Genetic diversity of taro (Colocasia esculenta (L.) Schott) in Vanuatu (Oceania): an appraisal of the distribution of allelic diversity (DAD) with SSR markers

In Vanuatu, an oceanic archipelago located in south-west Pacific, taro (Colocasia esculenta (L.) Schott) is one of the staple crops. An eco-geographical survey of its genetic resources was conducted in ten villages, each located on a different island. A sample of 344 landraces referred as the National Sample (NS) was collected. Its genetic diversity was assessed using nine microsatellites markers and then was compared with an International Core Sample (ICS) that was previously distributed in the ten villages of the study in order to test the geographical distribution of allelic diversity as an effective mean for the on-farm conservation of root crops. The ICS was composed of 41 accessions, including 23 originating from South-East Asia. The molecular dataset revealed in the NS (1) 324 distinct multilocus genotypes, (2) six genetic clusters mainly differentiated by rare alleles, (3) a geographical structure of the genetic resources of taro based, within each village, on the dominance of one or two of these clusters rather that their exclusivity, and (4) an analogy between the patterns of dominant clusters between villages and the past and present social networks. In addition, accessions from the ICS revealed 52 new alleles. Based on these findings, we formulate hypotheses regarding the processes involved in the genetic diversification of taro in Vanuatu. We also discuss the use of this set of microsatellite markers along with the molecular dataset obtained from this study as effective tools to monitor the diversity and evolution of taro in the future.     

Impact of destroying the structure of model gels on volatile release

The release of a strawberry aroma from different composite gels taken as models of fruit preparations and from a sucrose solution was investigated. The composition of the model systems differed with regard to the gelling agent, either pectin or carrageenan, and to the rigidity of the gel. With the use of atmospheric pressure chemical ionization-mass spectrometry, the release profiles of the aroma compounds were determined under stirring. At the same time, purge and trap measurements were performed to determine the release profiles of the aroma compounds without stirring. The comparison of the patterns obtained using these two complementary methods made it possible to determine how the structure of the matrix, the mechanical treatment, and the properties of the aroma compound affect aroma release. A far greater proportion of the aroma compounds was retained in the fruit preparation systems than in the sucrose solution. The different release profiles could be interpreted in terms of the volatility of the aroma compounds and of their diffusion through the gels.     

Inter-Alu PCR like genomic profiling in banana

Alu sequences are a major repetitive element of the primate genome. To date Alu sequences have seldom been reported in plant genomes. We report here an inter-Alu PCR like genomic profiling in banana using a single primer designed from a human Alu sequence. The different Musa species involved in the complex genome of banana cultivars can thus be discriminated. The use of this technique for monitoring germplasm or genotyping cultivars is discussed. This revised version was published online in July 2006 with corrections to the Cover Date.