Regions Of Eastern Australia Research Articles

Pratylenchus thornei populations reduce water uptake in intolerant wheat cultivars

Pratylenchus thornei is a major pathogen of wheat crops in the northern grain region of Eastern Australia with an estimated annual yield loss of $38 million. Damaged crops show symptoms of water and nutrient stress that suggest uptake is significantly affected. In order to understand the mechanisms involved in reducing water uptake and consequently plant yield, detailed measurements of water extraction and leaf area were conducted on a range of wheat cultivars with differing levels of tolerance and resistance to P. thornei.Planting wheat into high populations of P. thornei reduced the extraction rate (kl) in the intolerant cultivars; this in turn caused a delay in the root extraction velocity and effectively changed the crop lower limit. The early season stress applied by the reduced extraction rate impeded canopy development that consequently reduced demand for water and nutrients, growth and yield potential. The resulting yield loss was consistent across both a wet and a dry wheat growing season with the intolerant cultivar yielding 34% less than the tolerant cultivar. Understanding the mechanism with which P. thornei reduces yield allows the impact of P. thornei to be included in simulation models to better understand how to manage this constraint to the Australian grain industry.

Modelling the behaviour of crown rot in wheat caused by Fusarium pseudograminearum

Existing spatiotemporal models for disease progress are unsuitable for describing epidemics of residue-borne diseases of cereals like crown rot, caused by Fusarium pseudograminearum, which increase in incidence over successive years and where inoculum has a fixed location. Monte Carlo simulation was used to explore the behaviour of a simple mechanistic model for crown rot, in which inoculum from each infected plant in one season came into contact with a defined number of plants in the following season. Contacted plants became infected according to a probability of infection that was less than 1. Growth chamber experiments confirmed that contact between infested residue and plants was required for infection. Observed features of epidemics at a long term trial site, including disease progress and maximum incidence, were satisfactorily fitted by simulations with a starting incidence of 4 %, 12 plants contacted by inoculum from each infected plant, and probability of infection of 0.66. This confirms that our understanding of disease behaviour at moderate to high levels of incidence is basically correct. However, infection rate between seasons was sensitive to initial incidence, suggesting that dispersal methods such as ascospores or conidia may be important at low incidence. A simple descriptive model was developed for the disease in bread wheat in the northern grains region of eastern Australia. Inoculum potential was estimated from the square root of the product of crown rot incidence and yield (a surrogate for biomass) of the preceding crop. Incidence of disease was related to inoculum potential by an infection constant. Crown rot inoculum was assumed to decline exponentially with time between susceptible crops. These two relationships were combined to predict the behaviour of the disease in different rotation systems. Over time, crown rot incidence converged to an equilibrium level that was determined by the infection constant, average yield, and the survival rate of inoculum. Modelled epidemics behaved in a way that was consistent with field data for continuous wheat, wheat-chickpea and wheat-sorghum rotations. This descriptive model could be used in extension or as a way of understanding how management and environment affect the disease.

Root-lesion nematode (Pratylenchus thornei) reduces nutrient response, biomass and yield of wheat in sorghum–fallow–wheat cropping systems in a subtropical environment

Wheat in winter and grain sorghum in summer are the most important crops of the subtropical grain region of eastern Australia, where they are often grown in sequences of 1–4 years of each crop species separated by a long fallow period of 11–14 months. Growers have observed that the second wheat crop in sequence can appear nutrient deficient with poor growth and grain yield compared with the first or subsequent crops. To investigate this problem, wheat was grown in various field experiments as the first–fourth wheat in sequence after long fallow from sorghum sequences of various lengths (one–four years) to test for responses in biomass production and grain yield to fertilisers, biocidal fumigants and nematicides. Populations of root-lesion nematodes (Pratylenchus thornei) were greatest in the soil before the second wheat crop was sown than before the first or third wheat crops. Greatest responses in wheat growth were obtained to the nematicide aldicarb in various wheat sequence positions up to the fourth (up to 137% increased yield of second wheat). Aldicarb best protected the roots from P. thornei allowing increased nutrient response. The fumigants chloropicrin and dazomet caused substantial changes in soil microbial populations and available nutrients, but the systemic nematicides fenamiphos and aldicarb did not. Responses in grain yield were also obtained to N fertiliser and less frequently to P and Zn (41% increase of second wheat to NPZn fertiliser), with best overall responses to a combination of aldicarb and fertiliser. A range of tolerance to P. thornei, as judged by both grain yield from nil treatment and response to aldicarb and/or fertiliser, was identified among wheat cultivars. In comparison, one barley cultivar yielded maximally without treatment (up to 3.7 and 1.3 times the yield of the most intolerant and the most tolerant wheat cultivars, respectively). Integrated management using crop rotation with sorghum to reduce P. thornei populations combined with growing tolerant wheat and barley cultivars supplied with adequate fertiliser are practical measures to reduce the impact of P. thornei.

