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Published in Issue No. 132, page 1 to 9 - (34546) characters

On farm conservation of minor tubers in Peru: the dynamics of oca (Oxalis tuberosa) landrace management in a peasant community

Marleni Ramirez  Introduction
Only in the last two decades has the scientific community fully realized the fact that a great deal of plant genetic diversity was being conserved beyond the confines of ex situ gene banks. Farmers, in particular farmers in areas of crop origin and diversity, maintain, and continue generating plant genetic diversity (Altieri and Merrick 1987; Dennis 1987). Although several models for in situ conservation, including on-farm conservation, have been proposed (Brush 1991, 1995; Maxted et al. 1997; Qualset et al. 1997) there still remain a large number of unresolved questions that need to be answered. Some of these include how farmers manage on-farm diversity, what favors the maintenance of diversity, the relation between farmers’ knowledge and genetic diversity (Brush, 1999; Louette, 1999). For example, only a few studies have looked at the possible links between farmers’ knowledge, decision making and genetic variation in major crops (Bellon 1991; Louette 1999, for maize; Teshome et al. 1999a,b in sorghum). There is even less information regarding non-major crops or crop complexes, and only recently has research been designed that addresses these deficiencies (Jarvis and Hodgkin 1999).
In the indigenous community of Piccol, in southern Peru, subsistence farmers cultivate diverse tuber crops. The major tuber crop, potato, is closely associated in the crop rotation cycle with the so-called minor tubers: oca (Oxalis tuberosa), ullucus (Ullucus tuberosus) and mashua (Tropaeolum tuberosum). Of the minor tubers, oca is only second to potato in its reported landrace diversity and its contribution to the diet of subsistence farmers. There are no improved varieties of oca. Although the dynamics of potato landrace maintenance have been documented by Brush (1995), Brush et al. (1981) and Zimmerer (1996), only in the last few years has some attention being focused on the minor tubers (Fairlie et al.1999; CIP/UNEP 2000). This study presents data on landrace management of oca tubers by indigenous farmers in a community in southern Peru. Specifically, we describe what farmers conserve, their concerns regarding this crop, their management of landraces through time and the tuber seed sourcing mechanisms employed.
The first survey of minor tuber diversity took place during the harvest season of 1996. Twelve of a total of 18 families living in Piccol at the time were included in this survey. A successful effort was made to include all socio-economic groups in the community (see next paragraph). Semi-structured interviews and participant observation methods were employed. Adult men and women farmers were interviewed in depth regarding their knowledge of minor tubers and oca in particular. Conversations took place on farmers’ plots during harvest and/or during visits to their storage area. A six-quart measure of tubers was taken from the center of the pile of tubers and the farmer separated the landraces. For each landrace the following information was collected: name, uses as food and other, hardiness to hail and frost, performance with regard to pests and diseases, and perishability in storage. Questions about tuber seed selection criteria and sources of tuber seeds were also included. All interviews were conducted using the tubers as props since tuber names are not consistently used. A representative collection of the tuber landraces present in Piccol was carried at all times to show to the farmers in the case of doubts about placing a tuber as belonging to one landrace or another. Later, laminated photo cards of the tuber landraces were used as an aid in identification. A sample of the landraces grown by each family was collected and labelled for future reference. All landraces were additionally assigned a letter of the alphabet to help the researcher avoid any confusion caused by the use of the same name for different landraces and different names for the same landrace. Conversations were conducted in Spanish and Quechua and most of the respondents were women farmers. Markets used by Piccol farmers to supply tuber seeds were surveyed at harvest and at planting time and landrace diversity of minor tubers available for sale or barter, as well as their origin, were recorded.
To monitor the use of oca tuber stock over time, seven farming families were visited at harvest for the next 3 years. The storage areas were surveyed in each case in the company of either the husband or wife. The seven families closely represented the three existing wealth groups in Piccol. Wealth groups were revealed by a participatory wealth ranking exercise (sensu Grandin 1988) conducted in 1997 by the researcher.
