Genetic analysis of resistance to root-lesion nematode (Pratylenchus thornei) in wheat

The inheritance of resistance to root-lesion nematode was investigated in five synthetic hexaploid wheat lines and two bread wheat lines using a half-diallel design of F-1 and F-2 crosses. The combining ability of resistance genes in the synthetic hexaploid wheat lines was compared with the performance of the bread wheat line 'GS50a', the source of resistance to Pratylenchus thornei used in Australian wheat breeding programmes. Replicated glasshouse trials identified P. thornei resistance as polygenic and additive in gene action. General combining ability (GCA) of the parents was more important than specific combining ability (SCA) effects in the inheritance of P. thornei resistance in both F-1 and F-2 populations. The synthetic hexaploid wheat line 'CPI133872' was identified as the best general combiner, however, all five synthetic hexaploid wheat lines possessed better GCA than 'GS50a'. The synthetic hexaploid wheat lines contain novel sources of P. thornei resistance that will provide alternative and more effective sources of resistance to be utilized in wheat breeding programmes.

Potential to increase yield in lucerne (Medicago sativa subsp sativa) through introgression of Medicago sativa subsp falcata into Australian adapted material

The effect of interspecific heterosis in crosses between Medicago sativa subsp. sativa and M. sativa subsp. falcata was assessed. Three sativa and 3 falcata plants were crossed in a diallel design. Progeny dry matter yield and natural plant height were assessed in a replicated field experiment at Gatton, Queensland. Yield data were analysed using the method of residual maximum likelihood (REML) and Griffing's model 1. There were significant differences between the reciprocal, general combining ability (GCA), and specific combining ability (SCA) effects. As expected, S-1 populations were lower yielding than their respective intraspecific cross and falcata x falcata crosses were significantly lower yielding than sativa x sativa crosses. Some of the interspecific crosses indicated substantial SCA effects, yielding at least as well as the best sativa x sativa crosses. We have demonstrated the potential usefulness of unselected M. sativa subsp. falcata as a heterotic group in the improvement of yield in northern Australian adapted lucerne material, and discuss how it could be incorporated into future breeding to overcome the yield stagnation currently being experienced in Australian programs.

The productivity effects of cattle tick (Boophilus microplus) infestation on cattle, with particular reference to Bos indicus cattle and their crosses

In response to uncertainty among cattle producers in Australia regarding the need to treat Bos indices and B. indicus crossbreeds, the scientific literature relating to the productivity effects of Boophilus microplus on cattle of all breeds was reviewed. Estimates of the mean effect of each engorging tick (damage coefficient, d) were made from a simple analysis of the reported data. On average, each engorging female tick is responsible for the loss of 1.37 +/- 0.25 g bodyweight in B. taunts cattle. The comparable value for B. taurus x B. indicus cattle is 1.18 +/- 0.21 g/engorging tick. These values were not statistically significantly different, indicating that if a threshold approach to tick control were taken, then the threshold number of standard ticks would be the same regardless of cattle genotype. No studies provided useable estimates of the effect of tick infestation on pure B. indices cattle. An economic threshold for treatment, below which acaricide application is not beneficial, can be predicted, using known values for the cost of acaricide application and the price of beef. However, the application of a threshold approach to control has not been embraced by government advisers and runs contrary to the accepted principals of strategic control programs. (C) 2006 Elsevier B.V. All rights reserved.

Lack of intraspecific biological variation between two geographical populations of Oomyzus sokolowskii (Hymenoptera: Eulophidae), a gregarious larval–pupal parasitioid of Plutella xylostella (Lepidoptera: Plutellidae)

The chalcid, Oomyzus sokolowskii Kurdjumov has been recorded in many parts of the world as a major larval-pupal, gregarious endoparasitoid of the diamondback moth, Plutella xylostella (Linnaeus), a serious pest of brassica vegetable crops worldwide. This study investigated intraspecific variation between two populations of O. sokiolowskii, one from Cape Verde Islands, West Africa and the other from Hangzhou, China. In all crosses and backcrosses between the two geographical populations, the numbers of progeny and sex ratio of progeny were similar to those obtained within each of the populations, demonstrating complete reproductive compatibility between the two populations. The two populations showed similar responses to temperature with respect to development time and survival of immature stages. Observations on the interactions between the two O. sokolowskii populations and Cotesia plutellae (Kurdjumov), another major parasitoid of P. xylostella, showed that neither population could achieve successful parasitism of P. xylostella larvae already parasitized by C. plutellac. However, both O. sokolowskii populations could achieve hyperparasitism by ovipositing into a mid-late stage larva of C. plutellae developing inside the primary host. Contrary to earlier reports, no evidence of intraspecific variations in ability to hyperparasitize between these two populations of O. sokolowskii was found.

