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PubMed2004

Antimicrobial effects of Quercus ilex L. extract.

The antimicrobial activities of the methanol extract of Quercus ilex L. (Pirnal oak) leaves were tested in vitro against a wide range of human and plant-associated microorganisms. A total of 132 microbial organisms belonging to 55 bacteria and five fungi and yeast species were studied using a disc-diffusion method and microdilution assays. The results were evaluated as inhibition zones around the disc impregnated with Q. ilex extract at a concentration of 300 micro L/mL. The results showed that Q. ilex did not have any antifungal activities against Alterneria alternata, Aspergillus flavus, Fusarium oxysporum, Penicillum spp., whereas there were inhibition effects on the growth of all Candida albicans isolates. In total 97 bacterial strains (74%) were found to be resistant to Q. ilex extract. The remaining 35 (27%) strains of seven different bacteria genera including Brucella, Bacillus, Enterobacter, Neisseria, Pseudomonas and Escherichia were susceptible to the extract tested. The minimum inhibitory concentrations (MIC) of the extract ranged from 125 to 500 micro L/mL. These results suggest that Q. ilex possesses compounds with antibacterial and anticandidal properties.

Anti-Infective Agents↗
PubMed2004

Detection of quantitative trait loci controlling bud burst and height growth in Quercus robur L.

Genetic variation of bud burst and early growth components was estimated in a full-sib family of Quercus robur L. comprising 278 offspring. The full sibs were vegetatively propagated, and phenotypic assessments were made in three field tests. This two-generation pedigree was also used to construct a genetic linkage map (12 linkage groups, 128 markers) and locate quantitative trait loci (QTLs) controlling bud burst and growth components. In each field test, the date of bud burst extended over a period of 20 days from the earliest to the latest clone. Bud burst exhibited higher heritability (0.15-0.51) than growth components (0.04-0.23) and also higher correlations across field tests. Over the three tests there were 32 independent detected QTLs ( P<or=5% at the chromosome level) controlling bud burst, which likely represent at least 12 unique genes or chromosomal regions controlling this trait. QTLs explained from 3% to 11% of the variance of the clonal means. The number of QTLs controlling height growth components was lower and varied between two and four. However the contribution of each QTL to the variance of the clonal mean was higher (from 4% to 19%). These results indicate that the genetic architecture of two important fitness-related traits are quite different. On the one hand, bud burst is controlled by several QTLs with rather low to moderate effects, but contributing to a high genetic (additive) variance. On the other hand, height growth depends on fewer QTLs with moderate to strong effects, resulting in lower heritabilities of the trait.

Analysis of Variance↗
PubMed2003

Genus- and isolate-specific real-time PCR quantification of Erwinia on leaf surfaces of English oaks (Quercus robur L.).

In order to quantify pathogenic epiphytic bacteria on leaf surfaces of the important European forest tree Quercus robur without time-intensive cultivation and separation of microorganisms, methods were developed to selectively quantify DNA copy numbers of the genus Erwinia in DNA isolated from the leaf surface. By using the combination of the two different real-time PCR techniques SYBR-Green and TaqMan, methods were developed not only to allow quantification of the total DNA copy number of Erwinia on the oak leaf surface, but also to distinguish between two significantly different groups of Erwinia strains. In the present work, these techniques were successfully applied to quantify the copy number of the genus Erwinia and its subgroups compared with the total bacteria number in DNA samples extracted from the upper leaf surface of English oaks collected on the 4th of June 2001 (Julian day 155).

Bacteriological Techniques↗
PubMed2004

Genetic transformation of selected mature cork oak (Quercus suber L.) trees.

A transformation system for selected mature cork oak (Quercus suber L.) trees using Agrobacterium tumefaciens has been established. Embryos obtained from recurrent proliferating embryogenic masses were inoculated with A. tumefaciens strains EHA105, LBA4404 or AGL1 harbouring the plasmid pBINUbiGUSint [carrying the neomycin phosphotransferase II (nptII) and beta-glucuronidase (uidA) genes]. The highest transformation efficiency (4%) was obtained when freshly isolated explants were inoculated with A. tumefaciens strain AGL1. Evidence of stable transgene integration was obtained by PCR for the nptII and uidA genes, Southern blotting and expression of the uidA gene. The transgenic embryos were germinated and successfully transferred to soil.

Age Factors↗
PubMed2004

Detection of microsatellite instability during somatic embryogenesis of oak (Quercus robur L.).

