New insights in the recognition of the European ash speciesFraxinus excelsiorL. andFraxinus angustifoliaVahl as useful tools for forest management

Abstract

-Common ash (Fraxinus excelsior L.) and narrow-leaved ash (F. angustifolia Vahl) are the most common ash species in Western Europe. The former is considered to be a highly valuable timber tree and contamination of its seed lots by the latter is strongly undesirable. We studied molecular, physiological and morphological characteristics that can help to detect the presence of F. angustifolia at the population level, either in seed and/or seedling samples, or in adult ash leave samples from natural or managed populations. First we developed two molecular markers, which correspond to a RAPD-SCAR marker and a nuclear microsatellite-derived marker. Results indicate that these markers are almost specific to one or the other species for a set of populations sampled across Europe. Second, first year dormancy was studied using germination tests without stratification. F. excelsior seeds did not germinate at all, while germinations were observed in samples of F. angustifolia and introgressed populations after 16 weeks. In addition, F. angustifolia embryo/seed length ratios at the dispersal stage were significantly higher than those from F. excelsior populations. This study provides straightforward and robust tools for avoiding commercial problems of impurity of seed lots and can help forest managers to certify common ash stands.ashes / RAPD-SCAR / dormancy / discriminant markers / hybridization Résumé -De nouveaux outils pour la reconnaissance des frênes européens Fraxinus excelsior L. et F. angustifolia Vahl : une aide au diagnostic. Le frêne commun (Fraxinus excelsior L.) et le frêne oxyphylle (F. angustifolia Vahl) sont les deux espèces de frêne les plus répandues en Europe occidentale. Le frêne commun étant le seul à posséder une importante valeur commerciale, la contamination de lots de graines par du frêne oxyphylle est fortement indésirable. Nous avons étudié des caractéristiques moléculaires, morphologiques et physiologiques qui pourront se révéler très utiles à la détection de la présence de F. angustifolia à l'échelle populationnelle, dans des lots de graines ou de semis, ainsi que dans des échantillons de feuilles d'arbres adultes issus de populations naturelles ou exploitées. Nous avons développé deux marqueurs moléculaires, un SCAR-RAPD et un marqueur issu d'un locus microsatellite nucléaire. Testés sur un ensemble de populations européennes, ces marqueurs se sont révélés quasi-spécifiques de l'une ou l'autre des deux espèces. D'autre part, nous avons étudié la dormance des graines en première année par des tests de germination sans stratification. Aucune germination n'a été observée sur un ensemble de descendances de frêne commun, alors que des germinations ont été observées sur toutes les descendances de frêne oxyphylle après seize semaines, ainsi que sur certaines descendances issues de populations introgressées. Enfin, nous avons montré que les embryons de F. excelsior à maturité dispersive occupent significativement moins de place dans la graine que ceux de F. angustifolia. Cette étude permet de ...

Variabilité génétique des populations tunisiennes de Myrtus communis L. (Myrtaceae) estimée par des marqueurs isoenzymatiques et moléculaires (RAPD)

“…RAPD markers (Random Amplified Polymorphic DNA) are selectively neutral, involve a large number of loci and cover a larger part of the genome. They also provide more valuable information into population differentiation and help to elaborate efficient conservation strategies [16,18,23,42]. However, most RAPD loci are assumed to possess only two alleles and segregate as dominant markers, leading to an underestimation of the genetic diversity [30,45].…”

Molecular characterization and genetic relationships among most common identified morphotypes of critically endangered rare Moroccan species Argania spinosa (Sapotaceae) using RAPD and SSR markers

“…These markers are especially used in the molecular characterization of rare species including argan which are poorly known from the molecular point of view. The most crucial factor for this technique is the DNA quality and concentration offering the advantage of rapid screen for polymorphisms (Dax et al, 1993;Gérard et al, 2006). On the other hand, Simple sequence repeat (SSR) markers (microsatellites), also based on the PCR technique, are currently becoming the markers of choice for genetic fingerprinting studies because of their high polymorphism, co-dominance, multiallelism, abundance and uniform dispersion in plant genomes (de-Lucas et al, 2008;Gupta et al, 1996).…”

Morphological variability of Fraxinus angustifolia Vahl in the north-western Balkans

“…Extant genetic analyses of F. angustifolia have dealt with its variability in natural populations [18] and differences compared to F. excelsior [5,7,21]. The species was also included in a study of phylogenetic relationships in the genus Fraxinus [3,4].…”