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31.
32.
Eiji Tanaka Chihiro Tanaka Atsushi Ishihara Yasumasa Kuwahara Mitsuya Tsuda 《Journal of General Plant Pathology》2003,69(1):1-6
Aciculosporium take (Ascomycota; Clavicipitaceae) is a causal agent of witches' broom of
bamboo plants. The symptoms of this disease are believed to be induced by plant
hormones, particularly auxins. Indole-3-acetic acid (IAA) was identified in
cultures of this fungus in an l-tryptophan-supplemented liquid medium.
IAA production was confirmed on 30 isolates of A. take from various
hosts and locations at levels up to 1 mg/l. The biosynthetic pathway of
IAA in A. take culture was examined by analyzing intermediate products
and by feeding experiments. The results showed that the indole-3-pyruvic acid
pathway (l-tryptophan → indole-3-pyruvic acid → indole
acetaldehyde → IAA) was the dominant pathway in A. take.
Received: June 3, 2002 / Accepted: July 25, 2002 相似文献
33.
Hiromitsu Furuya Tsutomu Matsumoto Shin-ichi Fuji Hideki Naito 《Journal of General Plant Pathology》2003,69(2):115-119
Rice seedling growth, estimated by plant height and root development and discoloration, was better in pasteurized soil than
in unpasteurized soil obtained from a flooded rice field. Rice seedlings also grew better in sterilized soil modified by adding
roots harvested from the pasteurized soil than in soil modified by adding roots harvested from the unpasteurized soil. The
results demonstrate that seedling growth in the rice field soil was inhibited by soil microorganisms, even though no typical
symptoms such as seedling blight or damping-off appeared. Pythium aristosporum is suggested to be involved in the inhibition. Thus, it appears that inconspicuous restraint of rice seedling growth could
occur in soils of rice paddy fields.
Received: May 20, 2002 / Accepted: October 16, 2002
Acknowledgments The authors thank Dr. T. Ichitani, former professor at Osaka Prefectural University, for providing an isolate of Pythium aristosporum for comparison, and Mr. Mitsuaki Sato of Akita Prefectural College of Agriculture for technical assistance. 相似文献
34.
35.
Norman Owen-Smith 《Landscape Ecology》2004,19(7):761-771
Large mammalian herbivores are notorious for their propensity towards population irruptions and crashes, yet many herbivore populations remain relatively stable. I explore how resource heterogeneity within landscapes dampens population instability, using a metaphysiological modelling approach considering patch state distributions. Resource heterogeneity is functionally stabilizing through spreading consumption away from preferred resources before these become critically depleted. Lower-quality resources act as a buffer against starvation during critical periods of the seasonal cycle. Enriching resource quality is destabilizing, even if patch diversity is maintained, because food quantity then becomes the limitation. The potential consequences of landscape fragmentation are explored using the Serengeti ecosystem, characterised by broadscale resource gradients, as a hypothetical example. Further insights provided by the model are illustrated with specific examples concerning the effects of patch scales and waterpoint distribution. A metaphysiological modelling approach enables the basic consequences of landscape heterogeneity to be distinguished from further effects that may arise from specific patch scales and configurations, without the distracting detail of spatially explicit models. 相似文献
36.
37.
Characterizing historical and modern fire regimes in Michigan (USA): A landscape ecosystem approach 总被引:4,自引:0,他引:4
Cleland David T. Crow Thomas R. Saunders Sari C. Dickmann Donald I. Maclean Ann L. Jordan James K. Watson Richard L. Sloan Alyssa M. Brosofske Kimberley D. 《Landscape Ecology》2004,19(3):311-325
We studied the relationships of landscape ecosystems to historical and contemporary fire regimes across 4.3 million hectares in northern lower Michigan (USA). Changes in fire regimes were documented by comparing historical fire rotations in different landscape ecosystems to those occurring between 1985 and 2000. Previously published data and a synthesis of the literature were used to identify six forest-replacement fire regime categories with fire rotations ranging from very short (<100 years) to very long (>1,000 years). We derived spatially-explicit estimates of the susceptibility of landscape ecosystems to fire disturbance using Landtype Association maps as initial units of investigation. Each Landtype Association polygon was assigned to a fire regime category based on associations of ecological factors known to influence fire regimes. Spatial statistics were used to interpolate fire points recorded by the General Land Office. Historical fire rotations were determined by calculating the area burned for each category of fire regime and dividing this area by fifteen (years) to estimate area burned per annum. Modern fire rotations were estimated using data on fire location and size obtained from federal and state agencies. Landtype Associations networked into fire regime categories exhibited differences in both historical and modern fire rotations. Historical rotations varied by 23-fold across all fire rotation categories, and modern forest fire rotations by 13-fold. Modern fire rotations were an order of magnitude longer than historical rotations. The magnitude of these changes has important implications for forest health and understanding of ecological processes in most of the fire rotation categories that we identified.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
38.
