Susceptibility of source plants to sugarcane Fiji disease virus influences the acquisition and transmission of the virus by the planthopper vector Perkinsiella saccharicida

Fiji leaf gall (FLG) caused by Sugarcane Fiji disease virus (SCFDV) is transmitted by the planthopper Perkinsiella saccharicida. FLG is managed through the identification and exploitation of plant resistance. The glasshouse-based resistance screening produced inconsistent transmission results and the factors responsible for that are not known. A series of glasshouse trials conducted over a 2-year period was compared to identify the factors responsible for the erratic transmission results. SCFDV transmission was greater when the virus was acquired by the vector from a cultivar that was susceptible to the virus than when the virus was acquired from a resistant cultivar. Virus acquisition by the vector was also greater when the vector was exposed to the susceptible cultivars than when exposed to the resistant cultivar. Results suggest that the variation in transmission levels is due to variation in susceptibility of sugarcane cultivars to SCFDV used for virus acquisition by the vector.

Leadership training and regular communication identified as key strategies for the development of the Australian pineapple industry

Changes in the circumstances of the Australian pineapple industry left growers with a leadership vacuum, limited technical support and no funds for conducting research and marketing. Inspirational leadership training together with regular district farm meetings were used to assist the Australian pineapple industry to successfully adapt to these challenges. All growers were assigned to one of a number of regional grower study groups and regular on-farm meetings commenced to facilitate communication between growers, transfer of technology, awareness of industry affairs and an opportunity to become involved in industry business. A leader was appointed within each study group and these leaders attended a leadership course consisting of three, three-day modules. These original course graduates formed the nucleus of a new grower representative group which subsequently instigated levies to fund research and marketing. Two more courses have since been conducted to provide the depth of leadership to satisfy the growers' desire to rotate industry leadership on a regular basis.

Light environment and tree development of young Acacia melanoxylon in mixed-species regrowth forest, Tasmania, Australia

Blackwood (Acacia melanoxylon R. Br.) is a valuable leguminous cabinetwood species which is commonly found as a canopy or subcanopy tree in a broad range of mixed-species moist forests on tablelands and coastal escarpments in eastern Australia. This paper reports on the competitive light environment of a commercially valuable multi-species regrowth forest in NW Tasmania, in order to define some of the functional interactions and competitive dynamics of these stands. Comparative observations were made of the internal forest light environment in response to small-gap silvicultural treatments, in a young regenerative mix of three codominant tree species. Light measurements were made during periods of maximum external irradiance of the regrowth Eucalyptus obliqua/A. melanoxylon forest canopy at age 10.5 years. This was at a time of vigourous stand development, 4.5 years following the application of three experimental silvicultural treatments whose effects were observed in comparison with an untreated canopy sample designed as a control. Minimal irradiance was observed within and beneath the dense subcanopy of the native nurse species (Pomaderris apetala) which closely surrounds young blackwood regeneration. Unlike current plantation nurse systems, the dense foliage of the native broadleaved Pomaderris all but eliminated direct side-light and low-angle illumination of the young blackwood, from the beginning of tree establishment. The results demonstrated that retention of these densely stocked native codominants effectively suppressed both size and frequency of blackwood branches on the lower bole, through effective and persistent interception of sunlight. Vigorous young blackwood crowns later overtopped the codominant nurse species, achieving a predictable height of branch-free bole. This competitive outcome offers a valuable tool for management of blackwood crown dynamics, stem form and branch habit through manipulation of light environment in young native regrowth systems. Results demonstrate that effective self-pruning in the lower bole of blackwood is achieved through a marked reduction in direct and diffuse sunlight incident on the lower crown, notably to less than 10-15% of full sunlight intensity during conditions of maximum insolation. The results also contain insights for the improved design of mixed-species plantation nurse systems using these or functionally similar species' combinations. Based on evidence presented here for native regrowth forest, plantation nurse systems for blackwood will need to achieve 85-90% interception of external side-light during early years of tree development if self-pruning is to emulate the results achieved in the native nurse system.

Review of bats and SARS

Bats have been identified as a natural reservoir for an increasing number of emerging zoonotic viruses, including henipaviruses and variants of rabies viruses. Recently, we and another group independently identified several horse-shoe bat species (genus Rhinolophus) as the reservoir host for a large number of viruses that have a close genetic relationship with the coronavirus associated with severe acute respiratory syndrome (SARS). Our current research focused on the identification of the reservoir species for the progenitor virus of the SARS coronaviruses responsible for outbreaks during 2002-2003 and 2003-2004. In addition to SARS-like coronaviruses, many other novel bat coronaviruses, which belong to groups 1 and 2 of the 3 existing coronavirus groups, have been detected by PCR. The discovery of bat SARS-like coronaviruses and the great genetic diversity of coronaviruses in bats have shed new light on the origin and transmission of SARS coronaviruses.

The impacts and management of foxes Vulpes vulpes in Australia

1. The successful introduction of the red fox Vulpes vulpes into Australia in the 1870s has had dramatic and deleterious impacts on both native fauna and agricultural production. Historical accounts detail how the arrival of foxes in many areas coincided with the local demise of native fauna. Recent analyses suggest that native fauna can be successfully reintroduced to their former ranges only if foxes have been controlled, and several replicated removal experiments have confirmed that foxes are the major agents of extirpation of native fauna. Predation is the primary cause of losses, but competition and transmission of disease may be important for some species. 2. In agricultural landscapes, fox predation on lambs can cause losses of 1–30%; variation is due to flock size, health and management, as well as differences in the timing and duration of lambing and the density of foxes. 3. Fox control measures include trapping, shooting, den fumigation and exclusion fencing; baiting using the toxin 1080 is the most commonly employed method. Depending on the baiting strategy, habitat and area covered, baiting can reduce fox activity by 50–97%. We review patterns of baiting in a large sheep-grazing region in central New South Wales, and propose guidelines to increase landholder awareness of baiting strategies, to concentrate and coordinate bait use, and to maximize the cost-effectiveness of baiting programs. 4. The variable reduction in fox density within the baited area, together with the ability of the fox to recolonize rapidly, suggest that current baiting practices in eastern Australia are often ineffective, and that reforms are required. These might include increasing landholder awareness and involvement in group control programs, and the use of more efficient broadscale techniques, such as aerial baiting.

