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Key message: Two new major QTL were identified for powdery mildew resistance. We confirmed that the QTL on 7HS contributed mainly to the adult-plant resistance, while another one on chromosome arm 1HS made a significant contribution to the seedling resistance. Powdery mildew (PM), caused by Blumeria hordei, can occur at all post emergent stages of barley and constantly threatens crop production. To identify more genes for effective resistance to powdery mildew for use in breeding programs, 696 barley accessions collected from different regions of the world were evaluated for PM resistance at seedling and adult growth stages in three different states of Australia. These barley accessions were genotyped using DArTSeq with over 18,000 markers for a genome-wide association study (GWAS). Using the FarmCPU model, 54 markers showed significant associations with PM resistance scored at the seedling and adult-plant stages in different states of Australia. Another 40 markers showed tentative associations (LOD > 4.0) with resistance. These markers are distributed across all seven barley chromosomes. Most of them were grouped into eleven QTL regions, coinciding with the locations of most of the reported resistance genes. Two major MTAs were identified on chromosome arms 3HS and 5HL, with one on 3HS contributing to adult plant resistance and the one on 5HL to both seedling and adult plant resistance. An MTA on 7HS contributed mainly to the adult-plant resistance, while another one on chromosome arm 1HS made a significant contribution to the seedling resistance. [ABSTRACT FROM AUTHOR]

Earwigs have been observed as an irregular pest of increasing concern to farmers growing canola and other winter grain crops in Australia over the past decade. In this study, we tested how abiotic and biotic factors influence the feeding behaviour of earwigs. Studies were conducted with two Australian native species, Labidura truncata and Nala lividipes, and the introduced European earwig, Forficula auricularia. We constructed field‐based exclusion plots that prevented F. auricularia from moving in or out of a small area of canola. We monitored F. auricularia activity and the feeding damage to canola plants throughout the winter growing season. In the laboratory, we established microcosms containing crop seedlings, as well as aphids as an alternate food source, to examine the feeding behaviour of all three species. The native earwigs L. truncata and N. lividipes did not cause feeding damage to canola or wheat but were found to actively consume aphids when present. We conclude that these species are unlikely to cause significant (economic levels) of pest damage in a field environment. In the microcosm trial, F. auricularia caused considerable damage to canola seedlings and readily consumed aphids. Forficula auricularia also caused feeding damage to canola seedlings early in the winter growing season in the field trial. However, by the end of the season, F. auricularia presence was associated with increased canola biomass. Furthermore, F. auricularia did not damage canola until all nearby aphids were consumed. Together, our field and laboratory studies suggest F. auricularia can be an important predator of aphid pests in canola, indicating a dual role of this species as both a pest and a beneficial species in winter grain systems. [ABSTRACT FROM AUTHOR]

Black root rot disease of cotton seedlings caused by Thielavioposis basicola was first reported in New South Wales (NSW), Australia in 1990. In 2018, T. basicola was reclassified into a new genus Berkeleyomyces, accommodating two closely related species: B. basicola and B. rouxiae. However, species status of cotton-T. basicola in NSW remains unsolved. Ninety-five isolates recovered from black root rot diseased cotton seedlings sampled across NSW in 2017/18 season was subjected to morphological, multigene sequencing (ITS, MCM7, RPB2), and pathogenicity assessments for their species identification. Berkeleyomyces rouxiae was accurately identified as the causal agent of black root rot of cotton. [ABSTRACT FROM AUTHOR]

