共查询到20条相似文献，搜索用时 15 毫秒
1.
B. Scanu B. T. Linaldeddu A. Franceschini N. Anselmi A. Vannini A. M. Vettraino 《Forest Pathology》2013,43(4):340-343
An increasing decline and mortality of cork oak trees have been recently observed in central Italy and Sardinia Island. Following surveys conducted in three declining cork oak forests, a Phytophthora species was consistently isolated from soil samples collected from trees displaying different level of decline. Based on morphological features, growth rates at different temperatures and analysis of DNA sequences of the ITS region, all isolates were identified as Phytophthora cinnamomi Rands. This pathogen caused large brownish lesions on inoculated freshly cut branches of cork oak. It was re‐isolated from all infected tissues. These findings represent the first report of P. cinnamomi on cork oak trees in Italy. 相似文献
2.
Constança S. P. Camilo-Alves Margarida Vaz M. Ivone Esteves Da Clara Nuno Manuel De Almeida Ribeiro 《New Forests》2017,48(6):753-772
Chronic decline and Sudden death are two syndromes of cork oak (Quercus suber) dieback. Mortality is associated with water stress, but underlying physiological mechanisms are poorly understood. Here, we investigated the physiological performance of declining trees during the summer drought. Leaf water potential, gas-exchange, fluorescence of photosystem II and leaf and root starch concentration were compared in healthy (asymptomatic) and declining trees. Low annual cork increment in declining trees indicated tree decline for several years. All trees showed similar water status in spring. In summer, declining trees showed lower predawn leaf water potential (?2.0 vs. ?0.8 MPa), but unexpectedly higher midday leaf water potential than healthy trees (?2.8 vs. ?3.3 MPa). The higher midday water potential was linked to by means of strongly reduced stomatal conductance and, consequently, transpiration. This study is pioneer showing that declining trees had high midday water potential. A tendency for lower sap flow driving force (the difference between predawn and midday water potential) in declining trees was also associated with reduced photosynthesis, suggesting that chronic dieback may be associated with low carbon uptake. However, starch in roots and leaves was very low and not correlated to the health status of trees. Declining trees showed lower water-use efficiency and non-photochemical quenching in summer, indicating less resistance to drought. Contrarily to chronic decline, one tree that underwent sudden death presented predawn leaf water potential below the cavitation threshold. 相似文献
3.
The composition of the endophytic fungal assemblages in Quercus cerris, Q. pubescens and Q. robur, three oak species most susceptible to decline, was investigated in Fagarè (Padova), Ulignano (Pisa), and Radda in Chianti (Firenze). The endophytic assemblages were studied as a function of health status of the whole tree and of twigs and leaves. The effect of station altitude was tested on Q. cerris. Samples were gathered from healthy and declining trees. In April (bud opening time) 20 twigs and 10 leaves were collected from each tree. Fungi were isolated from twig segments and leaf portions. A total of 23 fungal genera with 27 different species were isolated, in addition to a few sterile mycelia. Eleven species were found to be common to all three oak species, while other species were found only on one oak species, suggesting host specificity. Among the fungal species isolated, some were known to be pathogenic (Apiognomonia quercina, Colpoma quercinum, Diplodia mutila, Phomopsis quercina). The colonization frequency (CF) of pathogenic species varied between 0.9% for A. quercina in Q. cerris and 60.2% for P. quercina in Q. robur. Analysis of variance showed a statistically significant difference among the oak species tested. The CF was higher in declining trees in comparison with healthy trees, and also in twigs vs. leaves. The CF was found to be higher for Q. cerris trees growing at sea level as compared with those situated at an elevation of 350–400 m. In stands where, on account of particular ecological conditions, pathogenic behaviour is displayed simultaneously by more than one endophytic fungal species, trees accentuate their decline. 相似文献
4.
Endophytic behaviour of Biscogniauxia mediterranea, the causal agent of charcoal disease of oak, was studied over two growing seasons on Quercus cerris in a forest in central Italy. Isolation of the fungus from asymptomatic tissues varied with tissue type, period of sampling and year. Presence of the fungus in asymptomatic plants was significantly higher in fall, compared with that in spring and summer. However, a significant effect of tissue water content on the presence of B. mediterranea was recognized. The results suggest that proliferation of B. mediterranea is favoured during the endophytic phase by a decrease in host water potential. 相似文献
5.
