«Andean roots and tubers: Ahipa, arracacha, maca and yacon M. Hermann and J. Heller, editors Promoting the conservation and use of underutilized and ...»
Pachitea, steep rocky open grassy slope, Huacachi, estación near Muña, 6500 ft, Macbride 4163. — Lima: Prov. Huarochirí: “in declivibus rupestribus prope Tambo, ad viam ferream inter oppida Lima et Oroya,” 2650 m, Weberbauer 165, type — Viso, sandy hillside, 2800 m, Goodspeed, Stork & Horton 11540 — Valley of Rio Rimac near Lima-Oroya highway at km 90 east of Lima, 3000 m, Goodspeed & Weberbauer 33059 — Matucana, 8000 ft, Macbride & Featherstone 326, 2949 — Rio Blanco, 12,000 ft, Macbride & Featherstone 730 — Prov. Canta: cerca a Culluay entre Canta y La Viuda, 3600-3700 m, Ferreyva 12964 — Pasco: Prov. Daniel Carrion, in shrub on southwestern canyon slope, Yanahuanca, 10 000 ft., Macbride & Featherstone 1244.
Promoting the conservation and use of underutilized and neglected crops. 21. 151 This species, which is known only from Peru, and A. peruviana have been generally confused, largely because of the inadequacy of the original description.
The involucels of the two species are entirely distinct. Arracacia incisa, with its conspicuous scarious involucels, deep purple flowers, and blunt, prominently ribbed fruit, is one of the most distinctive species of the genus. The taproot is fleshy and has a fragrance of anise (Mathias and Constance 1962).
188.8.131.52 Arracacia peruviana (Wolff) Constance Bull. Torrey Club 76: 45 (1949) Velaea peruviana Wolff, Bot. Jahrb. 40: 303 (1908).
Slender, branching, 0.6-0.9 m high, squamulose to scaberulous throughout, the stem base clothed with dry sheaths, from a branched taproot; leaves ovate-lanceolate, 20cm long, bipinnate, the leaflets ovate to lanceolate, acute, cuneate at base, the lower distinct and short-petiolulate, the terminal sessile and confluent, 2-5 cm long, 1-4 cm broad, coarsely sinuately lobed and mucronulate-serrate, squamulose on veins and margins, the lower surface paler and reticulate; petioles 10-30 cm long, sheathing below; cauline leaves pinnate, the uppermost with short, wholly sheathing petioles; inflorescence of alternate axillary peduncles, 7-15 cm long, squamulose at apex; involucre wanting, or of a single leaf sheath; fertile rays 5-10, slender, spreading, 4-8 mm long, squamulose especially at apex; involucel of 6-10 entire linear bractlets 5-9 mm long, exceeding flowers but shorter than fruit; fertile pedicels 2-6, spreading, 5-6 mm long, squamulose or scaberulous above; flowers reddish-brown, the petals obovate; stylopodium depressed, the styles slender, spreading-erect; carpophore unknown; fruit ovoid, 4-6 mm long, 3-4 mm broad, glabrous, the ribs filiform; vittae large, solitary in the intervals, 2 on the commissure; seed face deeply and narrowly sulcate.
List of exsiccatae: PERU. Ancash: Prov. Cajatambo, infra Ocros, 3000-3200 m, Weberbauer 2748, type. – Ayacucho: Prov. Huanta, mountains northeast of Huanta, Weberbauer 7513. – Lima: Prov. Yauyos: Cuchapaya-pampa, cerca (arriba) a Tupe, 2830 m, Cerrate 1027. – Moquegua: Prov. Mariscal Nieto: Carumas, Weberbauer 7269.
7 Variation of cultivated arracacha
7.1 Morphological variation There appears to be little morphological variation in the cultivated genepool of arracacha. Because of the dearth of experimental data, however, this is difficult to prove. Clearly, the storage root is the most variable plant part; three horticultural forms are generally recognized: yellow-rooted and white-rooted material and cultivars with additional purplish pigmentation (probably anthocyanins) in the outer cortex or in the region of the vascular bundles. Cultivars of the latter type are particularly frequent in collections of Peru. The former classification, however, is an artificial one, and, in reality there is a continuous range between the three ‘extremes’. Figure 26 shows root shapes in an Ecuadorean germplasm collection.
