共查询到20条相似文献，搜索用时 15 毫秒
1.
D. W. McKenzie 《The Journal of Horticultural Science and Biotechnology》2013,88(2):138-139
A strain of arabis mosaic virus, introduced in unsterilized compost, caused severe disease and complete loss of crop in cucumbers under glass. The virus was transmitted by sap inoculation to 42 out of 73 plant species. Infected Nicotiana clevelandii plants were freed from the virus when grown at 38° C. for three weeks. Although closely related serologically to isolates of arabis mosaic from raspberry and Sambucus nigra, the cucumber isolate did not protect some plants against the Sambucus isolate. Purified virus preparations contained “ spherical ” particles about 30 mμ diameter, and produced specific light-scattering zones in density-gradient centrifugation. 相似文献
2.
To aid effective conservation and management there is a need to understand the effect of landscape on species ecology. The
aim of this research was to assess the effect of landscape parameters on breeding success of barn owls throughout the Rother
and Arun River catchments, Sussex, UK. We used a Geographic Information System to describe the habitat mosaic and landscape
structure within an estimated home range area of 3 km2 around 85 artificial nest box sites. Results showed that land cover was less heterogeneous at successful sites, with home
ranges dominated by a few habitat types of regular patch shapes. Unsuccessful nesting sites had significantly more improved
grassland, suburban land and wetlands than successful sites. Cluster analysis and Principle Components Analysis was used to
assess the similarity of the habitat mosaic within these areas and pellet analysis was undertaken to assess barn owl diet
and prey availability. Ten prey species were recovered from pellets, field vole (Microtus agrestis), common shrews (Sorex araneus) and house mice (Mus musculus) making up nearly 90% of recoveries. However box sites varied in relative proportions of small mammal, and hence prey availability.
Results indicated that land use and landscape structure can affect breeding success in barn owls. Higher levels of poor quality
small mammal habitat were associated with unsuccessful sites. However, at a landscape scale, the habitat mosaic across the
study area lacked variation, limiting analysis and clear correlations between habitat type and positive breeding success,
suggesting that a finer scale was needed in future studies utilising this approach. 相似文献
3.
V. Venkataravanappa C. N. L. Reddy N. S. Chauhan B. Singh S. K. Sanwal M. Krishna Reddy 《The Journal of Horticultural Science and Biotechnology》2016,91(2):161-168
Ten okra (Abelmoschus esculentus L.) plants showing distinct yellow vein mosaic disease (YVMD) symptoms were collected from different fields in Karnataka State, India. The genomic DNA of the isolated viruses was amplified, cloned, and sequenced. Sequence analysis revealed that the DNA-A-like sequences of all ten isolates were identical. Sequence analysis of a representative virus isolate (OYSK2) with other begomovirus sequences available in GenBank showed ≥90% sequence identity with Bhendi yellow vein Maharashtra virus (BYVMaV; EU482411) and ≤89% homology with full-length Bhendi yellow vein mosaic virus (BYVMV) infecting okra on the Indian subcontinent. These results suggested that a new strain of BYVMaV was present in all ten samples collected from the field. A source of resistance to BYVMaV and naturally present virus isolates causing YVMD was identified by screening okra genotypes under artificial and natural inoculation conditions, respectively. None of the genotypes tested showed complete immunity to BYVMaV. However, the okra genotypes ‘Tulasi’ and ‘Trisha’ were only moderately susceptible under glasshouse and field conditions. The new begomovirus strain could be detected by dot-blot hybridisation using a non-radioactive DNA probe in the virus samples collected from both symptomless and symptomatic okra plants. 相似文献
4.
J. VINE Sallie O.P. Jones 《The Journal of Horticultural Science and Biotechnology》2013,88(3):281-284
The culture of hop shoot tips has proved highly effective in eliminating Prunus necrotic ringspot and hop mosaic virus from eleven varieties of hop. The culture technique was successful even when plants were raised from tips as long as 5 mm. 相似文献
5.
