Skin damage to two new mango cultivars during irradiation and cold storage.

Mangoes can express several skin disorders following important postharvest treatments. Responses are often cultivar specific. This paper reports the responses of two new Australian mango cultivars to some of these treatments. 'Honey Gold' mango develops "under skin browning" early during cold storage. This is thought to be partly caused by a discolouration of the latex vessels which then spreads to the surrounding cells. The symptoms appear to be worse in fruit from hotter production areas and that have been cooled to temperatures below 18C soon after harvest. Current commercial recommendations are to cool fruit to 18C, which limits postharvest handling options. Recent trials have confirmed that delayed or slowed cooling after harvest can reduce under skin browning. The defect may also be associated with physical injury to the skin during harvesting and packing. Irradiation is potentially an important disinfestation treatment for fruit fly in Australian mangoes. The 'B74' mango cultivar develops significant skin damage following irradiation, mainly due to discolouration of the cells surrounding the lenticels. Recent results confirmed that fruit harvested directly from the tree into trays without exposure to water or postharvest chemicals are not damaged by irradiation, while commercially harvested and packed fruit are damaged. Several major harvest and postharvest steps appear to increase lenticel sensitivity to irradiation. Further work is required to develop commercially acceptable protocols to facilitate 'Honey Gold' and 'B74' mango distribution and marketing.

Forest health guide: symptoms of insect and fungal damage on trees

The Forest health guide: symptoms of insect and fungal damage on trees is intended to help forestry and quarantine staff undertake tree health assessments, in both forest and urban environments. The guide is designed to be used as a quick reference to common symptoms of damage, not as an identification guide to particular insect pests and pathogens.

War damage; Kunstgewerbe, Berlin.

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Reducing skin damage and improving efficiency of Calypso mango

Calypso mango is a relatively new variety owned by DEEDI and managed/marketed by One Harvest (Queensland-based). It is a major mango variety for the retail chains. Its main limitation is a sensitive skin, which results in lenticel spotting and skin browning.

Kinetic mechanism of the interaction of D-cycloserine with serine hydroxymethyltransferase

The kinetic mechanism for the interaction of D-cycloserine with serine hydroxymethyltransferase (EC2.1.2.1) from sheep liver was established by measuring changes in the activity, absorbance, and circular dichoism (CD) of the enzyme. The irreversible inhibition of the enzyme was characterized by three detectable steps: an initial rapid step followed by two successive steps with rate constants of 5.4 X s-l and 1.4 X lo4 s-l. The first step was distinguished by a rapid disappearance of the enzyme absorbance peak at 425 nm, a decrease in the enzyme activity to 25% of the uninhibited velocity, and a lowering of the CD intensity at 432 nm to about 65% of the original value. The second step of the interaction was accompanied by a complete loss of enzyme.

Improved understanding of the damage, ecology, and management of mirids and stinkbugs in Bollgard II

In recent years mirids and stinkbugs have emerged as important sucking pests in cotton. While stinkbugs are causing damage to bolls, mirids are causing damage to seedlings, squares and bolls. With the increasing adoption of Bollgard II and IPM approaches the use of broad-spectrum chemicals to kill Helicoverpa has been reduced and as a result mirids and stinkbugs are building to levels causing damage to bolls later in crop growth stages. Studies on stinkbugs by Dr Moazzem Khan revealed that green vegetable bug (GVB) caused significant boll damage and yield loss. A preliminary study by Dr Khan on mirids revealed that high mirid numbers at later growth stages also caused significant boll damage and that damage caused by mirids and GVB were similar. Mirids and stinkbugs therefore demand greater attention in order to minimise losses caused by these pests and to develop IPM strategies against these pests to enhance gains in IPM that have been made with Bt-transgenic cotton. Progress in this area of research will maintain sustainability and profitability of the Australian cotton industry. Mirid damage at early growth stages of cotton (up to squaring stage) has been studied in detail by Dr Khan. He found that all ages of mirids cause damage to young plants and damage by mirid nymphs is cumulative. Maximum damage occurs when the insect reaches the 4th and 5th nymphal stages. He also found that mirid feeding causes shedding of small and medium squares, and damaged large squares develop as ‘parrot beak’ bolls. Detailed studies at the boll stage, such as which stage of mirids is most damaging or which age boll is most vulnerable to feeding, is lacking. This information is a prerequisite to developing an IPM strategy for the pest in later crop growth stages. Understanding population change of the pest over time in relation to crop development is an important aspect for developing management strategies for the pest which is lacking for mirids in BollgardII. Predators and parasitoids are integral components of any IPM system and play an important part in regulating pest populations. Some generalist predators such as ants, spiders, damsel bugs and assassin bugs are known to predate on mirids. Nothing is known about parasitoids of mirids. Since green mirid (GM), Creontiades dilutus, is indigenous to Australia it is likely that we have one or more parasitoids of this mirid in Australia, but that possibility has not been investigated yet. The impact of the GVB adult parasitoid, Trichopoda giacomelli, has been studied by Dr Khan who found that the fly is established in the released areas and continues to spread. However, to get wider and greater impact, the fly should be released in new locations across the valleys. The insecticides registered for mirids and stinkbugs are mostly non-selective and are extremely disruptive to a wide range of beneficial insects. Use of these insecticides at stage I and II will minimise the impact of existing IPM programs. Therefore less disruptive control tactics including soft chemicals for mirids and stinkbugs are necessary. As with soft chemicals, salt mixtures, biopesticides based on fungal pathogens and attractants based on plant volatiles may be useful tools in managing mirids and stinkbugs with less or no disruption. Dr Khan has investigated salt mixture against mirids and GVB. While salt mixtures are quite effective and less disruptive, they are quite chemical specific. Not all chemicals mixed with salt will give the desired benefit. Therefore further investigation is needed to identify those chemicals that are effective with salt mixture against mirids and 3 of 37 GVB. Dr Caroline Hauxwell of DPI&F is working on fungal pathogen-based biopesticides against mirids and GVB and Drs Peter Gregg and Alice Del Socorro of Australian Cotton CRC are working on plant volatile-based attractants against mirids. Depending on their findings, inclusion of fungal-based biopestcides and plant volatile-based attractants in developing a management system against mirids and stinkbugs in cotton could be an important component of an IPM approach.