Five microsatellite loci (QpZAG1/5, QpZAG9, QpZAG36, MSQ4, MSQ13) were used to test for genetic stability of three somatic embryogenic culture lines of Quercus robur L. and plantlets derived therefrom. DNA variation was detected among somatic embryos within all embryogenic lines, whereas no genetic instability was found among the regenerated plants. Two microsatellite loci revealed variation, and a locus-dependent instability was observed. The most polymorphic and useful microsatellite locus for detecting genetic variation was QpZAG9, with 28.5% of the investigated loci being variable.

Agriculture↗
PubMed2005

Assessment of ploidy stability of the somatic embryogenesis process in Quercus suber L. using flow cytometry.

Flow cytometry analyses were used to verify the ploidy stability of Quercus suber L. somatic embryogenesis process. Leaf explants of two adult cork oak trees (QsG0 and QsG5) of the North of Portugal were inoculated on MS medium with 2,4-D and zeatin. After 3 months, calluses with embryogenic structures were isolated and transferred to fresh MS medium without growth regulators and somatic embryo evolution was followed. Morphologically normal somatic embryos (with two cotyledons) and abnormal somatic embryos (with one or three cotyledons) were used in this assay. Flow cytometry combined with propidium iodide staining was employed to estimate DNA ploidy levels and nuclear DNA content of somatic embryos and leaves from mother plants. No significant differences (P< or =0.05) were detected among embryos, and between the embryos and the mother plants. Also, after conversion of these embryos, no significant morphological differences were observed among the somatic embryo-derived plants. These results and further studies using converted plantlet leaves and embryogenic callus tissue indicate that embryo cultures and converted plantlets were stable with regard to ploidy level. As no major somaclonal variation was detected our primary goal of "true-to-type" propagation of cork oak using somatic embryogenesis was assured at this level. The estimation of the 2C nuclear DNA content for this species is similar to the previously obtained value.

Flow Cytometry↗
PubMed2003

Fruit abortion, developmental selection and developmental stability in Quercus ilex.

Fruit abortion has been hypothesized to be a parental means of selective removal of propagules with low viability. In particular, aborted zygotes have been suggested to have developmentally deviant phenotypes, and surviving offspring may therefore give rise to adults with a developmentally stable phenotype. We tested predictions from this hypothesis using acorns of holm oaks Quercus ilex as a model system. Fecundity of oak trees was negatively related to mean fluctuating asymmetry of leaves, and abortion rates were positively related to leaf fluctuating asymmetry in at least one population. Aborted acorns were asymmetric in 83-99% of cases in three samples, while mature acorns were only asymmetric in 57-78% of cases. Acorn asymmetry was unrelated to germination probability and germination date, and had no significant effect on number of leaves, leaf mass, stem mass, seedling height or leaf area of seedlings. However, acorn asymmetry affected the trade-off between number and size of leaves in seedlings. Seedlings from asymmetric acorns showed a positive relationship between acorn size and number of leaves, but no relationships between acorn size and leaf area, while symmetric acorns showed the opposite. A positive relationship between acorn size and number of leaves in spring was found for naturally emerged seedlings that died during their first summer, whereas the number of leaves produced by surviving seedlings did not depend on acorn size. These findings are consistent with the hypothesis that stressed trees selectively abort propagules of low viability, and that developmental selection acts on a measure of developmental instability of fruits.

Adaptation, Physiological↗
PubMed2003

Phenological variation as protection against defoliating insects: the case of Quercus robur and Operophtera brumata.

Phenological synchrony between budburst and emergence of larvae is critical for the fitness of many spring-feeding insect herbivores. Therefore, large intraspecific variation in timing of budburst of the host may have a negative effect on the herbivore. We studied how asynchrony between emergence of larvae and budburst affects the fitness of Operophtera brumata (Lepidoptera: Geometridae), a major defoliator of Quercus robur, which can adapt to the phenology of a single tree. It is known that, in maturing leaves of Q. robur, accumulation of condensed tannins has a negative effect on growth of O. brumata. However, there is no information about the effect of hydrolysable tannins and other phenolics that are potential antifeedants. In this study, we also analysed changes in secondary chemistry of the foliage of Q. robur and how different compounds are correlated with growth and survival of O. brumata. The effect of asynchrony on O. brumata was studied in rearing experiments. The neonate larvae were incubated without food for different periods of time. The decline in nutritional quality of foliage was estimated by rearing cohorts of larvae with manipulated hatching times on the leaves of ten individual Q. robur trees. For the chemical analysis, the foliage of these trees was sampled at regular intervals. In the absence of foliage, mortality of neonate larvae started to increase exponentially soon after the larvae emerged. If the larvae missed budburst, the decline in nutritional quality of the foliage led to increased mortality and lower body mass (= fecundity). Hydrolysable tannins were not significantly correlated with performance of the larvae. Only condensed tannins were found to correlate negatively with the growth and survival of O. brumata. Certain individual trees were unsuitable hosts for O. brumata because the decline in quality of the foliage was very rapid. Based on regression equations for increasing rate of mortality and decreasing fecundity, we calculated that a relatively small mismatch of +/-30 degree days between budburst and hatching of larvae leads to a 50% decrease in the fitness of O. brumata. Thus, large phenological variation within a Q. robur stand can limit the colonisation of neighbouring trees by dispersing larvae. Furthermore, the hybridisation of moths adapted to phenologically different trees may lead to maladapted phenology of their offspring.

