Effects of Soil Flooding on the Survival of Two Potato Pathogens, Sclerotinia sclerotiorum and Verticillium dahliae

Results of studies on survival of sclerotia of Sclerotinia and microsclerotia of Verticillium, demonstrated that soil flooding in western Washington is a possible alternative field rotation practice for S. sclerotiorum (white mold), but not for V. dahliae (Verticillium wilt). Cone-tainer experiments in the greenhouse showed that flooding at 16.5 °C caused S. sclerotiorium sclerotia to lose viability between 12 and 24 weeks while a growth chamber experiment revealed that flooding for 18 weeks at 11 °C or 20 °C was sufficient. V. dahliae microsclerotia appeared resistant to flooding under greenhouse and field settings; recovery ranged within 5 to 10 % of the initial soil population after 6 and 12 months. Potatoes planted into field microplots either flooded or fallowed the previous summer had similar Verticillium wilt ratings and potato yield. Lack of control of V. dahliae by flooding may be due partly to relatively low soil temperatures in a cool, marine climate.     

Magnetic Field and Plasma Observations at Mars: Initial Results of the Mars Global Surveyor Mission

The magnetometer and electron reflectometer investigation (MAG/ER) on the Mars Global Surveyor spacecraft has obtained magnetic field and plasma observations throughout the near-Mars environment, from beyond the influence of Mars to just above the surface (at an altitude of approximately 100 kilometers). The solar wind interaction with Mars is in many ways similar to that at Venus and at an active comet, that is, primarily an ionospheric-atmospheric interaction. No significant planetary magnetic field of global scale has been detected to date (<2 x 10(21) Gauss-cubic centimeter), but here the discovery of multiple magnetic anomalies of small spatial scale in the crust of Mars is reported.     

Improved disease resistance in Rana rugulosa (Daudin) after β-glucan administration

There is an increasing problem with bacterial disease associated with stress in farmed frogs. In general, little is known about the immune system in farmed tropical ranid species and, in particular, about its functional ability. As part of a study on the non-specific immune system, immunostimulation by β-glucan was evaluated in preventing bacterial disease in cultured ranid frogs. Fifty frogs were grown to a mean weight of 40 g and separated into three experimental groups. These were exposed to a motile aeromonad bacterial challenge alone (Au), bacterial challenge with β-glucan (Au + glucan) or saline only (controls) to serve as controls. There were four replicate tanks containing five frogs per tank in each experimental group. After bacterial challenge, all the animals were observed twice daily, and the number of mortalities per tank was recorded. The liver was sampled in order to recover bacteria, and any colonies grown were identified. The survival of the β-glucan-treated frogs was significantly higher than that of the bacterial challenge group alone.     

Analysis of DNA relationships among Aeromonas species by RAPD (randomly amplified polymorphic DNA) typing

Genetic differences between a collection of aeromonads were studied in two laboratories by analysis of randomly amplified polymorphic DNA (RAPD). A single randomly designed primer, generated reproducible profiles of genomic DNA in both laboratories for Aeromonas salmonicida subspecies salmonicida, although the profiles differed between laboratories. Analysis of atypical strains of A. salmonicida and isolates of the A. hydrophila group produced scattered profiles in both laboratories. The uniform fingerprints produced for A. salmonicida subspecies salmonicida indicate genomic homogeneity. The scattered RAPD profiles of the motile aeromonads demonstrate the genomic diversity of this group. A group of unspeciated motile aeromonads gave uniform fingerprints, suggesting the possibility of a genomically homogeneous species. Although the RAPD technique is susceptible to the effects of minor technical variations, this study has demonstrated that where there is DNA similarity, it can be recognized, and where there is diversity, differentiation can be made. RAPD promises to be useful in epidemiological studies for rapid identification of bacteria where a source of reference DNA is available and may be useful in preliminary investigations of relatedness within groups.     

Defender: A high-yielding, processing potato cultivar with foliar and tuber resistance to late blight

