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Báo cáo khoa học: Mating system in a clonal Douglas fir (Pseudotsuga menziesii (Mirb) Franco) seed orchard. II. Effective pollen dispersal

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Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp quốc tế đề tài: "Mating system in a clonal Douglas fir (Pseudotsuga menziesii (Mirb) Franco) seed orchard. II. Effective pollen dispersal...
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Báo cáo khoa học: "Mating system in a clonal Douglas fir (Pseudotsuga menziesii (Mirb) Franco) seed orchard. II. Effective pollen dispersal" article Original Mating system in a clonal Douglas fir (Pseudotsuga menziesii (Mirb) Franco) seed orchard. II. Effective pollen dispersal D Prat Laboratoire INRA-ENGREF de sciences forestières, 14, Girardet, 54042 France Nancy cedex, rue (Received 15 February 1994; accepted 4 July 1994)Summary — Genetic variation of effective pollen received by individual ramets in a Douglas fir clonalseed orchard was not representative of the genetic variation of this clonal seed orchard. This deviationwas not due to selfing rate. Effective pollen dispersal might be responsible for this deviation. It was thenassessed around 3 individual ramets by comparing genotypes of effective pollen with those of pollinatorand surrounding trees located in a circle or in an ellipse focused on the receptor tree. The best predictionof genetic diversity of effective pollen was obtained considering a maximum pollination distance ofabout 20-30 m and an elliptical pollen dispersal. Effective pollen dispersal took place preferentially alongrows of trees and probably depended on the wind. As the flowering period was short and particularlysynchronous in the year of seed collection, reproductive phenology probably did not favour somepeculiar crosses. Matings between a few neighbour trees was probably the major cause of the homozy-gosity level in seed crop.isozyme / mating system / pollen dispersal / Pseudotsuga menziesii= Douglas fir / surroundingtreesRésumé — Régime de reproduction dans un verger à graines de Douglas (Pseudotsuga men-ziesii (Mirb) Franco. II. Dispersion du pollen. La diversité génétique du pollen reçu par des rametsindividuels d’un verger clonal à graines de Douglas n’était pas représentative de la diversité géné-tique de ce verger. Ceci ne résultait pas du taux d’autofécondation, comme l’ont montré des études anté-rieures. Une dispersion réduite du pollen pouvait en être la cause. Aussi, la dissémination du pollen aété étudiée autour de 3 ramets particuliers en comparant la diversité génétique du pollen efficacequ’ils ont reçu à la diversité génétique des arbres proches situés dans un cercle ou une ellipse. Lameilleure prédiction de la composition du nuage pollinique efficace a été obtenue en considérant lesarbres pollinisateurs situés à une distance maximale de 20-30 m et en pondérant leurs flux polli-niques à l’aide d’un modèle de dispersion du pollen en ellipse. La dissémination du pollen a eu lieu prin-cipalement le long des lignes de plantation mais les vents dominants paraissent aussi avoir une* Present address: INRA, station d’amélioration des arbres forestiers, Ardon, 45160 Olivet, Franceinfluence. Lesdécalages phénologiques entre arbres ne semblent pas responsables de croisements car, l’année de la récolte, la période de floraison a été particulièrement brève et syn-préférentielschrone. Les croisements, qui ont lieu principalement entre les quelques arbres voisins, sont vraisem- principale cause des excès d’homozygotie observés dans la semence commerciale.blablement ladispersion du pollen / effet de voisinage / isoenzyme / Pseudotsuga menziesii Douglas / =régime de reproductionINTRODUCTION position. A study of pollen dispersal was required to explain these unexpected pat- terns of paternity.In a clonal seed orchard, the genetic quality The aim of the present study was toof the crop is mainly affected by the genetic describe pollen dispersal patterns in a clonalvalue of clones and by the mating system, seed orchard in order to explain the geneticespecially selfing (Sorensen and White, structure of the seed crop. The analysis of1988). Various analyses of mating systems pollen dispersal included a study of pollina-in seed orchard have thus been carried out ...

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