Changes in soluble phenol contents of Scots-pine {Pinus sylvestris) phloem were studied after inoculation with Ophiostoma brunneo-ciliatum, a fungus associated with Ips sexdentatus. They were compared to the length of the fungus-induced reaction zone of the phloem, taken as an estimation for the trees' response efficiency against aggression.Five clones consisting of 14 trees were studied, and eight soluble phenolic metabolites were analysed in detail in reaction zones and in unwounded phloem sampled 3 weeks after inoculation.The stilbenes pinosylvin and pinosylvin monomethylether, and the flavonoid pinocembrin, were detected in reaction zones only. Concentrations of two p-coumaric-acid esters and an acetophenone glycoside decreased after inoculation. Variations of the flavonoids taxifolin and 3' taxifolin glucoside were inconsistent.One tree had longer reaction zones and a phenolic content different from the others. In unwounded phloem, concentrations of some phenolic compounds and in particular the ratio between the two pcoumaric-acid esters could be markers for trees' response efficiency. In the reaction zone, markers could be the ratios between concentrations of certain preformed compounds and concentrations of newly synthesized pinosylvin and pinocembrin.

Two fungus and one bark beetle species were introduced into Scots pine phloem'. The phenolic composition of the induced reaction zone in the phloem, studied by two dimensional thin layer ehromatography, greatly differed from that of the uninjured phloem. The eoneentration of three compounds increased, one of them considerably, while the concentration of four others decreased. These modifications were the same irrespeetive of the nature of the aggressor.

Summary — The relationships between quantitative variations of 2 flavanonols in Scots pine needles and Diprion pini larvae mortality were studied. Those 2 compounds were characterized as taxifolin (T) and its glucoside (TG) after hydrolysis and analysis by TLC, HPLC and spectrophotometry. Quantitative differences between 30 clones were more important for TG than for T, nevertheless clones which presented a content of taxifolin higher than 1.5 mg g -1 DW showed a T/TG ratio equal to or greater than 0.5 (fig 2). Quantitative changes were also observed throughout the year. The amount of taxifolin peaked in autumn as those of its glucoside decreased (fig 3). Darkness also induced a gradual increase of T but no significant effect on TG (fig 4). Storage of twigs during feeding tests and insect defoliation both induced a strong glucosilation of taxifolin in needles (table I). High rates of mortality of Diprion pini larvae were associated with the presence of T and TG both in needles and faeces ( (fig 3). De même, l'effet de l'obscurité sur les rameaux provoque une

Foliage edibility of Scots Pine clones for Diprion pini L. (Hym., Diprionidae). II. Relationships between the content of phenols within the needles and the mortality of D. pini larvae A comparative study has been done on the polyphenolic content of leaves sampled on 20 different clones of Scots pine by means of thin layer chromatography. Typical variations have been observed between these clones which were characterized by the lack or the presence of the hydroxycinnamic and stained compound by DMACA (F1 and F2) groups. The presence of these 2 last compounds seems to be linked to high rates of larva mortality (till 90 %) of Diprion pini which have been feeded by leaves coming from the clones. But, these results show that a precise study on the relationship leave‐insect should be lead in order to determine the right origin of the leave toxicity. Résumé Une étude qualitative et comparative du contenu polyphénolique a été menée sur les feuilles de différents clones de pins sylvestre au moyen de la Chromatographie bidimensionnelle sur couche mince de cellulose. D'importantes variations interclonales ont été mises en évidence par la présence ou l'absence de 2 groupes de composés: les acides hydroxycinnamiques et les composés réagissant au DMACA. La présence de ce dernier groupe de composés semble liée à des taux de mortalité élevés, pouvant atteindre 90 % après 9 jours, des larves de Diprion pini alimentées par le feuillage de ces clones. Cependant, l'ensemble des résultats montrent qu'une étude plus approfondie sur la relation feuille‐insecte devra être conduite en vue de déterminer la nature précise de la toxicité du feuillage. Zusammenfassung Zum Nahrungswert verschiedener Klone von Pinus sylvestris für Diprion pini L. (Hym., Diprionidae). II Beziehungen zwischen dem Phenolgehalt der Kiefernnadeln und der Mortalität von D. pini Es wurde der Phenolgehalt der Nadeln von 20 verschiedenen Klonen von Pinus sylvestris chromatographisch bestimmt. Dabei ergaben sich typische Variationen zwischen den Klonen, die durch die Anoder Abwesenheit der Phenolgruppen F1 und F2 charakterisiert waren. Die Anwesenheit der beiden Gruppen schien mit hohen Mortalitätsraten (bis 90 %) der Diprion‐Larven verbunden zu sein. Jedoch zeigen die Ergebnisse, daß für ein präzises Studium des Nadel/Insekt‐Komplexes die Bestimmung des Ursprungs der Nadel‐Toxizität erforderlich ist.

