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1.
The histological reaction of current shoots of the Japanese cedar,Cryptomeria japonica, inoculated withCercospora sequoiae was investigated. Wound periderm was formed on current shoots of the cedar on and after the 4th day after inoculation. In the cells of the cork layer, lignin and suberin were deposited, and a phenolic substance was accumulated. In other inoculated samples, plasmolysis, contraction of the cells and necrosis of the tissues were also observed. On the 32nd day, wound perioderm and phellogen were observed in samples of the tissue inside the necrotic tissues in response to hyphal invasion. Occurrence of wound periderm and phellogen in tissues of the needles was confirmed in the inoculated samples although no hyphae were observed in and around the tissues. These results suggest that this fungus causes necrosis of host tissues and induces defense responses. A part of this paper was presented at the 106th Annual Meeting of the Japanese Forestry Society (1995).  相似文献   

2.
Maize seedlings contain high amounts of glucosidically bound 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA). The effects of DIMBOA on the feeding behaviour and performance of two noctuids, Spodoptera exigua Hübner and S. frugiperda Smith, were compared. The question was raised whether S. frugiperda, preferring maize and other Poaceae, is better adapted to DIMBOA than S. exigua. In addition, the effects of DIMBOA on the mycelial growth of the plant pathogen Setosphaeria turcica Leonard et Suggs (causal agent of northern corn leaf blight) was assessed in vitro. DIMBOA had an antifeedant effect on S. exigua but stimulated feeding in S. frugiperda in dual-choice experiments. In a no-choice setup, larvae of S. exigua gained less biomass and had a prolonged development when feeding on an artificial diet containing DIMBOA. However, pupal weight was not significantly different between treatments. In contrast, larvae of S. frugiperda were not affected by DIMBOA. Strong detrimental effects of DIMBOA were found on the mycelial growth of the pathogen S. turcica.  相似文献   

3.
The decomposition of leaves, twigs and roots of two diameter classes (<1.5 mm, 1.5–5 mm) were examined in an alley cropping experiment withGliricidia sepium, Calliandra calothyrsus andSenna sianea in the subhumid savanna of Central Togo using the litterbag technique. The effect of the application of leaves and twigs as mulch or green manure was examined. Gliricidia showed the most rapid mass loss. For all species, leaves decomposed faster than roots. Twigs had the lowest decomposition rate except forCalliandra. The two diameter classes of roots decomposed differently in the three species:Gliricidia fine roots decomposed faster than its coarser root fraction, the coarse roots ofSenna decomposed faster than the fine roots.Termites influenced the mass loss of twigs and roots to varying extents for the different species. In the case of twigs this was markedly influenced by the mode of application: green manure showed more termite frass than mulch.Nutrient release resembled the mass loss patterns of the prunings except for K, which was leached independently from mass loss. The release of the different nutrients was in the order CaGliricidia andSenna seemed to be best for mulch and green manure production at our site.  相似文献   

4.
Green manure applications in alley cropping systems often include twigs despite their potential to absorb (immobilize) nitrogen (N). To assess the impact of twigs on net N mineralization or immobilization from hedge row cuttings, we separated cuttings fromCalliandra calothyrsus andGliricidia sepium into leaf-only, twig-only, and mixed (leaf + twig) fractions and incubated them with moist soil in the laboratory. Soil extractable inorganic N did no differ among treatments after two weeks, but after four and eight weeks was greatest in leaf-only, and least in twig-only treatments. After two weeks, extractable N from the leaf-only treatment rose steadily, while that from the twig-only and mixed treatments was variable due to periods of net mineralization and net immobilization. The pattern of variation in mixed treatments paralleled that of twig-only, indicating that net immobilization in the mixture was largely caused by the presence of twigs. Extractable N from the mixture was somewhat lower than that predicted from the sum of leaf-only and twig-only treatments. We conclude that twigs in green manure reduce short-term N availability to associated crops in agroforestry systems.  相似文献   

