Stef de Haan

Ex Situ Conservation Priorities for the Wild Relatives of Potato (Solanum L. Section Petota)

Crop wild relatives have a long history of use in potato breeding, particularly for pest and disease resistance, and are expected to be increasingly used in the search for tolerance to biotic and abiotic stresses. Their current and future use in crop improvement depends on their availability in ex situ germplasm collections. As these plants are impacted in the wild by habitat destruction and climate change, actions to ensure their conservation ex situ become ever more urgent. We analyzed the state of ex situ conservation of 73 of the closest wild relatives of potato (Solanum section Petota) with the aim of establishing priorities for further collecting to fill important gaps in germplasm collections. A total of 32 species (43.8%), were assigned high priority for further collecting due to severe gaps in their ex situ collections. Such gaps are most pronounced in the geographic center of diversity of the wild relatives in Peru. A total of 20 and 18 species were assessed as medium and low priority for further collecting, respectively, with only three species determined to be sufficiently represented currently. Priorities for further collecting include: (i) species completely lacking representation in germplasm collections; (ii) other high priority taxa, with geographic emphasis on the center of species diversity; (iii) medium priority species. Such collecting efforts combined with further emphasis on improving ex situ conservation technologies and methods, performing genotypic and phenotypic characterization of wild relative diversity, monitoring wild populations in situ, and making conserved wild relatives and their associated data accessible to the global research community, represent key steps in ensuring the long-term availability of the wild genetic resources of this important crop.

Distributions, ex situ conservation priorities, and genetic resource potential of crop wild relatives of sweetpotato [Ipomoea batatas (L.) Lam., I. series Batatas]

Crop wild relatives of sweetpotato [Ipomoea batatas (L.) Lam., I. series Batatas] have the potential to contribute to breeding objectives for this important root crop. Uncertainty in regard to species boundaries and their phylogenetic relationships, the limited availability of germplasm with which to perform crosses, and the difficulty of introgression of genes from wild species has constrained their utilization. Here, we compile geographic occurrence data on relevant sweetpotato wild relatives and produce potential distribution models for the species. We then assess the comprehensiveness of ex situ germplasm collections, contextualize these results with research and breeding priorities, and use ecogeographic information to identify species with the potential to contribute desirable agronomic traits. The fourteen species that are considered the closest wild relatives of sweetpotato generally occur from the central United States to Argentina, with richness concentrated in Mesoamerica and in the extreme Southeastern United States. Currently designated species differ among themselves and in comparison to the crop in their adaptations to temperature, precipitation, and edaphic characteristics and most species also show considerable intraspecific variation. With 79% of species identified as high priority for further collecting, we find that these crop genetic resources are highly under-represented in ex situ conservation systems and thus their availability to breeders and researchers is inadequate. We prioritize taxa and specific geographic locations for further collecting in order to improve the completeness of germplasm collections. In concert with enhanced conservation of sweetpotato wild relatives, further taxonomic research, characterization and evaluation of germplasm, and improving the techniques to overcome barriers to introgression with wild species are needed in order to mobilize these genetic resources for crop breeding.

Technical and Economic Analysis of Aeroponics and other Systems for Potato Mini-Tuber Production in Latin America