Genetic and postharvest factors affecting macadamia kernel quality

Macadamia (Macadamia integrifolia, Macadamia tetraphylla and hybrids) is cultivated in regions of Eastern Australia. Genotype and geographical location, a factor seldom studied, may influence kernel quality. Macadamias from three cultivars were harvested from three commercial plantations, each in a different region of Eastern Australia over three consecutive seasons. Kernel quality was assessed by whole kernel, shoulder damage, weight of pieces, oily kernels and dusty kernels. Whole kernel was strongly influenced by genotype. Shoulder damage and weight of pieces were variable and not related to genotype. Shoulder damage rates were low and numbers of oily and dusty kernels were negligible. The influence of genotype on whole kernel highlights the importance of cultivar selection from macadamia quality management. High kernel quality of kernels from nuts harvested and handled with care in this study emphasizes that the best practice postharvest management of macadamia nut-in-shell is the most important means of maintaining kernel quality. Key words: Macadamia, kernel quality, genotype, whole kernel, shoulder damage, geographical location, post-harvest handling.

Supporting wild pollinators in a temperate agricultural landscape: Maintaining mosaics of natural features and production

Pollination has received attention recently due to reported sharp declines of Apis mellifera in several locations, and it has been proposed that diverse native bee communities may be key for continued pollination of economically important crops. However, there is some inconsistency in the literature as to how these communities should best be managed. To address this issue, we collected bees from an intensively managed agricultural region in eastern Australia using blue vane traps. Both linear remnants of vegetation, which form part of a larger corridor network, and adjacent fields of native and exotic pastures, wheat, canola, and lucerne were sampled. A total of 3249 individual bees, representing four families and 36 species were collected. Highly modified environments of nectar-bearing crop supported the most species-rich bee assemblages, and the highest abundance of individual bee species. Distance from the remnants did not limit the body size of species occupying fields (up to 400m). However, richness of bee assemblages also responded positively to the presence of conservation land in nearby areas, or the number of remnant native trees surrounding traps. Linear remnants of native vegetation contributed to assemblage heterogeneity by adding unique species to the regional pool. Our findings indicate that agricultural industries that currently rely on pollination by A. mellifera should ensure that intensive land use is complemented by untilled areas in the form of conservation land, or farm dams and scattered trees in fields, to support wild pollinators that may act as insurance against further future losses of managed hives.

Plant phylogeny as a surrogate for turnover in beetle assemblages

The ability to extrapolate from the known to the unknown is essential if we are to use the turnover of overall biodiversity, as opposed to a few well-known groups, to inform conservation planning. We investigated the usefulness of using evolutionary relationships of plants as a surrogate for the turnover of their associated beetle assemblages. If plant traits that are important to insects are phylogenetically conserved, it follows that there will be a positive relationship between insect faunal dissimilarity and plant evolutionary distance. We collected beetles using pyrethrum knock-down methods from 40 plant species belonging to four plant families in the Sydney region of Eastern Australia. We developed a novel approach for estimating variance in the dissimilarity of beetle assemblages, as explained by plant phylogeny, by using phylogenetic eigenvectors as explanatory variables in a distance-based redundancy analysis. We found a highly significant relationship between faunal dissimilarity and plant evolutionary distance for the entire beetle assemblage, the herbivorous component, and the non-herbivorous component, indicating that beetles generally showed some preference for particular plant clades as habitat, regardless of feeding guild. When comparing observed dissimilarities with those predicted from 40 jack-knife replicates of a Generalised Dissimilarity Model, we were often able to predict beetle turnover from plant phylogenetic relationships, although the reliability of this result was highly variable. Nevertheless, the broad response of beetle assemblages to plant evolutionary relatedness indicates real potential for plant phylogenetic pattern to act as a useful surrogate for insect biodiversity, especially when supplemented with other environmental correlates.

