On the extent of genetic variation for transpiration efficiency in sorghum

A glasshouse study examined 49 diverse sorghum lines for variation in transpiration efficiency. Three of the 49 lines grown were Sorghum spp, native to Australia; one was the major weed Johnson grass (Sorghum halepense), and the remaining 45 lines were cultivars of Sorghum bicolor. All plants were grown under non-limiting water and nutrient conditions using a semi-automatic pot watering system designed to facilitate accurate measurement of water use. Plants were harvested 56-58 days after sowing and dry weights of plant parts were determined. Transpiration efficiency differed significantly among cultivars. The 3 Australian native sorghums had much lower transpiration efficiency than the other 46 cultivars, which ranged from 7.7 to 6.0 g/kg. For the 46 diverse cultivars, the ratio of range in transpiration efficiency to its l.s.d. was 2.0, which was similar to that found among more adapted cultivars in a previous study. This is a significant finding as it suggests that there is likely to be little pay-off from pursuing screening of unadapted material for increased variation in transpiration efficiency. It is necessary, however, also to examine absolute levels of transpiration efficiency to determine whether increased levels have been found. The cultivar with greatest transpiration efficiency in this study (IS9710) had a value 9% greater (P < 0.05) than the accepted standard for adapted sorghum cultivars. The potential impact of such an increase in transpiration efficiency warrants continued effort to capture it. Transpiration efficiency has been related theoretically and experimentally to the degree of carbon isotope discrimination in leaf tissue in sorghum, which thus offers a relatively simple selection index. In this study, the variation in transpiration efficiency was not related simply to carbon isotope discrimination. Significant associations of transpiration efficiency with ash content and indices of photosynthetic capacity were found. However, the associations were not strong. These results suggest that a simple screening technique could not be based on any of the measures or indices analysed in this study. A better understanding of the physiological basis of the observed genetic differences in transpiration efficiency may assist in developing reliable selection indices. It was concluded that the potential value of the improvement in transpiration efficiency over the accepted standard and the degree of genetic variation found warrant further study on this subject. It was suggested that screening for genetic variation under water-limiting conditions may provide useful insights and should be pursued.

Comparing physical activity questionnaires for youth: Seasonal vs annual format

Background: In large cohort studies of older children, self-report is the only practical way to assess physical activity. Assessing usual activity over the entire year is desirable, but children and adolescents may overestimate activities with high seasonal variability. Use of questionnaires in which individuals report each activity by season may improve accuracy. Methods: A total of 6782 girls and 5110 boys, aged 9–14 years in 1996, completed self-administered activity questionnaires in 1996 and in 1997. In 1996, participants reported the average time spent in each of 17 activities during the previous 12 months; in 1997, we also asked for the average time spent in the previous year, but within each of the four seasons. Results: Girls reported a median of 12.8 hours/week total activity in 1996 and 10.4 hours/week in 1997. For boys, the estimates were 15.5 hours/week and 13.4 hours/week, respectively. Girls and boys within 1-year age strata (e.g., comparison of 10-year olds in 1996 with 10-year olds in 1997) reported an average of 3.7 and 3.1 fewer hours per week, respectively, on the 1997 seasonal format versus the 1996 annual format questionnaire. In longitudinal analyses, the difference between the annual and the seasonal estimates was greater if participants did the activity in fewer seasons in 1997. Conclusions: In comparison to an annual format questionnaire, a seasonal format questionnaire may improve accuracy of self-report of physical activity by reducing over-reporting of activities in which pre-adolescents and adolescents engage in fewer seasons.

