Canopy carbon and oxygen isotope composition of 9-year-old hoop pine families in relation to seedling carbon isotope composition, growth, field growth performance, and canopy nitrogen concentration

Carbon isotope composition (delta C-13), oxygen isotope composition (delta O-18), and nitrogen concentration (N-mass) of branchlet tissue at two canopy positions were assessed for glasshouse seedlings and 9-year-old hoop pine (Araucaria cunninghamii Ait. ex D. Don) trees from 22 open-pollinated families grown in 5 blocks of a progeny test at a water-limited and nitrogen-deficient site in southeastern Queensland, Australia. Significant variations in canopy delta C-13, delta O-18, and N-mass existed among the 9-year-old hoop pine families, with a heritability estimate of 0.72 for branchlet delta C-13 from the upper inner canopy position. There was significant variation in canopy delta C-13 of glasshouse seedlings between canopy positions and among the families, with a heritability estimate of 0.66. The canopy delta C-13 was positively related to canopy N-mass only for the upper outer crown in the field (R = 0.62, p < 0.001). Phenotypic correlations existed between tree height and canopy delta C-13 (R = 0.37-0.41, p < 0.001). Strong correlations were found between family canopy delta C-13 at this site and those at a wetter site and between field canopy delta C-13 and glasshouse seedling delta C-13. The mechanisms of the variation in canopy delta C-13 are discussed in relation to canopy photosynthetic capacity as reflected in the N-mass and stomatal conductance as indexed by canopy delta O-18.

Burial depth and cultivation influence emergence and persistence of Phalaris paradoxa seed in an Australian sub-tropical environment

Emergence and persistence characteristics of Phalaris paradoxa seeds in no- and minimum-till situations and at different burial depths were studied in a sub-tropical environment. Three experiments were carried out using naturally shed seeds. In the first experiment, seedlings emerged from May through to September each year, although the majority of seedlings emerged in July. In the second experiment with greater seed density, cultivation in March of each year stimulated seedling emergence, altered the periodicity of emergence and accelerated the decline of seeds in the seedbank compared with plots that received no cultivation. The majority of seedlings in the cultivated plots emerged in May whereas the majority of seedlings in the undisturbed plots emerged in July. Emergence accounted for only 4-19% of the seedbank in both experiments over 2 years. Seed persistence was short in both field experiments, with less than 1% remaining 2 years after seed shed. In the third experiment, burial depth and soil disturbance significantly influenced seedling emergence and persistence of seed. Seedlings emerged most from seed mixed in the top 10 cm when subjected to annual soil disturbance, and from seed buried at 2.5 and 5.0 cm depths in undisturbed soil. Emergence was least from seed on the soil surface, and buried at 10 and 15 cm depths in undisturbed soil. Seeds persisted longest when shed onto the soil surface and persisted least when the soil was tilled. These results suggest that strategic cultivation may be a useful management tool, as it will alter the periodicity of emergence allowing use of more effective control options and will deplete the soil seedbank more rapidly.

Seed treatment with gibberellic acid and glycinebetaine improves seedling emergence and seedling vigour of rice under low temperature

Prevalence of low temperature at sowing results in poor rice seed germination, seedling establishment and vigour in several temperate rice growing countries around the world. Rice seed of four cultivars (Sasanishiki, H433, HSC-55 and Doongara) was soaked in various combinations of gibberellic acid(3) (GA(3)) and glycinebetaine (GB) in petri dishes placed in a low temperature glasshouse (18/13 degrees C; day/night) for 2 days. After the 2 days soak, 10 treated seed were transferred into plastic pots filled with soil and seedlings were grown in the same glasshouse, where seed was treated. Seedling emergence was least affected by low temperature in cold tolerant cultivar, HSC-55, while other three cultivars showed reduced seedling emergence. However, seedling emergence increased significantly in some cultivars in response to seed treatment with GA(3) and/or GB. Seedlings emerged faster even in the cold tolerant cultivar, HSC-55, as measured by reduced mean emergence time (MET), in response to GB. Seedling height and seedling dry matter also increased in response to both GA(3) and GB. Combined treatment of both GA(3) and GB was more beneficial in increasing seedling emergence and vigour than the treatment with only GA3 or GB. We demonstrated significant genotypic differences for seedling emergence and vigour and not all cultivars responded to the treatment with GA(3) and GB, under low temperature.

