Seasonal distribution of phytoplasmas in Australian grapevines   总被引：1，自引：0，他引：1  

F. E. Constable †§  K. S. Gibb  R. H. Symons 《Plant pathology》2003,52(3):267-276

The distribution and persistence of phytoplasmas were determined in Australian grapevines. Phytoplasmas could be detected using the polymerase chain reaction (PCR) from shoots, cordons, trunks and roots throughout the year, and phytoplasmas appear to persistently infect Australian grapevines from year to year. Phytoplasmas were not always detected in samples from the same sampling area from one sampling period to the next. Phytoplasma detection by PCR was improved by sampling from shoots, cordons and trunks, especially during October (early spring). The diseases expressed by the 20 grapevines used in the distribution and persistence studies were monitored. Australian grapevine yellows disease (AGY) was expressed by 17/20 grapevines at some time during the study, whilst only 4/20 and 15/20 grapevines expressed restricted growth disease (RG) and late season leaf curl disease (LSLC), respectively. All grapevines with RG and LSLC also had AGY. The three diseases were persistently expressed in some grapevines and remission of disease was observed in others. The results of PCR detection in the same grapevines indicated that phytoplasmas were more frequently detected in AGY-affected grapevines that also expressed RG and LSLC compared with grapevines expressing AGY alone. Phytoplasmas were detected in symptomless plant material but less frequently compared with AGY-affected material.  相似文献   

Habitat fragmentation in an urban environment: large and small fragments support different arthropod assemblages   总被引：1，自引：0，他引：1  

Heloise Gibb  Dieter F Hochuli 《Biological conservation》2002,106(1):91-100

We investigated the effects of fragmentation due to urbanisation on the species composition and functional roles of ants, beetles, spiders, flies and wasps. The study was conducted in 21 fragments of heath and woodland in south-eastern Australia classed as either ‘small’ (? 4 km²) or ‘large’ (? 80 km²). Arthropods were pitfall-trapped and identified to family or genus and morphospecies and microhabitat characteristics were recorded. Large fragments did not support more species per unit area than small fragments for most arthropods, although there were more species of ants per sampling unit in small than large woodland fragments, mainly due to a higher frequency of generalist species in smaller fragments. Large and small habitat fragments contained different assemblages of spiders, wasps and ants, indicating that predators and parasitoids are affected more strongly than other trophic groups. Arthropod assemblages within larger fragments where grids were furthest apart were less similar than those within smaller fragments where grids were closer together in woodland, but not in heath. The responses of arthropods to fragmentation suggest that, in addition to effects of reduced area and proximity to the urban matrix, changes in fire regimes and the degradation of habitats resulting from urbanisation, may have a role in altering arthropod assemblages, particularly affecting those species belonging to higher trophic levels. Management goals for urban remnants should identify mechanisms for controlling fire and anthropogenic disturbance such that they closely resemble the levels of these factors in larger fragments.  相似文献   

The diagnosis and treatment of vitamin B12 deficiency in young lambs     

K G Hogan  P P Lorentz  F M Gibb 《New Zealand veterinary journal》1973,21(11):234-237

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‘Candidatus Phytoplasma australiense’ is the phytoplasma associated with Australian grapevine yellows, papaya dieback and Phormium yellow leaf diseases     

Lia W. Liefting  Anna C. Padovan  Karen S. Gibb  Ross E. Beever  Mark T. Andersen  Richard D. Newcomb  David L. Beck  Richard L.S. Forster 《European journal of plant pathology / European Foundation for Plant Pathology》1998,104(6):619-623

Sequence comparisons and phylogenetic analysis of the 16S rRNA genes and the 16S/23S spacer regions of the phytoplasmas associated with Australian grapevine yellows, papaya dieback and Phormium yellow leaf diseases revealed minimal nucleotide differences between them resulting in the formation of a monophyletic group. Therefore, along with Australian grapevine yellows, the phytoplasmas associated with Phormium yellow leaf and papaya dieback should also be considered as Candidatus Phytoplasma australiense.  相似文献   

