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1.
In this paper, we demonstrate that 140 mg/kg of essential oil from the wood of yellow‐cedar, incense cedar, Port‐Orford‐cedar or western juniper strongly inhibits zoospore germination and hyphal growth of Phytophthora ramorum in culture. Four individual compounds in yellow‐cedar heartwood were also tested. Zoospore germination was reduced to 0% with 10, 100 and 1000 mg/kg of nootkatin, carvacrol and valencene, respectively. Nootkatone was the least active compound, with 3.5% zoospore germination at 1000 mg/kg. Sporangia germination was 0% with 500 mg/kg of nootkatin or carvacrol. The disruption of the zoospore outer membrane and the loss of sporangial contents were often observed and indicative of sporicidal activity. Hyphal growth was inhibited by 99.9% with 50 mg/kg of nootkatin or 500 mg/kg of carvacrol, but growth resumed upon removing the inhibitors. The zoosporicidal activity of yellow‐cedar heartwood shavings stored dry for approximately 10 years was consistent with the quantity of extractable compounds they contained. Thus, spreading fresh shavings or chips of yellow‐cedar heartwood with appreciable higher concentrations of the active compounds, over areas in infection zones where spores might be difficult to control such as trails and parking lots used by hikers and bicyclists, might be useful as part of an integrated program to minimize P. ramorum spore distribution. 相似文献
2.
Assessment of the eradication measures applied to Phytophthora ramorum in Irish Larix kaempferi forests 
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下载免费PDF全文 Phytophthora ramorum is the causal agent of the sudden larch death epidemic in Ireland and the UK. Within the EU, it is a quarantine pathogen and eradication measures are required if it is detected in horticultural or forest environments. Eradication measures in forests include the clearance of susceptible tree hosts from the infected stand along with all host known to support pathogen sporulation within a 250‐m buffer zone of the infected stand. Between 2010 and 2016, these measures have affected over 18,000 ha of Larix kaempferi forests in Ireland and the UK, but the epidemic continues to spread. An assessment of the efficacy of the eradication measures has not been published to date. Here, we provide details of the detection frequency of P. ramorum from aerial (rainwater) and terrestrial (soil, watercourses, plant material) sources in three forest locations in Ireland that had significant areas of L. kaempferi affected by P. ramorum before their removal. Monitoring of six plots with differing infection and eradication management histories was carried out from September 2013 to 2015. Presence of P. ramorum was confirmed by plating plant material onto selective media, followed by morphological identification. Phytophthora ramorum was detected in 65 of 1283 samples, in all sample types and in 17 of the 20 months sampled. Only three of the 295 soil samples were positive for P. ramorum, with all of these coming from an area under perennial standing water. The most positive samples came from a plot where symptomatic Larix trees had not been removed and the findings occurred consistently over the 2‐year study. Plots where infected Larix had been removed were rarely positive for P. ramorum across all the sample types indicating a level of success from the eradication measures in reducing pathogen levels on the sites. 相似文献
3.
M. Elliott G. Sumampong A. Varga S. F. Shamoun D. James S. Masri S. C. Brière N. J. Grünwald 《Forest Pathology》2009,39(4):266-278
Phytophthora ramorum, the cause of sudden oak death and ramorum blight, has three major clonal lineages and two mating types. Molecular tests currently available for detecting P. ramorum do not distinguish between clonal lineages and mating type is determined by cultural methods on a limited number of samples. In some molecular diagnostic tests, cross‐reaction with other closely related species such as P. hibernalis, P. foliorum or P. lateralis can occur. Regions in the mitochondrial gene Cox1 are different among P. ramorum lineages and mitochondrial genotyping of the North American and European populations seems to be sufficient to differentiate between mating types, because the EU1 lineage is mostly A1 and both NA1 and NA2 lineages are A2. In our study, we were able to identify P. ramorum isolates according to lineage using polymerase chain reaction‐restriction fragment‐length polymorphism (PCR‐RFLP) of the Cox1 gene, first by using ApoI to separate P. ramorum from other species and EU1 from North American populations, and then AvaI to distinguish between NA1 and NA2 genotypes. However, P. foliorum had the same restriction profile as P. ramorum NA1 isolates. 相似文献
4.