Bringing Scholarship and Judgement into the Australian Population Debate

Video Abstract: http://bit.ly/ocGEkd

Arthropod assemblages in tree canopies: a comparison of orders on box mistletoe (Amyema miquelii) and its host eucalypts

Parasitic plants, such as mistletoes, are important components of tree canopies, providing food and shelter for a range of vertebrates and invertebrates. Arthropods from several orders are known to inhabit mistletoes but no direct comparisons between these plants and their host plants have been conducted until present. In this study, the composition and abundance of arthropods occurring on hemi-parasitic box mistletoe, Amyema miquelii ((Lehm. ex Miq.) Tiegh., Loranthaceae), on Eucalyptus (L., Myrtaceae) trees from the south-west slopes region of eastern Australia were investigated. Here a comparison of the arthropod assemblages at the ordinal level is presented. Specimens of Insecta and Arachnida were sampled from box mistletoe and three of its most common host species, using restricted canopy fogging, in two consecutive years, in nine remnants of grassy-box woodlands. The same 10 arthropod orders were sampled from the mistletoes and their eucalypt hosts but the total density of arthropods was greater on the eucalypt foliage. The latter result might be attributed to the significantly greater nitrogen content of the eucalypt foliage than the mistletoe foliage. One year after de-faunation, all but one of the arthropod orders had re-colonised the mistletoe plants. The total abundance of arthropods (particularly Hemiptera and Hymenoptera) on the mistletoes was greater in the second year of sampling, in which drought conditions occurred. Future research of arthropod assemblages in tree canopies should be more inclusive of the full range of substrates or habitats within canopies. Furthermore, investigation of the nutritional quality of mistletoe foliage compared with their host trees is required for a better understanding of the factors driving variation in community composition of arthropod assemblages.

Rail survey plans to remote sensing: vegetation change in the Mulga Lands of eastern Australia and its implications for land use

There is a prevailing paradigm that woody vegetation is expanding at the expense of grassland with reduced burning under pastoralism in the Mulga Lands biogeographic region in eastern Australia. This raises the possibility that the region is acting as a carbon sink. Vegetation boundaries were precisely positioned from rail survey plans dating from 1895 to 1900. This baseline was compared with the position of boundaries on 1952 aerial photography and 2010 Google Earth imagery. The conversion of forest to non-forest by mechanical clearing was also mapped from satellite imagery. There was no consistent trend in the direction of boundary movement for mulga (Acacia aneura F.Muell. ex Benth.), gidgee (Acacia cambagei R.T. Baker) forest or miscellaneous other forest types. The stability of the boundaries, despite the transition from aboriginal management to rangeland pastoralism, contrasts with dramatic declines in tree cover resulting from mechanical clearing. Mapping of forest cover from satellite imagery reveals that conversion of forest to non-forest has reduced mulga forest to 74%, gidgee forest to 30% and miscellaneous forest types to 82% of their original area. Annual clearing rates for the period between 1997 and 2005 were 0.83, 0.95 and 0.43% for those forest types, respectively. Clearing has declined substantially in the period 2005–09 since the advent of recent regulations in Queensland. The area remains a source of carbon emissions but this situation may reverse if restoration of mulga dry forest becomes an attractive land use with an emerging carbon market.

