Showing papers by "International Potato Center published in 2001"

Geographic distribution of wild potato species.

Abstract: The geographic distribution of wild potatoes (Solanaceae sect. Petota) was analyzed using a database of 6073 georeferenced observations. Wild potatoes occur in 16 countries, but 88% of the observations are from Argentina, Bolivia, Mexico, and Peru. Most species are rare and narrowly endemic: for 77 species the largest distance between two observations of the same species is <100 km. Peru has the highest number of species (93), followed by Bolivia (39). A grid of 50 × 50 km cells and a circular neighborhood with a radius of 50 km to assign points to grid cells was used to map species richness. High species richness occurs in northern Argentina, central Bolivia, central Ecuador, central Mexico, and south and north-central Peru. The highest number of species in a grid cell (22) occurs in southern Peru. To include all species at least once, 59 grid cells need to be selected (out of 1317 cells with observations). Wild potatoes occur between 38° N and 41° S, with more species in the southern hemisphere. Species richness is highest between 8° and 20° S and around 20° N. Wild potatoes typically occur between 2000 and 4000 m altitude.

Potato systematics and germplasm collecting, 1989–2000

Abstract: This paper reviews the systematics of wild potatoes over the past 11 years, in reference to the latest comprehensive taxonomic treatment by Hawkes (1990. The potato: evolution, biodiversity and genetic resources. Belhaven Press, Washington, D.C.). Included here is information on monographs and floras, new germplasm collections made since 1988 compared to total potato distributional data, new taxonomic changes (including synonymy and new species descriptions), ingroup and outgroup relationships, intraspecific studies, diversity studies, and fingerprinting. In addition, data supporting taxonomic changes and phylogeny from ploidy levels, Endosperm Balance Numbers, and morphological studies of taxonomically important characters are reviewed. A revised list of 206 species is presented (from 232 in Hawkes) that incorporates recent synonymy of names, recognition of new names, and new species descriptions. New germplasm collections of 58 potato taxa were collected that did not occur in genebanks before 1988.

Global distribution of the potato crop

Abstract: The global distribution of potato area is described using country-level statistics and a new geo-referenced database. There are two main peaks in global potato distribution by latitude. The major peak is between 45°N and 57°N and represents potato production zones in the temperate climates where potato is a summer crop. The other peak is between 23°N and 34°N, and mainly represents production zones in the subtropical lowlands, where potato is a winter crop. Between 1950 and 1998 potato production area increased at low latitudes and decreased at high latitudes, particularly around 53°N (this zone includes parts of Belarus, Germany, Poland, Russia, and Ukraine). The northern limit of potato production coincides with the boundaries of agriculture and the presence of human population. The peak between 23°N and 34°N coincides with the area of highest population density (per area of land and per area of arable land). About 25% of the global potato area is in the highlands (above 1000 m).

Working with Resource-Poor Farmers to Manage Plant Diseases.

Abstract: Farmers in developing countries have substantial difficulty in managing plant diseases (4). Poor farmers’ understanding of disease processes is limited, and their disease management is often ineffective (21). This is, in part, because they cannot see the organisms that cause plant disease. They often lack access to information and technology that could help them raise healthy crops. Here we present and compare experiences in working with farmers to manage rice blast and potato late blight. In these cases, farmer groups learned about disease processes and management techniques, and tested promising crop varieties and breeding lines with the support of extension and research organizations.

Genome mapping in cassava improvement: Challenges, achievements and opportunities

Abstract: Breeding goals of yield increases, root quality improvement, and disease resistance in cassava are considerably slowed down by biological characteristics of the crop, which includes a long growth cycle, a heterozygous genetic background and a poor knowledge of the organization of crop diversity. These factors severely hamper the speed and ease of moving around useful genes in cassava. The consequences are that cassava production fails to keep up with demand, especially in regions where over90% of yield is consumed as food, leading to an increase in acreage of cassava fields mostly into marginal lands. The advent of molecular markers,genome studies and plant genetic transformation holds promise of providing ways around breeding obstacles in long growth cycle and heterozygous crops. A number of these new tools, including a molecular genetic map, markers linked to disease resistance genes, and marker-aided studies of complex traits now exist or are being developed for cassava at CIAT. Large scale sequencing and mapping of expressed sequence tags(ESTs) have been initiated, towards a transcript map of cassava and the implementation of the candidate-gene approach to complex trait mapping. A cassava bacterial artificial chromosome (BAC) library has also been constructed to expedite positional cloning of genes, known only by their phenotypes and their position relative to markers on a molecular genetic map and complementation studies of candidate loci. Studies of genes that control traits of agronomic importance, and their allelic diversity in nature,provides powerful tools for understanding the basis of crop performance and improvement.