The effects of water stress and defoliation by Lymantria dispar on the successful infection of the fungal pathogen Biscogniauxia mediterranea in seedlings of the Turkey oak (Quercus cerris) were studied under controlled conditions. Seedlings were inoculated by spraying with a spore suspension of Biscogniauxia mediterranea and were subjected to different levels of water stress, insect defoliation, and combinations of the two factors. The leaf water potential was periodically assessed throughout the experiment. The fungus was isolated exclusively from seedlings deprived of water, and insect defoliation increased significantly the proportion of fungus isolation when the water stress was moderate. Thus insect defoliation seems to promote fungal colonization in case of moderate water stress. 相似文献
6.
A noticeable decline and physiological weakening of pedunculate oak (Quercus robur L.) has been recorded in the past decade in lowland parts of Slovenia. The triggers were dry climate, unfavourable precipitation patterns and human influence that brought about changes in watercourses and water tables. Regeneration and future management of this tree species is therefore questionable. To define a critical groundwater table which would permit successful regeneration, planted and naturally grown seedlings were compared in two forests differing in the degree of decline and physiological weakness of adult pedunculate oak trees. Comparison of stomatal conductance and pre-dawn water potential (PWP) showed differences of seedlings between and within forest complexes. Stomatal conductance dropped below 100 mmol m−2 s−1 at PWP values below −1.0 MPa, while closure of stomata was caused by a PWP between −1.6 and −1.9 MPa. Increased water stress equalized photosynthetic yield in both natural and planted oaks below −1.4 MPa. 相似文献
7.
Constança de Sampaio e Paiva Camilo-Alves Maria Ivone Esteves da Clara Nuno Manuel Cabral de Almeida Ribeiro 《European Journal of Forest Research》2013,132(3):411-432
Mortality events in cork and holm oaks have occurred in the Mediterranean basin since the beginning of the XX century, but severity of decline increased during the 1980s. By that time, the exotic soil borne pathogen Phytophthora cinnamomi was often recovered from declining stands and since then it has been considered the main factor associated with decline. This work analyses data concerning P. cinnamomi surveys in cork and holm oaks trees, pathogenicity tests carried out in controlled experiments, studies about the influence of site characteristics in tree decline and approaches to control the disease. Results of field surveys showed that the pathogen is widespread and pathogenicity tests suggested that host susceptibility to the pathogen is moderate when seedlings are in appropriate watering conditions, particularly cork oaks. Occurrence of decline is also associated with soil characteristics that interfere with root expansion and water retention. We assessed the relative importance of each factor involved in decline and revised the role of P. cinnamomi in cork and holm oak decline. 相似文献
8.
Variations in tree ring growth of Quercus suber L. were analysed using dendrochronological techniques on cork oak discs from trees harvested in the cork producing region
of Alentejo, Portugal. A tree-ring chronology containing a strong common signal and covering the period from 1970 to 1995
was build for ca. 30-year-old cork oaks never submitted to cork harvesting using 14 trees that crossdated satisfactorily out
of 30 sampled trees. The tree ring indices correlated positively with September temperature (r = 0.48, P < 0.05) and very strongly with precipitation totals from previous October until current February (r = 0.82, P < 0.001) showing that the water stored in the soil during the autumn and winter months prior to the growing season has a
primordial effect on the growth of the given season. The effects of cork harvesting were analysed by comparing mean ring width,
mean annual vessel area, vessel density (n°vessels/mm2), and vessel coverage (percentage of transverse surface occupied by vessels) between three mature cork oak trees and three
young trees, for the period from 1987 to 1996, corresponding to the growth between two consecutive cork removals in the case
of mature trees. In 1988, 1989 and 1996 (corresponding to the first and second years after cork removal, and 1996 to a year
of cork removal), the ratios between ring widths of young versus mature trees was twice that for the rest of the period. However,
an effect of cork removal indicated by eventual alterations in vessel size and distribution in the wood rings corresponding
to the years 1988, 1989 and 1996 in the mature cork oaks was not observed. 相似文献
9.
Jaime Puértolas Marta Pardos María Dolores Jiménez Ismael Aranda José Alberto Pardos 《Annals of Forest Science》2008,65(6):611-611
10.
