Jean-Michel Favre

Genomic organization of molecular differentiation in Norway spruce (Picea abies).

Diversity and differentiation among three populations representing the geographical domains commonly recognized within the natural distribution area of Picea abies were analysed by using a set of 292 AFLP (amplified fragment length polymorphism), SSR (single sequence repeat) and ESTP (expressed sequence tags polymorphism) markers. As usually observed in forest trees, results showed high within‐population diversity (HS reaching 0.79) and low among‐population differentiation (GST≈ 2%). The genomic organization of differentiation was then investigated on the basis of a subsample of 150 AFLP, SSR and ESTP mapped markers. The number of the loci differentiating the Baltico‐Nordic from the central European populations (25 loci) and, within the central European populations, the Alpine from the Hercyno‐Carpathian populations (12 loci), were different. These 37 differentiated loci, with individual GST values ranging from 0.008 to 0.20, were evenly distributed on all linkage groups and mostly followed the neutral expectations, suggesting genome‐wide effects on differentiation. Nine of them however behave as ‘outlier’ loci indicating possible locus‐specific selective effects. Contribution of ongoing evolutionary forces and historical effects to the geographical differentiation of the species are discussed.

Early changes in auxin and ethylene production in vine cuttings before adventitious rooting

Node cuttings of ‘in vitro’ cultured grapevine were rooted in absence of any growth regulator, before the onset of the axillary bud. There were two peaks of ethylene production at 2 and 10–12 h, well marked in the top and bottom portions of the cuttings for the former. The level of IAA increased in the basal portions of the cuttings only, from the 4th hour, and culminated at the 24th hour. The wound ethylene of the first rise might be initiating the sequence of reactions leading to root formation. The second ethylene rise might result from the beginning of the increase of the IAA level.

High subculture frequency, maltose-based and hormone-free medium sustained early development of somatic embryos in maritime pine

SummaryEmbryonal-suspensor mass (ESM) lines characterized by a spiky, morphotype (i.e., developed, early embryos escaping from the ESM periphery) were recently shown to produce the best maturation yields in Maritime pine. How to select or preserve such a valuable morphotype during ESM maintenance (prior to maturation treatment) is still unknown. Several maintenance procedures were tested; 2400 ESM from 10 lines were subcultured each, 7 or 14 d on maltose- or sucrosecontaining medium without plant growth regulator (PGR) or supplemented with 2,4-dichlorophenoxyacetic acid and 6-benzylaminopurine or a low concentration of, abscisic acid. Multiple components analyses based on growth rate, macromorphology data, and micromorphology data, collected for 6 mo., allowed for the association, of the spiky morphotype with additional traits (defining the phenotype I) such as whitish aspect, high vigor, high growth rate, and complex cellular organization (resulting from high early embryogenic ability). Since a gradual increase in growth rate as well as a decrease in cellular organization were concomitantly, observed during the 6 mo, experiment, we concluded that ESM growth and early somatic embryo development were disconnected. In some lines, the progressive loss of early embryogenic, ability (aging process) could be decreased using maltose-based and PGR-free medium. For most lines, the aging effect was minimized using a weekly subculture. An improved procedure for ESM maintenance prior to the maturation step is thus proposed.

Does maternal environmental condition during reproductive development induce genotypic selection in Picea abies

In forest trees, environmental conditions during reproduction can greatly influence progeny performance. This phenomenon probably results from adaptive phenotypic plasticity but also may be associated with genotypic selection. In order to determine whether selective effects during the reproduction are environment specific, single pair-crosses of Norway spruce were studied in two contrasted maternal environments (warm and cold conditions). One family expressed large and the other small phenotypic differences between these crossing environments. The inheritance of genetic polymorphism was analysed at the seed stage. Four parental genetic maps covering 66 to 78% of the genome were constructed using 190 to 200 loci. After correcting for multiple testing, there is no evidence of locus under strong and repeatable selection. The maternal environment could thus only induce limited genotypic-selection effects during reproductive steps, and performance of progenies may be mainly affected by a long-lasting epigenetic memory regulated by temperature and photoperiod prevailing during seed production.RésuméChez les arbres forestiers, les conditions environnementales durant la reproduction peuvent influencer les performances des descendants. Ce phénomène reflète probablement la plasticité phénotypique, mais également il pourrait être associé à une sélection génotypique. Afin de déterminer si des effets sélectifs durant la reproduction sont spécifiques d’un environnement donné, deux familles d’épicéa commun non apparentées ont été obtenues par croisements dirigés dans deux environnements maternels contrastés (conditions chaude et froide). La première famille exprimait de larges différences phénotypiques entre les deux environnements tandis que la seconde ne montrait pas de différence significative. La transmission des polymorphismes génétiques a été étudiée au stade de la graine. Quatre cartes génétiques parentales couvrant 66 à 78 % du génome ont été construites. Aucun effet de sélection n’a été mis en évidence aux différents locus étudiés. L’environnement maternel n’induirait donc que des effets de sélection génotypique relativement faibles durant les stades de la reproduction. Les performances des descendants seraient principalement affectées par une mémoire épigénétique durable régulée par la température et la photopériode régnant durant la production des graines.