The following formulae were developed to estimate the yearly rate of landrace loss (RLL) and rate of landrace acquisition (RLA) in the farmers’ oca collections. The calculations take into account the presence or absence of a landrace, but not its abundance:

where LPy=number of landraces present the current year (y); LPy-1=number of landraces present the previous year; and NLy=either new or reintroduced landraces present during the current year.
A survey of plant diversity maintained in backyard gardens was undertaken in 1998 as well as a count of the potato landraces cultivated by Piccol farmers.
The community of Piccol
The community of Piccol (Calca Province, Taray District) is located on the Vilcabamba range, about 20 km away from the city of Cuzco at the end of a dirt path that connects with the paved road linking Cuzco with the town of Pisac. During the Land Reform of 1969, ex-tenants of a livestock hacienda owned by the Franciscan order organized to legally claim and register Piccol as a Peasant Community. Today’s Piccol residents are primarily subsistence agriculturalists that raise livestock as a secondary activity (Bianco 1996). At least one member of each family seeks temporary employment outside the community. Piccol residents are ethnically and linguistically Quechua and most adult women are most comfortable communicating in Quechua instead of Spanish. School age children and adult men are bilingual in Quechua and Spanish.
The community landholdings spread over 686 ha of land ranging from 3500 to 4200 m. Virtually all of the land has beendistributed among the 22 families that make up the community, and only 10 ha are communally farmed. Each family owns 6–10 plots of land, most of which are rainfed or secano (5–8 plots per family or an average of 3.3 ha per family) while fewer (1-3 plots per family or an average of 0.4 ha per family) are irrigated. The plots in secano (Spanish term for rainfed) are distributed in six sectors or muyuys that are subjected to a farm/fallow regime determined by the community as a whole. The sequence of cropping in each field for a given muyuy starts with potato in year one, minor tubers in year two, barley or tarwi (Lupinus sp.) in year three and then the sector remains fallow for 3-6 years after which the cycle starts again. In these plots, commercial fertilizer is only used for potato during the first year of the rotation cycle. Most of the harvest from secano fields is used for family consumption. On the other hand, irrigated plots are farmed intensively and often with the use of commercial inputs. Onions, early potatoes (mahuay), carrots and lettuce are grown in these fields and are destined primarily for the market.
On farm plant diversity
The plant diversity kept by Piccol farmers in fields and backyard gardens totaled 76 species but varied considerably from farmer to farmer (8–35 species). The lowest diversity count corresponds to the only farmer without a backyard garden. This farmer was not part of our study. Farmers grew tubers (potato, oca, ullucus and mashua) and fava beans, barley, onions, wheat, tarwi (Lupinus mutabilis) and quinua (Chenopodium quinoa) (Table 1). The main crops grown by Piccol farmers were the same from 1995 to 1997. Maize was planted by some farmers on irrigated land during El Niño 1998, a warming trend that effectively extended the altitudinal limit for maize growing in the area to 3600 m. During most years, Piccol farmers obtain maize from other communities by bartering native potatoes. Backyard gardens accounted for most of the diversity at the species level, or 69 plant species in total. Farmers’ gardens included an average of 23 (14–26) species. The majority of species was made up of vegetables, herbs and newly introduced tuber s (68% of all species). Fruit and wood trees accounted for 16% of species. Non-food flowering plants and bushes made up the other 16%. About half of all the species growing in backyard gardens were used for medicinal purposes, while over a third of them had food and other uses.
Diversity of tuber crops
All farmers surveyed grew 4–5 species of tuber crops that displayed high infraspecific diversity. Potato was the most diverse (10–31 landraces per farmer, x=18, s.d.=7.49) including native and improved landraces. Oca was the second most diverse, (5–16 landraces per farmer, x=10, s.d.=4.01), and mashua and ullucus combined were kept in less diverse combinations (3–8 landraces per farmer, x=4, s.d.=2.13). As in other communities in the area, most of the yearly calories are derived from potatoes, followed by the minor tubers and oca in particular. Only a few farmers took minor tubers in any important amounts to the markets, although the majority took a few pounds to a market at one point or another before the next planting. In addition, in most years, minor tubers are bartered for maize with farmers from lower altitude communities.