Producing large quantities of high quality mini-tubers at low cost is essential for an economically viable supply of seed potatoes. Here we systematize the technical and economic aspects of aeroponics and provide a benchmark comparison of this technology with other mini-tuber production systems as developed in Latin America: conventional, semi-hydroponics, and fiber-cement tiles technology. Research methodologies included: 3-year registration of cash flows and production registers of aeroponics, economic and technical surveys, in-depth inquiry with managers of technologies. Results show that aeroponics as promoted by the International Potato Center (CIP) has several advantages, including high multiplication rates (up to 1:45), high production efficiency per area (> 900 mini-tubers per m2), savings in water, chemicals and/or energy, and positive economic indicators. The fiber-cement tiles technology from Brazil is also shown to be highly efficient and slightly more robust compared to aeroponics. Preconditions for the successful adoption of the different technologies in developing countries are discussed.ResumenLa producción de grandes cantidades de mini-tubérculos de alta calidad y a bajo precio es esencial para un abastecimiento económicamente viable de semilla de papa. Aquí sistematizamos aspectos técnicos y económicos de aeroponía y se compara la línea de base de esta tecnología con otros sistemas de producción de mini-tubérculos que han sido desarrollados en América Latina: tecnología convencional, semi-hidroponía, tejas de fibrocemento. Metodologías de investigación incluyeron: registro de flujo de caja y registro de producción de aeroponía durante 3 años, encuestas económicas y técnicas, indagación en detalle con gerentes de tecnologías. Los resultados demuestran que la aeroponía tal como lo promueve el Centro Internacional de la Papa (CIP) tiene múltiples ventajas, entre ellas tasas altas de multiplicación (hasta 1:45), eficiencia alta de producción por área (> 900 mini-tubérculos por m2), ahorros en agua, químicos y/o energía, y indicadores económicos positivos. También se demuestra que la tecnología de tejas de fibrocemento de Brasil es muy eficiente y ligeramente más robusta comparada con aeroponía. Se discuten las condiciones previas para una adopción exitosa de las diferentes tecnologías en países en vía de desarrollo.

Traditional Processing of Black and White Chuño in the Peruvian Andes: Regional Variants and Effect on the Mineral Content of Native Potato Cultivars

Traditional Processing of Black and WhiteChuñoin the Peruvian Andes: Regional Variants and Effect on the Mineral Content of Native Potato Cultivars. Farmers in the high Andes of central to southern Peru and Bolivia typically freeze-dry potatoes to obtain chuño. Processing of so-called black chuño follows tending, treading, freezing, and drying. The making of white chuño is generally more complex and involves exposure of tubers to water. Regional variants exist for each of these processes, yet their influence on the nutritional composition of native potato cultivars is little known. Tubers belonging to four distinct cultivars and produced in a replicated trial under uniform conditions were processed into four types of chuño following standard traditional procedures (farmer-managed). These regional variants were documented, and the dry matter, iron, zinc, calcium, potassium, phosphorus, magnesium, and sodium content of the four resulting different types of boiled chuño determined at the International Potato Center’s Quality and Nutrition Laboratory (Lima, Peru). Content values were compared with those of boiled (unprocessed) tubers from the same experiment. Regional variants of processing are to a large extent determined by tradition, environmental condition, and market demand. The zinc, potassium, phosphorus, and magnesium content of all types of chuño decreases in comparison with unprocessed tubers. Concentrations of these same minerals decrease more drastically for white as compared to black chuño. The effect of the four regional variants of freeze-drying on the dry matter, iron, calcium, and sodium content of chuño differs by process and/or cultivar.Procesamiento tradicional dechuñonegro y blanco en los Andes Peruanos: Variantes regionales y efecto sobre el contenido de minerales en cultivares nativos de papa. Los agricultores de la zona Alto Andina del centro al sur del Perú y Bolivia someten a la papa a un proceso de congelado-secado para obtener chuño. El procesamiento del chuño negro involucra tender, pisar, congelar y secar. Por lo general la elaboración del chuño blanco es más compleja y requiere que los tubérculos se remojen en agua. Existen variantes regionales para cada uno de los procesos. Sin embargo, la influencia de estas sobre la composición nutricional de cultivares nativos es poco conocida. Tubérculos de cuatro cultivares distintos y producidos en un ensayo replicado bajo condiciones uniformes fueron procesados en cuatro ‘tipos’ de chuño siguiendo procedimientos tradicionales estándar (manejo de agricultor). Se documentaron las variantes regionales y se determinó el contenido de materia seca, hierro, zinc, calcio, potasio, fósforo, magnesio y sodio de los cuatro diferentes ‘tipos’ de chuño en el Laboratorio de Calidad y Nutrición del Centro Internacional de la Papa (Lima, Perú). Se compararon los valores de contenido del chuño con los de tubérculos hervidos (sin procesar) provenientes del mismo experimento. Los variantes regionales de procesamiento se determinan principalmente por tradición, condición ambiental y demanda de mercado. El contenido de zinc, potasio, fósforo y magnesio de todos los tipos de chuño disminuyó en comparación con tubérculos sin procesar. Las concentraciones de estos minerales disminuyó más drásticamente para chuño blanco comparado con chuño negro. El efecto de los cuatro variantes de congelado-secado sobre el contenido de materia seca, hierro, calcio y sodio del chuño varió dependiendo del proceso y/o cultivar.