Dosage Compensation And Sex Determination In Drosophila - Mechanism Of Measurement Of The X/A Ratio

We propose a molecular mechanism for the intra-cellular measurement of the ratio of the number of X chromosomes to the number of sets of autosomes, a process central to both sex determination and dosage compensation in Drosophila melanogaster. In addition to the two loci, da and Sxl, which have been shown by Cline (Genetics, 90, 683, 1978)and others to be involved in these processes, we postulate two other loci, one autosomal (ω) and the other, X-linked (π). The product of the autosomal locus da stimulates ω and initiates synthesis of a limited quantity of repressor. Sxl and π ,both of which are X-linked, compete for this repressor as well as for RNA polymerase. It is assumed that Sxl has lower affinity than π for repressor as well as polymerase and that the binding of polymerase to one of these sites modulates the binding affinity of the other site for the enzyme. It can be shown that as a result of these postulated interactions transcription from the Sxl site is proportional to the X/A ratio such that the levels of Sxl+ product are low in males, high in females and intermediate in the intersexes. If, as proposed by Cline, the Sxl- product is an inhibitor of X chromosome activity, this would result in dosage compensation. The model leads to the conclusion that high levels of Sxl+ product promote a female phenotype and low levels, a male phenotype. One interesting consequence of the assumptions on which the model is based is that the level of Sxl+ product in the cell, when examined as a function of increasing repressor concentration, first goes up and then decreases, yielding a bell-shaped curve. This feature of the model provides an explanation for some of the remarkable interactions among mutants at the Sxl, da and mle loci and leads to several predictions. The proposed mechanism may also have relevance to certain other problems, such as size regulation during development, which seem to involve measurement of ratios at the cellular level.

Micromechanisms of damage in a hypereutectic Ti-6Al-4V-B alloy

The tensile stress–strain response and fracture in a hypereutectic Ti–6Al–4V–1.7B (weight percent) alloy were investigated by employing interrupted tensile tests combined with acoustic emission measurements, with the aim to identify the cause for the observed low ductility in this alloy. These tests were complemented with microscopy. The alloy contains TiB whiskers of different length scales, the majority of which include micro-whiskers ( 5–10 μm length) and a few primary-whiskers ( 200–300 μm length). Although the fracture of both types of whiskers occur during deformation, the former leads to a gradual decrease in the secant modulus whereas initiation of the latter leads to a drastic drop in the modulus along with failure of the specimen, limiting the ductility.

Rain Damage to Strawberries Grown in Southeast Queensland: Evaluation and Genetic Control.

In Queensland, Australia, strawberries (Fragaria xananassa Duchesne) are grown in open fields and rainfall events can damage fruit. Cultivars that are resistant to rain damage may reduce losses and lower risk for the growers. However, little is known about the genetic control of resistance and in a subtropical climate, unpredictable rainfall events hamper evaluation. Rain damage was evaluated on seedling and clonal trials of one breeding population comprising 645 seedling genotypes and 94 clones and on a second clonal population comprising 46 clones from an earlier crossing to make preliminary estimates of heritability. The incidence of field damage from rainfall and damage after laboratory soaking was evaluated to determine if this soaking method could be used to evaluate resistance to rain damage. Narrow-sense heritability of resistance to rain damage calculated for seedlings was low (0.21 +/- 0.15) and not significantly different from zero; however, broad-sense heritability estimates were moderate in both seedlings (0.49 +/- 0.16) and clones (0.45 +/- 0.08) from the first population and similar in clones (0.56 +/- 0.21) from the second population. Immersion of fruit in deionized water produced symptoms consistent with rain damage in the field. Lengthening the duration of soaking of 'Festival' fruit in deionized water exponentially increased the proportion of damage to fruit ranging in ripeness from immature to ripe during the first 6-h period of soaking. When eight genotypes were evaluated, the proportion of sound fruit after soaking in deionized water in the laboratory for up to 5 h was linearly related (r(2) = 0.90) to the proportion of sound fruit in the field after 89 mm of rain. The proportion of sound fruit of the breeding genotype '2008-208' and 'Festival' under soaking (0.67, 0.60) and field (0.52, 0.43) evaluations, respectively, is about the same and these genotypes may be useful sources of resistance to rain damage.