Summary: Direct seeding is increasingly being used as a cost‐effective revegetation technique. Successful outcomes from direct seeding rely on effective weed control, particularly during the vulnerable seedling establishment phase. Post‐sowing weed control options are constrained by the need to protect seedlings from damage and few studies have compared the effectiveness of different weed control techniques. We evaluated the effect of preliminary hand weeding (with subsequent spraying), spraying monthly or spraying quarterly with glyphosate, on woody seedling emergence, survival and growth in trials sown either in spring or autumn at a riparian site in Victoria, southeastern Australia. Seedling numbers were recorded monthly for 6 months and at 12 months after sowing, with seedling survival and heights assessed at 12 months. Total seedling numbers were higher in subplots initially hand weeded than in subplots sprayed on either a monthly or quarterly basis, regardless of when direct seeding occurred, but weed control treatment had no effect on seedling survival. These results indicate that post‐sowing spraying limited rates of seedling emergence, either directly or indirectly. For direct seeding, hand weeding in the first few months after sowing may maximise rates of woody seedling emergence, while spraying with glyphosate may inhibit seedling emergence. [ABSTRACT FROM AUTHOR]

Selliera radicans is a creeping plant native to Chile, New Zealand and Australia. It is increasingly used in the ornamental industry, and there is interest in breeding it to create commercial varieties. The aim of this study was to determine the effects of different doses of gamma radiation applied to the seeds on the germination and development of seedlings (M1) and the LD50 of two accessions of Selliera radicans for use in the induction of mutations. Seeds of the Vichuquén and La Serena accessions were exposed to 0, 100, 200, 300, 400, 500, 600 and 700 Gy from a 60Co source. Weekly germination percentages along with seedling numbers and lengths were recorded. Vichuquén seeds were more sensitive to this physical agent. The LD50 was 243.9 Gy for Vichuquén and 445.6 Gy for La Serena. Seedling lengths reached almost 4 mm for Vichuquén and 11.3 mm for La Serena at 12 weeks after sowing. Doses lower than 200 Gy are recommended since higher doses do not allow the development of seedlings to the extended cotyledon stage. [ABSTRACT FROM AUTHOR]

In Australia, crown rot of cereals is predominantly caused by Fusarium pseudograminearum and Fusarium culmorum, and common root rot by Bipolaris sorokiniana. Fusarium graminearum is an important pathogen causing Fusarium head blight worldwide and has also been reported to cause crown rot of wheat. The comparative ability of F. pseudograminearum, F. culmorum, F. graminearum and B. sorokiniana to cause crown rot and common root rot across a range of winter cereal species requires investigation. In glasshouse trials, we inoculated one cultivar each of barley, bread wheat, durum wheat, oat and triticale with two strains of each of the four pathogens. At 21 days after inoculation, the sub-crown internode and leaf sheaths of each plant were visually rated for brown discoloration. Shoot length and dry weight of inoculated plants were compared with those of non-inoculated controls. Barley and bread wheat had the highest disease severity ratings on leaf sheaths and sub-crown internode (64.7-99.6%), whereas oat had the lowest disease severity ratings across all pathogens (<5%). The shoot length of all cultivars was significantly reduced (by 12.2-55%, P < 0.05) when exposed to F. pseudograminearum. This study provides a comparison of pathogenicity of crown rot and common root rot pathogens and demonstrates significant variation in visual discoloration and host response across a range of winter cereals. [ABSTRACT FROM AUTHOR]

Northern Australia's savannas are among the most fire‐prone biomes on Earth and are dominated by eucalypts (Eucalyptus and Corymbia spp.). It is not clear what processes allow this group to dominate under such extreme fire frequencies and whether a superior ability to compete for nutrients and water might play a role. There is evidence that eucalypts are adapted to frequent fires; juvenile eucalypts escape the fire trap by growing rapidly in height between fires. However, non‐eucalypts are less able to escape the fire trap and tend to have stand structures strongly skewed toward suppressed juveniles. The mechanisms that drive these contrasting fire responses are not well understood. Here, we describe the results of a controlled glasshouse seedling experiment that evaluated the relative importance of nutrient and water availability in determining height growth and biomass growth of two eucalypt and one noneucalypt tree species, common in northern Australian savannas. We demonstrate that growth of eucalypt seedlings is particularly responsive to nutrient addition. Eucalypt seedlings are able to rapidly utilize soil nutrients and accumulate biomass at a much greater rate than noneucalypt seedlings. We suggest that a seasonal spike in nutrient availability creates a nutrient‐rich microsite that allows eucalypt seedlings to rapidly gain height and biomass, increasing their likelihood of establishing successfully and reaching a fire‐resistant size. Our results extend our understanding of how eucalypts dominate northern Australian savannas under extremely high fire frequencies. [ABSTRACT FROM AUTHOR]

