Etude experimentale du transport de Pinoculum de Ceratocystis fimbriata f. platani par ľeau ?une riviere

Dissemination of Ceratocystis fimbriata f. platani inoculum by river water . C. fimbriata was detected up to 108 m downstream from pieces of diseased plane tree placed in a fixed site in a river in Southern France. Assessment of C. fimbriata was realized by a trapping method with healthy wood.     

Possibilités d'infection du platane par Ceratocystis fimbriata f. platani après contamination de l'eau où se développent des racines blessées

Infection of plane tree by Ceratocystis fimbriata f. platani after contamination of water as growing substrate of wounded roots. Plane tree seedlings (Platanus acerifolia) were cultivated during 1. year so as some roots emerged from the culture pot And grow in the water of a container placed below. In April, these roots were wounded and nearby, conidia suspension of C. fimbriata?. platam was injected into the water. 1 month later, foliage of some seedlings began to wilt and after 2 months, 7 out of 12 plane trees were drying. The pathogen was recovered from all parts of the roots above the water level inside the pots and as high as the collar for 4 plants.     

Une méthode simple de recherche de Ceratocystis fimbriata f. platani sur arbre en place

A simple method of diagnosing Ceratocystis fimbriata f. platani in standing trees. Bluish or purple streaks are found at the margins of lesions caused by Ceratocystis fimbriata f. platani. These contain the fungus systematically. Cores may be taken with an augur from any such streaks, the core then being cut into discs which are kept in a humid chamber at 20–25°C. C. fimbriata, if present, produces diagnostic endo-conidia after 2–4 days of incubation in 50–90 % of the samples.     

Electrophoretic protein profiles of strains of Ceratocystis fimbriata f. sp. platani

Soluble proteins extracted from the mycelium of strains of Ceratocystis fimbriata (Ell. et Halst) Davidson f. sp. platani Walter were separated on native and SDS-polyacrylamide gradient gel electrophoresis. The protein patterns were compared and the electrophoretic profiles of all the strains examined showed striking intraspecific similarities. The use or protein banding patterns as a diagnostic criterion to distinguish strains of C. fimbriata is discussed.     

Vascular modifications in Platanus acerifolia seedlings inoculated with Ceratocystis fimbriata f. sp. platani

Vascular modification of plane tree seedlings inoculated with Ceratocystis fimbriata f. sp. platani, the canker stain disease agent, were characterized using histochemical and scanning electron microscopy methods.     

Observation de sensibilités differentielles de quelques organes de Platanus acerifolia vis-à-vis de Ceratocystis fimbriata f. platani

Differences in susceptibility against Ceratocystis fimbriata f. platani between organs of Platanus acerifolia. Artificial inoculations in various organs of young plane-tree seedlings showed different degrees of susceptibility for different tissues. While herbaceous and slightly lignified parts (leaves, stem top) proved to be relatively resistant, rootlets were very effective sites of infection. The theoretical and epidemiological consequences of these findings are pointed out.     

Action in vitro de fongicides benzimidazoles et thiophanates sur Ceratocystis fimbriata E. et H. f. platani

In vitro action of selected benzimidazole and thiophanate systemic fungicides on Ceratocystis fimbriata E. et H. f. platani. The relative effects of several systemic fungicides (benzimidazoles: carbendazim, benomyl, and thiabendazole; and a thiophanate: methyl-thiophanate) of French strain of Ceratocystis fimbriata E. et H. (platani were studied in vitro by measuring mycelium diameter growth, percent conidiospore germination, and development from chlamydospores. Both strains were sensitive to carbendazim and methyl-thiophanate. These chemicals inhibited mycelium growth and development of chlamydospores.     

First hybrid plane trees to show resistance against canker stain (Ceratocystis fimbriata f. sp. platani)

Canker stain, caused by the ascomycete Ceratocystis fimbriata f. sp. platani, is a major threat to plane trees in Europe. The American plane tree (Platanus occidentalis) carries some genetic resistance, but this species is not adapted to the climatic conditions in Europe. Therefore, hybrids between susceptible oriental plane trees (Platanus orientalis) and resistant P. occidendalis were screened for disease resistance in France. Among 960 hybrids, we found 18 individuals which survived two successive inoculations. These putatively resistant trees were cut back and, after 18 months, on each tree 12 of the newly produced shoots as well as two roots, were inoculated again. From these trees, only one showed complete and another one partial resistance. This selection process resulting in the resistant clone ‘Vallis clausa’ is described in detail.     

Le Dépérissement du Chêne en Roumanie

Dieback of oak in Rumania . The paper summarises data on the distribution and development of oak dieback in Rumania and the most important results of phytopathological research. A comparison is made between dieback in Rumania and in the United States, with respect to the pathogenic organisms involved.     

Physiological responses of Eucalyptus spp. hybrids to infection by Ceratocystis fimbriata

In Brazil, the selection and planting of eucalyptus clones resistant to Ceratocystis fimbriata is the pre‐eminent control strategy for the wilt pathogen. However, little is known about host defence responses associated with resistance of eucalyptus to C. fimbriata infection. In this work, enzymatic activity, sugars, lignin, total phenols and phenolic compounds involved in the defence response of eucalyptus clones resistant (RC) and susceptible (SC) to the Ceratocystis wilt were evaluated. Changes were detected in the sugars produced by RC clones, with higher concentrations occurring compared with SC. A similar response occurred with lignin content at 28 days after inoculation (dai) in RC plants. SC plants had an increase in polyphenol oxidase and peroxidase activities at 7 dai. In contrast, RC plants demonstrated high activity of the same enzymes at 2 and 4 dai, decreasing afterwards. There was no difference in phenylalanine ammonia‐lyase activity between resistant and susceptible clones. Hydroxycinnamic acid concentration was higher in RC than in SC; however, there was no difference between RC and SC in flavonoid concentrations. RC had high concentrations catechin, chlorogenic acid and caffeic acid. Histochemical tests demonstrated the presence of phenolic compounds and lignin, at higher intensities, in xylem of RC plants. Inoculation with C. fimbriata induced defence responses in both resistant and susceptible eucalyptus clones, but both the intensity and speed of the responses were higher in RC. Alterations in the concentrations of sugars and lignin, as well as certain enzymes and phenolic compounds, could be used to predict the relative susceptibilities to Ceratocystis wilt of different phenotypes of eucalyptus clones.     

