Potato diversity at height: multiple dimensions of farmer-driven in-situ conservation in the Andes

In-situ conservation
Two types of in-situ conservation of crop genetic resources can be distinguished: farmer-driven and
externally driven. The first is subject of this thesis and refers to the persistence of potato genetic resources
in areas where everyday practices of farmers maintain diversity on-farm. The second concerns the more
recent phenomenon of Research & Development (R&D) interventions which aim to support in-situ
conservation by farmers. In this study, farmer-driven in-situ conservation of the potato in the central Andes
of Peru is investigated at different system levels from alleles, cultivars, and botanical species up to the level
of the landscape, as well as the interconnected seed and food systems. Dimensions of time and space are
inferred upon by taking both annual and longer-term spatial patterns into account. Further, diversity is
linked to selected farmer-based and external drivers.
Objective and study area
The overall objective of the study is to enhance our understanding of farmer-driven in-situ conservation
and the context in which it takes place. The main field research was conducted between 2003 and 2006 in
eight farmer communities following a north-south transect through the department of Huancavelica.
Communities were selected on the basis of distribution and distance along the north-south transect,
tradition of potato cultivation, ethnicity, and relative distance from major markets or cities. Depending on
the specific dimension of farmer-driven in-situ conservation investigated, a range of different methods
and tools were used. Chapter 1 provides a brief description of the study area and an overview of the research
methods used.
Species, cultivar and allelic diversity
In chapter 2 the species, morphological and molecular diversity of Andean potatoes in Huancavelica is
treated at different scales of conservation: farmer family, community, geographically distanced, regional,
in-situ and ex-situ subpopulations. The infraspecific diversity of in-situ collections was characterized using
morphological descriptor lists and 18 polymorphic microsatellite markers (SSR). Botanical species were
determined through ploidy counts in combination with morphological keys. Datasets were used for
descriptive statistics, (dis)similarity analysis, dendrogram construction, cophenetic analysis, matrix
correlations calculations (Mantel tests), and Analysis of Molecular Variance (AMOVA).
Results show that farmers in Huancavelica maintain high levels of species, morphological and molecular
diversity. All cultivated potato species with the exception of Solanum phureja and Solanum ajanhuiri proved
to be present. Tetraploid species were most abundant followed by diploids, triploids and pentaploids. A
total of 557 morphologically unique cultivars were identified based on the morphological characterization
of 2,481 accessions belonging to 38 in-situ collections. Genetic fingerprinting of 989 accessions belonging
to 8 in-situ collections resulted in the identification of 406 genetically unique cultivars. AMOVA shows that
the principal source of molecular variation is found within rather than between geographically distanced
and farmer family subpopulations. No evidence of genetic erosion was found as the contemporary regional
in-situ population and a geographically restricted subset of CIP´s ex-situ core collection share 98.8% of
allelic diversity. Yet, in-situ collections contain numerous unique genotypes.
Indigenous biosystematics
The indigenous biosystematics of potatoes (folk taxonomy, folk descriptors and nomenclature) is
investigated in chapter 3. The chapter includes an extensive literature review on the subject. Folk taxonomy
was investigated with the use of grouping exercises with farmers, participant observation, and comparison
of farmer-recognized groups with formal classification based on morphological descriptors and 18
polymorphic microsatellite markers (SSR). Analysis of the latter was based on (dis)similarity analysis,
dendrogram construction and consequent levels of coherent clustering by folk taxonomic entity (folk
specific and varietal taxon). Ethnobotanical free and indicated listing exercises with farmers were used for
research concerning folk descriptors. Descriptive statistics were used for analysis and interpretation.
Nomenclature was investigated by applying nomenclature surveys, participant observation and basic
ethnolinguistic analysis of regional names.
Folk taxonomy of the potato consists of no less than five ranks. The folk generic rank is composed of
three taxa: Araq Papa (semi-wild / consumed), Papa Tarpuy (cultivated / consumed), and Atoq Papa (wild /
not consumed). Folk specific taxa (= cultivar groups) and varietal taxa (= cultivars) within the generic taxon
of Papa Tarpuy are abundant. Use categories and agroecological criteria are of little importance in the folk
taxonomical system of the potato. Folk varietal taxa cluster well when using formal morphological
descriptors; folk specific taxa less so. A moderate concordance, albeit with considerable exceptions, exists
between folk specific or varietal taxa and their genetic make-up as characterized with molecular markers
(18 SSR microsatellites). The coherence of clustering in a dissimilarity tree varies for each folk specific or
varietal taxon considered. Farmers use 22 plant and 15 tuber folk descriptors with recognized character
states in the Quechua language. Farmers are well able to recognize specific cultivars based on aboveground
plant parts only (without exposing tubers). Nomenclature is regionally consistent for common cultivars,
while inconsistent for scarce cultivars. Primary cultivar names (nouns) generally refer to a folk specific taxon
through predominant metaphorical reference to tuber shape. Secondary cultivar names (adjectives)
predominantly provide direct reference to tuber color.