Influence of Corymbia hybridisation on crown damage by three arthropod herbivores.

Three common pests (eucalypt tortoise beetle Paropsis atomaria, leaf blister sawfly Phylacteophaga froggatti and eriophyid mites) of commercial spotted gum plantations were assessed for their crown damage levels on parent and hybrid Corymbia taxa ( Corymbia torelliana, C. citriodora subsp. variegata and their hybrid) at three common-garden field sites. Damage levels differed significantly between sites for all three herbivore species, and between taxa for eriophyid mites and P. atomaria. However, herbivore response to hybridisation only differed for P. atomaria between sites, even where damage levels did not. Hybrids exhibited three common patterns of susceptibility relative to parent taxa, being most commonly intermediate to their parents for crown damage (additive resistance pattern), or no difference between parents and hybrids, or with one incidence of dominance for susceptibility.

A case of true hermaphroditism reveals an unusual mechanism of twinning

Traditionally twins are classified as dizygous or fraternal and monozygous or identical (Hall Twinning, 362, 2003 and 735-743). We report a rare case of 46,XX/46,XY twins: Twin A presented with ambiguous genitalia and Twin B was a phenotypically normal male. These twins demonstrate a third, previously unreported mechanism for twinning. The twins underwent initial investigation with 17-hydroxyprogesterone and testosterone levels, pelvic ultrasound and diagnostic laparoscopy. Cytogenetic analysis was performed on peripheral blood cells and skin fibroblasts. Histological examination and Fluorescence in situ hybridization studies on touch imprints were performed on gonadal biopsies. DNA analysis using more than 6,000 DNA markers was performed on skin fibroblast samples from the twins and on peripheral blood samples from both parents. Twin A was determined to be a true hermaphrodite and Twin B an apparently normal male. Both twins had a 46,XX/46,XY chromosome complement in peripheral lymphocytes, skin fibroblasts, and gonadal biopsies. The proportion of XX to XY cells varied between the twins and the tissues evaluated. Most significantly the twins shared 100% of maternal alleles and approximately 50% of paternal alleles in DNA analysis of skin fibroblasts. The twins are chimeric and share a single genetic contribution from their mother but have two genetic contributions from their father thus supporting the existence of a third, previously unreported type of twinning.

A four-variable model for the pattern-forming mechanism in Hydra

A generalized Gierer-Meinhardt model has been used to account for the transplantation experiments in Hydra. In this model, a cross inhibition between the two organizing centres (namely, head and foot) are assumed to be the only mode of interaction in setting up a stable morphogen distribution for the pattern formation in Hydra.

Damage and physiological stress to juvenile eastern rock lobster (Sagmariasus verreauxi) discarded after trapping and hand collection

Large numbers of Sagmariasus verreauxi are trapped and hand collected in Australia, but discarded due to size and quota restrictions, and under the unevaluated assumption of few impacts. To test the validity of enforced discarding, trapped and hand-collected S. verreauxi (49-143. mm carapace length - CL) were examined for external damage, placed into cages, transferred to aquaria and monitored (with controls) over three months. Haemolymph was non-repetitively sampled immediately and at one, three, and seven days to quantify stress. Most trapped (64%) and hand-collected (79%) specimens were undersized (<104. mm CL), with the latter method yielding broader ranges of sizes and moult stages. Within-trap Octopus tetricus predation caused the only mortalities (3.3%). Hand collection resulted in much greater antennae and pereopod loss than trapping (53 vs. 4%) but, compared to controls, both methods evoked benign physiological responses that resolved within a week. While most wounded S. verreauxi regenerated all or some missing appendages post-moult, their mean CLs were less than those from intact conspecifics. Simple strategies, including larger mesh sizes, and/or installing modifications to reduce bycatch in traps, careful hand collection, and appropriate release techniques might minimise impacts (including predation) to unwanted S. verreauxi, and help to control stock exploitation. © 2012 Elsevier B.V.

Mechanism of the thermal decomposition of polystyrene peroxide

The thermal degradation of polystyrene peroxide was carried out using differential scanning calorimetry. The activation energy (E) was found to be 136 kJ mole–1 at all extents of decomposition. TheE value was found to correspond to-O-O-dissociation. The order of reaction was found to decrease from 2 to 1 as the decomposition progresse.