Adaptation, Physiological↗
PubMed2003

Delta(13)C and tree-ring width reflect different drought responses in Quercus ilex and Pinus halepensis.

Holm oak (Quercus ilexL.) and Aleppo pine (Pinus halepensisMill) are representative of two different functional types of trees extensively found in the Mediterranean: evergreen sclerophyllous and drought-adapted conifers. The former is considered a partially drought-tolerant species, whereas the latter is a typically drought-avoiding, water-saving species. We postulated that contrasting strategies in response to water deficits in Q. ilex and P. halepensis would lead to a differential sensitivity to changes in water availability. To test this hypothesis, we compared the response of both species in growth rate (measured as radial increments) and intrinsic water use efficiency WUE(i), as inferred from carbon isotope discrimination (Delta(13)C) in wood samples] among sites from different provenance regions in NE Spain. We found significant differences in Delta(13)C and growth among provenance regions, partly explained by contrasting water availability. Wood Delta(13)C was positively related with precipitation and the ratio between precipitation and potential evapotranspiration (P/ E). However, these relationships were stronger in P. halepensis (for P / E, r(2)=0.67, P <0.001) than in Q. ilex ( r(2)=0.42, P <0.01). In addition, radial growth was positively related with precipitation and Delta(13)C in P. halepensis ( r(2)=0.32 and r(2)=0.35, respectively, P <0.01), but not in Q. ilex. We concluded that P. halepensis was more sensitive than Q. ilex to water availability, showing faster increase in WUE(i) in response to water stress. We also found that the effect of north/south aspect on Delta(13)C and growth was site-specific, and unrelated to climatic variables.

Adaptation, Physiological↗
PubMed2003

Prolonged diapause of specialist seed-feeders makes predator satiation unstable in masting of Quercus crispula.

Quercus crispula (= Q. mongolica var. grosseserrata) is the predominant tree species in cool temperate, mixed broadleaf/conifer forests in northern Japan. We compared 11 years of data on acorn production in a population of Q. crispula, with data on seed-insect populations, to try to answer the following questions: (1) Does Q. crispula show a regular pattern of masting? (2) How long do principal seed predators remain in diapause? (3) How do the seed predators affect the pattern of predator satiation? Q. crispula showed a tendency to alternate bearing, with significant synchrony between individual trees. The principal acorn-feeding insects ( Curculio spp. weevils), which infested 25%-70% of matured acorns, generally exhibited a prolonged diapause of 2 years. No significant negative relationship was found between the rate of injury by the weevils and the density of mature acorns, indicating that simple predator satiation fails due to the synchrony of the life-cycle of acorn-feeding insects and the periodical production of acorns. However, the rate of injury by the weevils was negatively correlated with the relative abundance of mature acorns to the number of weevil larvae that had matured 2 years previously. Thus, the proportion of sound acorns notably increased in a rich crop after a disturbance in alternate bearing. Prolonged diapause of specific seed predators is critical in determining the peak year of sound-seed production.

Animals↗
PubMed2003

Seasonal changes in the photosynthetic capacity of canopy oak (Quercus robur) leaves: the impact of slow development on annual carbon uptake.

