Somaclonal variants of taro (Colocasia esculenta Schott) and yam (Dioscorea alata L.) are incorporated into farmers' varietal portfolios in Vanuatu

Taro (Colocasia esculenta) and the greater yam (Dioscorea alata) are staples in Vanuatu. The aim of the present study was to assess the role of somaclonal variations in the varietal diversification of these two clonally propagated crops. The study was conducted in six villages located each on distinct islands of Vanuatu, Melanesia. Overall, 203 varieties of taro and 80 varieties of yam were collected and DArTs were used for analysis. The overall quality of the DArT markers was high for both species. The percentage of polymorphic clones detected on the DArT array was low for taro (3 %) and high (13 %) for yam, with respectively 202 and 499 polymorphic clones. Each variety was characterized by its multilocus genotype based on its DArT presence/absence profile. For taro, the 203 varieties were represented by 126 unique genotypes and 34 distinct multilocus lineages (MLLs). The high number of unique genotypes and the presence of few varieties sharing a clonal origin, generated a high varietal richness index (R = 0.83). For yam, the 80 varieties were represented by seven unique genotypes and 16 MLLs. The low number of unique genotypes and the presence of numerous varieties sharing a clonal origin generated a low varietal richness index (R = 0.26). Possible factors contributing to these contrasting results are discussed. DArT markers provide evidence that somaclonal variants of taro and yam are selected as new varieties. Strategies aiming at strengthening communities' capacity to adapt to forthcoming changes should consider the introduction of allelic diversity into farmers' varietal portfolios. (Résumé d'auteur