Enhancing Vitamin A Intake in Young Children in Western Kenya: Orange-Fleshed Sweet Potatoes and Women Farmers Can Serve as Key Entry Points:

Abstract: In western Kenya, where vitamin A deficiency is common and the white sweet potato is an important secondary staple, orange-fleshed sweet potatoes were introduced and their consumption was promoted,...

Efficient plant regeneration from embryogenic suspension cultures of sweetpotato

Abstract: Using 15 Chinese and Japanese cultivars of sweetpotato, Ipomoea batatas (L.) Lam., we succeeded in developing an efficient plant regeneration system from embryogenic suspension cultures. The embryogenic callus derived from shoot apices of the 15 cultivars was used to initiate embryogenic suspension cultures in Murashige and Skoog (MS) medium containing 9.05 μM 2,4-dichlorophenoxyacetic acid (2,4-D). Rapidly proliferating and well-dispersed embryogenic suspension cultures were established. Cell aggregates 0.7–1.1 mm in size from embryogenic suspension cultures were transferred to solid MS medium supplemented with 9.05 μM of 2,4-D and formed embryogenic callus with somatic embryos. The embryogenic callus with somatic embryos was further transferred to MS medium supplemented with 3.78 μM of abscisic acid, resulting in the germination of somatic embryos. Within 20 wk after the initiation, the frequencies of cell aggregates forming plantlets reached approximately 100% for the 15 tested cultivars. These plantlets, when transferred to soil, showed 100% survival. No morphological variations were observed.

Association of Ecogeographical Variables and RAPD Marker Variation in Wild Potato Populations of the USA

Abstract: The goal of germplasm conservation in genebanks is to maximize genetic variation. Collecting explorations would be more efficient if factors that predict areas and habitats associated with greater genetic differences and diversity could be identified. Therefore, the objective of this research was to investigate whether ecogeographical variables have significant associations with patterns of genetic variation in wild potato populations. This study examined 96 wild potato populations collected from the southwestern USA. These were 43 populations of Solanum fendleri (2n = 4x = 48) and 53 populations of S. jamesii (2n = 2x = 24). These species represent two of the most predominant breeding systems found among Solanum species: tetraploid inbreeders and diploid outcrossers, respectively. Random amplified polymorphic DNA (RAPD) markers were used to assess populations in two ways: determination of simple genetic difference between pairs of populations, and genetic diversity of a population based on the frequency of that population's RAPD markers in the whole set. Results from 2282 comparisons indicated that patterns of genetic differences were not associated with any differences in ecogeographical structure assessed. Remarkably, even geographical separation of populations, a parameter usually considered important when collecting germplasm, did not predict genetic differences very well. Latitude, longitude, and heat-related factors significantly predicted genetic diversity in S. fendleri but not in S. jamesii. This experiment revealed few associations between ecogeographic parameters and genetic variation in the wild. It follows, therefore, that one should collect many populations and incorporate a manageable subset into the genebank on the basis of empirical measurements of genetic diversity.

Maca (Lepidium meyenii walp.; Brassicaceae): A nutritious root crop of the central andes

Abstract: This endemic highland crop of the central Andes is grown from central Peru to Bolivia and northwestern Argentina. Peruvian specimens of this species have been collected from puna grasslands in the Departments of Cusco, Junfn, Moquegua, Pasco and Puno, at elevations ranging between 3500-5000 m. It is also known to occur wild in the Ichuasi Mountains near Ilave in the Department of Puno, Peru, as well as near Torata and Carumas in the Department and Province of Moquegua. Commercial production of this small rosetteforming species (Fig, 1) is concentrated in the mountains surrounding Lake Junfn, where the roots are sold in the market towns of Carhuamayo and Ninacaca for distribution to the Lima market (1), and the mountainous area of Jarpa, west of Huancayo, where production is earmarked largely for the Chupaca market. Four varieties of maca are recognized by their Peruvian growers, according to the color of their root: cream-yellow; purple with white tap root and crown areas; solid purple; and, solid black. According to Lern (2), the yellow-colored roots, being preferred by the populace, are the ones most likely to be seen in native markets. Fresh maca is commonly prepared by baking in ground pits. However, the roots can also be dried in the sun and stored for several years until