5.
In the spring of 1998, an outbreak of the cedar processionary moth (CPM) [Traumatocampa ispartaensis (Doanlar and Avcí 2001)], a notodontid moth, began on 400 ha in a 75-year-old stand of Lebanon cedar (Cedrus libani A. Rich.) trees in the western Mediterranean region of Turkey. This was the first monitored outbreak of CPM in the Isparta region. Tree crowns recovered to near normal condition by the middle of each growing season (beginning of July) during the outbreak. From 1999–2003, CPM larvae were present in the same stands and again caused defoliation. The objective of this research was to explore dendrochronology as a means of determining the long-term role of CPM in tree growth and to quantify the historic importance of CPM. In 2003, increment cores were collected from 28 host and 10 nonhost dominant or codominant trees, and annual radial-growth indices from 1947–2003 were calculated for one nonhost and four host sample plots. Cedar tree-ring chronologies were analyzed for evidence of CPM. Tree-ring chronologies from nonhost cedar (undefoliated sample trees) were used to estimate potential growth in the host cedar (defoliated sample trees) during current and past outbreaks. The trees selected as host and nonhost were the same subspecies and varieties. We identified regional outbreaks of CPM by synchronous and sustained growth periods of the trees. Growth functions were defined as the cumulative sum of radial increments. Tree-ring evidence suggests that a large-scale outbreak began in 1954 (lasting from 1954–1961) and small outbreaks began in 1947 (1947–1951), 1985 (1985–1988), and 1998 (1998–2003) in the study area. The average reductions in diameter growth for the periods around 1947, 1954, 1985, and 1998 were 40, 28, 17, and 10% of potential, respectively. We concluded that a narrow latewood band is a significant historic indicator of defoliation by CPM, and the outbreaks appear to be associated with dry winter and spring weather prior to the fall and winter in which feeding occurred.  相似文献   

6.
To determine whether Monochamus alternatus can use the Japanese cedar (Cryptomeria japonica) as a host tree, experiments were conducted in a laboratory using three insect populations of different localities. Adult females chose Pinus densiflora bolts as oviposition substrate when supplied with cedar and pine bolts simultaneously, whereas some females from one locality oviposited on cedar bolts when supplied with them exclusively. Seventy-three percent of 40 eggs hatched in cedar bolts. When the first instar larvae were inoculated on cedar bolts, the development was stunted greatly and all died during the larval stage. Two of 20 larvae that were inoculated on cedar bolts at the third instar entered the diapause and one larva developed into an adult female, which produced viable eggs but was much smaller than those obtained from pine bolts. The results did not exclude the possibility that M. alternatus can use recently killed C. japonica trees as a host.  相似文献   

7.
The participation of active defense responses in the limitation of fungal spread in the sapwood of living sugi tree was determined. Isolates ofGuignardia cryptomeriae were inoculated to living trees, fresh logs, frozen and thawed logs and autoclaved logs, and the spread of wood discoloration and fungal hyphae was assessed. In autoclaved logs and freeze-treated logs, wood discoloration and reaction zone formation were not observed, and fungal hyphae of both of virulent and avirulent isolates grew rapidly in the wood. In fresh logs, wood discoloration and the formation of a pale reaction zone and transition zone were observed. Virulent isolates spread rapidly, but the spread of avirulent isolates was inhibited. In living trees, wood discoloration was observed and reaction zones were formed at lesion margins. These results indicated that constitutive defense mechanisms had no effect on the spread of both of virulent and avirulent isolates, and that active defense responses were important in the limitation of spread of fungal hyphae, hence in the limitation of wood discoloration. Further, it appeared that avirulent, but not virulent, races ofG. cryptomeriae were easily inhibited even by weak host responses. This study was presented at 105th and 106th Annual Meeting of the Japanese Forestry Society.  相似文献   

8.
In a growth chamber experiment, 70-day-old seedlings of 10 conifer species were inoculated with Colletotrichum gloeosporioides conidia to determine the host range of the fungus. Based on the percentage of seedlings affected and the disease severity on individual seedlings, the order of most to least susceptibility was: western hemlock (WH), mountain hemlock, western larch, Sitka spruce, Engelmann spruce, Douglas-fir (coastal form, then interior form), white spruce and ponderosa pine; lodgepole pine and western red cedar remained unaffected. Inoculation of WH needles showed that within 24 h C. gloeosporioides conidia germinate and appressoria (penetration structures) form. A growth chamber study demonstrated that the pathogen can infect WH at needle wetness periods as short as 15 min; number of needles affected was higher at 0.5 h, but did not increase further even when wetness was extended up to 8 h. The results are discussed in relation to blight management of greenhouse-grown conifer seedlings.Portion of a Bachelor of Science (Honors) thesis, Department of Biology, University of Victoria, Victoria, British Columbia.  相似文献   

