A comparison of two laboratory methods of maintaining field-collected Lymnaea tomentosa for the production of Fasciola hepatica metacercariae     

H.V. Whitlock  N.J. Campbell  D.C.M. Chow  S.J. Rolfe  C.J. Porter  J.D. Kelly 《Veterinary parasitology》1977,3(1):75-83

Four replicates of 50 field-collected Lymnaea tomentosa were maintained in two laboratory culture systems and their efficiency and practicability for the production of Fasciola hepatica metacercariae were assessed. There was no significant difference in the total number of metacercariae produced (56 552 from 64 snails in the closed container system and 54 073 from 82 snails in the shallow aquarium system).There was no significant difference between culture systems as assessed by snail survival, the number of infected snails or the number of infected snails harvested for the recovery of metacercariae. Within both systems there was a significant effect of snail size on the number of metacercariae produced. Optimum survival and production of metacercariae was achieved in young adult snails of 5–8 mm shell length at the time of infection.The collection of L. tomentosa from the field habitat and their maintenance in either culture system was shown to be a practical alternative to the breeding of laboratory adapted strains of L. tomentosa for the regular production of large numbers of F. hepatica metacercariae.  相似文献   

Temporal variation in nutrient status of a floodplain forest soil     

David L. Peterson  Gary L. Rolfe 《Forest Ecology and Management》1985,12(2):73-82

Seasonal variation in nutrient status of a floodplain soil was studied in a silver maple (Acer saccharinum L.) forest in central Illinois. Statistically significant temporal differences were measured in the concentration of NH₄-N, NO₃-N, and extractable P. Patterns of variation in NH₄-N and NO₃-N were related to organic C content and mineralization processes in the soil. Variation in extractable P was affected by flood-induced anaerobic conditions and soil pH. Temporal variation in soil nutrient status was one of the most dynamic features of nutrient cycling in the floodplain forest ecosystem. The potential for seasonal variation in the availability of nutrients should be considered when chemical data are used to characterize forest soil fertility and site productivity. Samples should be collected at several points in time if possible.  相似文献   

Dual control of avirulence in Leptosphaeria maculans towards a Brassica napus cultivar with 'sylvestris-derived' resistance suggests involvement of two resistance genes     

A. P. Van de Wouw  S. J. Marcroft  M. J. Barbetti  Li Hua  P. A. Salisbury  L. Gout  T. Rouxel  B. J. Howlett  M. H. Balesdent 《Plant pathology》2009,58(2):305-313

Blackleg disease (phoma stem canker) of Brassica napus (canola, oilseed rape) is caused by the fungus Leptosphaeria maculans . In some regions of Australia, resistance in oilseed rape cultivars derived from B. rapa subs . sylvestris (e.g. cv. Surpass 400) became ineffective within three years of commercial release. The genetic control of avirulence in L. maculans towards cv. Surpass 400 is described. When Australian field isolates were screened on this cultivar, three phenotypic classes were observed; virulent, intermediate and avirulent. Analysis of crosses between fungal isolates varying in their ability to infect cv. Surpass 400 demonstrated the presence of two unlinked avirulence genes, AvrLm1 and AvrLmS . Complementation of isolates (genotype avrLm1 ) with a functional copy of AvrLm1 , and genotyping of field isolates using a molecular marker for AvrLm1 showed that virulence towards Rlm1 is necessary, but not sufficient, for expression of a virulent phenotype on cv. Surpass 400. Taken together, these data strongly suggest that cv. Surpass 400, with ' sylvestris -derived' resistance, contains at least two resistance genes, one of which is Rlm1 .  相似文献   

Epidemiology of root rot caused by <Emphasis Type="Italic">Leptosphaeria maculans</Emphasis> in <Emphasis Type="Italic">Brassica napus</Emphasis> crops     

Susan J. Sprague  Barbara J. Howlett  John A. Kirkegaard 《European journal of plant pathology / European Foundation for Plant Pathology》2009,125(2):189-202

The infection of above-ground tissues of Brassica napus by Leptosphaeria maculans is well understood. However, root infection (root rot) under field conditions, the development of root rot over time and its relationship to other disease symptoms caused by L. maculans has not been described. A survey of B. napus crops was conducted in Australia to investigate the incidence and severity of root rot. Additionally, the pathway of root infection was examined in field experiments. Root rot was present in 95% of the 127 crops surveyed. The severity and incidence of root rot was significantly correlated with that of crown canker; however, the strength of this relationship was dependent on the season. Root rot symptoms appeared before flowering and increased in severity during flowering and at maturity, a pattern similar to crown canker suggesting that the infection of the root is an extension of the crown canker phase of the L. maculans lifecycle. All isolates of L. maculans tested in glasshouse experiments caused root rot and crown canker in B. napus and Brassica juncea. In the field, the main pathway of root infection is via invasion of cotyledons or leaves by airborne ascospores, rather than from inoculum in the soil. Root rot was present in crops in fields that had never been sown to B. napus previously, in plants grown in fumigated fields, and in glasshouse-grown plants inoculated in the hypocotyl with L. maculans.  相似文献   

Stifle osteochondritis dissecans in snow leopards (Uncia uncia)     

Herrin KV  Allan G  Black A  Aliah R  Howlett CR 《Journal of zoo and wildlife medicine》2012,43(2):347-354

