Factsheet Botanical Data: Yacón

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Authors: N. Dostert ; J. Roque; A. Cano; M. I. La Torre and M. Weigend. Publication: 2010 Drafting botanical monograph (factsheet) for Yacón.

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    FactsheetBotanical Data: Yacón Smallanthus sonchifolius  (Poepp.) H. Rob.      2 Project ........................................................................................................................................................................................................ Drafting botanical monographs (factsheets) for five Peruvian crops Factsheet – Botanical Data: Yacón – Smallanthus sonchifolius (Poepp.) H. Rob. ........................................................................................................................................................................................................ Authors: Nicolas Dostert, José Roque, Asunción Cano, María I. La Torre y MaximilianWeigendTranslation: Frederico LuebertCover picture: José Roque ........................................................................................................................................................................................................ Proyecto Perúbiodiverso – PBD: Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ) GmbH: Programa DesarrolloRural Sostenible – PDRSSecretaría de Estado de Economía Suiza – SECOMinisterio de Comercio Exterior y Turismo – MINCETUR Botconsult GmbHSan Marcos National University - Museum of Natural History ........................................................................................................................................................................................................    3 I.   B OTÁNY ...................................................................................................................................................................   Genus.   Smallanthus  belongs to the Asteraceae or Compositae family and is currently made up oftwenty-one species that used to be part of the genus Polymnia  (48, 49, 50, 67, 68, 69). Distributionof Smallanthus  is restricted to the Americas, and its center of diversity is in Central America and theAndes. Its species are, for the most part, perennial herbs; very rarely are they bushes or small trees.Only one is annual (17).Genus is characterized by surface (with slight indentions) and shape of the achenes (radiallythickened and laterally compressed), venation (almost always tri-nerved or palmate), presence ofone whorl on the outside of the phyllaries, lack of glands at the tip of the stamen, and shape of thehair on the corolla (with an acute tip). Morphology : S. sonchifolius  is a perennial herb that grows up to 1.5 m – 3 m in height and whosestem is cylindrical to angular, lined, hollow in maturity and densely pubescent at the apex (17, 67).Root system is formed by a rather ramified arrangement of adventitious roots and up to twentyfleshy, tuberous storage roots. The latter develop from a ramified system of subterranean rootstock,are primarily napiform, and can grow up to 25 cm in length and 10 cm in width and weigh between0.2 kg – 2.0 kg. Root bark and storage tissue color vary depending on clone: white, cream, pink(grooved), lilac, and even brown.Leaves are opposites with blades decurrent towards the petiole. Leaf blade is broadly ovate andhastate, connate or auriculate at the base; upper leaves are ovate-lanceolate; upper surface is hairyand the lower pubescent. Inflorescences are terminal, composed of 1 – 5 axes, each one with 3capitula; peduncles densely pubescent.Phyllaries are uniseried and ovates, up to 15 mm in length and 10 mm in width. Inflorescences(head) are yellow to orange with close to 15 ligulate flowers, which are female, have 2 or 3-teeth,and grow to 12 mm x 7 mm; disc flowers are male, about 7 mm long. Achene is, on average,between 3.7 mm – 2.2 mm (55), ellipsoidal, dark brown colored, with a smooth epidermis and a solidendocarp characterized by easy removal of the pericarp by slight rubbing. Some ecotypes do notproduce fruit and, if so, they are not viable (47). Taxonomy: Work carried out on Smallanthus  (or Polymnia  ) systematics has been almost entirelydone on herbarium specimens. At issue here is their reduced size and less than satisfactory qualitycaused by plant structure and size and limited access to most of the natural distribution areas. Forinstance, they generally lack subterranean organs (48, 67) and, consequently, determining SouthAmerican species is not an easy task (17).A new critical study of South American representatives of the genus is unquestionably necessary. Variability: Farmers can tell each yacon cultivar apart by stem and storage root color. There is,however, much less diversity in comparison with other comparable, useful plants. Estimates fornumber of cultivars place the figure somewhere between twenty and thirty (32, 33). Under controlledsituations, cultivars (i.e. genotypes) present significant differences in terms of these characteristics:storage root shape and weight, yield, and sugar, phenol, and DNA content as well as leafisoenzymes (18, 26, 27, 28, 29, 30, 35, 38, 62).Tello speaks of two phenotypic centers of diversity in Peru: the South, which encompasses theeastern slopes of the Andes found in the departments of Cuzco and Puno, and the North, comprisedof the Cajamarca and Contumaza provinces in the department of Cajamarca (60). Seminario et al.discuss finding four morphotypes in the North, set apart by different descriptors such as root colorand leaf shape, with type III the most frequent there, especially in zones where yacon iscommercially grown (52).    4 Mansilla furthermore brings up the fact that germplasm banks at the National Agricultural ResearchInstitute (INIA), International Potato Center (IPC), the National University of Cajamarca (NUC), andSan Antonio Abad University (SAAU) in Cuzco store 323 yacon clones; these institutions have alsoidentified thirty-five different morphtypes: 9 at INIA, 10 at IPC, 8 at NUC, and 8 at SAAU. Basedupon his study, he was able to conclude the central part of the country is where the greatestdiversity is found (34). II.   D IAGNOSTIC FEATURES AND POSSIBLE CONFUSIONS …….......................   Besides S. sonchifolius  , there are six other Smallanthus  species recognized in Peru (5). Two ofthese ( S. riparius  (H.B.K.) H. Rob. and S. siegesbeckius  (DC.) H.   Rob.) are deemed to belong to thesame group as yacon (a.k.a. “yacon group”) and are closely related to S. sonchifolius  due todistribution, habit, and morphology (17).Consequently, diagnostic features used by Wells are not always easy to interpret (see Table 1) (67),but, because yacon (or llacon) only reproduces vegetatively and is not harvested in wild populations,there is no real risk in confusing it with other species.   Table 1 : Diagnostic features of Peruvian Smallanthus  species within the “yacon group” (67) Feature S. siegesbeckius S. riparius S. sonchifolius  Disk flowersTubular flowers  Number ≤ 15 Number ≥ 30 Number ≥ 60 Ligulate flowers  5 – 6 mm long ≥ 10 mm long ca. 12 mm long Phyllaries   ≤ 1 cm ≥ 1 cm ≤ 15 mm long and ≥ 10 mm broad Palea  Involute margin Non-involute margin
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