The role of morphine-6-glucuronide (M6G) in pain control

Morphine-6beta-D-glucuronide (M6G) is an analgesically active metabolite of morphine, accounting for approximate to10% of the morphine dose when administered by systemic routes to humans. Although M6G is more hydrophilic than morphine, it crosses the blood-brain barrier, albeit relatively slowly. For this reason, it is generally thought that, after chronic dosing, M6G contributes significantly to the analgesic effects of systemically administered morphine. Owing to its polar nature, M6G is cleared from the systemic circulation primarily via renal elimination. As M6G accumulates in patients with renal impairment, there is an increased risk of M6G-induced respiratory depression in renal failure patients who are being dosed chronically with systemic morphine. Consistent with its analgesic and respiratory depressant properties, M6G binds to the p-opioid receptor in a naloxone-reversible manner. Although the affinity of M6G for the mu-opioid receptor is similar to or slightly less than that of morphine, preclinical studies in rodents show that M6G is one to two orders of magnitude more potent than morphine when administered by central routes. This major discrepancy between the markedly higher intrinsic antinociceptive potency of M6G relative to morphine, despite their similar p-opioid receptor binding affinities, is difficult to reconcile. It has been proposed that M6G mediates its pain-relieving effects through a novel 'M6G opioid receptor', while others have argued that M6G may have higher efficacy than morphine for transduction of intracellular events. When administered by parenteral routes to rodents, M6G's antinociceptive potency is no more than twofold higher than morphine. In humans, the analgesic efficacy and respiratory depressant potency of M6G relative to morphine have been assessed in a number of short-term studies involving the intrathecal or intravenous routes of administration. For example, in hip replacement patients, intrathecal M6G provided excellent postoperative analgesia but the occurrence of late respiratory depression in 10% of these patients raised serious concern about safety. In postoperative patients, intravenous M6G administered by means of patient-controlled analgesia (PCA), or bolus plus PCA, produced no analgesia in one study and limited analgesia in another. Similarly, there was a lack of significant analgesia in healthy volunteers who received intravenous M6G for the alleviation of experimental pain (carbon dioxide applied to the nasal mucosa). In contrast, satisfactory analgesia was produced by bolus doses of intravenous M6G administered to patients with cancer pain, and to healthy volunteers with experimentally-induced ischaemic, electrical or thermal (ice water) pain. Studies to date in healthy volunteers suggest that intravenous M6G may be a less potent respiratory depressant and have a lower propensity for producing nausea and vomiting than morphine. However, it is unclear whether equi-analgesic doses of M6G and morphine were compared. Clearly, more extensive short-term trials, together with studies involving chronic M6G administration, are necessary before the potential clinical utility of M6G as an analgesic drug in its own right can be determined.

Yield response of rice (Oryza sativa L.) genotypes to drought under rainfed lowlands 4. Vegetative stage screening in the dry season

Screening for drought resistance of rainfed lowland rice using drought score (leaf death) as a selection index has a long history of use in breeding programs. Genotypic variation for drought score during the vegetative stage in two dry season screens was examined among 128 recombinant inbred lines from four biparental crosses. The genotypic variation detected for drought score in the dry season was used to examine the reliability of the dry season screening method to estimate relative grain yield of genotypes under different types of drought stress in the wet season. Large genotypic variation for drought score existed in two experiments (A and B). However, there was no relationship between the drought scores of genotypes determined in these two experiments. Different patterns of development and severity of drought stress in these two experiments, i.e. slow development and mild plant water deficit in experiment A and fast development and severe plant water deficit in experiment B, were identified as the major factors contributing to the genotypes responding differently. Larger drought score in the dry season experiments was associated with lower grain yield under specific drought stress conditions in the wet season, but the association was weak to moderate and significant only in particular drought conditions. In most cases, a significant phenotypic and moderate genetic correlation between drought score in the dry season and grain yield in the wet season existed only when both drought score and grain yield of genotypes were affected by similar patterns and severity of drought stress in their respective experimental environments. The dry season environments used to measure genotypic variation for drought score should be managed to correspond to relevant types of drought environment that are frequent in the wet season. The efficiency of using the drought score as an indirect selection criterion for improving grain yield for drought conditions was lower than the direct selection for grain yield, and hence wet season screening with grain yield as a selection criterion would be more efficient. However, using drought score as a selection index, a larger number of genotypes can be evaluated than for wet season grain yield. Therefore, it is possible to apply higher selection intensities using the drought score system, and the selected lines can be further tested for grain yield in the wet season. (C) 2004 Elsevier B.V. All rights reserved.