Minor tubers in Piccol were usually grown in adjacent sections of the same field, less often, they were intercropped in alternating rows, and only occasionally were they found truly intercropped. Each species is planted using two tuber seeds at a time. Most farmers seem to combine seeds from different landraces while only a few farmers grew sections of single landraces for the market. Harvest of minor tubers runs from April until June and exceptionally into July. Harvest starts with oca and it is guided by different cues, but most of the time in responde to fear of infestation or worsening of the infestation by the Andean weevil (Microtrypes spp.). Ullucus was harvested next and mashua last. Mashua can be left on the ground due to its reported rusticity and resistance to pests.
Minor tuber farmer classification
Most Piccol farmers were knowledgeable about oca landraces’ names and how they differed from each other. Piccol farmers differentiated between tuber landraces by a suite of characteristics that primarily included the skin colour of the tuber, and the colour, shape and distribution of eyes on the tuber (in the case of oca and mashua); that secondarily included the texture and taste of the tuber and, only occasionally included the colour of the medula. Very few farmers mentioned any above-ground plant part as a landrace characteristic.
Table 2 includes all the oca landraces present in the farmers’ collections at the time of the first in-depth survey (1996) but it also includes a selection of oca landraces found at the time in neighbouring farmers’ markets. Piccol farmers grew twice as many named oca landraces as mashua (14:7) and there were only three ullucus landraces. In the case of oca, most farmers used names to differentiate one tuber from another, but occasionally they did not remember the names for particular tubers although the tubers were recognized as distinct from others. There did not seem to be much consistency in the use of names. For example, the same name was used for different landraces in the same community or the same landrace was known by different names by different farmers. Very few names were consistently applied to the same landrace (e.g. Q’ello kaitu) within the community.
Oca diversity and uses
Piccol farmers recognize two broad groups of oca—sweet and bitter. Sweet oca is usually consumed fresh while bitter ‘khaya’ oca landraces need to be processed before consumption. Processing of khaya oca landraces includes soaking whole tubers in pools of water for several days, followed by squeezing out the water and freeze-drying the shriveled tubers. At the time of the first survey none of the farmers cultivated khaya oca although some indicated interest in acquiring it. According to some farmers, the cultivation of khaya oca had fallen out due to the laborious processing and problems with access to pools of water. All the oca landraces grown in Piccol were sweet, although there was wide variation in sweetness or ability to accumulate sugars within this group. Table 3 lists the main culinary and agronomic characteristics that Piccol farmers recognize in the sweet oca landraces they cultivate. Shared characteristics permit the placement of oca landraces into three groups that are named after the most common adjectives used by farmers when describing them. Group 1 includes oca favored for their culinary performance. They are said to be naturally sweet ‘miski’ or requiring minimal exposure to the sun (solarization) before consumption. Miski oca are cooked by baking in the traditional oven made of sod clumps or watia right in the fields being harvested. Oca landraces in this group also possess a much appreciated quality in tubers, flouriness. On the minus side, they are poor performers against the main pest, the Andean weevil (Mycrotrypes spp.). Also, most bruise easily and do not keep well in storage so they must be consumed soon after the harvest. In contrast, Group 3 or ‘duro’ ocas are rather insipid but may develop sweetness after a long period of sunning. Most ocas in this group are tough and are generally consumed after boiling for a long time. However, ocas in this group show good pest resistance and most are edible even after a long time (up to 6 months) in storage without previous solarization. Group 2 or ‘intermediate’ ocas showed intermediate or a combination of characteristics from both groups.
Oca tuber seed management
Once harvested, usually by husband and wife, oca tubers are taken home for storage in a dark corner of a room where they are piled and covered loosely with grass (Stipa ichu). Evaluation of oca tubers as seed starts at harvest. Women farmers, who as a rule dig out the tubers from the furrow opened up by the grown men in the household, have a good sense of the quality of the harvest early on. Soon after the women in the household and occasionally the children separate the tubers into two main piles, for food and for seed. This is when women make decisions over whether they will save tuber seed for the next planting or will eat it all. Since women have cooking responsibilities this is easily accomplished. Most farmers destined the larger tubers for human consumption and the smallest tubers for household consumption or for the pigs. Tubers destined for seed were selected based on their size (medium size preferred over larger size), number of eyes (not too many or they may produce too many weak shoots), and their healthy appearance, since they will remain in storage for about five months before planting (Table 4). After the initial sorting, tubers are loosely piled and covered with straw and muna (Minthostachys spp.) this last to fend off insect pests.