This study describes the demographic features of a population of Sigmodon hispidus utilizing the habitat mosaic provided by a Carolina Bay on the Atlantic coastal plain of South Carolina. A total of 71 cotton rats were captured 160 times on a 4 ha grid during a winter decline from 25/ha to less that 1/ha. Body weights of adults declined until early February and then increased; those of subadults grew very slowly until February followed by a spurt in growth. Weight gain did not differ between survivors and non-survivors for males, but female survivors gained 1.5 g per week more than non-survivors. Female subadults exhibited higher mortality early in the decline and males later.Adult females were randomly distributed across 8 microhabitats, whereas adult males were almost exclusively confined to heavy Rubus cover. Subadult males used wet sites more than any other cohort; subadult females were widely distributed using drier sites most frequently. By the end of the decline, all survivors were localized in Rubus-dominated patches. No statistically significant changes in electromorph genotypes or allele frequencies were detected, but survivors had a higher frequency of the F-allele at the adenylate kinase locus than did non-survivors (42.3% vs. 16.7%).Our findings affirm the importance of a landscape perspective in understanding the population dynamics of cotton rats, and show how a habitat mosaic influences survival differentially among sex-age cohorts. 相似文献
6.
The intensively farmed coastal lowland landscape of Germany, adjacent to the North Sea, provides important foraging opportunities
for Black-headed, Common, Herring and Lesser Black-backed gull (Larus ridibundus, L. canus, L. argentatus and L. fuscus). We expected that spatial and temporal utilization of the landscape mosaic as well as behavioural traits and utilization
of food resources would differ between these closely related species, facilitating niche segregation. We recorded habitat
types and their utilization by the four species over a whole year. Furthermore, we related species abundance to several abiotic
parameters. Black-headed and Common gulls were the most numerous species in the study area throughout the year. In general,
the former species preferred bare fields with recently prepared soils and was often associated with tractors in the fields,
whereas the latter species was most often found on pastures. Black-headed gulls seem to have a higher ability to exploit ephemeral,
food sources associated with human activities whereas common gulls prefer habitats with low human activity and with naturally
distributed prey. The most prominent abiotic parameter influencing gull abundance was presence of tractors. Black-headed gulls
have most likely benefited from recent changes in agricultural practice, particularly the increase in cropped land, while
Common gulls may have suffered from a decline in pastures. At present, utilization of the farmland habitat mosaic leads to
niche segregation and supports coexistence, as two of the four gull species mainly forage in the marine environment, while
there is significant habitat partitioning between the other two temporally, spatially and behaviourally. 相似文献
7.
Background
Plant viruses are useful expression vectors because they can mount systemic infections allowing large amounts of recombinant protein to be produced rapidly in differentiated plant tissues. Pepino mosaic virus (PepMV) (genus Potexvirus, family Flexiviridae), a widespread plant virus, is a promising candidate expression vector for plants because of its high level of accumulation in its hosts and the absence of severe infection symptoms. We report here the construction of a stable and efficient expression vector for plants based on PepMV. 相似文献8.
Andrzej Pacak Katrin Geisler Bodil Jørgensen Maria Barciszewska-Pacak Lena Nilsson Tom Hamborg Nielsen Elisabeth Johansen Mette Grønlund Iver Jakobsen Merete Albrechtsen 《Plant methods》2010,6(1):26
Background
Gene silencing vectors based on Barley stripe mosaic virus (BSMV) are used extensively in cereals to study gene function, but nearly all studies have been limited to genes expressed in leaves of barley and wheat. However since many important aspects of plant biology are based on root-expressed genes we wanted to explore the potential of BSMV for silencing genes in root tissues. Furthermore, the newly completed genome sequence of the emerging cereal model species Brachypodium distachyon as well as the increasing amount of EST sequence information available for oat (Avena species) have created a need for tools to study gene function in these species. 相似文献9.
S. M. Paul KHURANA K.S. Bhargava 《The Journal of Horticultural Science and Biotechnology》2013,88(2):209-211
Seven aphids were tested for their ability to transmit 3 viruses of papaya. Mild mosaic virus (MMV) was transmitted by Aphis craccivora, A. gossypii and Myzus persicae. Distortion ringspot virus (DRV) was transmitted by A. nerii, Lipaphis pseudobrassicae and M. persicae. Ringspot virus (RSV) was transmitted only by M. persicae. Specificity of transmission by the aphid vectors of MMV and DRV was demonstrated. A. craccivora, A. nerii and L. pseudobrassicae are reported as new vectors of these viruses. 相似文献
10.