M. Elliott G. Sumampong A. Varga S. F. Shamoun D. James S. Masri N. J. Grünwald 《Forest Pathology》2011,41(1):7-14
There are three major clonal lineages of Phytophthora ramorum present in North America and Europe named NA1, NA2, and EU1. Twenty‐three isolates representing all three lineages were evaluated for phenotype including (i) aggressiveness on detached Rhododendron leaves and (ii) growth rate at minimum, optimum, and maximum temperatures. Closely related species P. foliorum and P. hibernalis were included in phenotypic tests since these species are encountered in nursery surveys for P. ramorum. Isolates from the NA2 and EU1 lineages were the most aggressive and isolates from the NA1 group were the least aggressive. The NA1 lineage of P. ramorum was the most variable in aggressiveness and growth rate. The variability in the NA1 lineage was due to the presence of non‐wild type (nwt) isolates. There was no significant difference in growth rate among NA1 wild type (wt), NA2, and EU1 lineages at any temperature tested. The difference between wt and nwt P. ramorum isolates is discussed. 相似文献
5.
M. Garbelotto 《Forest Pathology》2012,42(1):8-13
Variation in virulence was examined among isolates of Phytophthora ramorum from epidemiologically important or infectious (non‐oak) and transmissive dead‐end (oak) hosts from North America. Twelve isolates representative of the genetic, geographic and host range of P. ramorum in the western United States were inoculated on leaves of Umbellularia californica (bay laurel or bay) and stems of Quercus agrifolia (coast live oak). In spite of extreme genetic similarity among the isolates employed, and even within the same genotype, significant differences in lesion size were measured, suggesting virulence in this pathogen is also controlled by epigenetic factors. A strong positive correlation between lesion size on bay laurel and coast live oak provides experimental evidence P. ramorum is a generalist pathogen that lacks host specificity. Isolates from non‐transmissive oaks were significantly less pathogenic both on oaks and bays than isolates from infectious hosts. These results are essential to further our understanding of the epidemiology and evolutionary potential of this pathogen. A quantitative differential in virulence of isolates from hosts with different epidemiological roles has been described for many animal diseases, but is a novel report for a plant disease. 相似文献
6.
Von O. Holdenrieder 《Forest Pathology》1984,14(1):17-32
Investigations on biological control of Heterobasidion annosum in Norway spruce (Picea abies H. Karst.) with antagonistic fungi. I. Production of inoculum and interaction experiments in vitro. Thirty isolates of 22 fungal species were examined in vitro for sporulation, for germination of the spores, and for antagonism of mycelia against three strains of H. annosum. Viable spores were produced by 17 isolates, antagonism was shown by 28 isolates. 相似文献
7.
Chlamydospores of four isolates of Phytophthora cinnamomi were produced on mycelium grown on medium with or without 100 μg phosphite/ml, then tested for germination on medium containing no phosphite or 100 or 160 μg phosphite/ml. For each isolate when spores were produced on medium without phosphite, there was no effect of phosphite on germination. However, chlamydospores produced in the presence of 100 μg phosphite/ml showed significantly lower germination on media with no phosphite, 100 or 160 μg phosphite/ml than those produced in the absence of phosphite. For isolates known to be phosphite sensitive, the level of viable non‐germinated chlamydospores was higher amongst those produced on medium containing phosphite than amongst the controls, suggesting phosphite induces chlamydospore dormancy in some isolates of P. cinnamomi. Chlamydospores were produced uniformly across the radius of colonies on solid or liquid control media, but on media containing 100 μg phosphite/ml, chlamydospore production was lower in the centre of the colony and peaked at a point where mycelial morphology changed from tightly packed to sparse. This change in mycelial morphology and the peak in chlamydospore numbers did not occur when the pathogen was grown on liquid medium renewed every few days. In renewed medium, chlamydospores were evenly distributed across the radius of the colony. 相似文献
8.
Oospore viability, oospore germinability, and phenotypic variation among zoospore and hyphal tip derivatives of the standard and natural variant types of the hybrid alder Phytophthoras were investigated. Oospore viability in the standard hybrid, estimated by the tetrazolium bromide method, was low (≈ 31–36%). No germination was observed in more than 4000 oospores, although germination did occur in the Phytophthora cactorum, Phytophthora citricola and Phytophthora cambivora controls. This is consistent with the known meiotic irregularities in this hybrid. Mean oospore viabilities in the natural variants were significantly different (p < 0.001), ranging from approximately 24% in the UK variant to approximately 75% in the Dutch variant. Again, no oospore germination was observed. Zoospore and hyphal tip derivatives of the standard hybrid and of the Swedish and Dutch variants resembled the ‘parent’ isolate in phenotype. The derivatives of the German and UK variants, however, often differed from the parent type. Those of the UK variant were extremely and continuously variable in colony patterns, growth rates, temperature–growth relationships and fertility levels. Although these results do not support the view that the natural variants arise as genetic breakdown products of the standard hybrid, this possibility cannot yet be excluded. The apparent inviability of the oospores suggests that the mycelium and zoospores are mainly responsible for the survival and spread of the alder Phytophthoras in the field. 相似文献
9.