《Scandinavian Journal of Forest Research》2012,27(2):98-102
Abstract Characterization of the virulence of bark beetle-vectored fungi is important for assessing potential impacts of beetle outbreaks. Massive inoculation of trees with a cork borer appears to give the most accurate estimate of fungal virulence, but cork borer inoculation is time and labor intensive. In October 2003, 18 Pinus contorta var. latifolia were inoculated with a beetle-associated fungus, Grosmannia clavigera (Robinson-Jeffrey and Davidson) Zipfel et al., at densities of 200 and 800 cork borer holes m?2. In July 2004 nine trees were inoculated using bark flap inoculations. The fungal-induced moisture content reduction, sapwood occlusion area and needle discoloration were similar for the 800 cork borer holes m?2 density and for bark flap inoculations, while pathogenicity symptoms induced by the 200 cork borer holes m?2 were less intense. Bark flap inoculations were three times faster to perform than high-density cork borer inoculations, but differences in incubation time and yearly weather variation highlight the need for further studies. The bark flap method may be an efficient alternative to using massive inoculation densities when testing the ability of specific fungi to kill hosts, while the cork borer method may be a better method to assess pathogenic symptoms or the aggressiveness of specific fungi. 相似文献
11.
Opportunity for hybridization between two oak species in mixed stands as monitored by the timing and intensity of pollen production 总被引：1，自引：0，他引：1
M. Carolina Varela Rita Brás Isabel R. Barros Paulo Oliveira Carola Meierrose 《Forest Ecology and Management》2008
The opportunity of cross-pollination in mixed stands of two oak species (cork oak and holm oak) was studied by characterizing individual phenologies of flowering. In the spring of 1998 at one stand consisting of 64 marked trees, there was a period of 19 days when maximal pollen release in one species and stigma receptivity in the other occurred simultaneously, enabling interspecific gene flow in either direction. This happened in spite of an average time separation of 22 days between the two species, reflecting a considerable intraspecific variation in the timings of flowering. Flowering intensities (as estimated from male flower abundance) were high, but fruiting intensities were comparatively low. Shortly after pollination, considerable abortion of female flowers and early fruits was recorded. In 2000, the interspecific overlap of phenologies was drastically reduced due to a delay in cork oak flowering. On the other hand, the individual timings were repeatable for most trees, at least in holm oak. Two other mixed stands were subject of parallel studies, with similar results in all traits except for a less dramatic reduction in fruiting intensities. In spite of the high opportunity for cross-pollination in 1998, and given the lack of hybrids among the progenies from the subsequent fruiting season [Oliveira, P., Custódio, A.C., Branco, C., Reforço, I., Rodrigues, F., Varela, M.C., Meierrose, C., 2003. Hybrids between cork oak and holm oak: isoenzyme analysis. Forest Genet. 10, 283–298], it can be concluded that the prerequisite of cross-pollination is clearly insufficient for hybridization to succeed. Post-pollination processes must play an important role in the maintenance of reproductive isolation between the two species. 相似文献
12.
Harminder Preet Kaur Bahadurjeet Singh Amarjeet Kaur Sanehdeep Kaur 《Journal of pest science》2013,86(3):543-550
Fungal endophytes play a significant role in plant resistance to insects by altering the nutritional quality of plants or by production of various alkaloid-based defensive compounds. Ethyl acetate extract of endophytic Alternaria alternata isolated from Azadirachta indica A. Juss was tested for its bioactivity against Spodoptera litura (Fab.). Effect of different concentrations of ethyl acetate extract of A. alternata was assessed on growth and development of S. litura larvae. The results indicate higher larval mortality on diet supplemented with the fungal extract than control. Adverse effects of A. alternata were also observed on development of the insect. Ethyl acetate extract of the fungus also significantly reduced the adult emergence, longevity and reproductive potential of S. litura. Larvae feeding on diet supplemented with fungal extract showed significant reduction in relative growth and consumption rate, as well as efficiency of ingested and digested food. The antifeedant and toxic effects of A. alternata may be due to production of bioactive molecules by this fungus. 相似文献
13.
