2. LITERATURE REVIEW 2.1 Origin and distribution Tannia is native to tropical America, but is currently widely cultivated as a subsistence food crop in Asia, Africa and Polynesia (Bown, 2000). Of the five crops that fall into the Aroid subfamily, the only tannia came from Central and South America, others came from Southeast Asia (Lebot, 2009). When Europeans arrived, it was also known to be cultivated from southern Mexico to Bolivia in Latin America. Only during the 19th century did it spread widely throughout the tropical world. It is currently cultivated in tropical and subtropical areas, between 30⁰ north and 15⁰ south latitude. The main distribution areas of the crop include the Caribbean (Cuba, Dominican Republic, Puerto Rico, West Indies), Central and South America; United States (Florida, Hawaii), West Africa (Cameroon, Ghana, Nigeria, Togo) and tropical Asia (Indonesia, Malaysia, South Pacific Islands) (Perez, 2010). Tannia was introduced between the 16th and 17th centuries in central and West Africa, where it was given the common name cocoyam due to its resemblance to Colocasia. It was brought by Portuguese slavers to Sao Tome and Principe, where they had important trading bases, and was further spread by traders, missionaries and other travelers (Bown, 2000; George, 2011). It was introduced into Ethiopia in 1978 (Amsalu et al., 2008).2.2 BotanyTannia is a herbaceous, monocotyledonous, perennial plant, but for practical purposes it is harvested after 6 -12 months of growth (Castro, 2006; Ramesh et al. ., 2007; Photo briefly follows the C-3 route (kay, 1987). It can reach a height of about 2 m and have a short erect stem, presenting a corm or main underground stem in the centre...... paper ......l differences on the tannia accessions on the side length of the petiole, length and width of the leaf blade and size of the cormel. According to Lebot (2009), approximately 1000 accessions of X. sagittifolium, X. violaceum, nigrum, X. brasiliense and X. yucca have been collected from different parts of the world. Most have been collected from Cameroon, Equatorial Guinea, Gabon, Ghana and Togo the growth of numerous root and tuber crops; mainly in the southern and western parts of the country by small farmers (Asfaw, 2005). Both taro and tannia are grown mainly in the warm, humid areas of southwestern Ethiopia. A large tannia gene pool exists in farmers' fields and on farms in the area (Amsalu and Tesfaye, 2006), and more than 80 tannia accessions have been collected in the area (Amsalu et al., 2008).