wild potato genetic resources that is freely accessible to researchers and breeders. In that database there are a number of accessions that originated from distributed progeny of a single original germplasm collection. The logical assumption has been that although these samples are in different locations, they should be genetically equivalent. This study tests this hypothesis by comparing 17 pairs of accessions of 16 different potato species, which are reputed duplicates preserved in the potato genebanks of The International Potato Center (CIP) in Peru and of the U.S.A. (USPG). The RAPD marker analysis revealed that even though the average genetic similarity of reputed duplicates was quite high, there were a few with significant differences. Similarly, SSR markers identified three reputed duplicates that were genetically different. SSRs revealed a loss of markers for some inter-genebank comparisons, a probable indication of genetic drift. Duplicate potato collections between CIP and USPG are in most cases genetically identical. The few exceptions merit further investigation regarding causes and the impact on useful traits.ResumenUn esfuerzo común entre los miembros de la Asociación de Colaboradores de Bancos de Germoplasma de Papa (APIC) ha dado como resultado un inventario global de recursos genéticos de papa silvestre, de libre acceso a investigadores y mejoradores. En la base de datos existe un número de accesiones que se han generado a partir de la progenie distribuida de la colección original. La suposición lógica ha sido que aunque estas muestras están en diferentes lugares, deberían ser genéticamente equivalentes. Este estudio prueba esta hipótesis al comparar 17 pares de accesiones de 16 especies diferentes de papa, las cuales son consideradas como duplicados mantenidos en el banco de germoplasma del Centro Internacional de la Papa (CIP) en Perú y en los Estados Unidos de América (USPG). El análisis con el marcador RAPD reveló que a pesar de que la similaridad genética de duplicados putativos fue bastante alta, sin embargo, hubo algunos con diferencias significativas. Igualmente los marcadores SSR identificaron tres duplicados putativos genéticamente diferentes. Los SSR revelaron una pérdida de marcadores para algunas comparaciones entre bancos de genes, probable indicación de deriva genética. Los duplicados de las colecciones entre CIP y USPG son, en la mayoría de los casos, genéticamente idénticos. Las pocas excepciones que existen ameritan investigación futura para determinar las causas y su efecto en caracteres de interés.