Foliage edibility of different Scots Pine clones for Diprion pini L. (Hym., Diprionidae) III. Prospects for a genetic improvement of Pinus sylvestris Feeding tests of Diprion pini L. larvae have shown significant differences in needle nutritional capacity of 2 natural provenances and 27 Scots pine clones. Results are discussed for their interest in Scots pine breeding program. The distribution of “foliage noxiousness for Diprion” genetic variability must be carried on at both, provenance and individual level. The various modifications observed on insect development lead the breeder to consider foliage noxiousness as a complex quantitative trait, probably polygenic. On a methodological point of view, a relationship might exist between the presence in needles of 2 phenolic compound groups and foliage noxiousness. Nevertheless, these biochemical compounds can't be used as reliable genetic markers of Scots pine resistance to Diprion pini L. Résumé Des tests d'alimentation de larves de Diprion pini L. ont mis en évidence de fortes différences de qualité nutritionnelle des aiguilles entre 2 provenances naturelles et 27 clones de pin sylvestre. Les résultats sont discutés dans le cadre d'une stratégie d'amélioration du pin sylvestre. L'étude de l'organisation de la variabilité génétique du caractère «nocivité du feuillage pour le Diprion» mérite d'être poursuivie conjointement aux niveaux provenance et individuel. Les différentes perturbations observées sur le développement de l'insecte conduisent l'améliorateur à considérer la nocivité du feuillage comme un caractère quantitatif complexe, déterminé probablement par un grand nombre de gènes. Sur le plan méthodologique, la présence dans les aiguilles de 2 groupes de composés phénoliques semble être liée à la comestibilité du feuillage sans constituer un marquage génétique fiable des clones défavorables au Diprion. Zusammenfassung Zum Nahrungswert verschiedener Klone von Pinus sylvestris für Diprion pini L. (Hym., Diprionidae) III. Aussichten für eine genetische Verbesserung von Kiefern Fütterungsversuche haben gezeigt, daß sich der Nahrungswert von Kiefernnadeln zweier Herkünfte und 27 Klone für Diprion pini signifikant unterscheidet. Diese Ergebnisse werden im Hinblick auf ihre Bedeutung für ein Kiefernzuchtprogramm diskutiert. Die Untersuchungen zur genetischen Variablität von Kiefern, deren Nahrungswert für D. pini ungenügend ist, müssen sowohl auf der Ebene der Herkünfte als auch der der Individuen durchgeführt werden. Aufgrund der verschiedenartigen Störungen, die während der Entwicklung von D. pini auftreten, muß die Nichteignung einiger P. sylvestris‐Herkünfte/Klone als ein komplexes, quantitatives, vermutlich polygenetisches Problem angesehen werden. Aus methodischer Sicht könnte eine Beziehung zwischen dem Vorhandensein von 2 phenolischen Gruppen in den Nadeln und der Nichteignung der Nadeln als Futter für D. pini bestehen. Jedoch können diese biochemischen Komponenten nicht als zuverlässige genetische Kennzeichen für die P. sylvestris‐Resistenz gegenüb...