9.
[目的]研究银杏枝条部位、年龄对不定根形成的影响,并探讨其相应的叶、茎段中非结构碳水化合物(NSC)含量变化与扦插生根的关系。[方法]以50年生银杏树冠上、下部枝条的1、2和3年生位置的茎段为材料截取插穗,500 mg·L-1IBA与纯水对照处理基部60 s,在全光喷雾状态下研究扦插生根情况,并利用HLPC法分析相应部位叶和茎段中NSC含量。[结果]表明:银杏扦插不定根形成过程分为4个阶段,即0～4周愈伤形成期、4～6周愈伤膨大期、6～8周不定根开始形成期、8周后不定根伸长;生根部位主要在切口处。树冠上、下部位插穗的生根率未见明显差异,但随着枝龄的增加而明显降低。NSC分析表明:下部叶片NSC组分中多糖和总糖含量明显高于上部的,但茎段NSC的所有组分在上下部均无明显差异;随着枝龄的增加,相应位置叶片NSC各组分含量没有明显差异,但相应茎段NSC组分中葡萄糖、果糖、多糖、总糖、淀粉含量却明显降低,与生根率的变化趋势一致。此外,500 mg·L-1IBA处理并未明显提高生根率,还需进一步优化处理浓度。[结论]银杏树冠上部和下部枝条对不定根形成无影响;未处理枝条的枝龄与生根率呈负相关,而茎段NSC含量与生根率呈正相关;叶片NSC含量对不定根形成影响较小;生根方式以愈伤生根类型为主。该结论将为今后银杏扦插生根及其机制研究提供参考。  相似文献   

10.
During and after prolonged periods of rainfall in late spring, blighted young twigs of European beech (Fagus sylvatica) were frequently observed in several beech stands in south‐western and southern Germany. Long and short shoots of young understorey trees or lower branches up to 1.5 m above the soil level were affected. Symptoms also occurred regularly on twigs in heights up to 2 m and more above the ground. Necroses usually expanded within the current year’s tissue and often also reached into the previous year’s wood. Ponding rain water in the stands or along forest roads or open soil seemed to promote the disease. Of a total of 54 symptomatic twigs collected in four stands, 37 revealed Phytophthora isolates, of which 33 were P. plurivora and four were P. cambivora. Both species caused extensive lesions on beech twigs in laboratory pathogenicity tests. Patterns of the disease indicated that these pathogens, generally considered soilborne species, in most cases are transmitted from the soil to above‐ground parts of the trees via rain splash. In larger heights, however, other vectors such as snails might be responsible for transmission. Although Phytophthora spp. are well known as causal agents of seedling blight as well as root and cambium rot and aerial bleeding cankers of mature beech, to our knowledge this is the first report of a twig blight in beech associated with soilborne Phytophthora spp. In particular in periods of high precipitation, this disease might pose an additional threat to Central European beech forests, especially endangering the success of artificial and natural regeneration of beech in affected stands.  相似文献   

11.
补充营养材料对松褐天牛成虫存活期的影响   总被引：8，自引：2，他引：8       下载免费PDF全文
2000－2001年对马尾松不同龄级枝条及混合枝条饲养松褐天牛成虫的存活期及取食情况进行了研究。结果表明,不同龄级枝条对松褐天牛成虫存活期产生显著影响,混合枝条饲养平均存活期显著长于2年生枝条及3年生枝条饲养,而与当年生枝条饲养无显著差异。存活期的差异与取食密切相关,当年生枝条饲养具有最大的日均取食量,并极显著地大于2年生枝条饲养和3年生枝条饲养的相应值。混合枝条和单龄级枝条饲养日均取食量均无显著差异。混合枝条饲养处理当年生枝条被食面积占取食总面积的55％以上,3年生枝所占比例不足20％。研究显示松褐天牛自然状态下从不同级枝条中获取所需物质,以当年生枝条为主;无选择单龄枝饲养时通过增加取食来尽可能满足物质需要。  相似文献   