Application of physiological understanding in soybean improvement. I. Understanding phenological constraints to adaptation and yield potential

The purpose of this paper and its companion1 is to describe how, in eastern Australia, soybean improvement, in terms of both breeding and agronomy, has been informed and influenced over the past four decades by physiological understanding of the environmental control of phenology. This first paper describes how initial attempts to grow soybean in eastern Australia, using varieties and production practices from the southern USA, met with limited success due to large variety × environment interaction effects on seed yield. In particular, there were large variety × location, variety × sowing date, and variety × sowing date × density effects. These various interaction effects were ultimately explained in terms of the effects of photo-thermal environment on the phenology of different varieties, and the consequences for radiation interception, dry matter production, harvest index, and seed yield. This knowledge enabled the formulation of agronomic practices to optimise sowing date and planting arrangement to suit particular varieties, and underpinned the establishment of commercial production in south-eastern Queensland in the early 1970s. It also influenced the establishment and operation over the next three decades of several separate breeding programs, each targeting phenological adaptation to specific latitudinal regions of eastern Australia. This paper also describes how physiological developments internationally, particularly the discovery of the long juvenile trait and to a lesser extent the semi-dwarf ideotype, subsequently enabled an approach to be conceived for broadening the phenological adaptation of soybeans across latitudes and sowing dates. The application of this approach, and its outcomes in terms of varietal improvement, agronomic management, and the structure of the breeding program, are described in the companion paper.

Longitudinal patterns in bird reporting rates in a threatened ecosystem: Is change regionally consistent?

Work in many parts of the world has discussed the decline of biodiversity in regions dominated by agriculture. We report the results of a major study documenting the longitudinal profiles of birds between 1998 and 2009 within 66 patches of temperate woodland in a heavily cleared and grazed agricultural region of south-eastern Australia. Many researchers have forecast the loss of bird biota from this region and others that also were formerly dominated by temperate woodland. We had sufficient high quality data to analyse the longitudinal profiles of reporting rates for 76 of the 116 individual bird species recorded in our 12-year study. Unexpectedly, only four of the 76 species analysed (5.6%) exhibited a significant negative linear decrease in reporting rate. More surprisingly, 32 (42.1%) exhibited a significant positive linear increase in reporting rate, including several taxa of conservation concern. These increases occurred despite a series of below-average rainfall years. Reporting rates were too low to formally model long-term trends in some other bird species widely considered to be of conservation concern such as the Diamond Firetail ( Stagonopleura guttata) and Speckled Warbler ( Chthonicola sagittata). Many authors have used functional (and other) groups to forecast bird species likely to be lost from Australia’s temperate woodlands. However, we found no clear links between life history attributes and long-term trend patterns of species. Our findings contrast with recent findings from other temperate woodland-dominated regions in eastern Australia where losses in bird populations have been documented. However, they parallel other investigations such as in central New South Wales. These similarities among, and differences between, studies suggest regional differences in temporal patterns in bird population dynamics. Many of the observed changes in reporting rates were positive and they provide hope that forecast future losses of a large proportion of existing temperate woodland bird assemblages in south-eastern Australia may not be realised uniformly in all regions.

Six new, unusually small ants of the genus Leptomyrmex (Hymenoptera: Formicidae)

The ant genus Leptomyrmex contains 41 named taxa which are limited to eastern Australia, New Guinea and New Caledonia. While most species are large and distinctive, a few species are much smaller and have only recently been recognised as belonging to this genus. These six species, informally called micro-Leptomyrmex, are restricted to rainforests and wet sclerophyll forests in two relatively small regions of eastern Australia. All are described here for the first time and include L. aitchisoni n. sp., L. burwelli n. sp., L. dolichoscapus n. sp., L. garretti n. sp., L. pilosus n. sp. and L. ramorniensis n. sp.

Immunocontraception of Eastern Grey kangaroos ( Macropus giganteus) with recombinant brushtail possum ( Trichosurus vulpecula) ZP3 protein

This study examined the potential of a recombinant marsupial zona pellucida 3 protein as a contraceptive vaccine for the Eastern Grey kangaroo, a marsupial that is locally overabundant in several regions of eastern Australia. First, a pilot study using porcine zona pellucidae (PZP) demonstrated that ZP proteins, primarily the ZP3 component of PZP, are highly immunogenic in the grey kangaroo and produce a long-lasting humoral response to a single immunisation, as found in other marsupials. Immunisation with 300 μg of a non-glycosylated recombinant brushtail possum ZP3 (recBP-ZP3) protein in complete Freund's adjuvant produced a similar, significant and sustained antibody response, and none of the immunised kangaroos ( n = 7) produced offspring during the following breeding season compared with four out of the six control animals. An epitope analysis of the B-cell response to recBP-ZP3 using a brushtail possum ZP3 identified numerous B-cell epitope regions clustered around the N- and C-terminal regions of the protein. Two regions of interest for further fertility vaccine development based on their immunogenicity and fertility trials and functional studies in other species were found to be immunogenic. These results suggest that immunocontraception based on targeting the ZP3 protein within the zona pellucida may be an effective strategy for fertility reduction in Eastern Grey kangaroos.

