Agric Hum Values DOI 10.1007/s10460-015-9646-3 Effect of the management of seed flows and mode of propagation on the genetic diversity in an Andean farming system: the case of oca (Oxalis tuberosa Mol.) 1 1 2 1 Maxime Bonnave • Thomas Bleeckx • Franz Terrazas • Pierre Bertin Accepted: 3 August 2015 Ó Springer Science+Business Media Dordrecht 2015 Abstract The seed system is a major component of tra- cash and self-consumption landraces. Cash landraces were ditional management of crop genetic diversity in developing intensively exchanged; self-consumption landraces were countries. Seed flows are an important part of this system. isolated at the farmer level and prone to genetic drift and They have been poorly studied for minor Andean crops, complete loss. Merchants exported seeds of cash landraces especially those that are propagated vegetatively. We across Bolivia and into Peru and Argentina. New sexually examine the seed exchanges of Oxalis tuberosa Mol. (oca), a produced genotypes are less incorporated into cash landraces vegetatively propagated crop capable of sexual reproduc- than in self-consumed landraces. However, new genotypes tion. We studied the seed exchanges of four rural commu- incorporated into cash landraces are diffused faster and nities in Candelaria district (Cochabamba department, better, being more intensively exchanged. We propose Bolivia) at the international and local levels, emphasizing conservation strategies that can be applied to other vegeta- the spread of new sexually-produced genotypes through tively propagated and minor Andean crops. these exchanges. Interviews with 44 farmers generated socioeconomic, agronomic, crop diversity and seed Keywords Landrace diversity Á Minor crop Á Propagation exchange information, and data on the potential incorpora- mode Á Seed exchange Á Andes Á Wealth tion of new sexually-produced genotypes in the crop germplasm. We interviewed merchants to evaluate the input and output of genetic diversity in the communities studied. Introduction Results showed a positive effect of the farmers’ wealth on the diversity cultivated and on seed exchanges. Most seed Traditional management of crops is still practiced by a exchanges occurred at market, creating a distinction between large proportion of the world’s farmers, especially in developing countries. Those traditional practices, consid- ered to be the most fragile components of the agrarian & Maxime Bonnave systems, have a major influence on evolution processes and [email protected] the genetic diversity of crops (Vigouroux et al. 2011). In Thomas Bleeckx these systems, almost every farming practice results in an [email protected] effect on the global genetic diversity of crops. Franz Terrazas Oca is a clonally propagated tuber crop cultivated [email protected] mainly in the Andes. Consumed as a part of the local staple Pierre Bertin diet, oca follows potato, the main crop, in the agricultural [email protected] rotation and plays an important role in interfering in the life cycle of potato pests (Terrazas and Valdivia 1998). At the 1 Earth and Life Institute, Universite´ catholique de Louvain, Croix du Sud 2 – 11 (L7.05.11), 1348 Louvain-la-Neuve, difference of potato, oca cultivation has not spread Belgium worldwide and has not been the subject of intensive sci- 2 Fundacio´n PROINPA (Promocio´n e Investigacio´nde entific research. To our knowledge, no plant breeding Productos Andinos), Cochabamba, Bolivia programs have been conducted for this crop. 123 M. Bonnave et al. Similarly to the other tuber crops domesticated in the Seed exchanges are of crucial importance on the Andes (potato, mashua—Tropaeolum tuberosum R. & P.— dynamic conservation of genetic resources (Pautasso et al. and ulluco—Ullucus tuberosus C.), oca shows an important 2012). They have been very few studied for oca. However, intraspecific phenotypic variability and genetic diversity a well-developed literature is available for other Andean (Pissard et al. 2006, 2008a; Malice et al. 2009; de Haan tuber crops, especially for potato. Most farmers obtain their 2009). Moreover, studies demonstrated the existence of an tuber seeds by producing them. However, farmers usually intra-landrace diversity, genetically and/or phenotypically, replace their tuber seeds every 4–6 years, when seeds are for various landraces (Emshwiller 2006; Pissard et al. ‘tired’, which means that they observe a decrease in yield 2008b; Bonnave et al. 2014). Such phenomenon, along or vigor, probably due to pathogen accumulation (Bianco with an inconstancy of the folk naming system, has also and Sachs 1997; Zeven 1999; Ramirez 2002; Garcı´a and been observed in the Andes for potato (Quiros et al. 1990). Cadima 2003). In the case of potato, a formal seed system As farmers use very few morphological criteria (mainly exists, providing farmers with quality controlled seeds, based on the tuber color, shape and taste) to name their although it only covers 5 % of the potato seed demand in landraces, confusion between different genotypes can the Andes (Thiele 1998; Ezeta 2001). For the other Andean occur. When obtaining