Looking back to see ahead: Farmer lessons and recommendations after 15 years of innovation and leadership in Güinope, Honduras

Abstract: Guinope, Honduras was the site of a highly acclaimed people-centered development project in the 1980s. The ACORDE/Ministry of Natural Resource/World Neighbors Integrated Development Program (IDP) was unique for its time, since rather than relying on technology transfer, it promoted innovation skills for local generation of responses to needs. Furthermore, it was one of the first efforts in Latin America to employ villagers as principal agents of change. Fifteen years after the inception of the IDP and ten years after its completion, the authors interviewed farmers in their fields and held a series of participatory workshops over eighteen months with ten outstanding farmers who had become project leaders. The leaders identified influential factors behind their involvement and produced recommendations for rural development interventions. Further, a generalized concept map typifying ideal characteristics for farmer promoters was constructed. Recommendations for development agencies centered on project design and implementation, demanding a methodology for strengthening local innovative capacities, participation, and control over resources. Ultimately, the leaders downplayed the role of technologies in rural development and called for special attention to enabling communities to confront external pressures, in particular recent government ``modernization'' policies, that they felt threatened community livelihood.

Evaluation and analysis of reduction of late blight disease in a diploid potato progeny

Abstract: The rate of late blight disease was analysed for individuals of a diploid Solanum phureja–Solanum tuberosum dihaploid hybrid population (PD), using three different assessment techniques, in the laboratory, screenhouse, and field. These hybrids expressed low disease rates in the field, comparable to resistance based on intact R genes. However, none of the parents of PD expressed any R genes and the pattern of segregation within the PD population was not indicative of R-gene inheritance. The foliage (or leaflet) area diseased had the largest broad-sense heritability of all criteria analysed, in all tests performed. In the field evaluations, the PD population showed intermediate levels of broad-sense heritability for foliage area diseased, relative to the much larger heritability detected for the group of controls possessing R genes. Resistance in the field of the PD hybrids had very little genotype-environment (G × E) interaction, indicating stability of its expression. All genotypes without R genes exhibited heritable, reduced rates of late blight disease in the field, but they were susceptible with low heritability in screenhouse and laboratory tests. This differential expression of disease indicates that the plants' indirect response to unknown environmental stress in the field may have been measured. The value of the PD hybrids for breeding of late blight resistant potato and the use of the disease rate data for detection of the underlying quantitative trait loci are discussed.

Taxonomy and new collections of wild potato species in Central and Southern Peru in 1999

Abstract: Peru contains about half of the described wild potato taxa, and many of these are not yet preserved in genebanks. This paper reports results of the second of a series of five planned collecting expeditions to Peru. Collections were made in the central Peruvian departments of Ancash, Huancavelica, La Libertad, and Lima, from March 8 to April 25,1999. They follow collections in 1998 in the southern Peruvian departments of Apurimac, Arequipa, Cusco, Moquegua, Puno, and Tacna. We collected 101 germplasm accessions, including first germplasm collections of the following 22Solanum taxa:Solanum amayanum, S. anamatophilum, S. arahuayum (lost in germplasm increase),S. augustii, S. bill- hookeri, S. cantense, S. chavinense, S. chomatophilum var. subnivale, S. chrysoflorum, S. gracilifrons, S. hapalos um, S. huarochiriense, S. hypacrarthrum, S.jalcae, S. moniliforme, S. multiinterruptum f. longipilosum, S. multiinterruptum var. machaytambinum, S. peloquinianum, S. rhombilanceolatum, S. simplicissimum, S. taulisense (lost in germplasm increase), andS. wittmackii. In addition, new collections were made of the under-collected speciesS. hastiforme (three collections). The above taxonomy is that used in planning our expedition, that we compare to a new treatment of Peruvian wild potatoes published by C. Ochoa in 1999. This paper reports the collection and new species identifications of the 1999 collections, and germplasm conservation and survival of the 1998 and 1999 collections. In addition, chromosome counts are provided for 134 accessions from the 1998 and 1999 expeditions, including first reports forS. chomatophilum var. subnivale (2n = 2x = 24),S. megistacrolobum subsp.purpureum (2n = 2x = 24), andS. multiinterruptum var.multiinterruptum f.albiflorum (2n = 2x = 24); we also report the first triploid count of an accession ofS. immite.