Oca tuber seeds were generally stored as a mix of landraces, except when farmers were monitoring newly introduced tuber seeds, and then these were often kept in a separate pile. New or fresh tuber seeds (a batch of a known landrace that proceeds from another farmer, the market or an unknown landrace) were also planted separately from the other landraces. The first harvest of a newly introduced oca landrace was usually destined for seed and it was not consumed, with the intention of increasing the fresh/novel seed stock first. This appears to be related to the fact that introductions of new stock occur, in most cases, in small amounts, but also related to the practice of monitoring performance of the fresh oca seed at the new location.
Almost all Piccol farmers (94%; Table 4) contend that they need to renew their oca tuber seed stock every 3–6 years due to loss of tuber vigor. Farmers indicated that the tubers become progressively smaller and are riddled with pest and pathogens. In addition to the oca weevil, a nematode, mold and what appeared to be bacterial and viral lesions were observed in the tubers in storage. In most years, almost three of every four farmers supplied all the oca tuber seeds needed for planting from their own harvest stock. However, a fourth of the farmers supplemented their own tuber seeds with those acquired in the market and from relatives. Most of the time, and for most farmers, new or fresh oca tuber seeds are acquired a few landraces at a time and in small quantities. Small mounds of new oca tuber to be used as seeds were discovered only after careful inspection of the storage area and protracted questioning of the farmers. Some farmers believe that speaking about or showing the new oca seeds to strangers may spook them into not getting used to the new surroundings. As a consequence, acquisition of new tuber seeds may be underreported.
Although oca tuber seeds can be acquired at harvest, many are obtained at planting, to make up for losses in storage or after a poor harvest. It is, however, not too uncommon to consume the whole harvest of oca tubers thus not leaving any for seed for the next season. This occurs when farmers will not have enough land to cultivate minor tubers in the next planting season, after a poor harvest, or if the crop was already producing very poorly and the farmers decided to consume the whole crop. To start a tuber collection again, farmers usually provide labor to other farmers at harvest in exchange for tubers, borrow tuber seed from relatives or look for them in local markets. In the market, farmers were seen visiting several vendors before making purchases from two of them. Some farmers sought specific landraces when looking to acquire fresh tuber seeds.
Oca tuber seed markets frequented by farmers from Piccol included Pisac, Calca, Kello-Kello, all of these receiving their oca tubers from the highland communities near Pisac (about 5–10 km from Piccol) and from as far away as Paucartambo (about 80 km away from Piccol) from communities with fields at 3600 m and lower. The markets most often visited by farmers when in the city of Cuzco were Rosaspata and Puente del Ejercito whose seed sources are the neighboring communities around Piccol and other areas to the south east of Cuzco as far as Andahuaylillas (about 30 km away). Occasionally, farmers from Andahuaylas, about 150 km west of Cuzco bring oca for sale to the Cuzco markets. Farmers who can acquire tubers for seed from the markets soon after harvest have a much greater choice of tuber seeds than if they wait for planting time. A survey of local markets at harvest revealed two to three times the diversity of oca landraces than at planting (10 landraces per market day in May compared with three landraces per market day in September). At harvest, a third of the oca landraces found in Piccol were also found in Pisac but only half of those were found in the Calca market.
