Seeds, hands and lands : maize genetic resources of highland Guatemala in space and time

J. van Etten

Research output: Thesisinternal PhD, WU


Crop genetic resources are an important aspect of agricultural production. Agricultural innovation through plant breeding is generally seen as an efficient means to support food security and economic development in poor areas. Modern varieties of maize, a major cereal and the subject of this study, are at present used on roughly half of the tropical acreage of this crop. Several strategies are being developed to reach the other half, which involve farmers being more active in the innovation process. Field studies of farmers' seed and crop management aim to support the design of farmer-participatory plant breeding activities. In these approaches and studies there is a tendency to focus on seed selection as the core process of plant genetic innovation. The present study concentrates on the gene pool of maize in the western highlands ofGuatemala, as shaped by seed exchange and replacement by farmers. Maize is traditional in this area, and the main food crop.Chapter 1 gives a conceptual critique of existing models in participatory plant breeding. There is a tendency to focus on seed selection as the core process of plant genetic innovation. The present study argues that this model should be broadened and sees gene flow as a part of the creative process of crop evolution. This conceptual change implies that more attention should be paid to seed exchange, as seeds are a main vehicle for gene flow in cereals. Also, attention should not be paid only to individual decision making but also to the connections and structures which provide the conditions under which exchange takes place. Over longer periods, individual seed exchange transactions add up to a collective gene pool structure, with 'emergent' properties beyond the scope of individual farmers, but nevertheless important for the design of management strategies for crop genetic resources. The goal of this research is to gain insight into the shaping of the gene pool as a collective entity in the case of highlandGuatemala. To reach this goal, this study combines different research methods in an interdisciplinary way to reconstruct historical change and explain the current geographical structure in the maize gene pool.Chapter 2 explores the historiographic and ethnographic literature on highlandGuatemalato sketch five centuries of change in social connectivity and technological needs and identifying disasters with consequences for maize seed. It suggests that events like human disease epidemics of the colonial period, resulting in demographic decline, have had an important influence on the continuity and spatial distribution of maize genetic resources. Also it is pointed out that the twentieth century brought both regional social integration and local fragmentation, and that this, together with demographic recuperation, is important in relation to the maize biodiversity and farmers' knowledge about it. Concerns about diversity conservation should not lead to attempts to resist economic integration; the formerly closed character of communities is largely a colonial product and historical connections between communities are perhaps deeper than often thought. The same may go for maize genetic resources. Instead, maize agriculture should confront the challenges of modernity in ways that support collaboration between communities.Chapter 3 elaborates a more detailed study on historical change in farmer knowledge about maize diversity between 1927/1937 and 2004. In 1927 and 1937, two lists with local cultivars and their characteristics were drawn up by ethnographers for thetownshipofJacaltenango. Close inspection made clear that these two lists were rather consistent, and that a useful comparison with data on farmer knowledge in 2004 could thus be made. By using a sample of informants spread across several communities and ecologies in the township, an unequal spatial distribution of farmer knowledge was anticipated. A technique from cognitive anthropology, consensus analysis, was used to assess the likelihood of consensus about the presence of each cultivar. The current study found that absolute diversity losses were few, and involved cultivars that are probably not genetically unique, since they were introduced before 1937 as a result of labour migration to coffee farms. Many newly introduced maize types were reported by farmers. Seed introductions corresponded to different forms of regional mobility, including forced migration and maize trade. This chapter further highlights the importance of taking into account spatial differences in knowledge between communities in the same township. A previous study in the same area, based on interviews in several township head towns, concluded, incorrectly, according to the present study, that substantial cultivar losses had occurred.Chapter 4 investigates contemporary farmer seed exchange and replacement based on 257 formal interviews in the highland townships of Chimaltenango. The study focuses on (1) the spatial distribution of cultivar names, (2) seed sources and flows, (3) reasons to discard seeds and (4) variables explaining choices between different seed sources. The fourth element was based on the application of classification trees to the interview data, supplemented with spatial data from another source. The distribution of cultivar names suggested that regional exchange of seeds of traditional and modern varieties occurs, but is constrained by altitudinal differences in the landscape. The data also indicate that most seed flows are local, and that regional seed flows are mostly taking place within the administrative department. Regional seed flows originate often in cities. When farmers discarded seed lots they were mainly motivated by their disadvantages (high plants and long growing cycles). This result was consistent with the finding that regional seed introductions were associated with seed lots with short plants and short growing seasons. This confirms that regional seed exchange is an important source of innovations. It is argued that farmers are dependent on regional sources to counteract the local tendency of cultivars to become taller and tardier. This tendency is probably the result of unintended selection for more competitive plants.Chapter 5 is a study of the spatial distribution of maize populations. By investigating a collection of 80 samples of maize seed from the department of Chimaltenango, and five modern varieties, it attempts to infer the seed exchange processes shaping the current spatial structure of the maize gene pool. Location, altitude, morphological, phenological, and molecular marker (SSR) data were analysed. The analysis identified altitudinal differences in the landscape as an important constraining factor in seed exchange, which is related to adaptation as measured by yield. Locally it found evidence for an isolation-by-distance effect, which points to a falling intensity of seed exchange over longer distances. However, over longer ranges (>8 km), this effect disappears. This was interpreted as evidence for the existence of different mechanisms for local and regional seed exchange. In this chapter, evidence for the influence of modern varieties is also presented. This influence was detected for the lower areas only.Chapter 6 argues on the basis of the findings in the preceding chapters that farmers in highland Guatemala maintain maize genetic resources in open systems. Although local seed exchange is common and is an important shaping force for the maize gene pool, occasional regional seed exchange is important in both past and present. The present spatial distribution of maize populations reflects dynamic processes and should not be conserved as such. To innovate, farmers take direct advantage of the differences between crop populations evolving in different places, in order to achieve phenotypic changes in their own fields. It is not artificial selection that is the main creative force in local innovation - the dominant view among advocates of participatory plant breeding - but the flow of seed lots in the landscape. Consequently, efforts to support seed-based innovation should not only focus on selection or local adaptation, but strengthen the capacities of innovation through seed exchange between locales. Innovation should seek to further exploit ecological complementarities between areas (and not only the representation of broader zones of ecological adaptation). For this end, new regional infrastructures to handle seeds and information may need to be created.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Wageningen University
  • Richards, Paul, Promotor
  • Bregt, Arnold, Promotor
  • de Bruin, Sytze, Co-promotor
  • Maat, Harro, Co-promotor
Award date11 Oct 2006
Print ISBNs9789085044857
Publication statusPublished - 2006


  • farmers
  • knowledge
  • maize
  • plant breeding
  • plant genetic resources
  • genetic diversity
  • management
  • innovations
  • guatemala
  • zea mays


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