K. B. Ireland D. Hüberli B. Dell I. W. Smith D. M. Rizzo G. E. St. J. Hardy 《Forest Pathology》2012,42(4):305-320
Phytophthora ramorum is an invasive plant pathogen and the cause of considerable and widespread damage in nurseries, gardens and natural woodland ecosystems of the USA and Europe. It is considered to be a significant plant disease as it could cause biodiversity loss and severe economic losses in plant industries in areas where it is not yet known to exist, such as Australasia. Foliar susceptibility and sporulation potential were tested using detached‐leaf assays for 70 Australian native plant species sourced from established gardens and arboreta in California using a NA2 isolate of P. ramorum. Correa‘Sister Dawn’, Eucalyptus regnans, Isopogon cuneatus, I. formosus, Leptospermum scoparium, L. lanigerum and Melaleuca squamea were identified as potentially highly susceptible host species. Hedycarya angustifolia, Olearia argophylla, Phyllocladus aspleniifolius, Pittosporum undulatum and Podocarpus lawrencei were identified as potentially resistant. All 70 species were able to be infected with P. ramorum, as confirmed by reisolation. Putative sporulating hosts include five members of the Myrtaceae, Agonis flexuosa, Corymbia ficifolia, Eucalyptus haemastoma, E. delegatensis and E. viminalis. As a part of a precautionary strategy, the potentially highly susceptible species found in this study are suitable candidates for targeted surveillance programmes in high‐risk incursion areas of Australia and within the global horticultural trade. 相似文献
10.
Survival and vitality of Gremmeniella abietina on Pinus sylvestris slash was studied in northern Sweden during 2003 and 2004. Once a month between September 2003 and April 2004, two to three trees were cut down and debranched. Shoots with pycnidia were sampled at the felling date and then at every consecutive month. The percentage of germinated conidia from each shoot was calculated after 24, 48 and 72 h incubation. The vitality of G. abietina pycnidia in the slash remained high the whole period. Intact pycnidia were found on slash several months after the time of conidial sporulation, which indicates that new pycnidia may be produced on dead pine branches. Sampling of shoots from slash on 13‐ to 18‐month‐old clear‐cuts showed conidial germination capacity as high as in pycnidia collected in fresh slash. Due to survival of G. abietina in slash it is recommended to postpone planting of P. sylvestris seedlings in northern boreal areas to the third vegetation period after sanitary clear‐cuts. 相似文献
11.
Factors affecting discharge and germination of ascospores of Hypoxylon mediterraneum (De Not.) Mill.
Discharge and germination of ascospores of Hypoxylon mediterraneum (=Biscogniauxia mediterranea (De Not.) O. Kuntze) were studied. Discharge and germination of ascospores depend on the presence of water or high relative air humidity. Ascospores are ejected from stromata in forest for most of the year following periods of high precipitation. H. mediterraneum ascospores germinated under a wide range of biotic and abiotic conditions. The optimal temperature for germination was 35°C, but 25 and 30°C were still favourable, while 20 and 40°C reduced germination. Ascospores kept at 5°C were able to germinate after short exposure to temperatures ranging from 20 to 35°C. Germination rate depended on the ascospore density in in vitro experiments, and was highest at 106 ascospore/ml. Tissues of some host plants greatly increased germination rate. In vivo, ascospores germinated better on wounded axillary tissues than on unwounded ones. 相似文献
12.
James D. Haywood 《New Forests》1994,8(2):143-154
Seeds from 10 species were collected, sealed in fiberglass screen pouches, and stored under hardware-cloth cages on both a forest and cleared site for up to five years. At each site, half of the pouches were placed under leaf litter and the other half were planted in mineral soil. Liquidambar styraciflua and Callicarpa americana seeds had high germination rates under all conditions. Quercus falcata, Sassafras albidum, Rhus copallina, and Vaccinium arboreum required planting in mineral soil to ensure germination. Planted Myrica cerifera and Vitis aestivalis seeds germinated well on both sites. Myrica cerifera also germinated well if placed under litter on the forest floor and Vitis aestivalis if placed under litter on the cleared site. Germination of Crataegus uniflora seeds was erratic. Most Lonicera japonica were unsound when collected. Germination rates generally decreased over time, but some Sassafras albidum, Myrica cerifera, and Vaccinium arboreum seed germinated after four years, and Rhus coppalina, Callicarpa americana, Crataegus uniflora, and Vitis aestivalis seeds germinated after five years in the field. 相似文献
13.
