Genetic Diversification and Dispersal of Taro (Colocasia esculenta (L.) Schott).

Taro (Colocasia esculenta (L.) Schott) is widely distributed in tropical and sub-tropical areas. However, its origin, diversification and dispersal remain unclear. While taro genetic diversity has been documented at the country and regional levels in Asia and the Pacific, few reports are available from Americas and Africa where it has been introduced through human migrations. We used eleven microsatellite markers to investigate the diversity and diversification of taro accessions from nineteen countries in Asia, the Pacific, Africa and America. The highest genetic diversity and number of private alleles were observed in Asian accessions, mainly from India. While taro has been diversified in Asia and the Pacific mostly via sexual reproduction, clonal reproduction with mutation appeared predominant in African and American countries investigated. Bayesian clustering revealed a first genetic group of diploids from the Asia-Pacific region and to a second diploid-triploid group mainly from India. Admixed cultivars between the two genetic pools were also found. In West Africa, most cultivars were found to have originated from India. Only one multi-locus lineage was assigned to the Asian pool, while cultivars in Madagascar originated from India and Indonesia. The South African cultivars shared lineages with Japan. The Caribbean Islands cultivars were found to have originated from the Pacific, while in Costa Rica they were from India or admixed between Indian and Asian groups. Taro dispersal in the different areas of Africa and America is thus discussed in the light of available records of voyages and settlements.

Impact of past climatic and recent anthropogenic factors on wild yam genetic diversity.

Forests of the Dahomey Gap are considered as refugia for many species. They play a crucial role in providing ecosystem services in an area devoid of forests. However, the impact of the way they are managed on the biodiversity they host has barely been investigated. Wild yams existing in these forests play a crucial role in maintaining the genetic diversity of cultivated yams. Indeed, studies of farmer practices have shown that, by way of ennoblement, wild yams collected and selected in the forests and old fallow areas are integrated into the cultivated pool. However, the genetic structure of wild yams is poorly understood. Using nine microsatellite loci, we investigated the population genetics of Dioscorea praehensilis in five forests in Benin, involving different management strategies and bioclimatic areas. Populations of D. praehensilis were strongly differentiated, consistent with an ancient separation of the forests. While the D. praehensilis population in a holly forest was undergoing mutation and drift equilibrium, the population collected from the most conserved forest was in a bottleneck. Moreover, in two forests with different management strategies, accessions from other forests were found, resulting from the displacement of yams following farmer migrations. No isolation by distance was detected, but a differentiation was found between populations of the Sudano-Guinean climate and the Guineo-Congolian climate. Our findings suggest differentiation due to forest isolations under past climatic conditions and more recent tuber flow through anthropogenic impacts.

Permanent Genetic Resources added to Molecular Ecology Resources Database 1 June 2010 - 31 July 2010.

This article documents the addition of 205 microsatellite marker loci to the Molecular Ecology Resources Database. Loci were developed for the following species: Bagassa guianensis, Bulweria bulwerii, Camelus bactrianus, Chaenogobius annularis, Creontiades dilutus, Diachasmimorpha tryoni, Dioscorea alata, Euhrychiopsis lecontei, Gmelina arborea, Haliotis discus hannai, Hirtella physophora, Melanaphis sacchari, Munida isos, Thaumastocoris peregrinus and Tuberolachnus salignus. These loci were cross-tested on the following species: Halobaena caerulea, Procellaria aequinoctialis, Oceanodroma monteiroi, Camelus ferus, Creontiades pacificus, Dioscorea rotundata, Dioscorea praehensilis, Dioscorea abyssinica, Dioscorea nummularia, Dioscorea transversa, Dioscorea esculenta, Dioscorea pentaphylla, Dioscorea trifida, Hirtella bicornis, Hirtella glandulosa, Licania alba, Licania canescens, Licania membranaceae, Couepia guianensis and 7 undescribed Thaumastocoris species.

Use of cpSSRs for the characterisation of yam phylogeny in Benin.

The Dioscorea cayenensis - Dioscorea rotundata species complex is the most widely cultivated yam in West Africa. This species complex has been described as deriving from wild yams belonging to the Enanthiophyllum section through domestication by African farmers. To study patterns of yam evolution and to establish phylogenetic relationships existing between wild and cultivated species sampled in Benin, we investigated changes in chloroplast DNA simple sequence repeats (cpSSR) in 148 yam accessions selected to cover the wider possible genetic diversity existing in the country. Dioscorea cayenensis and D. rotundata share the same haplotype. The morphotype "abyssinica" appeared to be subdivided into 2 haplotypes. One of these haplotypes shares the same haplotype with the Dioscorea cayenensis - Dioscorea rotundata species complex and with morphotypes praehensilis, suggesting that they might belong to the same species. Relationships among sections Lasiophyton, Macrocapaea, Opsophyton, and Enanthiophyllum were clarified, and some taxonomic changes within the Enanthiophyllum section were suggested. Dioscorea minutiflora, D. smilacifolia, and D. burkilliana might be considered as 1 single genetic group, and they are suspected of belonging to the same species.

Transformation of haploid, microspore-derived cell suspension protoplasts of rice (Oryza sativa L.).

We compared the transient activity of three cereal gene-derived promoter-gus fusions and the efficiency of selection mediated by three different selectable genes in a polyethylene glycol transformation system with haploid cell suspension protoplasts of rice. The maize ubiquitin promoter was found to be the most active in transformed protoplasts, and selection on ammonium glufosinate mediated by the bar gene was the most efficient for producing resistant calluses. Cotransformation of protoplasts with two separate plasmids carrying the gus and the bar genes, at either a 2∶1 or 1∶1 ratio, led to 0.8 × 10(-5) and 1.6 × 10(-5) resistant callus recovery frequencies and 59.7 and 37.9 cotransformation efficiencies respectively. No escapes were detected in dot blot analyses of 100 resistant calluses with a probe consisting of the bar coding region. Cotransformation efficiency, based on resistance to basta and ß-glucuronidase staining of the leaf tissue of 115 regenerated plants, was 47%. Resistance tests and Southern analysis of seed progenies of three diploid transgenic plants demonstrated homozygous integration of multiple copies of the transgene at one locus at least in the first plant, heterozygous integration at one locus in the second plant and heterozygous integration at two loci in the third plant.

Plant regeneration from haploid cell suspension-derived protoplasts of Mediterranean rice (Oryza sativa L. cv. Miara).

More than 750 plants were regenerated from protoplasts isolated from microspore callus-derived cell suspensions of the Mediterranean japonica rice Miara, using a nurse-feeder technique and N6-based culture medium. The mean plating efficiency and the mean regeneration ability of the protocalluses were 0.5% and 49% respectively. Flow cytometric evaluation of the DNA contents of 7 month old-cell and protoplast suspensions showed that they were still haploid. Contrastingly, the DNA contents of leaf cell nuclei of the regenerated protoclones ranged from 1C to 5C including 60% 2C plants. This was consistent with the morphological type and the fertility of the mature plants. These results and the absence of chimeric plants suggest that polyploidization occurred during the early phase of protoplast culture.