«Andean roots and tubers: Ahipa, arracacha, maca and yacon M. Hermann and J. Heller, editors Promoting the conservation and use of underutilized and ...»
A second collecting period began in 1993, guided by the Programme of Roots and Tubers in the Andes (RTA), administered by the CIP and funded by COTESU (Cooperación Técnica Suiza - Swiss Technical Cooperation) for a 5-year period. More emphasis was placed on secondary Andean crops and the collecting activities were expanded to Bolivia, aiming mainly at in situ conservation.
8.4.1 Ecuador Ecuadorian Andean root and tuber germplasm is managed by the INIAP (Instituto Nacional Autónomo de Investigaciones Agropecuarias) at the Santa Catalina Research Station, located in Pichincha Province, Mejía Canton, at 3058 m (Tapia et al. 1996). The station keeps 777 accessions of Andean roots and tubers (November 1995), of which 32 correspond to yacon (jícama). Material is planted in the field once a year and duplicates are maintained in vitro, stored at 5°C. The provinces of Cañar, Azuay and Loja in Southern Ecuador have yielded the largest number of accessions for the Santa Catalina collection.
8.4.2 Peru Peruvian researchers are the ones in Latin America who dedicated most attention to yacon. Collecting efforts were initiated by Arbizu and Robles (1986) and several germplasm collections have been established in different sites of the country, holding a total of about 200 accessions. However, it is likely that many duplicates are included in this figure.
In the north of the country yacon material is maintained at the Los Baños del Inca research station, Cajamarca, where 45 accessions are being characterized and evaluated (Franco and Rodriguez 1997). The northern departments, Cajamarca and Piura, have been explored by Seminario (1995b), who collected 62 accessions in 1993-94.
The International Potato Center (CIP, Centro Internacional de la Papa) in Lima holds 44 accessions, including 37 from Peru, 4 from Bolivia and 1 from Argentina (Dr C. Arbizu, 1997, pers. comm.).
In the Ayacucho department, collections are kept by the University of Ayacucho (10 accessions) and the Instituto de Investigaciones Agrarias at the Canaan center (6 accessions) (De la Cruz 1995). Material is being maintained under field conditions and in vitro (De la Cruz and Jiménez 1997).
Material from southern Peru is concentrated in Cusco. The CICA (Centro Internacional de Cultivos Andinos) of the University of Cusco maintains 33 Yacon. Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson accessions at the Kayra research station (3249 m). A collection of 87 accessions is maintained by the CERGETYR (Centro de Recursos Genéticos de Tubérculos y Raíces) of the Cusco University at Ahuabamba (2000 m), in the Vilcanota river valley (Lizárraga et al. 1997). The University of Cusco has also initiated an in situ program at five localities ranging from 3000 to 3500 m asl (Meza 1995).
8.4.3 Bolivia Very little yacon material is held in ex situ collections in Bolivia. Just two accessions are reported at Toralapa (3400 m asl), Cochabamba. Much more important is the amount of material maintained within an in situ strategy (Rea 1995b). The conservation network involves 17 families in the La Paz department, which are currently managing 32 different morphotypes. The sites are distributed along a wide altitudinal gradient from 900 to 3600 m, with the largest concentration at 3100-3200 m asl. Information summarizing the experience is shown in Table 4.
8.4.4 Argentina The Cerrillos research station in Salta (INTA, Instituto Nacional de Tecnología Agropecuaria) has collaborated with CIP during collecting campaigns of Andean tubers in northwestern Argentina, but maintains only one yacon accession. A small in situ conservation project for several Andean crops including yacon is being set up in the Santa Victoria area, Salta province, northwest Argentina by the LIEY (University of Tucumán).
8.4.5 Availability of data on individual accessions Data available on individual accessions vary considerably from institution to institution. They usually indicate origin, collector and a few observations. In general little or no information is available on climatic, edaphic, ecological and agronomic data associated with the accessions, a fact that could constrain future evaluations.