Effect of time of day on grazing behaviour by lactating dairy cows     

M. J. Gibb  C. A. Huckle  & R. Nuthall 《Grass and Forage Science》1998,53(1):41-46

An experiment was conducted to examine the effect of time of day on the rate of intake of herbage by grazing dairy cows. Eight unsupplemented Holstein Friesian cows in their fourth month of lactation grazed grass swards maintained at a sward surface height of 6·5 cm. Commencing at 07.00, 11.30, 16.00 and 19.00 h, intake rates were estimated by measuring the liveweight change, corrected for insensible weight loss, over a period of 1 h while grazing. During the period of grazing, recordings of jaw movement activity were made to determine total eating time, number of grazing jaw movements (GJMs) and bites. Total eating time over 24 h was measured: once before and once after determination of intake rate.
Although time of day did not affect GJM rate, it had a quadratic effect on the proportion of GJMs represented by biting and non-biting jaw movements, resulting in a significant effect on bite rate. Bite rate showed a quadratic effect of time, decreasing between 07.00 and 11.30 h, and then increasing by 16.00 h to reach a maximum at 19.00 h (52·6, 47·5, 51·6 and 59·4 bites min⁻¹ respectively). Bite mass (mg fresh matter bite⁻¹) was greatest at 07.00 h because of the lower dry-matter (DM) content of the herbage and the presence of surface moisture at that time, but the effect of time of day was not significant. Mean bite mass measured as DM or organic matter (OM) differed significantly between the different times of day (332, 384, 481 and 402 mg DM and 302, 348, 438 and 367 mg OM bite⁻¹ respectively). The net result of these differences in bite rate and bite mass was a linear increase in DM and OM intake rate over the day. The magnitude of such differences will have profound effects on mean daily intakes when calculated as the product of total eating time and intake rate.  相似文献   

Congenital anemia, dyskeratosis, and progressive alopecia in Polled Hereford calves   总被引：1，自引：0，他引：1  

D J Steffen  H W Leipold  J Gibb  J E Smith 《Veterinary pathology》1991,28(3):234-240

A new syndrome of anemia, alopecia, and dyskeratosis was identified in Polled Hereford calves in this study. Cutaneous changes included hyperkeratosis and hair loss around the muzzle and ear margins, which progressed to a generalized alopecia and hyperkeratotic dermatitis. Histologically, orthokeratotic hyperkeratosis with dyskeratosis of epidermal and follicular keratinocytes was present. Alopecia was correlated with dyskeratosis of Huxley's layer and an increasing proportion of follicles in the telogen phase of the hair cycle. Dermatitis was characterized by a mild dermal mononuclear cell infiltrate and mild lymphocytic perivascular dermatitis. The anemia present at birth was nonprogressive and was classified as normochromic and normocytic to macrocytic. Reticulocytosis was absent, but bone marrow was markedly hyperplastic. Nuclear cytoplasmic asynchrony of the rubricyte and metarubricyte stages occurred in the bone marrow. Abnormal rubricyte nuclei and maturation arrest at the late rubricyte stage were common. Cytologic features of the erythroid series are similar to those of type I congenital dyserythropoietic anemia of human beings. Genealogic features suggest that this is a primary hereditary defect. The mode of inheritance, however, remains to be determined.  相似文献   

Conservation-oriented forestry and early successional saproxylic beetles: Responses of functional groups to manipulated dead wood substrates     