Land use and potato genetic resources in Huancavelica, central Peru.

Three specific dimensions of potato land use were researched to gain insights into possible contemporary changes affecting the in situ conservation of potato genetic resources: land use tendencies, rotation designs and their intensity, and sectoral fallowing systems. The main research method involved participatory cartography combined with in-depth consultation through interviews and focus group meetings with members of eight Andean highland communities. Land use tendencies between 1995 and 2005 show that the total cropping area dedicated to improved cultivars has grown fast whereas the area reserved for native-floury and native-bitter cultivars has remained more or less stable. Reduced fallow periods for existing fields and the gradual incorporating of high-altitude virgin pasture lands sustain areal growth. Although areas of improved cultivars are proportionally growing fastest at extremely high altitudes between 3900 and 4350 m, overall cropping intensity or fallowing rates are inversely related to altitude. No evidence of a straightforward replacement of one cultivar category by another was found. Inquiry into the dynamics of sectoral fallow systems over a 30-year period evidences the gradual disintegration and abandonment of these systems rich in cultivar diversity. Where sectoral rotation designs survive, local innovations have been adopted.

Potato Origin and Production

The extent of the potato gene pool, with its abundant landrace diversity and numerous wild relatives, offers a wide range of options for prospecting, prebreeding, and niche market development. Landraces are still widely produced by smallholder farmers in the center of origin and are a key component of complex production systems that cover multiple agroecologies and production objectives. Sustainable future conservation and use will require attention to systematic monitoring of potato genetic diversity, gap analysis, screening, and prebreeding. Modern and traditional uses are both main drivers behind the rational use of potato biodiversity. Both offer promise for the scientific advancement of potato chemistry and technology.

Unearthing unevenness of potato seed networks in the high Andes: a comparison of distinct cultivar groups and farmer types following seasons with and without acute stress

Farmer seed systems are considered pivotal to adaptation to climate change and the on-farm conservation of agrobiodiversity in centers of crop origin. To better understand their distinct role, we conducted a multipronged analysis of potato seed exchange networks in Peru’s central Andes distinguishing between cultivar groups and farmer types following cropping seasons with and without acute stress. Cultivar groups involved (i) bred varieties, (ii) commercial floury landraces, (iii) non-commercial floury landraces (single cultivars), (iv) non-commercial floury landraces (mixed cultivars), and (v) bitter landraces. Farmer types involved (i) general farmers, (ii) seed specialists, and (iii) custodian farmers. Documentation of seed acquisition and provision without differentiating between farmers and cultivar groups may not accurately reflect the fine-grained dynamics underlying seed networks. To test this, a semi-structured survey of 336 households was conducted in 2014-2015 to study seed procurement in two research sites. Results confirm that seed networks are uneven and distinct for cultivar groups and farmer types. Commercial floury landraces and bred varieties were dominant when it came to frequency of transactions, volumes and overall availability. Bitter landraces represent an extreme opposite case, being procured infrequently. Non-commercial floury landraces represent an intermediate case as they are regularly procured in comparatively small volumes. The influence of general farmers and traders within seed networks is essential for overall seed access. The role of specialists and custodians is less omnipresent; yet, both fulfill a unique role. Specialists as providers of large volumes of certified seed of commercial floury landraces and bred varieties. Custodians as a source of diverse non-commercial floury landraces. Seed networks did re-organize following seasons with acute seed stress. A notable shift involved a contraction of seed networks within sub-regional clusters. Following stress, the directionality of seed provision versus acquisition inverted. While average seed volumes acquired per transaction nearly halved, farmers´ net seed acquisitions surpassed provisions in response to stress. We suggest that the self-regulatory capacity of farmer seed networks represents a strong safety net through which smallholders can respond to crop failure and seed stress. Seed system interventions aimed at genetic resources conservation or relief should build on these seed networks.