Family dynasties in the Tasmanian native hen (Gallinula mortierii)

For species that form multi-generational and territorial family groups, resource-rich areas are predicted to support family dynasties in which one genetic lineage continuously occupies an area and may even expand to occupy surrounding areas. Data from a long-term study of Tasmanian native hens (Gallinula mortierii) support this prediction. The reproductive success and dispersal patterns of 18 hen lineages were monitored for seven breeding seasons and over several generations. The founder group with the highest average territory quality produced the highest total number of fledged young and the highest number of fledged linear descendants, accounting for 24% of the combined reproductive output of these 18 lineages. In the space of 6 years, this single genetic lineage expanded from one territory to occupy 12 of the 47 territories present in the population. This rate of expansion was over four times the population average for the same period. A multivariate analysis revealed that the success of a genetic lineage depended only on the number of high-quality territories surrounding the founder group. These results further demonstrate the resource-dependent nature of reproductive success in this species, and also highlight the potential importance of family dynasties in other cooperative species with complex social dynamics and dispersal patterns.

Spray drift of pesticides arising from aerial application in cotton

This paper presents results from field studies carried out during the 1993-1998 Australian cotton (Gossypium hirsutum L.) seasons to monitor off-target droplet movement of endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,4,3-benzodioxathiepin 3-oxide) insecticide applied to a commercial cotton crop. Averaged over a wide range of conditions, off-target deposition 500 m downwind of the field boundary was approximately 2% of the field-applied rate with oil-based applications and 1% with water-based applications. Mean airborne drift values recorded 100 m downwind of a single flight line were a third as much with water-based application compared with oil-based application. Calculations using a Gaussian diffusion model and the U.S. Spray Drift Task Force AgDRIFT model produced downwind drift profiles that compared favorably with experimental data. Both models and data indicate that by adopting large droplet placement (LDP) application methods and incorporating crop buffer distances, spray drift can be effectively managed.

Mark-recapture may reveal more about ecology than about population trends: Demography of a threatened ghost bat (Macroderma gigas) population

Since European settlement in Australia, the geographical range of ghost bats (Macroderma gigas) has contracted northwards. Ghost bats are thought to occur in disjunct populations with little interpopulation migration, raising concerns over the current status and future viability of the southernmost colony, which has also been threatened by mining activity. To address these concerns, demographic parameters of the southernmost colony were estimated from a mark-recapture study conducted during 1975-1981. Female bats gave birth to a single young in late spring, but only 40% (22-70%, 95% CI) of females bred in their second year, increasing to 93% (87-97%, 95% CI) for females greater than or equal to 2 years old. Sixty-five percent of juveniles caught were female. Annual adult survival ranged between 0.57-0.77 for females and 0.43-0.66 for males, and was lowest over winter-spring and greatest in autumn-winter. Juvenile survival for the first year ranged between 0.35-0.46 for females and 0.29-0.42 for males. Adult survival varied among seasons, was negatively associated with rainfall, but was not associated with temperature beyond being lower in late winter. Poor survival may result from the inferior daytime roosts that bats must use if water seepage forces them to leave their normal roosts. Although these age-specific rates of fecundity and survival suggested a declining population, mark-recapture estimates of the population trend indicated stability over the study period. Counts at daytime roosts also suggested a population decline, but were considered unreliable because of an increasing tendency of bats to avoid detection. It is therefore likely that some assumptions in estimating survival were violated. These results provide a caution against the uncritical use of population projections derived from mark-recapture estimates of demographic parameters, and the use of untested indices as the basis for conservation decisions.

Tree use, diet and home range of the koala (Phascolarctos cinereus) at Blair Athol, central Queensland

Free-ranging koalas (Phascolarctos cinereus) were monitored by means of radio-relocation in the area of Blair Athol Coal Mine and surrounding properties. Daytime tree use, home range and diet of these koalas was determined in spring and autumn, as was the leaf moisture composition of potential fodder species. Koalas used on average 93 (male koalas) and 56 (female koalas) trees during the period of observation, occupying home ranges of 135 and 101 ha respectively. Mean sightings per tree were 1.19 for both males and females and home-range sizes were not significantly different between sexes or seasons. Koalas were observed returning to previously used daytime roosting trees infrequently (

The breeding-season diet of wedge-tailed eagles (Aquila audax) in western New South Wales and the influence of Rabbit Calicivirus Disease