Climatic regulation of seed dormancy and emergence of diverse Malva parviflora populations from a Mediterranean-type environment

Malva parviflora L. (Malvaceae) is rapidly becoming a serious weed of Australian farming systems. An understanding of the variability of its seed behaviour is required to enable the development of integrated weed management strategies. Mature M. parviflora seeds were collected from four diverse locations in the Mediterranean-type climatic agricultural region of Western Australia. All of the seeds exhibited physical dormancy at collection; manual scarification or a period of fluctuating summer temperatures (50/20 degrees C or natural) were required to release dormancy. When scarified and germinated soon (1 month) after collection, the majority of seeds were able to germinate over a wide range of temperatures (5-37 degrees C) and had no light requirement. Germination was slower for seeds stored for 2 months than seeds stored for 2 years, suggesting the presence of shallow physiological dormancy. Seed populations from regions with similar annual rainfall exhibited similar dormancy release patterns; seeds from areas of low rainfall (337-344mm) were more responsive to fluctuating temperatures, releasing physical dormancy earlier than those from areas of high rainfall (436-444mm). After 36 months, maximum seedling emergence from soil in the field was 60%, with buried seeds producing 13-34% greater emergence than seeds on the surface. Scanning electron microscopy of the seed coat revealed structural differences in the chalazal region of permeable and impermeable seeds, suggesting the importance of this region in physical dormancy breakdown of M. parviflora seeds. The influence of rainfall during plant growth in determining dormancy release, and hence, germination and emergence timing, must be considered when developing management strategies for M. parviflora.

Field assessment of thermal after-ripening time for dormancy release prediction in Lolium rigidum seeds

Dormancy release was studied in four populations of annual ryegrass (Lolium rigidum) seeds to determine whether loss of dormancy in the field can be predicted from temperature alone or whether seed water content (WC) must also be considered. Freshly matured seeds were after-ripened at the northern and southern extremes of the Western Australian cereal cropping region and at constant 37degreesC. Seed WC was allowed to fluctuate with prevailing humidity, but full hydration was avoided by excluding rainfall. Dormancy was measured regularly during after-ripening by germinating seeds with 12-hourly light or in darkness. Germination was lower in darkness than in light/dark and dormancy release was slower when germination was tested in darkness. Seeds were consistently drier, and dormancy release was slower, during after-ripening at 37degreesC than under field conditions. However, within each population, the rate of dormancy release in the field (north and south) in terms of thermal time was unaffected by after-ripening site. While low seed WC slowed dormancy release in seeds held at 37degreesC, dormancy release in seeds after-ripened under Western Australian field conditions was adequately described by thermal after-ripening time, without the need to account for changes in WC elicited by fluctuating environmental humidity.

Stimulating dormancy release and emergence of annual ryegrass (Lolium rigidum) seeds using short-term hydrated storage in darkness

Experiments were performed to determine whether the dormancy release effect of hydrated storage in darkness (dark-stratification) is common amongst annual ryegrass populations and has the potential to occur under field conditions. Dormant seeds from all populations tested (22) became sensitive to light during dark-stratification, enabling them to germinate when subsequently exposed to light. Under controlled temperature (25/15degreesC), light (12-h photoperiod), and hydration (solidified agar-water) conditions, more seeds germinated by 28 days if the first 14 days were in darkness followed by exposure to light for 12 h per day than if they were exposed to light throughout or darkness throughout. Constraint over the conditions imposed during dark-stratification and germination was gradually reduced to investigate whether the dormancy release effect was diminished. Dark-stratification was effective in promoting germination when performed under natural diurnal temperatures, and burial in moist soil provided suitable conditions for dark-stratification to occur. The surface of moist soil, with natural diurnal temperatures and sunlight, was suitable for germination of dark-stratified seeds. Dark-stratification is a quick and effective means to enhance the sensitivity of dormant annual ryegrass seeds to light, enabling the majority of the population to germinate. However, large quantities of light are required to promote germination of dark-stratified seeds, so buried seeds must be moved to the soil surface to allow exposure to adequate light for germination.