ON-FARM ASSESSMENT OF CONSTRAINTS TO CHICKPEA (CICER ARIETINUM) PRODUCTION IN MARGINAL AREAS OF NORTHERN AUSTRALIA

Chickpea production in marginal (<600 mm annual rainfall) areas of the northern cropping region in eastern Australia is considered to be constrained by low rainfall, soils with low plant available water capacity (PAWC), subsoil salinity, low plant stature and poor fruit set. This study examines these constraints to assess the magnitude of their impact and if agronomic practices can improve potential production. Over three years a total of 42 commercial chickpea crops were monitored following a participatory action research approach focusing on perceived production constraints. Subsoil salinity significantly reduced PAWC for chickpea compared to wheat. However, PAWC for chickpeas from the majority of sites monitored was comparable to other areas. The supply of water between flowering and maturity was significantly related to yield. The agronomic practice of levelling following deep planting improved the lowest pod height by 10 cm and plant stresses experienced during flowering caused a 50 % loss of potential fruit. Constraints impacting on the supply and storage of soil water could be minimized by selecting paddocks with low chloride levels in the upper layers and sowing crops when the available soil water is greater than 100 mm. Reducing fruit loss at flowering has the potential to improve yields significantly. The mechanisms behind this loss were not identified but are worthy of further research.

Attractiveness of a novel omnivore bait, PIGOUT®, to feral pigs (Sus scrofa) and assessment of risks of bait uptake by non-target species

Following a bait-preference pilot study on captive feral pigs, a series of field studies assessed the attractiveness and target-specificity of a prototype manufactured feral pig bait (PIGOUT®). Two promising test baits and fresh meat reference baits were biomarked with iophenoxic acid and aerially distributed in 100-km2 blocks of land infested with feral pigs in western Queensland to assess field uptake and target-specificity without prefeeding. Uptake was assessed by measuring blood iodine levels in aerially shot feral pigs. In all, 80% of feral pigs sampled in a non-toxic PIGOUT®-baited area had significantly elevated blood iodine, compared with 52% of sampled feral pigs in a meat-baited area (although slightly different baiting strategies were employed). No age or sex bias was evident in PIGOUT®-consuming feral pigs. No monitored manufactured baits were consumed by non-target species in 500 bait-nights. Attractiveness and target-specificity trials of ground-laid, unfenced PIGOUT® baits compared with reference baits were subsequently undertaken in several regions of eastern Australia. Results showed that PIGOUT® was consumed readily by feral pigs at all sites, and that it offered significant improvement in target specificity when compared with unfenced wheat or meat baits. However, the baits were consumed by small numbers of macropods, birds and possums. Available evidence indicates that the target-specificity of PIGOUT® bait is highest in the rangelands, reducing slightly in temperate areas and subalpine forests, where abundance of small animals is higher.

Phylogeography of pollinator‐specific sexually deceptiveChiloglottistaxa (Orchidaceae): evidence for sympatric divergence?

Divergence in sexually deceptive orchids is thought to occur through shifts in the attraction of specific pollinators, a process that is mediated by changes in the floral odours that lure sexually excited male insects. We investigated the origin of reproductive isolation in a sexually deceptive species complex of Chiloglottis R.Br. (Orchidaceae: Diurideae). Two geographically separated montane regions in eastern Australia were sampled, each containing sympatric pairs of orchid taxa presently found under the name, Chiloglottis pluricallata. Behavioural tests confirmed at least three distinct orchid taxa that specifically attract different pollinators. An artificial crossing experiment among two taxa from one region demonstrated their interfertility, and confirmed isolation to be a function of pollinator attraction. A phylogeographic analysis using amplified fragment length polymorphisms (AFLPs) indicated that samples from each geographical region are most closely related, a pattern consistent with in situ or sympatric divergence. However, an extensive population genetic study on two taxa from one region failed to entirely reject the possibility of intertaxon gene flow. Although clear genetic differentiation of the taxa is evident in two out of three sites where both grow in direct sympatry, overall, the two taxa are not strongly distinguished by AFLP markers. The reconstruction of a simple bifurcating pattern of divergence may be confounded by a combination of contemporary population-level processes operating within each taxon, the retention of ancestral polymorphism or intertaxon gene flow.