The variation in root shape is modest compared with that of other roots and tubers.
From the comparative richness of varietal names (Arbizu and Robles 1986; Meza
1995) and available descriptions, it is reasonable to assume that Peru has the greatest morphological diversity in arracacha of all countries.
The only segregating population known is one that resulted from (selfpollinated) seed progenies of the commercial Brazilian clone. This progeny shows a wide range of white to intensely yellow root colour, but purple genotypes also occur at a low frequency. The Brazilian clone is therefore highly heterozygous.
Fig. 26. Variability of arracacha storage root variability in Ecuadorean germplasm collection (Photo courtesy INIAP).
Promoting the conservation and use of underutilized and neglected crops. 21. 153 Fig. 27. Leaf variation of cultivated arracacha across species range. All leaves are from plants of the same age and growth conditions (cultivated in pots in greenhouses). Provenance of accessions used (from left to right and top to bottom): Colombia: MH1358 (Cundinamarca, 4°18’N), MHIF1342 (Huila, 2°05’N); Ecuador: ECU1155 (Imbabura, 0°13’N), ECU1232 (Cotopaxi, 0°47’S), ECU1168 (Cotopaxi, 1°04’S), ECU1206 (Bolívar, 1°32’S), ECU1186 (Cañar, 2°43’S); Peru: CA5026 (Lima, 12°20’S), MH546 (Cusco, 13°00’S); Chile MHCN1250 (Arica, 18°50’S); Brazil: MH800 (São Paulo, 20°40’S), CNPH90437 (Distrito Federal, approx. 16°S); note the leaf of MH800 shows virotic leaf deformation. This is the commercial clone used all across Brazil and CNPH90437 is an F1 genotype resulting from selfing MH800. Scale: 30 cm.
Arracacha (Arracacia xanthorrhiza Bancroft) Figure 27 presents the leaf variation found in arracacha cultivars across the species range. By comparison with Fig. 24, it becomes clear that leaf variation in wild Arracacia species is much greater. Leaf shape of arracacha may vary as much within one accession as between accessions of a collection. Mazón (1993) struggled to describe leaf characters but concluded that only the degree of (purple) petiole pigmentation is a suitable and consistent leaf descriptor.
Future germplasm evaluations should consider the allocation of dry matter to the rootstock, which appears to be variable (see Table 4). Also, the variation of generative plant parts holds potential for the development of germplasm descriptors (see Section 4.2.2).
7.2 Chromosome number Chromosome counts in root tips of cultivated arracacha have consistently shown a mitotic number of 44, both in Peruvian (Blas and Arbizu 1995; Blas 1996; 65 accessions) and Ecuadorean material (Mr J.J. Vásconez, 1996, pers. comm.). Blas and Arbizu report the same number for two “wild arracacha” accessions from Peru.
Apioid genera have mostly haploid series of 11 chromosomes (Darlington and Wylie
1955) and it therefore seems likely that arracacha is a tetraploid. Tetravalent pairing in meiosis was recently observed in Ecuadorean arracacha (Mr C. Salazar, 1996, pers.
comm.). Constance et al. (1976) report 44 chromosomes for 15 specific taxa of Mexican Arracacia and the same number in the closely related genus Tauschia.
7.3 Molecular variation To overcome the difficulties involved in differentiating arracacha cultivars morphologically, Mazón (1993) and Erazo et al. (1996) conducted studies aimed at finding isozyme polymorphisms. Although both authors used a range of plant tissues, extraction procedures and buffer systems, little or no isozyme variation was found in a collection comprising Bolivian, Brazilian, Chilean, Ecuadorean and Peruvian germplasm (see Fig. 28). Of 20 isozyme systems showing enzymatic activity, only three (esterases, phosphoglucoisomerase and phosphoglucomutase) showed modest polymorphisms in starch gels (Mazón 1993).
Preliminary work using PCR-amplified DNA from random-sequence decamer primers has yielded promising results in terms of molecular polymorphisms for application in fingerprinting of arracacha cultivars. Thus Blas et al. (1997) and Castillo (1997) report the occurrence of DNA polymorphisms in 48% and 85% of primers assayed, respectively. Castillo (1997), however, concludes from his work that overall molecular diversity in his (Ecuadorean) material is low.