H. Gibb  R.B. Pettersson  J. Hilszczański  J.P. Ball  O. Atlegrim 《Biological conservation》2006,129(4):437-450

New conservation-oriented forestry aims to maintain intact populations of forest organisms by improving the conservation value of managed forests and providing protected areas. We tested the conservation value of treatments of dead wood for assemblages of early successional saproxylic beetles. In nine areas in northern Sweden, we selected one clear-cut, one mature managed forest and one reserve. In 2001-2002, we placed three blocks of spruce logs, each containing control, burned and shaded logs and a high stump (“snag”) at each site. Saproxylic beetles emerging from the dead wood were collected using emergence traps and beetles flying close to it were collected using flight-intercept traps. After one year of exposure, assemblage composition was examined, with respect to nutritionally-defined functional groups, red-listed species and fire-favoured species. Experimental snags were most complementary to control logs, supporting different assemblages of cambium consumers and fungivores and supporting more red-listed individuals. Burned logs supported depauperate assemblages, particularly with respect to cambium consumers, while shading of logs affected assemblages of fungivores, but only on clear-cuts. Despite containing less dead wood, managed forests provided valuable habitat, supporting similar assemblages of saproxylic beetles to reserves. Most functional groups were less abundant on clear-cuts than in older forests, but fire-favoured species were more common on clear-cuts, suggesting that clear-cuts may support assemblages of species associated with natural disturbances, if suitable substrates are available. Utilization of logs by saproxylic beetles changes over time, so long-term monitoring of our experimental logs will determine their lifetime conservation value.  相似文献   

Volatile constituents of fermented sugar baits and their attraction to lepidopteran species     

El-Sayed AM  Heppelthwaite VJ  Manning LM  Gibb AR  Suckling DM 《Journal of agricultural and food chemistry》2005,53(4):953-958

The volatile compounds emanating from four fermented sugar baits, palm sugar, golden cane syrup, port wine, and molasses, were isolated by headspace sampling and analyzed by gas chromatography-mass spectrometry. Three classes of compounds including esters, alcohols, and aromatic compounds were identified in the headspace of the four fermented sugar baits. There was a high degree of qualitative similarity between the headspace contents of the four fermented sugar baits, although quantitatively they varied considerably. Ethyl acetate, 3-methylbutanol, ethyl hexanoate, 2-phenylethanol, ethyl octanoate, ethyl (E)-4-decenoate, ethyl decanoate, and ethyl dodecanoate were the major compounds identified in the headspace of the four fermented sugar baits. The efficacy of the four fermented sugar baits was investigated in field trapping experiments. Fermented palm sugar and golden cane syrup were superior in attracting significant numbers of moths as compared to port wine and molasses. Fermented molasses was the least attractive among the four baits. Over 90% of the insects caught were noctuids with Graphania mutans and Tmetolophota spp. being the main noctuids captured (over 55%) in the four fermented sugar baits. Male and female G. mutans were equally attracted to the four sugar baits. A number of tortricid species were also trapped.  相似文献   

Effluents from livestock: Gasser,J. K. R. (Editor), Applied Science Publishers Ltd,London, 1980, 712 pp. Price: £32.00     

J.A.C. Gibb 《Agricultural Systems》1981,7(3):239-240

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Sward structure management for a maximum short‐term intake rate in annual ryegrass     

M. F. Amaral  J. C. Mezzalira  C. Bremm  J. K. Da Trindade  M. J. Gibb  R. W. M. Suñe  P. C. de F. Carvalho 《Grass and Forage Science》2013,68(2):271-277

This study tested the hypothesis that different sward structures, which were constructed by varying the pre‐ and post‐grazing sward heights of annual ryegrass pasture (Lolium multiflorum Lam.) in southern Brazil, affect the short‐term intake rate (STIR) by dairy cows. Treatments consisted of four sward‐management strategies defined by a combination of two pre‐ (25 and 15 cm) and two post‐grazing sward heights (10 and 5 cm): 15‐05, 15‐10, 25‐05 and 25‐10. A completely randomized block design with four replicates was used for the experimental design. The STIR was determined by the double‐weighing technique. Jaw movements were evaluated using automatic recorders (IGER Behaviour Recorder). The results showed that treatment 25‐10 allowed the animals to collect more herbage with a greater bite mass and thus resulted in a greater STIR. Treatments in which sward height was reduced to 10 cm generally favoured the ingestion process than treatments with a post‐grazing sward height of 5 cm.  相似文献