Late-season non-selective herbicide application reduces Lolium rigidum seed numbers, seed viability, and seedling fitness

Experiments were conducted to investigate the effect of Lolium rigidum (annual ryegrass) seed developmental stage and application rate of glyphosate and SpraySeed (paraquat 135 g/L+ diquat 115 g/L) on the number, germinability, and fitness of seeds produced. Glyphosate (450 g/L) was most effective when applied at a rate of 0.5-1 L/ha during heading and anthesis, reducing the number of filled seeds produced compared with unsprayed plants. Application post-anthesis, when seeds were at the milk to soft dough stage, was less effective. SpraySeed was most effective when applied post-anthesis, during the milk and early dough stages of seed development at a rate of 0.5-1L/ha, resulting in the production of few viable seeds. Although some filled seeds were produced, most of the seeds were dead. Application during anthesis or once the seeds reached soft dough stage was less effective. For both herbicides, those seeds that were capable of germinating were smaller and had slower radicle and coleoptile growth, resulting in slower early seedling growth and reduced biomass production within the first month of growth. Additionally, glyphosate application reduced the proportion of seeds exhibiting dormancy. The anticipated reduction in seed competitive ability and altered emergence timing resulting from late-season herbicide application, even when application timing is not optimal, could be exploited to reduce the likelihood of successful L. rigidum establishment in the following season.

Community-acquired methicillin-resistant Staphylococcus aureus carrying Panton-Valentine leukocidin genes: Worldwide emergence

Infections caused by community-acquired (CA)-methicillin-resistant Staphylococcus aureus (MRSA) have been reported worldwide. We assessed whether any common genetic markers existed among 117 CA-MRSA isolates from the United States, France, Switzerland, Australia, New Zealand, and Western Samoa by performing polymerase chain reaction for 24 virulence factors and the methicillin-resistance determinant. The genetic background of the strain was analyzed by pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST). The CA-MRSA strains shared a type IV SCCmec cassette and the Panton-Valentine leukocidin locus, whereas the distribution of the other toxin genes was quite specific to the strains from each continent. PFGE and MLST analysis indicated distinct genetic backgrounds associated with each geographic origin, although predominantly restricted to the agr3 background. Within each continent, the genetic background of CA-MRSA strains did not correspond to that of the hospital-acquired MRSA.

Emergence of community-acquired methicillin-resistant Staphylococcus aureus (MRSA) infection in Queensland, Australia

Objectives: To investigate the incidence and epidemiology of non-multiresistant methicillin-resistant Staphylococcus aureus (nmMRSA) infection in south-east Queensland, Australia. Study design: A retrospective survey was done of hospital records of all patients who had non-multiresistant MRSA isolated at Ipswich Hospital (a 250-bed general hospital, 40 km south-west of Brisbane, Queensland, Australia) between March 2000 and June 2001. Laboratory typing of these isolates was done with antibiogram, pulsed-field gel electrophoresis, bacteriophage typing and coagulase gene typing. Results: There were 44 infections caused by nmMRSA. Seventeen infections (39%) occurred in patients from the south-west Pacific Islands (predominantly Samoa, Tonga and New Zealand). Laboratory typing showed that the isolates in Pacific Islanders were Pacific Island strains, and 16/17 of these infections were community acquired. Twenty-three infections (52%) occurred in Caucasians. Eleven of the isolates from Caucasians (48%) were a new predominantly community-acquired strain that we have termed the ‘R’ pulsotype, nine (39%) were Pacific Island strains, and three (13%) were health care institution-associated strains. Four infections occurred in patients who were not Caucasians or Pacific Islanders. Overall, 34 of all 44 infections (77%) were community' acquired. Conclusions: Non-multiresistant MRSA infection, relatively frequently observed in Pacific Islanders in south-east Queensland, is now a risk for Caucasians as well, and is usually community acquired. Clinicians should consider taking microbiological specimens for culture and antimicrobial susceptibility testing in patients with suspected staphylococcal infections who are not responding to empirical therapy with β-lactam antibiotics.

