Populus nigra L. : Bilan des connaissances actuelles, le programme national de conservation, la constitution d'un reseau europeen

National audienc

Genetic variation of the riparian pioneer tree species Populus nigra L. 1. Study of population structure based on isozymes

International audienc

Genetic variation of the riparian pioneer tree species Populus nigra. II. Variation in susceptibility to the foliar rust Melampsora larici-populina

International audiencePartial resistance of Populus nigra L. to three races of the foliar rust Melampsora larici-populina Kleb. was studied in a field trial and in laboratory tests, using a collection of P. nigra originating from different places throughout France. No total resistance was found. The partial resistance was split into epidemiological components, which proved to be under genetic control. Various patterns of association of epidemiological components values were found. Principal components analysis revealed their relationships. Only 24% of the variance of the field susceptibility could be explained by the variation of the epidemiological components of susceptibility. This variable was significantly correlated with susceptibility to the most ancient and widespread race of the pathogen, and with the variables related to the size of the lesions of the different races. Analysis of variance showed significant differences in susceptibility between regions and between stands within one region. Up to 20% of variation was between regions, and up to 22% between stands, so that these genetic factors appeared to be more differentiated than the neutral diversity (up to 3.5%; Legionnet & Lefevre, 1996). However, no clear pattern of geographical distribution of diversity was detected

Pinus nigra network : France

International audienc

Sexual and asexual reproduction in natural stands of Populus nigra

19 ref.International audienc

Programme national de conservation de Populus nigra

National audienc

Intensification of agriculture, landscape composition and wild bee communities: A large scale study in four European countries

The impacts of agricultural practices and landscape composition on bee communities were investigated in 14 sites located in four Western European countries (Belgium, France, the Netherlands and Switzerland). Standardized interviews with farmers assessed agricultural practices in terms of agricultural inputs (nitrogen fertilization and pesticides), livestock density and crop types. The proportion of semi-natural habitats was calculated for each site. We showed negative effects of agricultural intensification on species richness, abundance and diversity of wild bees. By contrast, bee species richness increased with the amount of semi-natural habitats in the landscape. Using a co-inertia analysis, we found an opposition between two types of agricultural specialization: towards crop production or towards animal husbandry. Species richness, abundance and diversity of wild bees were greater in sites turned towards crop production. In these sites, flowering crops provided abundant food resources for bees whereas, in the other group of sites, intensive animal husbandry led to landscapes dominated by forage crops rather than flower-rich permanent grasslands. We also showed that bumblebees seemed to be less sensitive to agricultural intensification than solitary bees

Perspectives d'amélioration génétique des peupliers en France

National audiencePoplar national catalogue includes 22 cultivars. In fact, only five clones of foreign origin are largely planted. This narrow genetic base raises the problem of important sanitary risks. Two programmes are engaged in France on poplar breeding and genetics. The INRA breeding programme has two objectives : constitution of breeding populations of Populus nigra, P. deltoides and P. trichocarpa and clonal selection. Breeding populations are based on collections assembled and tested by INRA since 1964 and have been enlarged through factorial mating designs involving these three species. First selections are composed of clones of Populus deltoides for the South-West of France and interamericain hybrids for northern parts of France. The objective is registration in 2005. The AFOCEL breeding programme focuses on short term selection with release of new clones in five years. These clones come from foreign selections or after recombinations between these clones. New tools such as molecular markers are developed to test their potential for marker-aided selection.Le catalogue national des peupliers comprend 22 cultivars. Le constat est qu'en fait, seulement cinq clones, d'origine étrangère, sont largement diffusés. Cette base génétique réduite soulève le problème de risques sanitaires importants. La France présente deux programmes distincts d'amélioration génétique des peupliers. Le programme d'amélioration de l'INRA présente un double objectif d'amélioration de population de Populus nigra, P. deltoides et de P. Trichocarpa, et de sorties variétales. Les populations d'amélioration sont en cours de constitution à partir de collections de base rassemblées et testées depuis 1964 par l'INRA et à partir de plans de croisements factoriels impliquant ces trois espèces. Les premières sélections sont composées de clones de P. deltoides pour le Sud-Ouest de la France et d'hybrides interaméricains pour le Nord de la France. L'objectif est de proposer des clones à l'homologation en 2005. Le programme de sélection AFOCEL se focalise sur le court terme avec des sorties variétales prévues dans cinq ans. Ces clones proviennent de sélections étrangères ou de recombinaisons à partir de ces cultivars. De nouveaux outils biotechnologiques, comme l'utilisation de marqueurs moléculaires, sont en cours de développement pour une aide potentielle à la sélection