A protocol for the production of complete plantlets through multiple shoots from the cotyledon-derived calli of ash gourd (Benincasa hispida L.) is described. The embryos were excised from mature seeds and cultured on Murashige and Skoog (MS) medium supplemented with 6-benzylaminopurin (BAP, 1–5 μM). After 10 days the well-developed green cotyledons from the growing embryos were isolated and cultured on MS medium fortified with 2,4-D (1–6 μM). The cultured cotyledons gave rise to luxuriantly growing calli after 6 weeks. These calli were subcultured on MS medium supplemented with various concentrations of BAP (1–6 μM) alone or in combination with naphthalene acetic acid (NAA, 0.2 and 0.5 μM) for regeneration. The regenerated shoots were multiplied and rooted on quarter strength MS medium supplemented with indole-3-butyric acid or NAA (1–5 μM). The rooted shoots were transplanted to soil with 90% success. 相似文献
39.
Judith Hübschen Lilo Kling Ulrike Ipach Volker Zinkernagel Nathalie Bosselut Daniel Esmenjaud Derek J.F. Brown Roy Neilson 《European journal of plant pathology / European Foundation for Plant Pathology》2004,110(8):779-788
Xiphinema diversicaudatum and X. index are vector nematode species of economic importance in viticulture regions as they can transmit Arabis Mosaic, Grapevine Fanleaf and Strawberry Latent Ringspot viruses to grapevine. Wang et al. (2003) designed species-specific diagnostic primers from ribosomal genes for both these vector species as well as a vector and a non-vector species X. italiae and X. vuittenezi, respectively. Our study aimed to confirm the specificity and determine the sensitivity and reliability of the primers for the two vector species, X. diversicaudatumand X. indexwhen challenged with closely related longidorid species and general nematode communities typical of vineyard soil. With one exception, no PCR product was observed when the primers were tested against six Longidorus, one Paralongidorus and one Xiphinema non-target species. Occasionally (three out of eight replicate PCR reactions) a weak PCR product was noted when primers for X. index were tested with L. elongatus. Furthermore, when challenged with a range of non-target nematode species comprising the nematode community typical of viticulture soil, no PCR product was amplified. An experimental dilution series of extracted DNA rigorously demonstrated that DNA from an equivalent single specimen of the target virus-vector species, X. diversicaudatum and/or X. index, could be detected amongst 1000 equivalent non-targetX. vuittenezi. Also, extracted DNA from an equivalent single target specimen was detected when added to DNA extracted from the overall soil nematode community. The primers were assessed further by using serial mixtures of actual nematodes rather than extracted DNA to simulate field soil. Using this method, a single target nematode could be detected amongst 200 non-target specimens. Given their specificity, sensitivity and reliability, it appears that these diagnostic primers will be of great benefit to phytosanitary/quarantine services related to the viticulture industry. 相似文献
40.
K Christiana Grim Thomas McCutchan Jun Li Margery Sullivan Thaddeus K Graczyk Glenn McConkey Michael Cranfield 《Journal of zoo and wildlife medicine》2004,35(2):154-161
Captive juvenile African black-footed penguins (Spheniscus demersus) housed in an outdoor enclosure at the Baltimore Zoo have an average 50% mortality from avian malarial (Plasmodium sp.) infection each year without intense monitoring for disease and chemotherapeutic intervention. During the 1996 malaria transmission season, the safety and efficacy of an anti-circumsporozoite (CSP) DNA vaccine encoding the Plasmodium gallinaceum CSP protein against P. relictum were studied. The goal was to reduce clinical disease and death without initiating sterile immunity after release into an area with stable, endemic avian malaria. The birds were monitored for adverse clinical signs associated with vaccination, the stimulation of an anti-CSP antibody response, and protection afforded by the vaccine. The presence of P. relictum in trapped culicine mosquitoes within the penguin enclosure was monitored to assess parasite pressure. Among the vaccinated penguins, the parasitemia rate dropped from approximately 50% to approximately 17% despite intense parasite pressure, as determined by mosquito infection rate. During the year of the vaccine trial, no mortalities due to malaria occurred and no undesirable vaccination side effects occurred. This is the first trial of an antimalarial vaccine in a captive penguin colony. 相似文献