Effect of NaCl on emergence and growth of a range of provenances of Eucalyptus citriodora, Eucalyptus populnea, Eucalyptus camaldulensis and Acacia salicina

High salt levels in mine spoils have been identified as one of the major chemical limitations to plant establishment after coal mining in central Queensland. Soil solution extracts from spoils indicated that EC levels of up to 26 dS/m could be encountered. Glasshouse trials examined the emergence and growth of Eucalyptus citriodora, Eucalyptus camaldulensis and Eucalyptus populnea provenances and Acacia salicina subjected to such EC levels. Relatively low levels of salt (100 mM NaCl, or 11 dS/m) with respect to the levels encountered on mine spoils, were enough to substantially reduce the rate and percentage emergence of all eucalypt provenances. A. salicina was found to be superior to the eucalypts in its ability to emerge and survive under saline conditions. It was the only species to have seedlings emerge and survive at 200 mM NaCl (20 dS/m), and the effect of salt on decreasing seedling dry weight was less pronounced for A. salicina than for any of the eucalypts. Established plants survived the range of salt treatments far better than emerging seedlings, with survival of established plants being reduced only at 300 and 400 mM NaCl (28 and 36 dS/m, respectively). A. salicina performed significantly better at 300 and 400 mM NaCl than most of the eucalypts studied. (c) 2006 Elsevier B.V. All rights reserved.

The use of transcriptional profiles to predict adult mosquito age under field conditions

Age is a critical determinant of an adult female mosquito's ability to transmit a range of human pathogens. Despite its central importance, relatively few methods exist with which to accurately determine chronological age of field-caught mosquitoes. This fact is a major constraint on our ability to fully understand the relative importance of vector longevity to disease transmission in different ecological contexts. It also limits our ability to evaluate novel disease control strategies that specifically target mosquito longevity. We report the development of a transcriptional profiling approach to determine age of adult female Aedes aegypti under field conditions. We demonstrate that this approach surpasses current cuticular hydrocarbon methods for both accuracy of predicted age as well as the upper limits at which age can be reliably predicted. The method is based on genes that display age-dependent expression in a range of dipteran insects and, as such, is likely to be broadly applicable to other disease vectors.

Reliability and validity of physical fitness field tests for adults aged 55 to 70 years

The aim of this study was to examine the reliability and validity of field tests for assessing physical function in mid-aged and young-old people (55–70 y). Tests were selected that required minimal space and equipment and could be implemented in multiple field settings such as a general practitioner's office. Nineteen participants completed 2 field and 1 laboratory testing sessions. Intra-class correlations showed good reliability for the tests of upper body strength (lift and reach, R= .66), lower body strength (sit to stand, R= .80) and functional capacity (Canadian Step Test, R= .92), but not for leg power (single timed chair rise, R= .28). There was also good reliability for the balance test during 3 stances: parallel (94.7% agreement), semi-tandem (73.7%), and tandem (52.6%). Comparison of field test results with objective laboratory measures found good validity for the sit to stand (cf 1RM leg press, Pearson r= .68, p< .05), and for the step test (cf PWC140, r= −.60, p< .001), but not for the lift and reach (cf 1RM bench press, r= .43, p> .05), balance (r= −.13, −.18, .23) and rate of force development tests (r= −.28). It was concluded that the lower body strength and cardiovascular function tests were appropriate for use in field settings with mid-aged and young-old adults.