Reinforcement drives rapid allopatric speciation

Allopatric speciation results from geographic isolation between populations. In the absence of gene flow, reproductive isolation arises gradually and incidentally as a result of mutation, genetic drift and the indirect effects of natural selection driving local adaptation(1-3). In contrast, speciation by reinforcement is driven directly by natural selection against maladaptive hybridization(1,4). This gives individuals that choose the traits of their own lineage greater fitness, potentially leading to rapid speciation between the lineages(1,4). Reinforcing natural selection on a population of one of the lineages in a mosaic contact zone could also result in divergence of the population from the allopatric range of its own lineage outside the zone(4-6). Here we test this with molecular data, experimental crosses, field measurements and mate choice experiments in a mosaic contact zone between two lineages of a rainforest frog. We show that reinforcing natural selection has resulted in significant premating isolation of a population in the contact zone not only from the other lineage but also, incidentally, from the closely related main range of its own lineage. Thus we show the potential for reinforcement to drive rapid allopatric speciation.

Adsorption of argon from sub- to supercritical conditions on graphitized thermal carbon black and in graphitic slit pores: A grand canonical Monte Carlo simulation study

In this paper we consider the adsorption of argon on the surface of graphitized thermal carbon black and in slit pores at temperatures ranging from subcritical to supercritical conditions by the method of grand canonical Monte Carlo simulation. Attention is paid to the variation of the adsorbed density when the temperature crosses the critical point. The behavior of the adsorbed density versus pressure (bulk density) shows interesting behavior at temperatures in the vicinity of and those above the critical point and also at extremely high pressures. Isotherms at temperatures greater than the critical temperature exhibit a clear maximum, and near the critical temperature this maximum is a very sharp spike. Under the supercritical conditions and very high pressure the excess of adsorbed density decreases towards zero value for a graphite surface, while for slit pores negative excess density is possible at extremely high pressures. For imperfect pores (defined as pores that cannot accommodate an integral number of parallel layers under moderate conditions) the pressure at which the excess pore density becomes negative is less than that for perfect pores, and this is due to the packing effect in those imperfect pores. However, at extremely high pressure molecules can be packed in parallel layers once chemical potential is great enough to overcome the repulsions among adsorbed molecules. (c) 2005 American Institute of Physics.

Behaviour of the energy gap in a model of Josephson coupled Bose-Einstein condensates

In this work we investigate the energy gap between the ground state and the first excited state in a model of two single-mode Bose-Einstein condensates coupled via Josephson tunnelling. The ene:rgy gap is never zero when the tunnelling interaction is non-zero. The gap exhibits no local minimum below a threshold coupling which separates a delocalized phase from a self-trapping phase that occurs in the absence of the external potential. Above this threshold point one minimum occurs close to the Josephson regime, and a set of minima and maxima appear in the Fock regime. Expressions for the position of these minima and maxima are obtained. The connection between these minima and maxima and the dynamics for the expectation value of the relative number of particles is analysed in detail. We find that the dynamics of the system changes as the coupling crosses these points.

Population pharmacokinetics of metformin in late pregnancy

The pharmacokinetic disposition of metformin in late pregnancy was studied together with the level of fetal exposure at birth. Blood samples were obtained in the third trimester of pregnancy from women with gestational diabetes or type 2 diabetes, 5 had a previous diagnosis of polycystic ovary syndrome. A cord blood sample also was obtained at the delivery of some of these women, and also at delivery of others who had been taking metformin during pregnancy but from whom no blood had been taken. Plasma metformin concentrations were assayed by a new, validated, reverse-phase HPLC method, A 2-compartment, extravascular maternal model with transplacental partitioning of drug to a fetal compartment was fitted to the data. Nonlinear mixed-effects modeling was performed in'NONMEM using FOCE with INTERACTION. Variability was estimated using logarithmic interindividual and additive residual variance models; the covariance between clearance and volume was modeled simultaneously. Mean (range) metformin concentrations in cord plasma and in maternal plasma were 0.81 (range, 0.1-2.6) mg/L and 1.2 (range, 0. 1-2.9) mg/L, respectively. Typical population values (interindividual variability, CV%) for allometrically scaled maternal clearance and volume of distribution were 28 L/h/70 kg (17.1%) and 190 L/70 ka (46.3%), giving a derived population-wide half-life of 5.1 hours. The placental partition coefficient for metformin was 1.07 (36.3%). Neither maternal age nor weight significantly influenced the pharmacokinetics. The variability (SD) of observed concentrations about model-predicted concentrations was 0.32 mg/L. The pharmacokinetics were similar to those in nonpregnant patients and, therefore, no dosage adjustment is warranted. Metformin readily crosses the placenta, exposing the fetus to concentrations approaching those in the maternal circulation. The sequelae to such exposure, ea, effects on neonatal obesity and insulin resistance, remain unknown.