The potato cultivar Defender is high-yielding, white-skinned, and notable for having foliar and tuber resistance to late blight infection caused byPhytophthora infestans (Mont.) de Bary. It was released in 2004 by the USDA-ARS and the agricultural experiment stations of Idaho, Oregon, and Washington. Defender is suitable for processing into french fries and other frozen potato products directly from the field or from storage. Defender also may be used for fresh markets in regions such as California, where cultivars with long tubers and white skin are traditionally grown. Resistances to late blight and other potato diseases make Defender an ideal candidate for organic potato production. Defender consistently produced greater total and U.S. No. 1 yields than ‘Russet Burbank’ in Idaho trials. In early harvest trials conducted in the western U.S., average total yields of Defender were 17% and 23% greater than yields for ‘Ranger Russet’ and ‘Shepody’, respectively. In full-season trials conducted in the western U.S., Defender averaged 10% and 15% higher yields than Ranger Russet and Russet Burbank, respectively. Specific gravity of Defender is consistently high, with values comparable to those of Ranger Russet; tuber ascorbic acid (Vitamin C) levels are also high. In addition to late blight, Defender also is resistant to tuber early blight (Alternaria solani, (Ellis & G. Martin), L.R. Jones & Grout), potato virus X, and net necrosis; it has moderate levels of resistance to Verticillium wilt (Verticillium dahliae, Kleb), pink rot, foliar early blight, corky ringspot, and Erwinia soft rot. Defender is susceptible to scab (common and powdery) and potato leafroll virus; it has moderate susceptibility to dry rot (Fusarium spp.) and potato virus Y. Susceptibilities to internal necrosis, tuber greening, and blackspot bruise also have been noted, but may be minimized through cultural and harvest practices.     

“Take only photographs and leave only footprints”?: An experimental study of the impacts of underwater photographers on coral reef dive sites

Impacts caused by recreational scuba diving on coral reefs vary widely among different dive locations and individual divers. Linear modelling was used to explore a range of individual and situational risk factors associated with divers who damaged corals in the Great Barrier Reef Marine Park. Recreational divers were followed for 10–15 min, and all contacts with, and damage to corals were recorded. Information on the dive site, diving experience, gender, and use of an underwater camera were recorded. Thirty-two out of 214 divers (15%) damaged or broke corals, mostly by fin kicks (95%). Impacts were most likely to be caused by male divers, in the first 10 min of the dive, at sites with a large abundance of branching corals. Specialist underwater photographers caused more damage on average (1.6 breaks per 10 min) than divers without cameras (0.3 breaks per 10 min). To explore the effects of gender and use of a camera further, we issued single-use underwater cameras to 31 randomly chosen divers and compared their behaviour to a control group. Use of a camera had no influence on the rate or amount of damage caused by these naïve photographers, but male divers were more likely to break corals and caused significantly more damage, on average, (1.4 breaks per 15 min) than female divers (0.3 breaks per 15 min). Variability in the amount of damage caused by divers in our sample reflected the very different underwater behaviours exhibited by specialist and non-specialist photographers, and male and female divers. Greater understanding of the causes of harmful behaviours by these groups will allow better targeting of on-site interpretative and cautionary information and may prove to be a more palatable management strategy than regulation of site use.     

The distribution and prevalence of Theileria buffeli in cattle in Queensland

The distribution and prevalence of Thelleria buffeli in Queensland cattle were investigated using serum samples and blood films collected primarily for brucellosis surveillance and tick fever diagnosis. Serums from 8654 cattle from 357 farms throughout Queensland were examined by an indirect fluorescent antibody test for antibody to T buffeli. In addition, 347 peripheral blood films collected from 147 farms in south-eastern Queensland were examined for piroplasms of T buffeli. The overall herd and animal prevalences for T buffeli were 75% and 41%, respectively. There was significant variation among regions in both herd and animal prevalences (P less than 0.001). Herd and animal prevalences were highest in the north and east decreasing westward. The results indicate that T buffeli is more widespread in Queensland than previously thought.     

Characterisation of ovine mast cells derived from in vitro culture of haemopoietic tissue.

Ovine mast cells generated in vitro from bone marrow (BMMC) were compared with mucosal mast cells (MMC) isolated from parasitised abomasum. Ultrastructurally, the granules of BMMC were partially developed and immature. Both cells types contained beta-hexosaminidase, arylsulfatase, histamine, dopamine and sheep mast cell proteinase (SMCP). Greater amounts of beta-hexosaminidase, but less SMCP, histamine and arylsulfatase were present in BMMC. Stimulation with calcium ionophore A23187 caused the secretion of granule constituents and generation of leukotriene C4 by BMMC in a dose-dependent manner. An additional [3H]diisopropylfluorophosphate-binding 31,500 mol. wt. serine esterase, antigenically related to SMCP (27,000 mol. wt.) was present in cultures of BMMC but was not detected in isolated MMC. Both enzymes were detected in BMMC by Day 7 of culture and were secreted concomitantly following stimulation of BMMC with ionophore.     

Comparison of three methods of thiamine supplementation by measurement of urinary thiamine excretion in sheep

The relative efficacy of thiamine supplementation to sheep by injection, subcutaneous implant and orally administered protected thiamine bolus was compared in two experiments using a grass and hay ration and a ration containing bracken rhizomes to induce thiamine deficiency. In both experiments, urinary excretion of thiamine was significantly higher in supplemented sheep than in the controls, and in sheep supplemented by injection than in sheep supplemented by implant or protected boluses. Thiamine excretion was lower in sheep fed the ration containing bracken rhizomes than in sheep fed the grass ration.