Yingzhen Yang Alex Costa Nathalie Leonhardt Robert S Siegel Julian I Schroeder 《Plant methods》2008,4(1):6
Background
A common limitation in guard cell signaling research is that it is difficult to obtain consistent high expression of transgenes of interest in Arabidopsis guard cells using known guard cell promoters or the constitutive 35S cauliflower mosaic virus promoter. An additional drawback of the 35S promoter is that ectopically expressing a gene throughout the organism could cause pleiotropic effects. To improve available methods for targeted gene expression in guard cells, we isolated strong guard cell promoter candidates based on new guard cell-specific microarray analyses of 23,000 genes that are made available together with this report. 相似文献11.
Eastern grey squirrels (Sciurus carolinensis) and North American red squirrels (Tamiasciurus hudsonicus) were studied among wooded patches within an agricultural mosaic. Fifteen sites south of Ottawa, Canada, with differing landscape and local features were censused using tracking boards placed in a woods or wooded fencerow. Regression analyses of landscape compositional and physiognomic variables within a 1-km radius isolated the best predictors of grey and red squirrel abundance and activity. Grey squirrels were found in both small woods and fencerows in farm landscapes but were not found in large woods. A polynomial regression of wooded patch size explained 79% of the variance in grey squirrel abundance. Grey squirrel activity was correlated with the percent cover of soybeans in the landscape. Red squirrels were found in fencerows, small and large woods; activity was correlated with the percent cover of both woods and corn crop in the surrounding landscape. These results indicate that distributions of both species are influenced by multiple landscape elements, but that grey squirrels may rely on fragmented agricultural landscapes whereas red squirrels make more use of both native woodland and altered landscapes. 相似文献
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13.
Recent research shows that land use history is an important determinant of current ecosystem function. In the United States,
characterization of land use change following European settlement requires reconstruction of the original property mosaic.
However, this task is difficult in unsystematically surveyed areas east of the Appalachian Mountains. The Gwynns Falls watershed
(Baltimore, MD) was originally surveyed in the 1600-1700s under a system of warrants and patents (commonly known as ‘metes
and bounds’). A method for the reconstruction and mapping of warrant and patent properties is presented and used to map the
original property mosaic in the Gwynns Falls watershed. Using the mapped mosaic, the persistence of properties and property
lines in the current Gwynns Falls landscape is considered. The results of this research indicate that as in agricultural areas,
the original property lines in the Gwynns Falls watershed are persistent. At the same time, the results suggest that the property
mosaic in heavily urbanized/suburbanized areas is generally ‘reset.’ Further, trends in surveying technique, parcel size,
and settlement patterns cause property line density and property shape complexity to increase in the less urbanized upper
watershed. The persistence of original patterns may be damping expression of heterogeneity gradients in this urban landscape.
This spatial pattern of complexity in the original mosaic is directly opposite of hypothesized patterns of landscape heterogeneity
arising from urbanization. The technique reported here and the resulting observations are important for landscape pattern
studies in areas settled under unsystematic survey systems, especially the heavily urbanized areas of the eastern United States.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
Recent research shows that land use history is an important determinant of current ecosystem function. In the United States,
characterization of land use change following European settlement requires reconstruction of the original property mosaic.
However, this task is difficult in unsystematically surveyed areas east of the Appalachian Mountains. The Gwynns Falls watershed
(Baltimore, MD) was originally surveyed in the 1600-1700s under a system of warrants and patents (commonly known as ‘metes
and bounds’). A method for the reconstruction and mapping of warrant and patent properties is presented and used to map the
original property mosaic in the Gwynns Falls watershed. Using the mapped mosaic, the persistence of properties and property
lines in the current Gwynns Falls landscape is considered. The results of this research indicate that as in agricultural areas,
the original property lines in the Gwynns Falls watershed are persistent. At the same time, the results suggest that the property
mosaic in heavily urbanized/suburbanized areas is generally ‘reset.’ Further, trends in surveying technique, parcel size,
and settlement patterns cause property line density and property shape complexity to increase in the less urbanized upper
watershed. The persistence of original patterns may be damping expression of heterogeneity gradients in this urban landscape.