Annual spatial patterns
Annual spatial management of the potato consists of cropping and labor calendars, field scattering practices,
and genotype by environmental management. These three dimensions of agrobiodiversity management
are explored in chapter 4. A structured survey was conducted to investigate the potato cropping and labor
calendars. Participatory cartography resulted in the detailed mapping of 601 scattered potato fields,
including their cultivar content, belonging to a total of 122 households. A genotype by environment (GxE)
experiment employing 4 environments and 31 cultivars was conducted following an altitudinal transect.
Data obtained was analyzed and interpreted using descriptive statistics, correlation analysis, Geographical
Information Systems (GIS), Additive main Effects and Multiplicative Interaction (AMMI) analysis, and analysis
of variance (ANOVA).
The annual distribution of tasks and labor is primarily an adaptation to the single-season rain-fed
character and climate extremes of high-altitude agriculture. Three different footplough-based tillage
systems allow farmers to efficiently manage scarce labor availability for soil preparation. Native-floury, nativebitter
and improved potato cultivars show considerable overlap concerning their altitudinal distribution
patterns. The notion that these cultivar categories occupy separate production spaces (so-called “altitudinal
belts”) is rejected as results show that differences between the altitudinal medians for areal distribution by
altitude of the different cultivar categories are modest (chapter 4). Field scattering is based on a combined
logic which results in a patchy distribution of potato genetic diversity across the agricultural landscape.
Depending on the community, farmers annually crop an average of 3.2 to 9.1 potato fields measuring
between 660 to 1,576 m² and containing up to a hundred cultivars per field. However, neither field scattering
nor the management of high levels of diversity by farmers is a direct consequence of niche adaptation as
most cultivars are versatile (chapter 4). Rather, it is suggested that farmers conduct annual spatial
management by deploying combined tolerance and resistance traits imbedded in particular cultivar
combinations in order to confront the predominant biotic and abiotic stresses present in different
agroecologies. Andean farmers manage GxE adaptation for overall yield stability rather than fine-grained
environmental adaptation of native cultivars.
Dimensions of land use
Three specific dimensions of potato land use were researched in order 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 (chapter 5). The main research method
involved participatory cartography using printed poster-size high-resolution Quickbird satellite images
combined with in-depth consultation through interviews and focus group meetings with members of the
communities. A total of 4,343 fields and their 1995-2005 crop contents were mapped. The evolution over a
30-year time-span (1975-2005) of traditional sectoral fallow systems (“diversity hotspots”) was documented
for each community. Data was analyzed using descriptive statistics and Geographical Information Systems
(GIS). Processes of change and adaptive innovation were documented by building case studies.
Land use tendencies between 1995 and 2005 shows that the total cropping area dedicated to improved
cultivars has grown fast while the area dedicated to 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. Areal growth is particularly fast at extreme altitudes between
3,900 and 4,350 m. However, fallow periods at these altitudes are still relatively long compared to fields at
lower altitudes. Results show that fallowing rates increase by altitude for all cultivar categories, but tend to
be lowest for improved cultivars followed by native-floury and native-bitter cultivars. There is no evidence
of a straightforward replacement of one cultivar category by another resulting in the replacement and loss
of infraspecific diversity. 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. They are replaced
by more individualist management regimes based on household decision making. Nowadays, the spatial
patterning of potato genetic diversity within the agricultural landscape is increasingly characterized by
patchy distribution patterns rather than its concentration within a single communal sector. Where sectoral
rotation designs survive local innovations have been adopted.