Jalil Karami Mohamad Reza Kavosi Manoochehr Babanezhad Khadije Kiapasha 《Journal of Sustainable Forestry》2018,37(5):429-444
Biscogniauxia mediterranea (De Not.) Kuntze, is a widespread fungus, causes outbreaks of Charcoal disease on cork oak and dieback thousands oak trees in recent years in Iran. Yet no efficient and effective management methods have been found to control the disease. The present study aimed to provide a suitable method for charcoal disease management through silviculture operations, systemic pesticides and biological compounds. The results showed that, simultaneous implementation of silvicultural practices (scarification+sanitation), use of systemic fungicides and Trichoderma compounds, reduce the number and depth of cankers, increase callus thickness, and ultimately improve health of the diseased trees. But disease severity and fungi activity were increased when scarification operation implements alone. The greatest effectiveness of the treatments and health condition improvement of the diseased trees was observed 12 months after applying the treatments. Then, preventive and therapeutic effectiveness of the treatments reduced over time. Sanitation and scarification practices can increase soil permeability and also destroy the larvae, pupa or adult insects and oak borer beetles that play an important role in disease outbreaks. Therefore, simultaneous implementation of sanitation and scarification practices with application of biological and systemic compounds can reduce primary source of pathogen inoculum and help trees to recover their health. 相似文献
14.
Quercus suber L. is an important species producing cork whose wood characteristics have not been investigated a lot. Cork oak wood vessels
are a striking feature and the most abundant wood tissue largely influencing density and permeability. Vessel size and distribution
were studied in approximately 40 year-old and never debarked cork oaks by continuously measuring along the radial direction
in the transverse section of wood discs taken at 1.3 m of height using image analysis techniques. The vessel size increases
with age from 7660 ± 2286 to 21136 ± 6119 μm2, the conductive area from 5.4 ± 2.2 to 11.6 ± 3.9%, and the vessel density remains approximately constant between 5.2 ± 1.5
and 7.3 ± 3.5 vessels/mm2. In comparison with ring-porous and some evergreen oaks, cork oaks show a similar conductive area but smaller vessels. Vessel
architecture is known to play an important role on oaks tolerance to hydric stress, and these cork oak trees were growing
under very harsh edaphoclimatic conditions, not tolerated by other oaks. The well-developed and deep root system allowing
access to constant water supply may contribute to the cork oak’s relatively high conductive area. 相似文献
15.
The species composition of the endophytic mycobiota in leaves of Japanese beech trees (Fagus crenata) and the sources for leaf infections were studied in a forest reserve situated in central eastern Honshu, Japan. To clarify the mechanism of infection of leaves, half of the branches were covered with polyethylene bags and species composition and levels of endophytic fungal infection were then compared with those of unbagged controls. Isolations were carried out from the leaves, petioles, and current‐year twigs of both, bagged and unbagged branches. Additionally, species composition was detected in overwintered terminal buds of beech trees and in the leaves of potted seedlings that had been placed in the field in different seasons. The species assemblage of the unbagged leaves, petioles, and current‐year twigs was dominated by Mycosphaerella buna, Ascochyta fagi, Periconiella sp., and Tritirachium sp. Other frequently recovered species were Xylaria sp., Phomopsis sp., and Tubakia dryina. Mycosphaerella buna and A. fagi were never isolated from leaves on bagged branches. A. fagi was, however, detected on both bagged and unbagged petioles and current‐year twigs at comparatively low isolation frequencies. The detection of Periconiella sp. on all occasions in both bagged and unbagged leaves was a characteristic feature that differs from those of the other three dominant endophytic fungi. The fungus was also detected without significant differences in bagged and unbagged petioles and current‐year twigs on most sampling dates. Furthermore, Periconiella sp. was isolated from immature twigs inside the bud scales. Tritirachium sp. was frequently detected in unbagged leaves and petioles and in both bagged and unbagged current‐year twigs, and rarely in bagged leaves and petioles, but was never recovered from terminal buds. The results of the potted seedling experiments revealed that all four dominant species had airborne inocula. The infection of leaves by M. buna occurs exclusively by airborne propagules, i.e. ascospores in spring and conidia in autumn. In Periconiella sp. hyphal growth of the fungus from immature twigs inside the buds into the leaf tissues was suggested in addition to infection by airborne inocula. Tritirachium sp. hyphae were suggested to grow from previous‐ to current‐year twigs. Ascochyta fagi was present in the outermost scales of overwintered terminal buds, but no systemic growth of the fungus into the petioles and current‐year twigs was observed. Our technique of covering the branches before new leaves unfolded was effective in preventing infection by airborne inocula of endophytic fungi. 相似文献
16.