12.
We caught the adults of a secondary wood-boring insect, Callidiellum rufipenne (Motschulsky), on Japanese cedar, Cryptomeria japonica D. Don., trees and logs with manipulated bark water contents to clarify the mechanism of host selection by C. rufipenne. More C. rufipenne were trapped when the bark water content range was ca. 120–200%. Fewer C. rufipenne were trapped at higher and lower bark water contents. These findings indicate that C. rufipenne adults do not simply select weakened or dying trees. Bark water content is one of important factors for C. rufipenne choosing their host for oviposition.  相似文献   

13.
Port Orford cedar (Chamaecyparis lawsoniana) is endemic to northern California and southwestern Oregon and is considered a foundation species that plays critical roles in riparian areas and on nutrient‐poor soils. Since 1952, a non‐native, pathogenic oomycete (Phytophthora lateralis) has been spreading throughout the range of the cedar. Most spread occurs by vehicles carrying infested soil along gravel roads primarily used for timber harvest. In a previous study conducted in 1998 and 1999, Port Orford cedar and P. lateralis were censused in a 37‐km2 study area and dendrochronology was used to reconstruct the history of pathogen invasion. That work, which represents the only detailed analysis of spread rates for P. lateralis, showed that the first successful invasion into the study area took place in 1977 and that 43% of the susceptible host sites (stream crossings) were infested by 1999. In the work presented here, all sites that were uninfested in 1999 were re‐censused in 2012, extending the historical reconstruction of P. lateralis spread to 35 years. Two new infestations were initiated between 1999 and 2012, suggesting that the rate of spread of P. lateralis has slowed greatly. Between 1980 and 1989, the average number of new site infestations was 1.8 infestations per year, while between 1990 and 1999 the average was 0.4 infestations per year and between 2000 and 2009 the average was 0.2 infestations per year. Several potential explanations for the reduced number of new infestations are discussed.  相似文献   

14.
The decline of virgin fir (Abies firma) forest at Mt. Oyama has been reported. Related field observations suggest that high acidity fog is linked with its decline. However, cedar (Cryptomeria japonica) in the same area shows no symptoms of decline. For assessing effects of acid fog on membrane-bound calcium (mCa) of the leaf mesophyll cells, 9-year-old seedlings of fir (Abies firma) and 8-year-old seedlings of cedar (Cryptomeria japonica) were exposed twice a week to simulated acid fog (SAF at pH 3 with pH 5 as control) for 2 h per day in a chamber during May–December 2007 (except August). Current and 1-year-old needles were collected from seedlings and analyzed at 1-month intervals. For current-year needles of fir, mCa levels in cells exposed to SAF at pH 3 were significantly lower than in cells exposed to pH 5, especially during September 2007–March 2008. In contrast, it is noteworthy that mCa levels of cedar were maintained as virtually constant irrespective of SAF acidity, indicating that fir is more sensitive to acid fog than is cedar. Based on these results, mCa loss by acid fog might also be caused in the declining virgin fir forest at Mt. Oyama.  相似文献   

15.
Chestnut blight is a stem‐girdling disease of Castanea caused by the fungal pathogen Cryphonectria parasitica. Chestnut blight affects all Castanea species to some degree. In Asian species, chestnut blight is a commercially relevant disease which primarily affects nut production. In American and European species, chestnut blight has caused significant declines in wild populations and continues to negatively affect nut production in the European chestnut (C. sativa). Despite the profound effect of this disease in the Castanea genus, very little is known concerning the factors involved in the host–pathogen interaction between C. parasitica and its Castanea hosts. This review summarizes information on known mechanisms and metabolites involved in the host–pathogen interaction and contributes original information on the pathogen in relation to susceptible and putatively resistant genotypes with a view to furthering research that will promote a better understanding of this devastating disease and enable its control.  相似文献   

