Diversité chimique et biofortification des plantes à racines et tubercules tropicales cultivées : caractérisation des parents et élaboration de protocoles permettant l'optimisation de la sélection

Agronomie selection generates and maintains agrobiodiversity which can be regarded as an essential resource. To describe phenotypic diversity, genotypes as well as their chemical expression, chemotypes, have been widely used. Tropical root and tuber crops are vegetatively propagated and their genetic bases are often narrow. Therefore, unveiling the impressive phenotypic diversity is still rather difficult through genotyping alone, whereas chemotype studies are very informative. Tropical root crops are staples and represent a good source of compounds related to health benefits and used in food and pharmaceutical indu stries. Those crops have keyroles to play in food security for developing countries and so plant breeding cannot be neglected. Biofortification is effective and does not imply change of dietary behaviours. Analysing, computing and compiling data bases for chernical data on diversity of neglected crops are still needed. Biofortification involving mass selection and profiling of numerous accessions is , however, time-consuming. Thus, efficient protocols and tools facilitating this process are required. Chemotypic variability within Vanuatu germplasm was characterised through core samples from different species and relationships between primary compounds, secondary metabolites and local preferences have been studied. Useful correlations were shown, thus clarifying traditional selection process. This process has permitted the definition of ideotypes that will be interesting for the management of breeding programmes. At least for the two most important species in Vanuatu - taro Colocasia esculenta and the greater yam Dioscorea alata - our work is the fust broad screening of germplasm. The study of carotenoid and anthocyanin content indicates that sorne cultivars show potential for commercial exploitation. With the aim of improving staple foods by plant breeding, we identified accessions to be selected as parents for future crosses. (Résumé d'auteur)