Ecological restoration is urgently needed to arrest and reverse land degradation, reinstate ecosystem services and recover threatened species. Tree planting is a commonly used strategy to restore forests; however, planted seedlings often experience low survival and slow growth during the establishment period. Critical evaluation of factors that lead to poor establishment is vital to improve practice but is often constrained by a lack of monitoring and reporting.We took advantage of a large monitoring dataset (~7,000 native trees from 23 species) to interrogate an extensive suite of environmental conditions and plant characteristics that potentially contributed to poor survival and growth of seedlings in a restoration planting in southeast Queensland, Australia.The initial height of planted seedlings strongly influenced survival and growth. Intermediate heights generally performed best and the optimal heights for different species were significantly but weakly modulated by functional traits including SLA, lamina area and leaf structure (compound vs. simple). Survival was lowest when seedlings were planted in high bulk density soils on hot days, and growth was fastest in plots with higher average elevation.Synthesis and applications. In this large restoration experiment in Australia's subtropics, initial seedling height was a much stronger predictor of rainforest seedling survival than plant functional traits. We recommend planting rainforest seedlings between 25 and 35 cm tall, especially in restoration projects facing a high likelihood of hot weather during planting and establishment. [ABSTRACT FROM AUTHOR]

Seed germination traits are key drivers of population dynamics, yet they are under-represented in community ecology studies, which have predominately focussed on adult plant and seed morphological traits. We studied the seed traits and germination strategy of eight woody plant species to investigate regeneration strategies in the arid zone of eastern Australia. To cope with stochastic and minimal rainfall, we predict that arid seeds will either have rapid germination across a wide range of temperatures, improved germination under cooler temperatures, or dormancy and/or longevity traits to delay or stagger germination across time. To understand how temperature affects germination responses, seeds of eight keystone arid species were germinated under laboratory conditions, and under three diurnal temperatures (30/20°C, 25/15°C and 17/7°C) for 30 days. We also tested for decline in seed viability across 24 months in a dry-aging treatment (~20°C). Six of the eight arid species studied had non-dormant, rapidly germinating seeds, and only two species had physiological dormancy traits. Seed longevity differed widely between species, from one recalcitrant species surviving only months in aging (P50 = <3 months) and one serotinous species surviving for many years (P50 = 84 months). Our results highlight the importance of understanding the reproductive strategies of plant species in arid environments. Rapid germination, the dominant seed trait of species included in this study, allows arid species to capitalise on sporadic rainfall. However, some species also exhibit dormancy and delayed germination; this an alternative strategy which spreads the risk of germination failure over time. [ABSTRACT FROM AUTHOR]