8.5 Gaps in existing collections An important deficiency in the existing germplasm collections is the limited amount of wild forms available. One ‘wild’ yacon accession from Ecuador is held by CIP (Ishiki et al. 1997) and three more are at the CICA center, Kayra, Cusco. However, these are most likely wild Smallanthus species other than S. sonchifolius. Positively wild S. sonchifolius material would provide not only valuable information on the phylogeny of the species but may be useful in future breeding programmes.
Furthermore, wild species may represent an interesting source of valuable genes.
Material from the dry inter-Andean valleys is better represented in the collections than material from the humid eastern slopes. Assuming that yacon evolved in the forested slopes of the Andes, diversity is presumably higher in that region.
Communities in the humid slopes are generally more isolated and less connected to the main road systems; this increases the likelihood of finding rare clones in these areas.
Promoting the conservation and use of underutilized and neglected crops. 21. 227 Table 4. Material held in situ in the La Paz Department, Bolivia
8.6 Conservation of the cultivated yacon and its wild relatives No survey of the conservation status of Smallanthus species has been made. It would be important to evaluate their presence in the existing national parks and reserves.
However, Smallanthus species may not be favoured by pristine, conventional protected environments. As plants adapted to invade vegetation gaps, Smallanthus may also prefer disturbed habitats created by human intervention. If this proves to be true, an ideal environment would be areas where slash-and-burn agriculture is practised. This also may be valid for the relatives or wild forms of other crop species and it would be important to consider areas like these within the framework of park and reserve systems.
An interesting example of these aspects is present in the Machu Picchu sanctuary in Peru. Sanctuary officials have always tried to expel the peasants established within the limits of the sanctuary. However, besides the growing of yacon landraces, the activities of these people create an environment ideal for at least two wild Smallanthus species and many other crop-related species (e.g. Cyphomandra, Physalis). It would be very important to carefully evaluate if these peasants and the partially disturbed environment that they create do not actually belong in the sanctuary. In areas like this, a compromise between conservation efforts aiming at different aspects (historical, biological and agronomical) should be possible.
Closely related to the last consideration is the idea of in situ conservation, a system that maintains not only the germplasm but also all the information associated with that germplasm. Rea (1995a) has described a successful in situ conservation system set up in Bolivia that could be used as a model in other areas of the Andes.
Yacon can be grown in vitro using modified Murashige & Skoog media (Kuroda et al. 1993; Estrella and Lazarte 1994). De la Cruz and Jiménez (1997) and Velasque and Ortega (1997) have evaluated several alternative modified Murashige & Skoog media to reduce growth and extend in vitro conservation for at least 6 months.
Promoting the conservation and use of underutilized and neglected crops. 21. 229 9 Breeding There are no reports of breeding attempts involving yacon. Characterization and evaluation of existing accessions in germplasm banks are being carried out in Ecuador (Castillo et al. 1988; Tapia et al. 1996), northern Peru (Seminario 1995b; Franco and Rodríguez 1997) and southern Peru (Lizárraga et al. 1997). Kuroda and Ishihara (1993) were able to select lines of higher sugar content by tissue culture. Nevertheless, no information is available on selected yacon clones being released for wider cultivation.
A first difficulty while breeding yacon will be its reduced fertility However, this is by no means an insurmountable hurdle. On the other hand the presence of staminate and pistillate flowers makes pollination control considerably easier than in other Compositae, such as sunflower, which requires the use of male sterility to facilitate hybridization.
Yacon is especially amenable to in vitro culture, opening an attractive window of opportunities for modern biotechnological manipulation. However, it is essential to define objectives in order to apply the tools available.
Future breeding and selection objectives may diverge depending on the type of farmers, production scale, fresh produce, industrial processing (e.g. purified oligofructans, syrup, chips) and target market (Andean, international). For example, throughout the Andes clones with yellow flesh are preferred at the market level (see data by Rea in Table 4, Tapia et al. 1996), while other types are cultivated mainly for family consumption. In contrast, westernized supermarkets may favour a wider range of flesh colours. A more uniform size would be another important characteristic to standardize commercialization and processing.