Oca landrace turnover
The time series data in Tables 5 and 6 show that landraces flow in and out of individual collections and the community in a dynamic pattern. Table 5 shows the results of monitoring the oca stock of seven families over 4 years. Every year, very few landraces were found in every farmer’s collection (100% of farmers) and they changed from year to year (landrace N in 1996, and G and K in 1998). Moreover, not one landrace was present in every farmer’s collection over the 4 years. Looking at all the collections, over a third of the landraces (38%) were present in somebody’s collection in any one year (e.g. N, I, M, B, E, G, J, and K). Starting in 1996, initially rare landraces either became common (e.g. I, G) or decreased to the point of disappearance (e.g. C, F). More common landraces (found in four or more of the farmers’ collections) gradually spread to other farmers’ collections (e.g. M, E, and J). This seems to indicate an active diffusion of landraces within the community. In this sample of farmers, from about a quarter to a third of the landraces were found only in a few collections and were thus deemed rare. On most years, about half of all the landraces were found distributed among just a few farmers.
The tracking of farmers’ oca collections over 4 years indicates that the introduction of novel or fresh tuber seeds and the abandonment of some landraces is a continuous process. It combines opportunistic and deliberate acquisition of landraces and the elimination of others. Table 6 presents in detail the changes in the oca stock of two farmers that secured their tuber seeds from various sources. The first farmer dropped two landraces (consumed what it had of L and J landraces) in one year (1996), dropped three more the next year (F, H and N landraces in 1997) and incorporated six landraces (Z, Q, N1, I, R and Y) at the next planting in 1997 for harvest in 1998. By the third year of tracking, her collection was made up of two thirds fresh landraces and one third of landraces that had persisted since the start of monitoring. By the fourth year of monitoring, less than a fifth of the landraces present corresponded to the original complement of landraces. The second farmer also followed a pattern of gaining and discarding landraces but by the fourth year still retained half of the original complement of landraces. It is also clear that landraces that are lost one year can be recovered in subsequent years. Recovered landraces are usually the fresh tuber seed of the same landrace obtained from another farmer or the market. Overall, at least a third of the landraces introduced were not known by some of the farmers who ranged in age from their mid-twenties to late thirties.
Even after the dynamic turnover of landraces in 4 years of farming, representatives of the three groups of oca landraces were included in both farmers’ collections. Since the miski and duro groups show very contrasting characteristics of use and susceptibility to pests, indexes of loss and acquisition were estimated for both groups for the whole sample of farmers. Table 7 shows a comparison of the rates of landrace loss (RLL) and landrace acquisition (RLA) estimated for the two groups of oca for all farmers in the sample. Miski landraces were lost/discarded twice as frequently as oca landraces in the duro group (0.33 compared with 0.18). Lost landraces were recovered and/or new ones with similar characteristics were incorporated into the collections at a higher rate for miski than for duro ocas (0.33:0.18). Of the seven miski landraces incorporated into the collections less than half (3/7) were obtained from the market and 2/7 from a relative. At least two farmers announced their search for a specific type of miski landrace and only one was able to buy it from the market. The source of the remaining miski landraces is unknown. Of the four duro landraces reintroduced to the collections, at least one was sourced from another community. Within each group there was wide variation from one year to the next in the rates of loss and acquisition but over the study period both oca groups were replaced at the same rate that they were lost.
Discussion and conclusions
Farmers’ concerns and landrace diversity
Farmers who grow oca invariably declare that they do so because of the high culinary value attached to the crop. In a diet notorious for its absence of sweet flavours (Johns 1990), the oca crop is often praised for its sweet landraces. Oca landrace collections kept by farmers, however, reflect additional concerns (sensu Bellon 1995) with the crop. Four years of tracking oca landrace use showed that farmers kept a combination of landraces that differentially addressed their culinary, agronomic and food security concerns. Landraces with high culinary value, but high pest susceptibility and low storability were maintained in mixes with landraces with low culinary value, but high pest resistance and good storability. The evident trade-offs between the landrace groups maintained by farmers appear to fulfil short- and medium-term food needs, to provide variety to the diet and to support diversity maintenance.
It was also clear that the farmers’ concerns were not met by any one landrace nor a few of them, but rather by a diverse mix, where none of the landraces performed optimally. The redundancy of landraces, or several landraces addressing similar concerns, also increased the probability of addressing priorities even if collections experienced losses. A similar abundance of diversity has been reported for other crops, such as native potato (Brush 1991) and rice (Dennis 1987), among others.