Wild lettuce (Lactuca serriola L.) is a significant emerging agricultural and environmental weed in many countries. This invasive species is now naturalised in Australia and is claimed to cause significant losses within the agricultural industry. Sustainable management of wild lettuce has been hampered by a lack of detailed knowledge of its seed ecology. Laboratory-based studies were performed to examine the potential influence of environmental factors including temperature and light conditions, salinity, pH, moisture availability and burial depth on the germination and emergence of two spatially distant populations of wild lettuce. Results suggested that the germination of wild lettuce seeds occurred across a broad range of temperature conditions (12-h cycle: 30°C/20°C, 25°C/15°C and 17°C/7°C) for both populations. We also found that these seeds are non-photoblastic; germination was not affected by darkness, with >80% germination in darkness for both populations at all tested temperature ranges. Germination significantly declined as salinity and osmotic stress increased for both populations, with seeds from the Tempy population were more affected by NaCl >100 mM than seeds from Werribee, but in neither population was there any observed effect of pH on germination (>80% germination in both populations at all tested pH ranges). For both populations, germination significantly decreased as burial depth increased; however, the two populations differed with regard to response to burial depth treatment, whereby seeds from the Tempy population had higher emergence than those from Werribee at 0.5 cm burial depth. These results suggest that light-reducing management techniques such as mulching or use of crop residues will be unsuccessful for preventing germination of wild lettuce. By contrast, burial of seeds at a depth of at least 4 cm will significantly reduce their emergence. The seed ecology of two spatially varied populations of Lactuca serriola was examined to understand the effect of various environmental factors. Results show >80% germination across a range of temperatures; however, emergence decreased with increase in burial depth. To manage this species, we recommend burying the seeds at least 4 cm deep to reduce emergence and subsequent establishment. [ABSTRACT FROM AUTHOR]

Highlights • Insufficient N accounts for a 40% loss in wheat yields in Australia. • Tillage; time of sowing; summer fallow weeds; and low seedling density also limit yields. • Frost and heat stress account for losses of 16%–26% relative to water-limited yield potential. • Multiple limiting factors interact differently in different seasons and environments. • Emerging management practices can boost the yield frontier by 30%. Abstract Closing the yield gap is essential for global food security and for farmers who face increasing costs of production. Recent work showed that Australia's wheat growers are achieving about half their water-limited yield. While quantifying the yield gap is a necessary first step towards closing them, the next step is to understand which factors constrain rainfed grain growers from achieving their water-limited yields. Here we conducted in silico experiments over 15 years at 50 weather stations to ascertain the impact on grain yield of suboptimal practices against the 'best management practice' rules that were used to calculate the benchmark water-limited yields. Average national losses per suboptimal practice were: the average N fertiliser application rate – 40%; conventional tillage – 33%; suboptimal weed control during the summer fallow – 26%; low seedling density – 12%; and a two week delay in sowing – 7%. Combining two suboptimal practices does not necessarily lead to an additive effect on yield. Other factors that contribute to the yield gap include biotic stresses such as plant diseases, insects and other pests, in-crop weeds and extreme weather events (e.g. floods, strong winds and hail). In addition to calculating the impact of causes of the yield gap we investigated the opportunity to lift the water-limited yield by adopting an emergent new management practice of sowing on an optimised site specific date that is earlier than the traditional sowing window as described for the currently accepted best practice. We found that this emergent practice, matched with slower maturing varieties and additional N inputs as required, has the potential to increase wheat yields nationally by 30%. Frost and heat stress accounted for losses of 16% to 26% depending on the stress function used. Allowing for the impact of frost and heat stress reduced the yield potential of both the current and emergent water-limited yields yet it did not reduce the advantage of the emergent practice. [ABSTRACT FROM AUTHOR]

Large-scale re-introductions of locally extinct digging mammal assemblages have been implemented at a number of arid zone sites, with the aim of conserving mammal species and restoring ecosystem function. Previous studies have focused on the ways in which foraging pits benefit plants, but the effects of herbivory by digging mammal assemblages are poorly understood. We used a randomised block design with control, procedural control and exclusion plots (n = 10) to experimentally test the net effect of a re-established mammal assemblage of bridled nailtail wallabies, Onychogalea fraenata , greater bilbies, Macrotis lagotis , brush tailed-bettongs, Bettongia penicillata , and burrowing bettongs, Bettongia lesueur , on plants in the Australian arid zone. We found that the re-established mammal assemblage limited natural seedling abundance and consumed transplanted seedlings. Plant composition between treatments did not differ, but perennial forbs and subshrubs, which are known food items of the re-introduced mammals, were most abundant in mammal exclusions. Furthermore, a landscape-scale survey showed that composition in the re-introduction area differed significantly from an adjacent control. When conceptualising the role of mammalian ecosystem engineers in arid environments, negative effects on plants from herbivory and soil disturbance must be considered alongside the better studied processes of nutrient cycling and seedling establishment. [ABSTRACT FROM AUTHOR]