a genotype they do not own, tuber crop (oca, mashua and ulluco) such system does not farmers can therefore incorporate it in a morphologically exist. Therefore, a vast majority of Andean tuber seeds are similar landrace, therefore creating intra-landrace diversity. obtained by informal sources such as direct exchanges Farmers usually obtain these genotypes from seed between families in the same community, local markets, exchanges. However, sexual reproduction or mutation agricultural fairs, traditional seed routes passing by villages accumulation may also be the source of new genotypes. recognized for their seed production or during celebrations. Oca has a fully functional sexual reproduction system Seeds can be purchased or obtained by traditional methods (Trognitz et al. 1998) and sexual reproduction leading to such as barter, gift, loan or inheritance, and as a payment productive plants has been observed in Bolivia in field for work or by collaborative work (production is split conditions. Moreover, surveys showed that an incorpora- between a farmer who supplied seeds and another who tion of sexually produced genotypes into the cultivated supplied land) (Brush et al. 1981; Thiele 1998; Garcı´a and germplasm was highly probable, although unconsciously Cadima 2003). Zimmerer (2002) showed that farmers tend realized by the farmers. This incorporation would take to acquire new seeds from extracommunity sources and place when, to replenish seed stocks, farmers would gather that seeds flows are not circumscribed at the household and tubers of k’ipas. K’ipa is a quechua term meaning volun- community level. Ramirez (2002) observed that in Peru teer plants of a crop species emerging in sites of former farmers used oca seeds coming from production sites sit- fields in the years following cultivation of this crop. It uated 80 km away. According to Espinoza (1998), seeds should not be confused with k’ita, which is the quechua can be distributed across the country via the markets of the term for wild relatives. At this moment, tubers arising from big cities. Finally, Andean tubers seeds flows take place vegetative propagation of the landraces previously culti- within and among the different agroecological habitats vated in these fields and tubers arising from recent sexually where they are cultivated, especially among different alti- produced genotypes would be mixed up because of the tudinal levels (farmers sow seeds that are considered very few morphological criteria used to differentiate lan- ‘‘tired’’ at higher altitude and then bring them down again) draces (Bonnave et al. 2014). Brush et al. (1981) and Johns (Brush et al. 1981; Thiele 1998; Zimmerer 2002; Terrazas and Keens (1986) made a similar hypothesis on the use of and Valdivia 1998). potato k’ipas in Bolivia. Moreover, Quiros et al. (1992) A decrease in the number of oca landraces cultivated by observed active incorporations of sexually-produced new farmers (provoking irreparable genotypic erosion) has been potato genotypes in Peru. Farmers would collect botanical described in the literature for communities in Bolivia, Peru seeds, sow them in beds and carry out a selection of the and Ecuador (Bianco and Sachs 1997; Tapia and Estrella best new landraces based on the size, number and quality 2001; Garcı´a and Cadima 2003). The causes of this erosion of the tubers. Similarly, cassava (Manihot esculenta C.) could be diverse, including: the increasing linkage of farmers in Guyana actively seek volunteer plants arising production to the market, which demands only a few uni- from sexual reproduction and take care of these plants until form varieties; loss of traditional knowledge and familiar maturity. When they are judged satisfactory, these new germplasm because of rural exodus; decreasing demand in genotypes are multiplied as a new landrace or assigned to cities from the poor social prestige of consuming oca; and a an existing landrace (Elias et al. 2001). For more infor- rise in pests and diseases (Terrazas and Valdivia 1998; mation on mixed clonal/sexual systems, we invite the Huama´n 2001). reader to consult the extensive literature review by McKey This study approaches the landrace diversity, the seed et al. (2010). exchanges and the management of sexually produced new 123 Effect of the management of seed flows and mode of propagation on the genetic diversity in an… genotypes of oca in four semi-traditional communities of The entire region, considered as a microcenter of bio- Bolivia in order to gain a better understanding of the diversity for Andean tubers, presents ideal climatic and dynamics influencing landrace/genotypic diversity at the pedagogical conditions for their production. However, as community level (the studied communities can not be for all mountainous areas, heterogeneity is observed in considered as fully traditional as they are highly influenced altitude, climatic conditions and soil composition, which by the nearby Colomi market, which involves modern creates diversity in the agricultural practices and cultivated socioeconomic actors and modern transportation routes).