Mass mortality of oak trees has been occurring in Japan since the late 1980s. The fungus Raffaelea quercivora has been frequently isolated from discoloured sapwood in dead or wilting trees and inoculation experiments have shown it to be capable of causing wilting and xylem discoloration in several oak species, notably Quercus crispula and Q. serrata. In this study, we inoculated seedlings of six Fagaceae species with R. quercivora and, after 56 days, measured the vertical length of the discoloration and the areas of discoloured and non‐conducting sapwood on stem cross‐sections. The sapwood discoloration and the water non‐conduction areas were larger in Q. crispula and Q. serrata than in the other species. 相似文献
17.
Hakimeh Ziaie Juybari Mohammad Ali Tajick Ghanbary Heshmatollah Rahimian Kaivan Karimi Mahdi Arzanlou 《Forest Pathology》2019,49(6)
A total of 4,009 endophytic fungal isolates were recovered from healthy leaves, bark and xylem of Citrus sinensis in different seasons and age‐classes. Corresponding to those factors, the majorities of fungal isolates were recovered from leaves, 2‐yr‐old trees and winter, respectively. Fungal isolates were initially categorized based on cultural and morphological characters, and representatives of each morphotype were subjected to molecular identifications based on ITS‐rDNA and β‐tubulin sequences. All isolates obtained in this study belonged to the phyla Ascomycota and Basidiomycota assigned to 30 fungal taxa. The most abundant fungal species were Alternaria spp. Species diversity indices of Margalef richness and Shannon–Wiener revealed a high diversity of fungal taxa recovered from leaf and during winter. Frequency (%) of fungal endophytes was highest in winter followed by summer, autumn, and spring significantly, whereas the corresponding sequence was winter, autumn, summer and spring for the diversity of endophytic fungi. Overall, the results of this study based on the community and diversity of endophytic fungal species in C. sinensis showed that the type of plant tissue, season of sampling and age of tree play a driving role on their abundance while their diversity was mainly dependent on the type of plant tissue, season of sampling than on the age of tree. 相似文献
18.
Filipe Xavier Catry Francisco Moreira Inês Duarte Vanda Acácio 《European Journal of Forest Research》2009,128(3):231-240
Cork oak (Quercus suber) forests are acknowledged for their biodiversity and economic (mainly cork production) values. Wildfires are one of the main
threats contributing to cork oak decline in the Mediterranean Basin, and one major question that managers face after fire
in cork oak stands is whether the burned trees should be coppiced or not. This decision can be based on the degree of expected
crown regeneration assessed immediately after fire. In this study we carried out a post-fire assessment of the degree of crown
recovery in 858 trees being exploited for cork production in southern Portugal, 1.5 years after a wildfire. Using logistic
regression, we modelled good or poor crown recovery probability as a function of tree and stand variables. The main variables
influencing the likelihood of good or poor crown regeneration were bark thickness, charring height, aspect and tree diameter.
We also developed management models, including simpler but easier to measure variables, which had a lower predictive power
but can be used to help managers to identify, immediately after fire, trees that will likely show good crown regeneration,
and trees that will likely die or show poor regeneration (and thus, potential candidates for trunk coppicing). 相似文献
19.
The association between water stress and susceptibility of Quercus cerris to the fungal parasite Hypoxylon mediterraneum was studied in field-grown trees and greenhouse-grown seedlings. Susceptibility of Q. cerris to the fungus, expressed as extension of wood discolorations, increased in field-grown trees during drought and increased in greenhouse-grown seedlings in response to limited water supply. In both seedlings and trees, spread of the fungus in the vascular system was higher when leaf water potentials were low than when leaf water potentials were high, and was significantly correlated to loss of hydraulic conductivity of xylem. The presence of the fungus in the xylem suggests that H. mediterraneum could use embolized vessels to spread in the host. 相似文献
20.
Thirty‐two oak stands in southern Sweden, 27 with predominantly declining trees and five with a higher proportion of healthy trees were investigated regarding the presence of soilborne Phytophthora species. Phytophthora quercina, an oak‐specific fine root pathogen, was isolated from rhizosphere soil samples in 10 of the 27 declining stands. Additionally, P. cactorum and P. cambivora were recovered from one stand each. No Phytophthora species were isolated from the healthy oak stands. The soil conditions at the sites from which Phytophthora spp. were recovered ranged from mesic sediments to moraines, with clayey to silty textures and with soil pH (BaCl2) between 3.5 and 5.0. The results show that P. quercina is geographically widespread in oak stands in southern Sweden and indicate that this pathogen may be one of the factors involved in oak decline in Northern Europe as has already been shown for western, Central and parts of southern Europe. 相似文献