Tuber seed turnover and sourcing
Most oca farmers indicated that they renew tuber seed stock every 3–6 years, ostensibly to refresh their collections by the introduction of vigorous material. As a consequence, although most farmers used their own seed at every planting, there was some infusion of tuber seed from other sources, to make up for culled or lost landraces. After 4 years of cropping, even though landrace collections had changed in their composition, they still maintained representatives from all oca groups. The most contrasting oca landrace groups were lost and recovered at different rates. Landraces with high culinary value but high susceptibility to pest/disease were lost and recovered at a higher rate than the less palatable but better pest performer landraces. It is suggested that farmers replenish collections to counter the effects of pest/disease on their culinary favorites.
Oca landrace management practiced by Piccol farmers appears more purposeful than has been reported by Zimmerer (1996) for potato landraces in Paucartambo, Peru. A comparison of farmer practices regarding tuber seed management shows that farmers from Piccol and Paucartambo share some similarities but differ in important aspects. Both groups of farmers select tuber seeds at harvest en masse. For Paucartambo farmers agro-ecological factors selected tuber seeds. As one farmer is cited as saying, “the good seed tubers appear in the harvest”. Direct selection of potato landraces with very high culinary value was rare. Collection and use of true seed potato was an even rarer occurrence. Thus Zimmerer (1996) concludes that Paucartambo farmers exert very little manipulation on their landrace mixes. In contrast, oca landrace stock in Piccol is renewed every 3–6 years. As has been documented by this study, landraces were discarded and acquired in a dynamic fashion over a four year period. It is proposed that farmer behaviour during replenishment of lost/discarded oca landraces is more deliberate than previously thought. Oca stock replenishment required farmers to seek and acquire seed stock regularly, albeit a few kilograms at a time. Farmers were observed selectively buying tuber seed mixes from the market, borrowing seeds from relatives and sometimes seeking out specific landraces for purchase. The fact that miski landraces were lost and replenished at a higher rate than duro landraces suggests that perhaps they were acquired at different rates. Farmers also kept track of recently acquired novel landraces. They were stored and later sown separately from the rest of the landraces. All of these observations point to farmers actively engaged in the replenishment of their oca collections.
When women farmers select seed from their own harvest they do it en masse and appear to respond to the overall quality of the tubers rather than to specific landraces. This is similar to selection reported for potato (Brush 1981). On the other hand, when women and men acquire tuber seeds in the market, they choose some landrace mixes over others. Furthermore, this study has shown that replenishment of oca stock was not usually with the same landraces, but commonly with landraces that perform similarly. Thus farmers appeared to display loyalty to a type of oca rather than to specific landraces. This is consistent with the fact that when asked, very few farmers expressed a desire to acquire specific oca landraces; still, their practices were successful in replenishing their collections with highly valued landraces. When unknown landraces were acquired farmers indicated that they liked how they looked. It is possible then that farmers recognize a complex of colours and shapes (selection for perceptual distinctiveness; sensu Boster 1985) associated with landraces with similar performance. This is not difficult to imagine since oca tuber landraces show great variation in colour of the skin, tuber shape and shape and colour of the eyes. In fact, Guaman (1997) found that some oca groupings based on some of these characteristics matched the farmers’ use groups of Bolivian landraces.
In conclusion, the diverse landraces maintained by subsistence farmers in this Andean community show contrasting traits that reflect their multiple concerns with the crop. Timeline data reveals that landrace composition of farmers’ collections is fluid and that tuber seeds are acquired from a wide area. Farmers discard and incorporate known and new landraces readily. Different landraces were lost or discarded at different rates apparently in response to their pest/disease hardiness. Farmers’ management of tuber seed over time restored the integrity of the collections to reflect the farmers’ concerns.
I gratefully acknowledge the field assistance of Ing. A. Farfan, A. Andia, M. Kana and the cooperation of Ing. R. Ortega. Thanks also to Emma Garver and Nate Hersh who provided assistance and companionship. I am specially thankful to the farmers of Piccol for their friendship and interest in this work. This study was supported by the McKnight Foundation and the Pennsylvania State University.
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