Three snow leopard (Uncia uncia) cubs, female and male siblings and an unrelated female, had lameness attributed to osteochondritis dissecans (OCD) lesions noted at 6, 8, and 10 mo of age, respectively. All cubs were diagnosed with OCD via radiographs. The sibling cubs both had lesions of the right lateral femoral condyles, while the unrelated cub had bilateral lesions of the lateral femoral condyles. Subsequently, OCD was confirmed in all three cases during surgical correction of the lateral femoral condyle lesions via lateral stifle arthrotomies, flap removal, and debridement of the defect sites. Histopathology also supported the diagnosis of OCD. Postoperatively, the sibling cubs developed seromas at the incision sites and mild lameness, which resolved within a month. To date, two cubs have been orthopedically sound, while one of the sibling cubs has developed mild osteoarthritis. OCD has rarely been reported in domestic felids, and to the authors' knowledge these are the first reported cases of OCD in nondomestic felids.  相似文献   

Theriogenology question of the month     

RM Radcliffe  TH Witte  SL Fubini  NG Ducharme  SH Cheong  RO Gilbert 《Journal of the American Veterinary Medical Association》2012,241(4):439-442

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Sustainable Strategies for Managing Brassica napus (Oilseed Rape) Resistance to Leptosphaeria maculans (Phoma Stem Canker)     

Bruce D. L. Fitt  Neal Evans  Barbara J. Howlett  Mike Cooke 《European journal of plant pathology / European Foundation for Plant Pathology》2006,114(1):1-1

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Genetic Linkage Maps and Genomic Organization in Leptosphaeria maculans     

Marie-Line Kuhn  Lilian Gout  Barbara J. Howlett  Delphine Melayah  Michel Meyer  Marie-Hélène Balesdent  Thierry Rouxel 《European journal of plant pathology / European Foundation for Plant Pathology》2006,114(1):17-31

Leptosphaeria maculans is a haploid outcrossing ascomycete with a genome size of about 34 Megabases (Mb) which is predicted to have between 10,000 and 12,000 genes. The chromosomes of L. maculans are of a size range (0.7–3.5 Mb) and number (15–16) that can be readily resolved by pulsed field gel electrophoresis. Chromosome length polymorphisms are generated by meiosis giving rise to size differences as high as 57%, in the case of the ribosomal DNA-harbouring chromosome whose size varies between 1.8 and 4.2 Mb. Genetic maps are characterised by linkage groups comprising an accumulation of markers based on retrotransposon sequences. This, along with sequencing of pericentromeric regions and stretches of ORF-rich regions, suggest that the genome of L. maculans consists of a mosaic of GC-equilibrated coding regions with no or few transposons, and of stretches of highly degenerated and truncated retrotransposons, encompassing very few genes. Chromosome length polymorphisms are linked with the loss of dispensable regions. We suggest that the degree of length polymorphism for a particular chromosome correlates to the amount of dispensable retrotransposons, and that some gene-rich chromosomes may be less prone to undergo chromosome length polymorphisms than other chromosomes.  相似文献   

Serum bile acids in captive bustards     

Howlett JC  Hölzer W  Bailey TA  Wernery U  Samour JH  Naldo JL 《Zentralblatt für Veterin?rmedizin. Reihe B. Journal of veterinary medicine. Series B》1999,46(10):701-705

Blood samples were collected from clinically normal male and female houbara (Chlamydotis undulata macqueenii), kori (Ardeotis kori), buff-crested (Eupodotis ruficrista gindiana) and white-bellied bustards (E. senegalensis) to determine serum bile acid concentrations. Bile acid concentrations were determined by analysis with an Ultrospec 3000 ultraviolet/visible spectrophotometer, using an enzymatic bile acid test. The results provided values of serum bile acid concentrations for the four species, with means +/- standard errors of 35.8 +/- 2.8 mumol; 51.1 +/- 5.0 mumol; 18.4 +/- 2.1 mumol and 20.8 +/- 5.4 mumol for the houbara, kori, buff-crested and white-bellied bustard, respectively. Although no gender or age differences were detected within species, the results demonstrated significant differences in concentrations in clinically normal individuals between the different species.  相似文献   

Reaction of Brassica juncea (Indian Mustard) Lines to Australian Isolates of Leptosphaeria maculans under Glasshouse and Field Conditions     

Agus Purwantara  Phillip A. Salisbury  Wayne A. Burton  Barbara J. Howlett 《European journal of plant pathology / European Foundation for Plant Pathology》1998,104(9):895-902

Brassica juncea (Indian mustard) lines from diverse geographical locations around the world and from Australian breeding programs were screened for resistance to the blackleg fungus, Leptosphaeria maculans, in both glasshouse and field trials. The five Australian L. maculans isolates used in glasshouse trials could be classified into two groups; those that attacked all B. juncea lines, and those that attacked none. All these isolates caused lesions on cotyledons of B. napus cultivars including Westar, Glacier and Quinta, suggesting that they are in Pathogenicity Group 4 as described by Koch et al. (1991). The two isolates that attacked B. juncea also attacked B. napus lines to a similar extent, but did not attack the two B. carinata lines tested. Brassica lines were sown in a blackleg disease nursery at Lake Bolac, Victoria, Australia, and five indicators of blackleg disease were measured (survival rate, disease rating, disease incidence, external and internal lesion length). All 92 B. juncea lines developed blackleg symptoms. Although they displayed a high disease incidence in the field, almost all of the B. juncea lines were more blackleg-resistant than a B. napus cultivar, Dunkeld, which is amongst the most resistant cultivars in commercial production in Australia. Four B. carinata lines were more resistant than any of the B. juncea lines, suggesting that this species may be a useful source of blackleg resistance in B. napus breeding programs.  相似文献