Aggressiveness,cultural characteristics and genetic variation of Ceratocystis fimbriata on Eucalyptus spp.

Ceratocystis wilt caused by Ceratocystis fimbriata is currently one of the most important diseases affecting Eucalyptus in Brazil. This disease is controlled by planting resistant clones; however, possible variability in the pathogen population may compromise the selection of resistant genotypes. Therefore, this study aimed to evaluate the aggressiveness of C. fimbriata isolates obtained from Eucalyptus spp, as well as their cultural characteristics and genetic variation of their ITS rDNA gene region. We found a significant isolate × clone interaction, with the isolate RM35 being the most aggressive and presenting a broader spectrum of aggressiveness, causing greater xylem discoloration on a larger number of clones. This isolate is the most suitable for artificial inoculations focusing on the selection of resistant materials. Clones CLR‐236 and CLR‐212 were identified as the most resistant and clones CLR‐223 and CLR‐240 as the most susceptible and those that are recommended as reliable comparators in artificial inoculations. All isolates were morphologically similar and differed from C. fimbriata from sweet potato by the formation of a wide mouth endoconidiophore that produces doliform endoconidia. According to the culture media and temperature applied, the most favourable conditions for mycelial growth were observed using malt extract agar (MEA) and temperatures ranging from 24 to 26°C. There was no correlation between sporulation and aggressiveness. Great variation in ITS sequences was observed, and a total of five ITS genotypes were identified among the ten isolates tested.     

Production d'hydrolases dégradant des polyosides pariétaux par Rigidoporus lignosus,un des agents du pourridié blanc de l'Hévéa

Cell wall-degrading enzymes produced by Rigidoporus lignosus in vitro and in vivo. Secretion of 3 polysaccharide degrading enzymes (cellulase, xylanase, endopolygalacturonase) by R. lignosus, responsible for white root rot of Hevea, was studied in culture and during pathogenesis.     

Une méthode d'inoculation pour l'évaluation précoce du comportement du Mélèze vis a vis du Lachnellula willkommii

An inoculation method for early assessment of Larch resistance to Lachnellula willkommii . Efficiency of inoculation with mycelium and ascospores was compared on 4–13-year-old Larix decidua. Only mycelium induced high infection rates. Mycelial inoculum was contained in colonized sorghum-straw pieces and was introduced in 1 mm diameter holes drilled through the bark in April/May. The main infection was detectable as early as 18 months after inoculation and infection rate increased only until the 28th month after inoculation. The susceptibility of the branches did not depend on their age, their position in the trees, the age of inoculated shoots or the management of the trees. Susceptibility was even for the 1–2-yr-old parts of the stems and branches but the oldest parts of the stems were less susceptible. The inoculation method was effective for detecting differences in susceptibility among trees. One seedling from the Alps, and clone 3001–00035, which is the mother of resistant hybrids, were the least susceptible.     

The response of Populus ‘NE 42’ (P. maximowiczii × P. trichocarpa) to infection by Ceratocystis fimbriata isolated from cacao-tree and plane

Shoots of a poplar clone susceptible to a Ceratocystis fimbriata strain from poplar were inoculated with strains of the fungus isolated from cacao-tree and plane. Disease symptoms and pathological changes in shoots as well as the development of the fungus in tissues are reported.     

Etude comparative du contenu phénolique du genre Quercus et de ses zoocécidies

Comparative Study of Phenolic Contents in Oak Galls. Determinations on galls of Quercus show that phenolic compounds and especially tannins do not systematically accumulate in these proliferations. On the contrary, their phenolic content is highly variable and differs between species. Their composition depends apparently not only on the pathogenic agent and the attacked organ, but also on the physiological state of the plant.     

Test ?inhibition de ľactivité cambiale du Peuplier par Hypoxylon mammatum: mise au point et application

Test of inhibition of cambial activity of poplar by H. mammatum: development and application. A test was developed in vitro in order to estimate the inhibition of hosts’cambium by H. mammatum and applied to a large number of poplar clones. Toxicity of the culture filtrate appears to be selective but not necessarily specific.     

Epidémiologie du Lophodermium pinastri (Schrad.) Chev.

Epidemiology of the needle-cast fungus of pines (Lophodermium pinastri): results of four years studies with the aid of a Hirst spore trap . This study is dealing with the results of laboratory and forest (Haguenau) observations on the biology of the needle cast fungus of pines. The spores were harvested during a period of four years with a Hirst spore trap and their germination rate was studied. The results obtained permit to apply chemical treatments with a certainty of success.     

La variabilité du pouvoir pathogène de Nectria ditissima agent du chancre du hêtre

Variability in the pathogcnicity of Nectria ditissima Tul. cause of beech canker . Four mycelial strains of Nectria ditissima Tul. were inoculated into young beeches of two different provenances. The size of bark necrosis was assessed monthly from December to June. The strains can be separated into three groups of aggressiveness according to the size of the necrosis, its persistence and also the hormonal disturbances resulting from pathogenesis. The results reported here suggest a differential interaction between N. ditissima and its host Fagus sylvatica.