Evaluation trials have yielded some potentially useful correlations. Productivity (t/ha) is correlated with number of roots/plant (Franco and Rodriguez 1977). The refractive index of the root juice as a rapid estimator of sugar content, a measurement commonly used in other crops, is also valid for yacon (Kuroda and Ishihara 1993).
Yacon. Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson 10 Ecology of the species There is very little published information about the environmental requirements of yacon, as there has been virtually no conventional research on yacon ecophysiology.
Yacon and most yacon relatives are believed to have evolved in the humid eastern slopes of the Andes not far from the equator, a region with mild temperatures and generally with abundant rainfall although with a distinct dry period. These conditions have probably shaped yacon’s ecological requirements.
10.1 Photoperiod Yacon has been described as day-neutral for stem and tuberous root formation (National Research Council 1989). However, this process begins very late in the growing season at higher latitudes (23°S, Jujuy province, Argentina; 46°S, Otago province, New Zealand). This behaviour may indicate that the plant has a weak short-day response.
10.2 Temperature requirements While native from subtropical to warm-temperate environments, yacon shows a high plasticity, being able to grow and produce in a wide altitudinal range (900-3500 m in Bolivia, Peru and Ecuador; 600-2500 m in northwestern Argentina; 600 m in Brazil;
sea level in New Zealand and Japan). Aerial parts are frost-sensitive, with leaves damaged at -1°C. Cultivation is common in some regions with light frost, like the Ecuadorian highlands or many inter-Andean valleys in Peru, Bolivia and northwestern Argentina, because in these regions frosts generally occur at the end of the growing season. In New Zealand, stems were killed almost to the ground by
-3 to -4°C, and a temperature of -7°C for several hours damaged all underground organs. Temperatures below 10-12°C combined with high solar radiation led to chilling damage of the leaves (Grau 1993). Optimum growth occurs in the range 18°C. Foliage is able to tolerate high temperatures (at least up to 40°C) without damage symptoms, provided that an adequate water supply is maintained. Low night temperatures appear to be necessary for optimum storage root formation.
Farmers in Argentina and southern Bolivia indicate that medium-altitude sites (1500m) are best for storage root production while warmer lowland sites are better for ‘seed’ (rhizome) production, but root yields are lower.
10.3 Water requirements Adult yacon plants possess a developed canopy with a high transpiration capacity, requiring a good and regular water supply. Irrigation is a necessary complement in most dry Andean intermontane valleys where yacon is cultivated. Production areas in Bolivia receive 300-600 mm, while 800 mm are considered the optimum. In many regions temporary wilting is very common on sunny summer days, even when the soil has an adequate water level. On the other hand, yacon can survive long dry spells. However, productivity is significantly affected under these conditions. While irrigation may be critical in some cases, overwatering can lead to cracking of the root Promoting the conservation and use of underutilized and neglected crops. 21.
skin, which affects the exterior quality and market value and may promote root rot during storage.
10.4 Soil requirements Yacon adapts to a wide variety of soils, but does better in rich, moderately deep to deep, light, well-structured and well-drained soils. Growth is poor in heavy soils.
It grows very well in the humus- and mineral-rich soils of the Andean slopes after slashing and burning of the forest. Very good crops are also obtained in sandy river terraces in the Tarija area, Bolivia, and in lateritic soils corrected with dolomite in the state of São Paulo, Brazil. Yacon can tolerate a wide pH range, from acid to weakly alkaline.
Yacon. Smallanthus sonchifolius (Poepp. & Endl.) H. Robinson 11 Agronomy
11.1 Propagation Yacon is propagated vegetatively with 8-12 cm long offsets (‘seeds’) taken from the underground and aboveground rootstock (‘crown’), with a few or no roots attached.
The rootstock can be divided into pieces easily, and these offsets are normally obtained during the harvesting of the roots. Storage roots with no stem attached are not able to produce shoots.
Aerial stem cuttings can be easily rooted if protected from desiccation. Rooting is best under mist, and it can be significantly accelerated using auxins (Indol-butyric acid).
11.2 Crop husbandry Field preparation varies considerably from region to region and by production scale.
The system used at present in the Cusco region, southeast Peru, may be very similar to the one used at the time of yacon domestication. According to Lizárraga et al.