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Contact: berville@supagro.inra.fr; The genetic base of sunflower elite lines is very narrow, due to many years of selection and breeding. To broaden the genetic diversity of the cultivated sunflower, in 1995 73 wild sunflower populations were crossed with 3 cultivated lines (Testers), and 219 hybrid offspring's were evaluated in the field. GCA and SCA effects were computed suggesting for all traits a genetic potential for improvement through selection. Study of the hybrids revealed that the wild accessions bear different genetic abilities to combine with the testers for traits of morphological architecture, phenology and yield (seed weight and seed oil). The variance due to GCA and SCA showed that gene action was additive for days to flowering, branching and plant height. Genotypes derived from the same geographic origin may have either good or poor general combing ability. The correlation between GCA and per se genotype performance was positive for all traits except for seed oil content. This was the first attempt to evaluate wild-cultivated hybrids in sunflower on a large scale and will be the starting point for the management of hybrid Helianthus annuus populations for breeding. GCA and SCA estimations will facilitate the definition of strategies to manage and exploit the natural diversity for this crop

Apart from the wild species P. orientalis and P. occidentalis, the cultivated plane trees constitute a wide and heterogeneous group, with uncertain genetic status and largely debated names. The recent canker stain problem in Europe makes it necessary at the present time to consider the genetic resources and to determine the genetic bases of all these trees. To attain this objective, a genetic molecular approach was used to analyze 60 trees of P. orientalis and P. occidentalis,different London planes (P. hispanicaand P. densicoma), a few controlledP. occidentalis × P. orientalishybrids and particular trees from arboreta and old parks. Molecular analysis involved thirty RAPD fragments generated with nine primers, PCR-RFLP in the 5S RNA genes and mitochondrial polymorphisms revealed by RFLP method. Clones were recognized amongP. hispanica and P. densicomatrees. A Correspondence Analysis and a dendrogram constructed according to the genetic distances confirmed the supposed hybrid origin of P. hispanica and P. densicoma between P. occidentalisand P. orientalis. Contribution ofP. orientalis to their constitution seems more important than that of P. occidentalis. Mitochondrial DNA polymorphisms indicated that crosses occurred in both directions. Moreover, P. occidentalis as female parent led toP. densicoma whereas P. orientalis as female parent led to P. hispanica. Low prevalence of pure species individuals and confusion risks with hybrid trees even for old trees are highlighted.