Infection and disease development of Quambalaria spp. on Corymbia and Eucalyptus spp.

Quambalaria spp. are eucalypt leaf and shoot pathogens of growing global importance, yet virtually nothing is known regarding the manner in which they infect and colonize their hosts. A study of the infection process of Q. pitereka and Q.eucalypti on Corymbia and Eucalyptus species was thus undertaken using light, scanning and transmission electron microscopy after artificial inoculation. Conidial germination was triggered when relative humidity levels exceeded 90% and commenced within 2 h in the presence of free water. Light reduced germination but did not prevent germination from occurring. Conidial germination and hyphal growth occurred on the upper and lower leaf surfaces with penetration occurring via the stomata or wounds on the leaf surface or juvenile stems. There was no evidence of direct penetration of the host. Following penetration through the stomata, Q. pitereka and Q. eucalypti hyphae grew only intercellularly without the formation of haustoria or interaction apparatus, which is characteristic of the order Microstromatales. Instead, the presence of an interaction zone is demonstrated in this paper. Conidiophores arose through stomatal openings producing conidia 7 days after infection.

Multidrug-resistant extraintestinal pathogenic Escherichia coli of sequence type ST131 in animals and foods.

Multidrug-resistant Escherichia colt sequence type 131 (51131) has recently emerged as a globally distributed cause of extraintestinal infections in humans. Diverse factors have been investigated as explanations for ST131's rapid and successful dissemination, including transmission through animal contact and consumption of food, as suggested by the detection of ST131 in a number of nonhuman species. For example, ST131 has recently been identified as a cause of clinical infection in companion animals and poultry, and both host groups have been confirmed as faecal carriers of ST131. Moreover, a high degree of similarity has been shown among certain ST131 isolates from humans, companion animals, and poultry based on resistance characteristics and genomic background and human and companion animal ST131 isolates tend to exhibit similar virulence genotypes. However, most ST131 isolates from poultry appear to possess specific virulence genes that are typically absent from human and companion animal isolates, including genes associated with avian pathogenic E. coli. Since the number of reported animal and food-associated ST131 isolates is quite small, the role of nonhuman host species in the emergence, dissemination, and transmission of ST131 to humans remains unclear. Nevertheless, given the profound public health importance of the emergent ST131 clonal group, even the limited available evidence indicates a pressing need for further careful study of this significant question.

Innovative new production systems for low-chill stonefruit in Australia and South-East Asia: a review

Fruit size and quality are major problems in early-season stonefruit cultivars grown in Australia and South-East Asia. In Australia, Thailand and Vietnam, new training and trellising systems are being developed to improve yield and fruit quality. Australian trials found that new training systems, such as the Open Tatura system, are more productive compared with standard vase-trained trees. We established new crop-loading indices for low-chill stonefruit to provide a guide for optimum fruit thinning based on fruit number per canopy surface and butt cross sectional area. Best management practices were developed for low-chill stonefruit cultivation using growth retardants, optimizing leaf nitrogen concentrations and controlling rates and timing of irrigation. Regulated deficit irrigation (RDI) improved fruit sugar concentrations by restricting water application during stage II of fruit growth. New pest and disease control measures are also being developed using a new generation of fruit fly baits. Soft insecticides such as (Spinosad) are used at significantly lower concentrations and have lower mammalian toxicity than the organophosphates currently registered in Australia. In addition, fruit fly exclusion netting effectively eliminated fruit fly and many other insect pests from the orchard with no increase in diseases. This netting system increased sugar concentrations of peach and nectarine by as much as 30%. Economic analyses showed that the break-even point can be reduced from 12 to 6 years Open Tatura trellising and exclusion netting.

Cu2+ inhibition of gel secretion in the xylem and its potential implications for water uptake of cut Acacia holosericea stems

Maintaining a high rate of water uptake is crucial for maximum longevity of cut stems. Physiological gel/tylosis formation decreases water transport efficiency in the xylem. The primary mechanism of action for post-harvest Cu2+ treatments in improving cut flower and foliage longevity has been elusive. The effect of Cu2+ on wound-induced xylem vessel occlusion was investigated for Acacia holosericea A. Cunn. ex G. Don. Experiments were conducted using a Cu2+ pulse (5 h, 2.2 mM) and a Cu2+ vase solution (0.5 mM) vs a deionized water (DIW) control. Development of xylem blockage in the stem-end region 10 mm proximal to the wounded stem surface was examined over 21 days by light and transmission electron microscopy. Xylem vessels of stems stood into DIW were occluded with gels secreted into vessel lumens via pits from surrounding axial parenchyma cells. Gel secretion was initiated within 1-2 days post-wounding and gels were detected in the xylem from day 3. In contrast, Cu2+ treatments disrupted the surrounding parenchyma cells, thereby inhibiting gel secretion and maintaining the vessel lumens devoid of occlusions. The Cu2+ treatments significantly improved water uptake by the cut stems as compared to the control. © 2013 Scandinavian Plant Physiology Society.