Eduardo Somarriba 《Agroforestry Systems》1986,4(3):233-238
This paper reports on the effects that livestock have on seed germination of guava (Psidium guajava L.). Experiments here reported were intended to simulate gastric scarification using different soaking periods in a 0.01 N HCl solution alone or combined with rumen treatments. Additional experiments evaluated germination of defecated and nondefecated seeds germinated in petri dishes and in cow dung.Passage through the digestive tract of cattle did not affect seed germination of guava. Lowered germination was obtained for seeds germinated in cow dung as compared to laboratory germinated seeds. Nevertheless this difference may reflect an inadequate surface-volume ratio of the cow pat used. Large variations in germination between years were recorded. Nothing is known about the effects this may have on the ecology of pasture invasion by guavas. 相似文献
14.
15.
Demel Teketay 《New Forests》1996,11(2):155-171
The germination requirements of five Senna species: S. bicapsularis, S. didymobotrya, S. multiglandulosa, S. occidentalis and S. septemtrionalis have been investigated. Seeds possess dormancy which is caused by their hard seed coats hampering maximum, uniform and rapid germination. To overcome this dormancy, seeds of the five species were pre-treated with (a) mechanical scarification, (b) concentrated sulphuric acid for 15, 30, 45 and 60 minutes and (c) boiling water for 15, 30, 45 and 60 seconds. To determine the effects of temperature on the germination of seeds, pre-treated seeds from each species were incubated at 10, 15, 20, 25 and 30°C. Germination was also tested in the dark. Both acid treatment and mechanical scarification resulted in fast and uniform germination. The highest germination (95–100%) for all species was obtained from seeds treated with sulphuric acid for 60 minutes. Mechanical scarification resulted in 100% germination in all the species except S. septemtrionalis (59%). Boiling water improved germination significantly in S. didymobotrya (98%), S. occidentalis (82%) and S. septemtrionalis (97%), but had very little effect on S. multiglandulosa and reduced germination in S. bicapsularis. Senna seeds germinated over a wide range of temperatures with the optimum temperatures for germination falling around 20–25°C. Germination was either completely inhibited or very low at 10°C. Seeds of all species germinated both in light and dark conditions. 相似文献
16.
Phytophthora cambivora is a soil‐borne pathogen responsible for root and collar rot of woody species including Castanea spp., on which it causes Ink disease. P. cambivora does not produce chlamydospores, and the prevalence of a single mating type in nature limits the production of oogonia and oospores. Thus, survival of P. cambivora, in the absence of suitable hosts, relies mainly on sporangia, zoospores and mycelium. However, inoculum survival in soils or substrates represents a major factor in disease epidemics and is probably dependant on environmental factors. The aim of this article was to study the behaviour of P. cambivora in a peat‐based substrate (PbS) in the absence of a host, under controlled conditions, and by varying the substrate water regimes. Total inoculum in the substrate was quantified by qPCR, using customized rDNA primer sets, whilst zoospores were quantified after elution, and their vitality was determined by a specific staining procedure. Inoculum infectivity was assessed using chestnut root baits. Results indicated that during the initial 48 h after infestation (matric potential, pF 1.2; 70% water content), the inoculum level increased producing microsporangia and mycelium before decreasing, regardless of the water regime applied. The number of free zoospores increased over a period of (maximum) 7 days after substrate inoculation. Vitality of zoospores declined to 45% at day 18, with no statistical differences amongst water regime treatments. Both rDNA and zoospore number increased in flooded samples at day 23, illustrating the vitality of the inoculum. Inoculum was able to infect chestnut root baits up to 45 days at pF 1.2 and 3.5, before and after flooding, but at pF 6.3, only in the absence of flooding. Although based on experiments carried out in microcosms, these results highlight an unexpected resistance of P. cambivora zoospores to environmental constraints. Furthermore, the infectivity ability of the inoculum to survive in PbS over time even in the absence of the host adds relevance to the risk of movement of soil and substrates associated with plant trading worldwide. 相似文献
17.
