2. LITERATURE REVIEW2.1 Origin and distributionTannia is native to tropical America, but is currently widely grown as a subsistence food crop in Asia, Africa and Polynesia (Bown, 2000). Of five crops belonging to the aroid subfamily, the only tannia came from Central and South America, the others came from Southeast Asia (Lebot, 2009). When Europeans arrived, it was further known that it was cultivated from southern Mexico to Bolivia in Latin America. It was not until the 19th century that it became widely distributed throughout the tropical world. Currently it is cultivated in tropical and subtropical zones, between latitudes 30⁰ North and 15⁰ South. The main areas of distribution 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 to Central America and West Africa, where it was given the common name taro due to its resemblance to Colocasia. It was introduced by Portuguese slavers to Sao Tome and Principe, where they had important trading bases, and later spread by traders, missionaries and other travelers (Bown, 2000; George, 2011). It was introduced to Ethiopia in 1978 (Amsalu et al., 2008).2.2 BotanyTannia is a herbaceous, monocotyledonous and perennial plant, but for practical reasons it is harvested after 6 to 12 months of growth (Castro, 2006; Ramesh et al., 2007; Synthetic photo, it follows route C-3 (kay, 1987). It can reach a height of about 2 m and have a short, erect stem, having a bulb or main underground stem in the middle of the paper......l differences between tannia accessions on the length of the petiole, length and blade width and cormel size. According to Lebot (2009), around 1000 accessions of X. sagittifolium, X. violaceum, X. nigrum, X. brasiliense and X. yucca have been collected from different parts of the world. The majority was collected in Cameroon, Equatorial Guinea, Gabon, Ghana and Togo. Ethiopia, with its diverse agroecologies and suitable environments, allows the growth of many root and tuber crops; mainly in the south and west of the country by small farmers (Asfaw, 2005). Taro and tannia are grown mainly in the hot and humid areas of southwestern Ethiopia. In the region, there is a large tannia gene pool in farmers' fields and farms (Amsalu and Tesfaye, 2006), and more than 80 tannia accessions have been collected in the region (Amsalu et al.., 2008).