Recent findings have shown that photosynthesis in the skin of the seed of Posidonia oceanica enhances seedling growth. The seagrass genus Posidonia is found only in two distant parts of the world, the Mediterranean Sea and southern Australia. This fact led us to question whether the acquisition of this novel mechanism in the evolution of this seagrass was a pre-adaptation prior to geological isolation of the Mediterranean from Tethys Sea in the Eocene. Photosynthetic activity in seeds of Australian species of Posidonia is still unknown. This study shows oxygen production and respiration rates, and maximum PSII photochemical efficiency (Fv : Fm) in seeds of two Australian Posidonia species (P. australis and P. sinuosa), and compares these with previous results for P. oceanica. Results showed relatively high oxygen production and respiratory rates in all three species but with significant differences among them, suggesting the existence of an adaptive mechanism to compensate for the relatively high oxygen demands of the seeds. In all cases maximal photochemical efficiency of photosystem II rates reached similar values. The existence of photosynthetic activity in the seeds of all three species implicates that it was an ability probably acquired from a common ancestor during the Late Eocene, when this adaptive strategy could have helped Posidonia species to survive in nutrient-poor temperate seas. This study sheds new light on some aspects of the evolution of marine plants and represents an important contribution to global knowledge of the paleogeographic patterns of seagrass distribution. [ABSTRACT FROM AUTHOR]

Key message: A gene conferring seedling resistance to Puccinia triticina was mapped to chromosome 2BS in the wheat Morocco. The gene was shown to be distinct and was therefore designated Lr73. Abstract: The wheat genotype Morocco, widely susceptible to isolates of Puccinia triticina, was resistant to an Australian isolate of this pathogen collected in 2004. Genetic studies established that the resistance in Morocco was also present the Australian wheat genotypes Avocet, Halberd, Harrier, Tincurrin and a selection of cultivar Warigal lacking the resistance gene Lr20. Genetic studies based on a cross with Halberd showed that the gene is dominant and located on chromosome 2BS ( XwPt8760-4 cM- Lr73-1.4 cM- XwPt8235). The gene was genetically independent of the Lr13, Lr16 and Lr23 loci, also located on chromosome 2BS, indicating that it is distinct. The locus designation Lr73 was therefore assigned. On the basis of multi-pathotype tests, it is likely Lr73 is also present in the Australian wheat cultivars Clearfield STL, Federation (with Lr10), Gatcher (with Lr10 and Lr27+ Lr31), Marombi (with Lr1 and Lr37), Pugsley (with Lr1 and Lr37), Spear (with Lr1), Stiletto and Tarsa (with Lr1). Gene Lr73 is unlikely to be of value in resistance breeding. However, recognising Lr73 is important to avoid its inadvertent selection in breeding programmes. Furthermore, the apparent rarity of avirulence for genes like Lr73, sometimes referred to as 'fossil' resistance genes, makes them of interest in terms of the evolution of disease resistance in host plants and of virulence in the respective rust pathogens. [ABSTRACT FROM AUTHOR]