A total of 2071 individual prey items were identified from 34 active and 55 inactive wedge-tailed eagle nests following the 1995, 1996 and 1997 breeding seasons. Overall, the eagle's diet was comparable to that reported in other studies within semi-arid regions, with rabbits, reptiles and macropods accounting for 47.8, 22.6 and 13.7% of prey items, respectively. In spring 1996 rabbit calicivirus moved into the study area, resulting in a 44-78% reduction in rabbit abundance (Sharp et al. 2001). An index was developed to enable the time since death for individual prey items to be approximated and a historical perspective of the eagle's diet to be constructed. Rabbits constituted 56-69% of dietary items collected during the pre-rabbit calicivirus disease (RCD) samples, but declined to 31% and 16% in the two post-RCD samples. A reciprocal trend was observed for the proportion of reptiles in the diet, which increased from 8-21% of pre-RCD dietary items to 49-54% after the advent of RCD. Similarly, the proportion of avian prey items was observed to increase in the post-RCD samples. These data suggested that prey switching may have occurred following the RCD epizootic. However, a lack of data on the relative abundances of reptiles and birds prevented an understanding of the eagle's functional responses to be developed and definitive conclusions to be drawn. Nevertheless, the eagles were observed to modify their diet to the change in rabbit densities by consuming larger quantities of native prey species.

Seasonal Effects on Transient Evoked Otoacoustic Emission Screening Outcomes in Infants versus 6-Year-Old Children

The purpose of this study was to compare transient evoked otoacoustic emission (TEOAE) screening outcomes (pass/fail) across the seasons (spring, autumn, and winter) between infants and schoolchildren. A total of 526 infants (275 boys, 251 girls) with a mean age of 2.0 months (SD = 0.38 months) and 975 schoolchildren (513 boys, 462 girls) with a mean age of 6.2 years (SD = 0.36 years) were screened using the ILO Otodynamics Quickscreen program. The same TEOAE pass/fail criterion was applied to the two groups. The results indicated a significant difference in pass rates between infants (91.2% of 1052 ears) and schoolchildren (86.0% of 1950 ears). A seasonal effect was found only for schoolchildren, with a significantly lower pass rate in winter than in spring or autumn. There was no difference in pass rates between spring and autumn. Implications for the seasonal effect on TEOAE screening outcomes for infants and schoolchildren are discussed.

Behaviour of the black flying fox Pteropus alecto: 2. Territoriality and courtship

Flying foxes are commonly thought of as highly social mammals, yet little is known about the dynamics of their social interactions at a day roost. The aim of the present study was to examine the nature of the seasonal activities of territoriality and courtship amongst wild flying foxes in Australia. Focal observations were conducted at two permanent roosts of black flying foxes Pteropus alecto during periods of peak social interaction in the summers of 1999 and 2000 in urban Brisbane, Queensland. Observations of male territoriality were conducted at dawn and began eight weeks prior to the commencement of mating. The majority of defense bouts (87%) consisted of ritualised pursuit, while 13% of bouts involved physical contact expressed as either wrestling or hooking. One male with an unusually large territory took significantly longer to defend it than other males with less territory to defend. Observations of courtship revealed repetitive courtship sequences, including pre-copulatory approaches by the males, copulation attempts and grooming/resting periods. Thirty-four complete courtship sequences incorporating 135 copulation attempts were recorded over two seasons. Females actively resisted courtship approaches by males, forcing males to display a continuous determination to mate over time where determination can be considered an indicator of 'fitness'. The courtship bout length of females with suckling young was significantly longer ((x) over bar +/- SE; 230.9 +/- 22.16 s) than that of females unencumbered by large pups (158.5 +/- 9.69 s), although the length of copulations within those courtships was not (45.6 +/- 5.19 versus 36.2 +/- 3.43 s).