16.
Sweet crab apple (Malus coronaria) is a popular ornamental tree planted in gardens and urban forests in South Korea. In 2018, severe symptoms were observed on street plantings of sweet crab apple in Jinju, South Korea including shoot blight: shoot tips, twigs and foliage of infected trees turned brown, and dried completely. The causal agent isolated from the disease lesions was identified as Pseudomonas viridiflava based on biochemical tests, pathogenicity, and 16S rRNA and rpoD gene sequencing. On artificial inoculation, this pathogen not only caused shoot blight on sweet crab apple, but also bulb rot and leaf blight on onion. Here, we report the occurrence of bacterial shoot blight caused by P. viridiflava in sweet crab apple for the first time in the world.  相似文献   

17.
In order to clarify the effects of tree species on organic matter dynamics in soil, we investigated the amount of forest floor material, leaf litter decomposition rate, soil chemical characteristics, soil respiration rate and cellulose decomposition rate in a Japanese cedar forest (cedar plot) and an adjacent Japanese red pine forest (pine plot) established on a flatland. The amount of forest floor material in the cedar plot was 34.5 Mg ha−1 which was greater than that in the pine plot. Because the leaf litter decomposition rate was higher in the pine plot than in the cedar plot, it is likely that the difference in the amount of forest floor material between the plots is caused by the difference in the leaf litter decomposition rate. The C concentrations of soil in the cedar plot were 1.2–2.1 times higher than those in the pine plot. Soil pH(H2O)s in the cedar plot were significantly higher than those in the pine plot. The soil respiration rates and the rates of mineralized C in the cedar plot byin vitro incubation were higher than those in the pine plot. From this result, it is assumed that soil organic matter in the cedar plot was decomposed relatively faster compared with the pine plot. Furthermore, microbial activities, which were reflected as cellulose decomposition rates in the cedar plot, were higher than those in the pine plot. A part of this paper was presented at the 109th Annual Meeting of the Japanese Forestry Society (1998).  相似文献   

18.
The Palaearctic leaf beetle Chrysomela lapponica usually feeds upon willows in the northern region of its occurrence. However, in Central Europe, some populations are known that have specialised on birch. In this study, we investigated the significance of other herbivores occurring together on the same host plants as possible exploitative competitors of C. lapponica. Two populations were studied: a population from Finland specialised on the willow Salix borealis, and a population from the Czech Republic, specialised on the birch Betula pubescens. Abundances of folivorous and suctivorous insects on both host plants were recorded at both population sites. The willow leaf beetle Phratora vitellinae was the most abundant herbivorous insect at both study sites on willow. A field study was conducted to examine the effects of P. vitellinae on the performance of C. lapponica. The presence of P. vitellinae larvae on the same twig upon which C. lapponica larvae were feeding did not affect increase of body weight in C. lapponica larvae. Thus, the high resource availability of both willows and birches suggest that interspecific competition is unlikely to be a selection factor driving the evolution of host shift in C. lapponica.  相似文献   

19.
The larch brown rust caused byTriphragmiopsis laricinum was found onLarix cajandri in Primorsky Territory, Russia. This was a new host and locality record for the pathogen. Preliminary survey of the disease incidence in several localities in East and Northeast Russia and Yakutia-Sakha Republic indicated the restricted distribution of the rust in a few localities in Primorsky Territory. As previously reported in China,T. laricinum was proved to form uredinia in nature and to be able to propagate vegetatively by urediniospores. This suggests the fungus could become a devastating pathogen threatening a large-scale larch plantation in Far East of Russia. Field observations and the failure of basidiospore inoculation onto larch needles suggest the heteroecious life cycle ofT. laricinum.  相似文献   

20.
In glasshouse experiments, Cylindrocladium quinqueseptatum, which was associated with outbreaks of leaf spot and shoot blight in a young plantation of Eucalpytus microcorys in north Queensland during the 1982 and 1983 autumns, was pathogenic on seedlings of E. microcorys and caused varying degrees of leaf spot and shoot blight in ten species of Eucalyptus from major taxonomic groupings of the genus, When the outbreaks occurred, the weather was unusually showery with minimum temperatures above 16°C. In vitro studies showed that free water was essential for conidial germination, which occurred between 14–32°C. The optimum for mycelial growth was 28.5°C. In vivo studies showed that leaf penetration. by germinated conidia was via the stomata. Mancozeb was more effective at controlling the disease than benomyl, captan or copper oxychloride. The potential importance of C. quinqueseptatum and options for control in young Eucalyptus plantations are discussed.  相似文献   

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