Genetic improvement of lucerne for anthracnose (Colletotrichum trifolii) resistance

Anthracnose, caused by Colletotrichum trifolii, is one of the most serious diseases influencing lucerne persistence and productivity in eastern Australia. The disease is largely controlled by plant resistance; however, new pathotypes of C. trifolii have developed in Australia, seriously limiting the productive life of susceptible cultivars. This paper describes an incompletely recessive and quantitatively inherited resistance to C. trifolii identified in a clone (W116) from cv. Sequel. S-1, F-1, F-2 and backcross populations of W116 and D (highly susceptible clone) were studied for their reaction to C. trifolii race 1. Resistance was found to be quantitatively inherited, and quantitative trait loci associated with resistance and susceptibility were identified in a backcross population (D x W116) x D using random amplified polymorphic DNA and amplified fragment length polymorphic markers. A multi-locus region on linkage group 4 was found to contribute significantly to the resistance phenotype. The application of DNA markers to allow exploitation of this quantitatively inherited resistance in lucerne breeding is discussed.

Is the distribution of Fiji leaf gall in Australian sugarcane explained by variation in the vector Perkinsiella saccharicida?

Fiji leaf gall (FLG) is an important virally induced disease in Australian sugarcane. It is confined to southern canegrowing areas, despite its vector, the delphacid planthopper Perkinsiella saccharicida, occurring in all canegrowing areas of Queensland and New South Wales. This disparity between distributions could be a result of successful containment of the disease through quarantine and/or geographical barriers, or because northern Queensland populations of Perkinsiella may be poorer vectors of the disease. These hypotheses were first tested by investigating variation in the ITS2 region of the rDNA fragment among eastern Australian and overseas populations of Perkinsiella. The ITS2 sequences of the Western Australian P. thompsoni and the Fijian P. vitiensis were distinguishable from those of P. saccharicida and there was no significant variation among the 26P. saccharicida populations. Reciprocal crosses of a northern Queensland and a southern Queensland population of P. saccharicida were fertile, so they may well be conspecific. Single vector transmission experiments showed that a population of P. saccharicida from northern Queensland had a higher vector competency than either of two southern Queensland populations. The frequency of virus acquisition in the vector populations was demonstrated to be important in the vector competency of the planthopper. The proportion of infected vectors that transmitted the virus to plants was not significantly different among the populations tested. This study shows that the absence of FLG from northern Queensland is not due to a lack of vector competency of the northern population of P. saccharicida.

The production of male of-only offspring in beef cattle - a proof of principle project

The Australian beef industry places the greatest value in bulls, in comparison to cows, for prime beef production. Male carcasses can be sold for a larger profit due to their increased muscle mass. This project aims to demonstrate the feasibility of producing male animals that can sire male only offspring, through a transgenic approach in mice that could later be translated into livestock production systems. The mouse Sry (Sex determining region on the Y) gene has been shown to provide the initiating molecular signal leading to male sex determination in mammals. Sry has also been shown to cause sex reversal in XX mice transgenic for the gene. In this project Sry will be targeted to a locus not subject to X-inactivation on the X chromosome of XY mice. These mice will be bred to determine how the transgene is passed on, to determine expression of the transgene, and to assess its activity in causing XX sex reversal. The male mice transgenic for the Sry gene on their X chromosome will be produced using tetraploid aggregation, which in a single step produces 100% ES cell derived embryos. The same target locus can later be used to introduce the bovine SRY gene onto the X chromosome of bovidae species and using germ cell transplantation produce sex reversed animals. This would bypass the need for expensive chimera crosses and provide farmers with a stud bull capable of producing only sons.