This spatial pattern of complexity in the original mosaic is directly opposite of hypothesized patterns of landscape heterogeneity
arising from urbanization. The technique reported here and the resulting observations are important for landscape pattern
studies in areas settled under unsystematic survey systems, especially the heavily urbanized areas of the eastern United States.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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17.
Miriam M. Hansbauer Ilse Storch Felix Knauer Stefan Pilz Helmut Küchenhoff Zsolt Végvári Rafael G. Pimentel Jean Paul Metzger 《Landscape Ecology》2010,25(3):407-417
Even among forest specialists, species-specific responses to anthropogenic forest fragmentation may vary considerably. Some
appear to be confined to forest interiors, and perceive a fragmented landscape as a mosaic of suitable fragments and hostile
matrix. Others, however, are able to make use of matrix habitats and perceive the landscape in shades of grey rather than
black-and-white. We analysed data of 42 Chiroxiphia caudata (Blue Manakin), 10 Pyriglena leucoptera (White-shouldered Fire-eye) and 19 Sclerurus scansor (Rufous-breasted Leaftosser) radio-tracked in the Atlantic Rainforest of Brazil between 2003 and 2005. We illustrate how
habitat preferences may determine how species respond to or perceive the landscape structure. We compared available with used
habitat to develop a species-specific preference index for each of six habitat classes. All three species preferred old forest,
but relative use of other classes differed significantly. S. scansor perceived great contrast between old forest and matrix, whereas the other two species perceived greater habitat continuity.
For conservation planning, our study offers three important messages: (1) some forest specialist species are able to persist
in highly fragmented landscapes; (2) some forest species may be able to make use of different anthropogenic habitat types
to various degrees; whereas (3) others are restricted to the remaining forest fragments. Our study suggests species most confined
to forest interiors to be considered as potential umbrella species for landscape-scale conservation planning. 相似文献
18.
19.
Samuel A. Cushman 《Landscape Ecology》2016,31(3):481-489
Background
Applications of entropy and the second law of thermodynamics in landscape ecology are rare and poorly developed. This is a fundamental limitation given the centrally important role the second law plays in all physical and biological processes. A critical first step to exploring the utility of thermodynamics in landscape ecology is to define the configurational entropy of a landscape mosaic. In this paper I attempt to link landscape ecology to the second law of thermodynamics and the entropy concept by showing how the configurational entropy of a landscape mosaic may be calculated.Result
I begin by drawing parallels between the configuration of a categorical landscape mosaic and the mixing of ideal gases. I propose that the idea of the thermodynamic microstate can be expressed as unique configurations of a landscape mosaic, and posit that the landscape metric Total Edge length is an effective measure of configuration for purposes of calculating configurational entropy.Conclusions
I propose that the entropy of a given landscape configuration can be calculated using the Boltzmann equation. Specifically, the configurational entropy can be defined as the logarithm of the number of ways a landscape of a given dimensionality, number of classes and proportionality can be arranged (microstates) that produce the observed amount of total edge (macrostate).20.
D. G. A. Walkey 《The Journal of Horticultural Science and Biotechnology》2013,88(3):283-287
The apical tip-culture technique has been used to produce virus-free rhubarb from infected plants of the varieties Timperley Early, Victoria and Prince Albert. Growth on various nutrient media was compared. The survival rate of the tips was directly related to their size within the range 300–2,500 μ (diam.). After initial culture on filter paper in sterile tubes, the young plants were transferred to autoclaved sand watered with mineral nutrient on which they made better growth than on other media.Turnip mosaic, cherry leaf-roll, strawberry latent ringspot and cucumber mosaic viruses, in various combinations, were eliminated by this method. Arabis mosaic was removed from most plants but a few retained this virus. This retention was not related to the size of the tip taken. 相似文献