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Sessile Oak (sessile + oak)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

Is there a higher risk for herbivore outhreaks after cold mast years?

ECOGRAPHY, Issue 6 2000
An analysis of two plant/herbivore series from southern Norway
Historical data on two plant-herbivore interactions from southern Norway were used to test the hypothesis that the degree of herbivore outbreaks in post-mast years is negatively related to summer temperatures in the mast year, because plants are more depressed after a high seed production if temperatures and thus the photosynthetic activity is low. The plant species were the sessile oak Quercus petraea and the bilberry Vaceinium myrtillus. For the former species post-mast years were identified from reports given by the local forest authorities for the period 1930,48, and from acorn export curves for the period 1949,98, For the latter species, post-mast years were identified mainly from bilberry export curves for the period 1920,31, from game reports for the period 1932,78. and from diary notes for the period 1979,87. The herbivore species used were the green oak leaf roller moth Tortrix viridana and the capercaillie Tetrao urogallus. Eight moth outbreaks on oak forests were reported by the forest authorities in the period 1930,98, and they all started in a post-mast year of the sessile oak. There were however also eleven post-mast years without moth outbreaks. According to game reports, observations and autumn counts, all increases in the autumn population size of capercaillie during 1920 88 occurred in or after a year with high bilberry production. Among i8 post-mast years, there were seven with strong increase, seven with slight or moderate increase, and four with no increase. For both herbivore species, post-mast years with marked population increases had significantly lower summer temperatures in the preceding (mast) year than had post-mast years with no or slight increases. For moth populations there also was a negative effect of high temperatures in April, possibly because moth eggs tend to hatch too early relative lo budburst if spring temperatures are high. For the capercaillie, high amount of precipitation in June , July seemed to have some negative impact on the autumn population sizes, as also found in previous studies. [source]

Hyperparasitic Stagonospora sp. on Botryosphaeria stevensii

FOREST PATHOLOGY, Issue 6 2003
L. Vajna
Summary An unknown fungus, Stagonospora sp., has been found on and in stromata of Botryosphaeria stevensii Shoemaker anamorph (Diplodia mutila Fr. & Mont.) and Diatrypella quercina (Persoon) Nitschke. Microscopic investigations indicated that the fungus might be a hyperparasite of some ascomycetous fungi, necrotrophs or weak parasites on sessile oak [Quercus petraea] and turkey oak (Quercus cerris). Dual culture studies carried out with monoconidial isolates of Stagonospora sp. and B. stevensii have demonstrated that Stagonospora sp. is a necrotrophic mycoparasite which might suppress, to some extent, the natural population of B. stevensii. Botryosphaeria stevensii is one of the biotic factors causing oak decline. Morphology of the fungus and symptoms of mycoparasitic interaction are described. Stagonospora sp. found in Hungary is assumed to be identical with hyperparasitic Stagonospora sp. reported from Germany and Austria as parasite of Ascodichaena rugosa and Ascodichaena mexicana in Mexico. This is the first record of hyperparasitic Stagonospora sp. of B. stevensii and D. quercina. Résumé Un champignon inconnu, Stagonospora sp, a été trouvé sur et dans les stromas de Botryosphaeria stevensii Shoemaker (anamorphe Diplodia mutila Fr. & Mont.) et Diatrypella quercina (Persoon) Nitschke. D'après les études microscopiques, le champignon pourrait être un hyperparasite de champignons ascomycètes, nécrotrophes ou parasites de faiblesse du chêne sessile [Q. petraea] et du chêne chevelu (Quercus cerris L.). Des confrontations en culture d'isolats monoconidiens de Stagonospora sp. et Botryosphaeria stevensii montrent que Stagonospora sp. est un mycoparasite nécrotrophe qui pourrait limiter dans une certaine mesure les populations naturelles de Botryosphaeria stevensii. Botryosphaeria stevensii est un des facteurs biotiques associés au dépérissement des chênes. La morphologie du champignon et les symptômes de l'interaction mycoparasitaire sont décrits. L'espèce de Stagonospora trouvée en Hongrie est supposée identique au Stagonospora décrit en Allemagne et Autriche comme parasite de Ascodichaena rugosa et au Mexique sur Ascodichaena mexicana. Cette étude constitue la première mention de Stagonospora sp. hyperparasite de B. stevensii et D. quercina. Zusammenfassung Eine bisher unbekannte Art von Stagonospora wurde in und auf Stromata von Diatrypella quercina (Persoon) Nitschke sowie der Anamorphe (Diplodia mutila Fr. & Mont.) von Botryosphaeria stevensii Shoemaker nachgewiesen. Mikroskopische Beobachtungen legen eine hyperparasitische Lebensweise auf zu den Ascomyceten gehörenden, nekrotrophen Parasiten und Schwächeparasiten von Trauben- (Q. petraea) und Zerreiche (Quercus cerris) nahe. Dualkulturen von Monokonidien-Isolaten von Stagonospora sp. und B. stevensii zeigten, dass es sich bei der Stagonospora -Art um einen nekrotrophen Mycoparasiten handelt, der möglicherweise unter gewissen Umständen die Entwicklung natürlicher Populationen von B. stevensii zu hemmen vermag. B. stevensii ist einer der biotischen Faktoren des ,,Eichensterbens". Die in Ungarn nachgewiesene Art dürfte mit derjenigen Stagonospora -Art identisch sein, welche Ascodichaena rugosa in Deutschland und Österreich sowie Ascodichaena mexicana in Mexico parasitiert. Bei der vorliegenden Arbeit handelt es sich um den ersten Nachweis einer hyperparasitischen Stagonospora -Art auf B. stevensii und D. quercina. [source]

Transcriptome analysis of bud burst in sessile oak (Quercus petraea)

NEW PHYTOLOGIST, Issue 4 2006
Jérémy Derory
Summary ,,Expression patterns of hundreds of transcripts in apical buds were monitored during bud flushing in sessile oak (Quercus petraea), in order to identify genes differentially expressed between the quiescent and active stage of bud development. ,,Different transcriptomic techniques combining the construction of suppression subtractive hybridization (SSH) libraries and the monitoring of gene expression using macroarray and real-time reverse transcriptase polymerase chain reaction (RT-PCR) were performed to dissect bud burst, with a special emphasis on the onset of the process. ,,We generated 801 expressed sequence tags (ESTs) derived from six developmental stages of bud burst. Macroarray experiment revealed a total of 233 unique transcripts exhibiting differential expression during the process, and a putative function was assigned to 65% of them. Cell rescue/defense-, metabolism-, protein synthesis-, cell cycle- and transcription-related transcripts were among the most regulated genes. Macroarray and real-time RT-PCR showed that several genes exhibited contrasted expressions between quiescent and swelling buds, such as a putative homologue of the transcription factor DAG2 (Dof Affecting Germination 2), previously reported to be involved in the control of seed germination in Arabidopsis thaliana. ,,These differentially expressed genes constitute relevant candidates for signaling pathway of bud burst in trees. [source]