The photosynthetic development of pedunculate oak ( Quercus robur L.) sun leaves in a mature woodland canopy in Oxfordshire, southern England, was investigated in situ during 3 years with contrasting weather conditions. Development of full photosynthetic capacity (indicated by light-saturated net assimilation rates, A(max), typical of the summer period) took between approximately 50 and 70 days after budbreak in different years. This slow development means that these leaves do not utilise a substantial fraction of the seasonal peak of solar irradiance. During the late autumn senscence period the photosynthetic capacity declined over a 2-week period, but as this is a time of low irradiance, the loss of potential photosynthesis was relatively small. The consequences of these developmental changes and differences in bud break dates for daily and seasonal leaf carbon balance were investigated through a simple light-response photosynthetic model. Seasonal changes in photosynthetic capacity would decrease annual carbon uptake per unit leaf area by about 23% compared to that potentially possible if leaves photosynthesised at peak rates throughout the growing season. This difference is likely to be up to 30% larger in years with late budburst and as low as 18% in years with early budburst.

Carbon↗
PubMed2004

The effect of climate on the phenology, acorn crop and radial increment of pedunculate oak (Quercus robur) in the middle Volga region, Tatarstan, Russia.

Our data, collected in the extreme east of Europe, show that a significant biological effect of climate change has been experienced even in territories where temperature increase has been the lowest. This study documents the climatic response of pedunculate oak (Quercus robur) growing near its north-eastern limits in Europe. It demonstrates the potential of oak trees in old-growth forest to act as proxy climate indicators. Many factors may influence the temporal stability of the growth-climate, acorn crop-climate and first leafing-climate relationships. Climate data, climatic fluctuations, reproduction, genetics and tree-age may relate to this instability. Our results stress that an increase in climate variability or climatic warming resulting from warmer winters or summers could affect the oak population in eastern Europe in a similar way to that in western Europe. These findings, from remnants of oak forest in the middle Volga region of Russia, allow a further understanding of how species could be affected by future climates.

Acclimatization↗
PubMed2005

Post-fire, seasonal and annual dynamics of the ectomycorrhizal community in a Quercus ilex L. forest over a 3-year period.

Two study plots, burned and control, were established in autumn 1998 in a Quercus ilex forest located in northern Spain, part of which had been affected by a low intensity fire in 1994. Soil samples for ectomycorrhizae (ECM) were taken over a 3-year period in each study plot in spring, summer, autumn and winter. ECM morphotypes were identified and the relative abundance of each morphotype in each soil sample calculated, along with species richness, Shannon diversity index and percentage of mycorrhization in each soil sample. The relative abundance of certain ECM morphotypes differed between burned and control plots, and the percentage of mycorrhizal tips was significantly lower in the burned than in the control plot. Nevertheless, there were no significant differences in the diversity, species richness or species composition of the ECM community in the burned and control plots. The dominant ECM morphotypes in both stands were Cenococcum geophilum and several thelephoroid fungi. Sphaerosporella brunnea and Pisolithus tinctorius thrived especially in the burned plot, whereas three ectomycorrhizal morphotypes assigned to the genus Hebeloma were especially abundant in the control plot. There was no significant variation in the relative abundance of the ECM morphotypes between seasons, but ECM community species richness was highest in autumn and lowest in summer. The percentage of mycorrhizal tips reached a maximum in winter, with its minimum in autumn. Collection of samples over the 3-year period also enabled us to detect a significant increase in percentage of ECM colonisation in the burned stand over time.

Biodiversity↗
PubMed2006

Differential expression of two class III chitinases in two types of roots of Quercus robur during pre-mycorrhizal interactions with Piloderma croceum.

Expression of two plant chitinase genes, representing members of class III chitinases, was studied in Quercus robur roots during interactions in a pre-mycorrhizal stage with the ectomycorrhizal fungus Piloderma croceum. Chitinase gene expression was compared in lateral roots destined to form ectomycorrhiza, and in principal roots that are not directly involved in mycorrhizal interactions. The transcript level of the first chitinase (QrchitIII-1) was upregulated in lateral roots, whereas no significant differential expression was observed in principal roots. The second chitinase (QrchitIII-2) was regulated neither in lateral nor in principal roots in presence of the fungus. Because P. croceum did not induce significant chitinase responses in principal roots, the enhanced expression of QrchitIII-1 in lateral roots after inoculation may be related to some steps in symbiosis ontogenesis.

Chitinases↗
PubMed2002

High accumulation of legumin and Lea-like mRNAs during maturation is associated with increased conversion frequency of somatic embryos from pedunculate oak (Quercus robur L.).

