This study aims to understand the genetic diversity of traditional Oceanian starchy bananas in order to propose an efficient conservation strategy for these endangered varieties. SSR and DArT molecular markers are used to characterize a large sample of Pacific accessions, from New Guinea to Tahiti and Hawaii. All Pacific starchy bananas are shown of New Guinea origin, by interspecific hybridization between Musa acuminata (AA genome), more precisely its local subspecies M. acuminata ssp. banksii, and M. balbisiana (BB genome) generating triploid AAB Pacific starchy bananas. These AAB genotypes do not form a subgroup sensu stricto and genetic markers differentiate two subgroups across the three morphotypes usually identified: Iholena versus Popoulu and Maoli. The Popoulu/Maoli accessions, even if morphologically diverse throughout the Pacific, cluster in the same genetic subgroup. However, the subgroup is not strictly monophyletic and several close, but different genotypes are linked to the dominant genotype. One of the related genotypes is specific to New Caledonia (NC), with morphotypes close to Maoli, but with some primitive characters. It is concluded that the diffusion of Pacific starchy AAB bananas results from a series of introductions of triploids originating in New Guinea area from several sexual recombination events implying different genotypes of M. acuminata ssp. banksii. This scheme of multiple waves from the New Guinea zone is consistent with the archaeological data for peopling of the Pacific. The present geographic distribution suggests that a greater diversity must have existed in the past. Its erosion finds parallels with the erosion of cultural traditions, inexorably declining in most of the Polynesian or Melanesian Islands. Symmetrically, diversity hot spots appear linked to the local persistence of traditions: Maoli in New Caledonian Kanak traditions or Iholena in a few Polynesian islands. These results will contribute to optimizing the conservation strategy for the ex-situ Pacific Banana Collection supported collectively by the Pacific countries.

Bioversity International Parc Scientifique Agropolis 2 F 34397 Montpellier Cedex 5 France

Centre de Coopération Internationale en Recherche Agronomique pour le Développement Avenue Agropolis F 34398 Montpellier Cedex 5 France

Institut Agronomique néo Calédonien Connaissance et Amélioration des Agro Systèmes BP 32 98880 La Foa Nouvelle Calédonie

Institute of Experimental Botany Centre of the Region Haná for Biotechnological and Agricultural Research Šlechtitelů 31 CZ 78371 Olomouc Czech Republic

Pacific Community Land Resources Division Centre for Pacific Crops and Trees Private Mail Bag Suva Fiji Islands

Service du Développement Rural Département de la Recherche Agronomique BP 100 98713 Papeete Tahiti Polynésie française

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