Allozyme polymorphisms in tetraploid potato gene pools and the effect on human selection

Abstract: The need for broadening a crop’s genetic base may be determined by comparing allele frequencies within the gene pools of farmer selections in their centers of diversity with that of modern breeding populations. The genetic structure of Andean and Chilean potato farmer selections was investigated with the aid of nine isozymes, which have been studied in detail and used to characterize North American cultivars and advanced breeding lines. These isozymes are associated with the most-important agronomic or quality characters in the North American gene pool. By comparing these data with previous analyses of the North American gene pool, allozyme frequency changes for nine loci were monitored. Allozyme frequency changes were not always due to genetic drift, but resulted also from directional selection of isozyme marker linked quantitative trait loci (QTLs) affecting agronomic or quality characters. Changes in allozyme frequency can also occur as a consequence of pleiotropy, i.e. the isozyme itself may be involved in the expression of a phenotype. These allozyme frequency changes may reflect the manipulation of the potato genome by breeders. There were allozymes in some North American cultivars that were not observed in the farmer selections from the Andes and Chile. This confirms that breeders have already introgressed exotic genes from wild and other primitive cultivated tuber-bearing Solanum species. On this basis, the need for broadening the genetic base for specific chromosomes (or chromosome regions) should be based on analysis with these and other genetic markers available in potato.

Virus Diseases of Potatoes

Abstract: More than 30 different viruses are known to affect potatoes, contributing to degeneration of the crop. In response, major efforts have been made to control virus diseases by eliminating them from propagation stocks and developing resistant cultivars, procedures whose effectiveness rely on proper identification of viruses and their detection by means of sensitive and accurate virus detection technology. Keywords: potato; virus; resistance; seed production

Heterothallism in Peronospora farinosa f.sp. chenopodii, the causal agent of downy mildew of quinoa (Chenopodium quinoa)

Abstract: Heterothallism in Peronospora farinosa f.sp. chenopodii, the causal agent of downy mildew of quinoa (Chenopodium quinoa) is reported for the first time. Downy mildew is the most important disease of this crop in the Andean region. Eight single-lesion isolates from different regions in Peru and Bolivia were crossed in all possible combinations using a detached leaf assay, to determine the mating system of the downy mildew pathogen. The presence of two mating types, P1 and P2, was revealed showing that P. farinosa f.sp. chenopodii is heterothallic. It is suggested that frequent sexual reproduction is an important evolutionary force in this pathogen in South America.

A genetic linkage map of sweetpotato (Ipomoea batatas (L.) Lam.) based on AFLP markers.

Abstract: Amplified Fragment Length Polymorphism (AFLP) based genetic linkage maps were developed for hexaploid sweetpotato (Ipomoea batatas (L.) Lam., 2n = 6x = 90) using a segregating population derived from a biparental cross between the cultivars 'Tanzania' and 'Bikilamaliya'. A total of 632 ('Tanzania') and 435 ('Bikilamaliya') AFLPs could be ordered in 90 and 80 linkage groups, respectively. Total map lengths were 3655.6 cM and 3011.5 cM, respectively, with an average distance of 5.8 cM between adjacent markers. The genetic linkage analysis was performed in two steps. First a framework map was elaborated from the single dose markers. Interspersed duplex and double-simplex markers were used to detect homologous groups within and corresponding linkage groups among the parental maps. The type of polyploidy (autopolyploidy vs. allopolyploidy) was examined using the ratio of linkage in coupling phase to linkage in repulsion phase and the ratio of non-simplex to simplex markers. Our data support the predominance of polysomic inheritance with some degree of preferential pairing.

The effect of low nitrogen supply on yield and water-use efficiency of sweet potato (Ipomoea batatas L.).