Using crop simulation to generate genotype by environment interaction effects for sorghum in water-limited environments

Multi-environment trials (METs) used to evaluate breeding lines vary in the number of years that they sample. We used a cropping systems model to simulate the target population of environments (TPE) for 6 locations over 108 years for 54 'near-isolines' of sorghum in north-eastern Australia. For a single reference genotype, each of 547 trials was clustered into 1 of 3 'drought environment types' (DETs) based on a seasonal water stress index. Within sequential METs of 2 years duration, the frequencies of these drought patterns often differed substantially from those derived for the entire TPE. This was reflected in variation in the mean yield of the reference genotype. For the TPE and for 2-year METs, restricted maximum likelihood methods were used to estimate components of genotypic and genotype by environment variance. These also varied substantially, although not in direct correlation with frequency of occurrence of different DETs over a 2-year period. Combined analysis over different numbers of seasons demonstrated the expected improvement in the correlation between MET estimates of genotype performance and the overall genotype averages as the number of seasons in the MET was increased.

Effect of Metalaxyl Resistance and Cultivar Resistance on Control of Phytophthora nicotianae in Tobacco

Phytophthora nicotianae is a devastating root and stem pathogen of tobacco (Nicotiana tabacum) in South Africa. Growers strive to control the resulting disease, known as black shank, with metalaxyl treatments and resistant cultivars. The aim of this study was to consider whether development of metalaxyl resistance in P. nicotianae has contributed to poor disease control and if recently developed cultivars with high levels of resistance require metalaxyl for effective control. One hundred and thirty-two isolates of P. nicotianae were screened for sensitivity to metalaxyl. P. nicotianae isolates from most tobacco farms were metalaxyl sensitive. Growth of most isolates was inhibited completely at 1.0 μg a.i./ml. However, isolates from the MKTV tobacco producing area showed EC50 values ranging from 1.02 μg a.i./ml to 3.57 μg a.i./ml. Twenty-one tobacco cultivars were planted and treated with and without metalaxyl in two different growing seasons to evaluate their resistance to P. nicotianae and the value of using metalaxyl. Hicks was the most susceptible cultivar. Vuma/3/46, LK30/40/60-1, and LK33/60 exhibited the greatest resistance to P. nicotianae. Use of metalaxyl in combination with moderately resistant cultivars such as NC60 × TL33 and LK10/80/60 effectively reduced black shank in the field. Resistant cultivars were healthy and no significant difference between metalaxyl treated and untreated plants was observed.

Airborne pollen of Brisbane, Australia: a five-year record, 1994-1999

The seasonal incidence of pollen in the atmosphere of Brisbane has been established from a near continuous. volumetric trapping program over the five-year period, July 1994-June 1999. Grass pollen accounts for 71.6% of the average annual pollen load with highest densities (up to 150 grains/m(3)) recorded in summer and autumn. Significant contributions were also made by taxa of the Cupressaceae (8.7%) and Urticaceae (1.8%) during spring and of the Pinaceae (4.5%) during winter. Pollen seasons of the Casuarinaceae (6.5%) and Myrtaceae (3.2%) are more extended, the former peaking in late winter and the latter in late spring. The onset and duration of the Poaceae and Urticaceae seasons varied from year to year, being later when precipitation levels were low in the late spring-early summer months. Total pollen numbers and grass pollen densities are substantially less than those recorded from southern Australia. Nevertheless, respiratory disease in Brisbane affects up to 10% of the population, and airborne pollen of Poaceae, Urticaceae, Cupressaceae, Pinaceae, and Myrtaceae have been implicated in the release of allergens.

Airborne Pinus pollen in the atmosphere of Brisbane, Australia and relationships with meteorological parameters

