Cultivation and possible domestication of feral and possibly wild yams (Dioscorea spp.) in Southwest Ethiopia: ethnobotanical and morphological evidence.

The far Southwest Ethiopians transplant wild plant species to their gardens. One of such plant is the Dioscorea that we studied to assess the knowledge of wild yam and process of domestication. The study links two types of evidence to obtain insight about the process of yam domestication. We analyze two data sets derived from (1) ethnobotanical survey using 231 semi-structured interviews; and (2) morphological study in 47 yam accessions. Our study revealed that domestication is still active in some villages. Knowledge of yam domestication was shared by 44% of the farmers' even by those that have never practiced its domestication. Farmers who can describe the trend of domestication and the morphotypes of domesticate represented 21 and 28%, respectively. Farmers who have recent transplants in their garden varied from 4% in Bench to 10% in Sheko. The domestication process described by the two ethnic groups is similar. The duration of domestication can take up to six years, but with most of the individuals, it only takes three to five years. By linking the two types of evidence, two evolutionary processes are distinguished: (1) populations of recent domesticate expressing a domestication syndrome possibly belongs to the wild D. abyssinica or D. praehensilis, and (2) plants of incipient domesticate that might be derived from volunteers or diverse types of hybrids. Each of these processes can lead to integration of wild genotypes into the cultivated gene pool, and hence, enhance genetic diversity of cultivated yams. The domestication practices of traditional farmers should thus be taken into account if yam conservation and improvement plans need to be established.

Indigenous biosystematics of yams (Dioscorea spp.) in Southwest Ethiopia: folk taxonomy, ethnolinguistic analysis, and folk descriptors.

BACKGROUND: In Southwest Ethiopia, various plant species are coexisting in wild and cultivated forms. This provides an ideal setting for studying folk biosystematics of neglected species. One of such species is the Dioscorea species, in which we studied to assess the commonly applied folk wisdom of identifying, naming, and classifying yams by Sheko and Bench farmers. METHODS: This study was conducted in Bench-Maji and Sheka Zones using 272 farmers. Data on the lists of local names and system of folk taxonomy; the inherent logic, etymons, and consistency of names; and the folk descriptors and other criteria involved in taxonomy were collected. Data were collected by establishing participatory research appraisal tools, i.e., informant interviews and researcher direct observation. RESULTS: The result suggests that there exists a well-developed folk taxonomic system in Sheko and Bench. This is evident in the recognition of four distinct folk ranks: sub-variety, variety, supra-variety, and folk generic. Taxa assigned to each ranks have distinct features that mark them as members of a separate categories. Farmers over-differentiate 58 individual taxa at the intraspecific levels. Of these, 37 represented varietal taxa while the rest are sub-varietal taxa. Structurally, over 78% of the varieties are labeled with unitary names while all the sub-varieties consisted of binomial names. Farmers used a total of 26 characters and 74 character states for identifying the different taxa. More than 84% of these refer to aspects of plant characteristics. Tuber characters played a key role in the local identification of varietal and sub-varietal taxa while contexts and gender played a key role in the recognition of supra-variety groups. CONCLUSIONS: This study documented a great wealth of knowledge on indigenous biosystematics of yams, constitutes an essential step towards setting development priorities aimed at in situ conservation. The study clearly demonstrated the value of folk biosystematics for assessing the actual extent and spatial dynamics of yam diversity in traditional farming.