Abstract: A pot experiment was conducted in a tropical mid-elevation environment to evaluate sweet potato clones of different origin and breeding intensity for traits related to growth phenomena, nitrogen use efficiency (NUE), and transpirational water use efficiency (WUE) as affected by different levels of N fertilisation. Genotypes with small canopies were associated with a consistently positive response to increasing N supply and with efficient translocation of dry matter and N to storage roots. Genotypes with high canopy net assimilation rates had a high proportion of sun leaves and high chlorophyll content in leaves. N stress lead to increased transpiration per unit leaf area and decreasing WUE. We found clear effects of genotype and nitrogen supply on WUE.

Use of DNA Markers in introgression and isolation of genes associated with durable resistance to rice blast

Abstract: Rice blast caused by Pyricularia grisea Sacc. (= P. oryzae Cav., teleomorph Magnaporthe grisea Barr.), is one of the most widespread and destructive diseases of rice. Incorporation of blast resistance genes into elite rice cultivars has been a priority in rice breeding for decades in virtually all rice growing countries. Although resistance to blast is often short-lived, some cultivars are considered to possess durable resistance (Johnson 1981). Durable resistance is thought to be associated with partial resistance that is in many cases under oligo-or polygenic control (Higashi and Kushibuchi 1978; Higashi and Saito 1985; Wang et al. 1994; Parlevliet 1988). For example, the rice cultivar Moroberekan displays durable resistance to blast in upland conditions (Bidaux 1978; Ahn 1994; Fomba and Taylor 1994). The use of molecular markers has facilitated studies of the genetic basis of this durable blast resistance (Wang et al. 1994; Chen et al. 1997; Inukai and Aya 1997; Inukai et al. 1997).

La información y el conocimiento como insumos principales para la adopción del manejo integrado de plagas

Abstract: Information and knowledge as the principal inputs for the adoption of integrated pest management. There are few examples of integrated pest management (IPM) implementation in the Andean Region. One of these was the MIP-Andes project,which was carried out between 1993 and 1996,with the participation of the International Potato Center (CIP) and CARE-Peru.The objective of this project was to train farmers in the management of Premnotrypes spp.This paper presents an analysis of what happens when farmers’ knowledge interacts with technical information about IPM, based on the experience of the MIP-Andes project. A model is proposed to simplify the process of interpretation of IPM information. Formation, modification and reinforcement of knowledge interactions were observed; but some also that generated confusion, particularly when the farmers could not interpret the information appropriately due to the form in which they received it. The influence of knowledge and other factors in decision-making to adopt IPM practices was determined and it is concluded that knowledge is an essential factor but it is not the only factor that determines adoption. In order to achieve the adoption of IPM,integrating farmers’ knowledge and technical information is considered to be the main level of integration. However other levels of integration are also required, such as crop management practices, the community, organizations and institutional and governmental policies.

Detecção sorológica de vírus por ncm-elisa em lavouras de batata-doce no estado do rio grande do sul, brasil

Abstract: O Estado do Rio Grande do Sul e o principal produtor de batatadoce do Brasil, porem a produtividade bastante baixa tem sido atribuida parcialmente a infeccao por virus. Neste trabalho sao apresentados os resultados preliminares da utilizacao de um kit serologico, atraves da tecnica da membrana de nitrocelulose - ELISA (NCM-ELISA), produzido pelo Centro Internacional de la Papa, Lima, Peru, para a deteccao dos seguintes virus que afetam a especie: Sweet potato feathery mottle virus (SPFMV), Sweet potato mild mottle virus (SPMMV), Sweet potato latent virus (SPLV), Sweet potato chlorotic flecks virus (SPCFV), Sweet potato mild speckling virus (SPMSV), Sweet potato chlorotic stunt virus (SPCSV) e o virus C-6. Foram analisadas 338 amostras, coletadas aleatoriamente de 18 lavouras de batata-doce, da principal regiao produtora do Estado, detectando-se as seguintes percentagens de infeccao: SPFMV 13,02; SPLV 2,66; SPCFV 0,59; SPMSV 0,89; e SPCSV (Ky-cp) 0,29. Os virus C-6, SPMMV e a estirpe Mistura 1 do SPCSV nao foram detectados. Os dados obtidos revelaram, surpreendentemente, baixa incidencia de virus, considerando a origem do material de propagacao e os processos de cultivo utilizados.