Cai-Ru Guo Ji-Qi Lu Dong-Zhi Yang Lin-Ping Zhao 《Forest Ecology and Management》2009,258(7):1497-1502
Rodents usually exert important role, through their scatter seed hoarding behavior, on plant regeneration in the field. To investigate the effects of burial and insects infection on germination and seedling growth of acorns of Quercus variabilis, perfect and infected acorns were buried in the soil among four depths, 0 cm, 4 cm, 8 cm and 12 cm, to simulate the seed hoarding behavior by rodents in the field. The results showed that (1) the germination rate were both high, under 4 cm burial depth, for perfect and infected acorns (92% and 53% separately), and decreased significantly with increased burial depth; (2) perfect acorns germinated better in 4 cm burial depth group by autumn of first year; (3) there 32% (perfect) and 26% (infected) acorns with 0 cm burial depth, on the soil surface, germinated successfully; for infected acorns, the 4 cm depth group had the best germination or seedling recruitment in both the first year and the second year; (4) acorns of Q. variabilis exhibited dormancy period ca 7 months; (5) burial, infection, and the interaction between these two factors influenced several aspects including stem height, leaf weight, Tannic acid, and biomass within seedling growth; (6) the results from this study suggest that proper burial would be helpful for the germination and seedling growth, and seedlings of shallow buried acorns had an advantage in their early development; and (7) infection by insects will not inevitably influence seedling early development. 相似文献
18.
The aim of this study was to assess the effect and importance of the feeding of the pine top weevil (Pissodes piniphilus) on the germination of Endocronartium pini (syn. Peridermium pini) in Scots pine (Pinus sylvestris), and thus to establish the possibility of the E. pini infection via insect woundings. Germination tests were therefore carried out on current and previous year needle and phloem extracts. Elucidation of the importance of pathogen infection for the insect's feeding preference was also required; for this purpose feeding preference tests were carried out with healthy and infected pine branches using the pine top weevil as a test insect. Weevil feeding increased the germination of E. pini aeciospores on pine extracts. Germination on previous year annual-shoot extracts was lower than that on current year annual-shoot extracts. The advance of the growing season increased this trend, but weevil feeding increased germination on extracts from older annual shoots to the levels found on extracts from current annual shoots. Spores germinated equally well on needle extracts and on phloem extracts. The weevils ate more often on infected branches than on healthy branches. E. pini infections may occur via woundings on branches and weevil feeding may facilitate this. 相似文献
19.
In this study, we investigated whether birds could be vectors facilitating long‐distance spread of Phytophthora ramorum in Britain. Migratory bird species associated with the main sporangium‐producing host plants and most likely to pick up P. ramorum spores were considered. Swabs were taken from the flank and “feet” of 1,014 birds over a 12‐month period (April 2011–March 2012) in the west of Britain and subsequently analyzed for the presence of P. ramorum using nested PCR. Ten positive samples from 10 birds were identified: three in Cornwall, one in Devon, three in Gloucestershire, two in north Wales and one in Merseyside. Phytophthora ramorum was detected on samples from four species of thrushes (Redwing Turdus iliacus, Fieldfare T. pilaris, Blackbird T. merula and Song Thrush T. philomelos) and one species of warbler (Chiffchaff Phylloscopus collybita). All birds that tested positive were sampled in late autumn and winter (October–February), when long‐distance movements (over 100 km) would have stopped. The low incidence of P. ramorum found using PCR suggests that the incidence of inoculum, whether viable or not, on birds was low. The apparently low incidence of inoculum on birds suggests migratory passerine birds can carry P. ramorum inoculum on their feathers and “feet,” albeit at low frequency. The dates of positive samples indicate that birds would not have been moving long distances at the time but further work is needed to estimate the extent of their contribution to the spread of P. ramorum in Britain. 相似文献
20.
《Scandinavian Journal of Forest Research》2012,27(1):1-6
Abstract The effect of soaking on germination and occurrence of fungal infections on Norway spruce (Picea abies (L.) Karst.) seeds and germinants was studied in three commercial seed lots. Treatments in which seeds were soaked in water for 24 h or in which the water was changed during the soak did not have an effect on the species diversity or on the abundance of the fungi isolated from the seeds. Different fungi were found in different seed lots. Most of those isolated are saprophytic or weakly pathogenic, but pathogens such as Sirococcus conigenus (D.C.) P.F. Cannon &; Minter and Trichothecium roseum (Pers.) Link were also isolated. Soaking increased germination energy but had no effect on final germination percentage. The number of mouldy seeds and germinants with disease symptoms was different among seed lots when seeds were germinated on water agar. When germinated in low humified Sphagnum peat, no differences in the emergence of disease symptoms were observed among seed lots. The frequency of disease was lower in peat than in water agar. Soaking had no effect on disease emergence in germination trials on either water agar or in Sphagnum peat. 相似文献