Arracacha (Arracacia xanthorrhiza Bancroft) 8 Conservation and use
8.1 Genetic erosion and germplasm collecting Undoubtedly, countless generations of farmers, especially the more diversityminded individuals who share with the modern plant collector a fascination about variation in crop plants, have brought upon us the extant diversity of arracacha and other traditional crop plants. This should not be mistaken with the recently evolving and increasingly popular belief that farmers per se are germplasm conservationists, and that crop germplasm can be conserved in situ, in complementarity with genebanks, as it were. Andean farmers indeed use germplasm, whether for economic, medicinal, culinary, aesthetic or other purposes, but chiefly for the diversification of diets that often cannot be supplemented, or only insufficiently so, from markets for lack of integration in the money economy. The fact that one still finds amazingly diverse crop germplasm in poor areas of the Andes is not necessarily proof of the curatorial attitude of farmers, but rather a sign of their dependence on genetic diversity in their fields as an insurance against famine and disease. As farmers are (successfully) integrated into national market economies and have access to external food sources, education and health, an objective that all Andean societies aspire to, dependence on native food sources decreases, and germplasm inevitably is lost to some extent. This is an incremental process and farmers will retain what they still consider useful. I have traveled widely across the Andes and gathered local evidence for the loss of cultivars of arracacha and other crops, particularly in those countries that have lower overall indices of poverty and seem to ‘progress’ economically faster than other countries (Argentina, Chile, Colombia, Ecuador). In light of this experience, the vigorously promoted view on in situ crop conservation would appear highly objectionable.
The conservation of germplasm, as opposed to its use, is a conscious effort to preserve what is today obsolete or currently not needed, in the belief that such material will be valuable at a later stage for the extraction of interesting traits from ‘undesirable’ genetic backgrounds. This is what farmers cannot and will not do.
Little is known about the disappearance of arracacha genotypes. This process is commonly referred to as genetic erosion, but strictly speaking, what is meant is the loss of genes or unique linkage groups of genes. Whether genotypes or genes, for that matter, are actually disappearing would require knowledge of the structure of genetic diversity, which, in the case of arracacha, we do not have.
There is, however, indirect evidence for the loss of genotypes in some areas.
During germplasm-collecting trips, farmers interviewed often recall clones that are no longer around. Much of the production destined for commerce is from a limited number of genotypes and these tend to replace varieties that, for one reason or another, are less attractive to produce. It has been argued that potatoes and other clonally propagated tuber crops of the Andes have not suffered the extent of genetic erosion as previously thought, and that, in spite of the introduction of modern cultivars, many of the rarer genotypes are still used. This argument overlooks the Promoting the conservation and use of underutilized and neglected crops. 21. 157 economic dimension of the problem. Even if a genotype survives in some remote location, it might become unreasonably costly to spot and collect it. It is therefore a good precautionary principle to preserve this material now, which has also been the rationale behind the collecting of arracacha germplasm in the past.
Since arracacha cannot be propagated from the storage root, which is the economic product, germplasm collections are not possible from markets, unless the rootstock is on offer which seems to be exceedingly rare and restricted to parts of Colombia (see Section 5). Collecting localities given in catalogues (Arbizu and Robles 1986; Tapia et al. 1996), therefore, nearly always represent actual growing sites.
Cormels are available from arracacha plants in all stages of development and this in combination with the year-long crop duration ensures accessibility to cormels yearround. Even when the crop has been harvested, its crowns (aboveground plant parts) are stored and farmers are normally willing to derive cormels for the visitor. The crowns are not eaten and, since they are stored far in excess of re-planting needs, they are not as highly valued as other (edible) tubers upon which poor people rely in periods of food scarcity. Obviously, collecting at harvest time is more rewarding to germplasm collectors as they can observe root and plant morphology and record uses. Once collected, the cormels can be stored conveniently in paper bags for several weeks at ambient temperatures. On arrival at the genebank, the cormels should be cleaned and surface-sterilized. It is also possible to excise meristems or shoot-tips from the cormels for tissue culture.
Herbaria will be of virtually no help to map out promising areas for arracacha germplasm explorations because of the scarcity of herbarium specimens both in Latin America and in collections known for their New World holdings (for example Missouri and New York Botanical Gardens). Sexual seeds are rarely available from fields and they are of little significance to the germplasm collector.