Relationships between weather parameters andairborne pollen loads of Pinus inBrisbane, Australia have been investigated overthe five-year period, June 1994–May 1999.Pinus pollen accounts for 4.5% of the annualairborne pollen load in Brisbane where thePinus season is confined to the winter months,July–early September. During the samplingperiod loads of 11–>100 grains m3 wererecorded on 24 days and 1–10 grains m3 on204 days. The onset and peak dates wereconsistent across each season, whereas the enddates varied. The onset of the Pinuspollen season coincided with the coolestaverage monthly temperatures (< 22°C),lowest rainfall (< 7mm), and four weeks afterdaily minimum temperatures fell to 5–9°Cin late autumn. Correlations obtained betweendaily airborne Pinus pollen counts andtemperature/rainfall parameters show thatdensities of airborne Pinus pollen arenegatively correlated with maximum temperature(p < 0.0001), minimum temperature (p < 0.0001)and rainfall (p < 0.05) during the mainpollination period. The mean duration of eachpollen season was 52 days; longer seasons wereshown to be directly related to lower averageseasonal maximum temperatures (r2 = 0.85,p = 0.025). These results signify that maximumand minimum temperatures are the majorparameters that influence the onset andduration of the Pinus pollen season inthe environs of Brisbane. Respiratory allergyis an important health issue in Brisbane,Australia, but it remains unknown whether ornot airborne Pinus pollen is acontributing factor.

Seasonal changes in the diving performance of the bimodally respiring freshwater turtle Rheodytes leukops in a natural setting

The objective of this study was to investigate how seasonally fluctuating environmental conditions influence the diving performance of the highly aquatic, bimodally respiring turtle Rheodytes leukops in a natural setting. Over four consecutive seasons (Austral autumn 2000 to summer 2001), the diving behaviour of adult turtles was recorded via pressure-sensitive time-depth recorders within Marlborough Creek, central Queensland, Australia. Short surfacing intervals recorded for R. leukops in winter suggest that the species utilizes aquatic respiration as an overwintering strategy to prevent the development of a metabolic acidosis during the long inactive dives observed during the season. As water temperature increases and aquatic P-O 2 decreases, R. leukops switches from facultative to obligate air-breathing, presumably because of the increased metabolic cost associated with aquatic respiration under summer conditions. Increases in mean surfacing time from winter to spring and summer are attributed to seasonal changes in behaviour possibly associated with foraging rather than to the physiological state of the turtle, given that no difference in median surfacing time among seasons was observed.

The coincidence of thrips and dispersed pollen in PNRSV-infected stonefruit orchards - a precondition for thrips-mediated transmission via infected pollen

Recent laboratory studies have demonstrated that Prunus necrotic ringspot virus (PNRSV) (family Bromoviridae) can be readily transmitted when thrips and virus-bearing pollen are placed together on to test plants. For this transmission mechanism to result in stonefruit tree infection in the field, PNRSV-bearing pollen must be deposited onto surfaces of stonefruit trees on which thrips also occur. In a previous paper, we demonstrated that almost all pollen in a PNRSV-infected Japanese plum orchard in southeastern Queensland was deposited onto flowers, whereas few grains occurred on leaves and none on stems. Here, we present results of our investigation of thrips species composition, distribution and abundance on stonefruit trees in the same study area as our previous pollen deposition study. We collected a total of 2010 adult thrips from 13 orchards during the 1989, 1991 and 1992 flowering seasons of which all but 14 were in the suborder Terebrantia. Most (97.4%) terebrantian thrips were of three species, Thrips imaginis, Thrips australis and Thrips tabaci. Thrips tabaci as well as species mixtures that included T imaginis, T australis and T tabaci have been shown to transmit PNRSV via infected pollen in laboratory tests. Adult thrips were frequently collected from flowers but rarely from leaves and never from stems. Large and significant differences in numbers of T imaginis, T australis and T tabaci adults in flowers occurred among orchards and between seasons. No factor was conclusively related to thrips numbers but flowers of late-flowering stonefruit varieties tended to hold more thrips than those of early-flowering varieties. Our results indicate that the common thrips species present on stonefruit trees in the Granite Belt are also ones previously shown to transmit PNRSV via infected pollen in the laboratory and that these thrips are concentrated in stonefruit flowers where most stonefruit pollen is deposited. These results contribute to mounting circumstantial evidence that stonefruit flowers may be inoculated with PNRSV via an interaction of thrips with virus-bearing pollen and that this transmission mechanism may be an important cause of new tree infections in the field.