Variation in the Dendrobium speciosum (Orchidaceae) complex: a numerical approach to the species problem

The Dendrobium speciosum Sm. (Dendrobium sect. Dendrocoryne: Orchidaceae) complex is a taxonomic problem because of intrapopulational and interpopulational heterogeneity. The pattern of morphological variation exhibited is partly associated with geographical regions in eastern Australia, from the base of Cape York Peninsula to eastern Victoria. Variation within the species was investigated by multivariate and univariate analyses of data obtained from living specimens. The analyses that differentiate section Dendrocoryne species do not form discrete groups for previously recognised regional or any other variants of Dendrobium speciosum, providing no support for recognising subgroups of Dendrobium speciosum at species level. Dendrobium speciosum is regarded as a variable species forming a complex continuum. In some designated areas, the varieties speciosum, hillii, grandiflorum, curvicaule, pedunculatum and capricornicum can be retained. It is strongly recommended that all individuals be specified by their geographical origin since this is the only system that provides unambiguous identification.

Drain it, dam it: alteration of water regime in shallow wetlands on the New England Tableland of New South Wales, Australia

Shallow, still-water wetlands on the New England Tablelands, an upland region of eastern Australia, have changed in the past 160 years in their types, abundance and in the diversity of their water regimes. These changes have been natural, intentional or the unintentional consequences of management actions. Changing attitudes and land-use and management practices have led to a large proportion of natural wetlands being drained or dammed, but with a relatively high proportion of those remaining being conserved in some way. The water regimes of those that remain have been greatly altered, usually increasing their stability (more continuously either inundated or dry). Farm dams and domestic water-storage dams are two new and distinct wetland types that are far more numerous than the wetland types in the original landscape. We discuss how changes in water regime have modified wetland attributes. Two case studies: Mother of Ducks Lagoon and the Llangothlin group of lagoons, are used as examples of how attitudes towards wetlands and reasons for water regime alteration have interacted with the tenure and management of wetlands on local, regional, national and international scales.

Climatic controls upon dust storm occurrence in eastern Australia

Dust storms occur over large areas of arid and semi-arid Australia and are responsible for eroding large quantities of topsoil, yet the climatic controls on their occurrence are poorly understood. The Et Index of wind erosion, described here, uses readily available meteorological data to identify two major wind erosion regions in eastern Australia and describes seasonal controls of wind conditions and soil moisture upon dust storm occurrence. These results provide a better understanding of the drought–dust storm relationship in Australia, and the model has applications in broadscale wind erosion studies in the arid and semi-arid developing world.

Randomly amplified polymorphic DNA variation in populations of eastern Australian koalas, Phascolarctos cinereus.

Randomly amplified polymorphic DNA (RAPD) variation in populations of the koala, Phascolarctos cinereus, was investigated, revealing significant differences in the level of diversity between southern and northern regions of eastern Australia. Of the 20 polymorphic RAPD markers identified in koalas, 4-7 were polymorphic in southern populations, while 12-17 were polymorphic in northern populations. Analysis of molecular variance revealed a significant difference in the estimated variance between koalas from northern and those from southern regions (P < 0.001), where populations from the north were greater than twice as variable as their southern cousins. The total genetic diversity observed was attributed to regional differences (30.91%), population differences within a region (11.77%), and differences among individuals within a population (57.32%). For the within-region analyses, a large proportion of the genetic diversity was attributable to individual differences within a population, 80.34% for the north and 91.23% for the south. These results demonstrate that RAPD markers are useful for determining population structure among koalas.