The expression patterns of the storage protein legumin gene and Em- and dehydrin-like homologues were investigated in somatic embryos from Quercus robur L. The effect of different maturation treatments (1% agar, 6% sorbitol, or 5% polyethylene glycol) and partial desiccation on transcript accumulations as well as conversion capacity of somatic embryos was also investigated. Differential expression of putative Em- and two dehydrin-like homologues (designated as Dhn1a and Dhn1b) was detected in somatic oak embryos with heterologous probes. Low expression levels of legumin, Em- and dehydrin-like mRNAs were detected in somatic embryos prior to maturation treatment. A high accumulation of these transcripts was found in embryos that had been cultured on media supplemented with 6% sorbitol or 1% agar. These embryos also showed a high conversion frequency into plantlets. In contrast, no improvement in plant conversion as well as a low accumulation of legumin, Em-like and Dhn1b-like transcripts was observed in embryos that were matured on polyethylene glycol medium. Partial-desiccation treatment significantly enhanced the plant conversion. Nevertheless, a decline in expression of legumin, Em-like and Dhn1a-like homologues was detected upon dehydration. In contrast, Dhn1b and oak homologues to peach dehydrin were also strongly expressed in desiccated embryos. In addition, the treatment of embryos with abscisic acid promoted the accumulation of all investigated transcripts. These results suggest that the regulation of the legumin storage protein gene and Lea-like homologues in somatic oak embryos is under developmental control and that their regulation can be influenced by manipulating the culture conditions.

Abscisic Acid↗
PubMed2003

Resprouting ability of Quercus crispula seedlings depends on the vegetation cover of their microhabitats.

To examine the effects of vegetation cover on the resprouting abilities of Quercus crispula seedlings, in each of three consecutive years, we artificially clipped seedlings growing in microhabitats with differing degrees of vegetation cover. We also investigated the relationship between the level of total nonstructural carbohydrate (TNC) and resprouting ability. Seedlings with clipped shoots in gaps produced larger resprouting shoots than those in the understory. Moreover, both the percentage of resprouting seedlings and the survival ratio in seedlings with clipped shoots were negatively correlated with the degree of vegetation cover. Seedlings stored high levels of TNC, especially in their roots, and their TNC levels were negatively correlated with the degree of vegetation cover. There were also positive relationships between the TNC levels in their roots and the degree of resprouting. Hence, we conclude that release from vegetation cover enhanced the resprouting ability of Q. crispula seedlings by increasing their levels of stored carbohydrate. The key variables affected were the resprouting ratio (the proportion of seedlings capable of producing new shoots) and the size of the resprouted shoots.

Biomass↗
PubMed2004

Geographical distribution of two haplotypes of chloroplast DNA in four oak species (Quercus) in Japan.

Chloroplast DNA polymorphism in four oak species (Quercus serrata, Q. mongolica var. crispula, Q. dentata and Q. aliena) was studied using collections from a total of 127 localities in Japan and South Korea on the basis of five intergenic spacers (trnD-trnT, trnT-trnL, rps14-psaB, trnS-trnT and trnQ-trnS). Although no variation existed in sequences among the four species, a single nucleotide (T/C) substitution in the trnQ-trnS intergenic spacer was found in all the four species, resulting in two haplotypes (T- and C-type). Phylogenetic analyses of the four species and related species showed that the C-type is derived and even likely of monophyletic origin, while the T-type is ancestral. Geographically, the T-type is widespread from South Korea to Japan, whereas the C-type is restricted to eastern Japan with rare exceptions. "Eastern Japan" approximately coincides with the distribution range of the boreal conifer forest during the last glacial maximum. Overall evidence suggests that the mutation from T- to C-type occurred in an individual of one of the four oak species and then was transferred to all the species by hybridization in eastern Japan, and that the Kanto District provided individuals with the C-type with a refugium during the last glacial maximum.

Base Sequence↗
PubMed2005

Sex allocation of a cosexual wind-pollinated tree, Quercus dentata, in terms of four currencies.

Sex allocation of a cosexual wind-pollinated species, Quercus dentata (Fagaceae), was analyzed using biomass, carbon, nitrogen and phosphorus as currencies based on data accumulated for 61 individuals from 1997-2004. Strongly female-biased sex allocation was indicated when measured in terms of biomass and carbon, but no significant bias was detected when measured in terms of nitrogen or phosphorus. From an adaptive viewpoint, there is little support for strong female-biased sex allocation, suggesting that sex allocation in terms of nitrogen or phosphorus is closer to the real picture. The relative sex allocation considerably varied from year to year, but the relative femaleness of individuals in the population was rather constant across years. No significant correlation was observed between relative sex allocation and fecundity or tree height, but individuals that showed very low fecundity tended to produce only acorns.

Carbon↗