Farmer seed systems
Farmer seed systems can be conceived as an overlay of crop genetic diversity determining its temporal
and spatial patterning. Chapter 6 investigates the relation between selected farmer seed system components
(storage, health and procurement) and infraspecific diversity of potato in Huancavelica. A sampling exercise
was carried out in farmer seed stores in order to gain insight into the internal organization of seed stores
and how this relates to the management of infraspecific diversity. Virus infection rates were determined by
taking seed tuber samples of diverse cultivars from farmer’s storage facilities. ELISA tests were conduced
for APMoV, PLRV, PMTV, PVY and PVX. Seed procurement was investigated through a series of structured
surveys focusing on household seed exchange, the role of regular markets and biodiversity seed fairs, and
seed provision after severe regional frost. Data was analyzed and interpreted using descriptive statistics.
Potato seed stores contain different seed lots, reflecting the rationales underlying management of
cultivar diversity at the field level and the overall structure of infraspecific diversity. Seed health of farmer
conserved cultivar stocks in Huancavelica is affected by Diabrotica leaf beetle and contact transmitted
viruses (APMoV, PVX) while aphid and powdery scab transmitted viruses (PMTV, PLRV, PVY) are of limited
importance. During normal years without extreme events seed exchange of native-floury cultivars is
practiced by few households and characterized by a limited number of transactions involving small
quantities of seed of few cultivars covering relatively short distances. Native-bitter and uncommon nativefloury
cultivars are rarely exchanged and generally reproduced year after year by the same households
that maintain them. High-altitude diversity-rich communities tend to be net seed exporters. However, the
capacity of the farmer seed system to annually widely supply and distribute infraspecific diversity is limited.
Regular markets have a decentralized capacity to supply and widely distribute seed of a limited number of
well-known cultivars. Frequencies of seed exchange at biodiversity seed fairs are low and involve small
quantities of a few uncommon cultivars. The resilience of the farmer seed system to cope with severe regional
seed stress is insufficient for households to be able to restore volumes and cultivar portfolios within a
short period of time.
The potato-based food system
The role of biodiverse potatoes within the human diet in Huancavelica is investigated in chapter 7. Analysis
to determine the dry matter, gross energy, crude protein, iron (Fe) and zinc (Zn) content of 12 native-floury
cultivars (fresh / boiled tuber samples) and 9 native-bitter cultivars (boiled unprocessed / boiled processed
tuber samples) was conduced. Additionally, the nutritional composition of the native-floury cultivars was
determined after 3 and 5 months of storage under farmer conditions. A food intake study was conducted
during two contrasting periods of food availability (abundance versus scarcity) in order to quantify and
characterize the contribution of the potato, different cultivar categories and other food sources to the diet
of children between 6 and 36 months of age and their mothers. The specific method consisted of direct
measurement of food intake by weight during a 24 hour period for each household (77 households). Further,
the overall nutritional status of 340 children aged between 4 and 16 years was determined. Selected cultural
connotations of the highland diet were investigated through participant and ethnographic observation,
surveys, and workshops.
Results show that several native-floury cultivars contain higher contents of specific nutrients (protein,
iron) than those commonly reported as representative for native potato cultivars. This suggests that
infraspecific diversity can make a valuable contribution to enhanced nutrition. Storage does not affect the
nutritional quality of native-floury cultivars very significantly while traditional freeze-drying of native-bitter
cultivars considerably reduces protein and zinc content. The research shows that malnutrition in
Huancavelica is primarily a consequence of micronutrient deficiency and secondarily of insufficient total
energy coverage. The highland diet is heavily dependent on staple foods, particularly potato and barley,
and generally short in vegetable, fruit, meat and milk intake. The potato contributes significantly to the
nutritional balance and the recommended requirements for energy, protein, iron and zinc of women and
children during periods of both food abundance and scarcity. Improved and native-floury cultivars
complement each other as each category provides the bulk of potatoes consumed at different moments in
time. The consumption of diverse potato cultivars is entangled with cultural constructions of meals and
local perceptions of preference traits and quality. The potato itself, as a food item, is no socioeconomic class
marker. However, certain dishes or products and the overall cultivar diversity grown and used by a household
shape perceptions of relative wealth.
Conclusions and implications
Chapter 8 highlights the main conclusions of the study and provides answers to the original research
questions while taking the different system levels explored throughout the thesis into account. Selected
priority areas of future research are identified and, where appropriate, links to other parts of the Andes are
drawn. Furthermore, the implications for externally driven R&D oriented in-situ conservation efforts seeking
to support dynamic and ongoing farmer-driven conservation are discussed. It is argued that the science
and practice of R&D oriented in-situ conservation lag behind the policy commitments to its implementation
and that institutional learning from diverse projects already implemented throughout the Andes and the
diffusion of key lessons is essential for the success of future interventions.