An improved understanding of important ecophysiological mechanisms underpinning tree water and nutrient use is necessary for developing and testing effective revegetation and restoration techniques in disturbed landscapes. A field trial was established in Central Queensland, Australia, to evaluate tree ecophysiological response to site management methods, including site preparation, herbicide application versus top soil removal (scalping) and fertilisation versus non-fertilisation. The influence of site management practices on plant survival, growth and foliar ecophysiological traits of Acacia disparrima (M. W. McDonald and Maslin) and Eucalyptus crebra (F. Muell.) seedlings was investigated within 22 months following tree planting. There was no difference in the survival of A. disparrima and E. crebra in response to the site preparation. However, there was a significant difference in growth response with both species showing greater mean periodic height gain in the herbicide areas compared to the scalped areas. Plant growth and survival of both species were unaffected by fertilisation, regardless of site preparation treatment. We suggest that the effects of fertiliser may have been masked by drought conditions experienced by seedlings in the first 6 months after planting. Neither site preparation nor fertilisation affected the leaf-level ecophysiological traits of seedlings, including foliar total N, photosynthetic capacity, instantaneous water-use efficiency, carbon isotope composition and stomatal conductance, irrespective of species. Scalping was more effective than herbicide application to suppress weeds and reduced the costs of site preparation and maintenance. Surprisingly, scalping had no impact on plant survival and foliar ecophysiological traits. However, it should be noted that the scalping may not be a sustainable practice in plantation establishment with short rotations where organic matter levels may not have a chance to recover between disturbances. [ABSTRACT FROM AUTHOR]

Slender Banksia ( Banksia attenuata) is a primary component of declining Banksia woodlands around Perth, south-western Australia. It is important that its re-establishment be promoted, but there are little data on its growth rates and response to applied nutrients. To quantify longer-term growth rate, I periodically measured heights of Slender Banksia planted mid-2005 over 7½ years. Without fertiliser, these seedlings grew slowly to about 1½ m. In mid-2009, I planted Slender Banksia on the same site, with and without fertiliser tablets, and evaluated survival, growth and root development over 1½ years. First-summer Slender Banksia seedling survival of around 30% was not unusual for this species. Low-phosphorus native plant fertiliser tablets increased growth significantly. [ABSTRACT FROM AUTHOR]

Plant and animal survey detection rates are important for ecological surveys, environmental impact assessment, invasive species monitoring, and modeling species distributions. Species can be difficult to detect when rare but, in general, how detection probabilities vary with abundance is unknown. We developed a new detectability model based on the time to detection of the first individual of a species. Based on this model, the predicted detection rate is proportional to a power function of abundance with a scaling exponent between zero and one that depends on clustering of individuals. We estimated the model parameters with data from three independent datasets: searches for chenopod shrub species and coins, experimental searches for planted seedlings, and frog surveys at multiple sites in sub-tropical forests of eastern Australia. Analyses based on the detection time and detection probability suggest that detection rate increases with abundance as predicted. The model provides a way to scale detection rates to cases of low abundance when direct estimation of detection rates is often impractical. [ABSTRACT FROM AUTHOR]

Background and Aims A trade-off between shade tolerance and growth in high light is thought to underlie the temporal dynamics of humid forests. On the other hand, it has been suggested that tree species sorting on temperature gradients involves a trade-off between growth rate and cold resistance. Little is known about how these two major trade-offs interact. Methods Seedlings of Australian tropical and cool-temperate rainforest trees were grown in glasshouse environments to compare growth versus shade-tolerance trade-offs in these two assemblages. Biomass distribution, photosynthetic capacity and vessel diameters were measured in order to examine the functional correlates of species differences in light requirements and growth rate. Species light requirements were assessed by field estimation of the light compensation point for stem growth. Results Light-demanding and shade-tolerant tropical species differed markedly in relative growth rates (RGR), but this trend was less evident among temperate species. This pattern was paralleled by biomass distribution data: specific leaf area (SLA) and leaf area ratio (LAR) of tropical species were significantly positively correlated with compensation points, but not those of cool-temperate species. The relatively slow growth and small SLA and LAR of Tasmanian light-demanders were associated with narrow vessels and low potential sapwood conductivity. Conclusions The conservative xylem traits, small LAR and modest RGR of Tasmanian light-demanders are consistent with selection for resistance to freeze–thaw embolism, at the expense of growth rate. Whereas competition for light favours rapid growth in light-demanding trees native to environments with warm, frost-free growing seasons, frost resistance may be an equally important determinant of the fitness of light-demanders in cool-temperate rainforest, as seedlings establishing in large openings are exposed to sub-zero temperatures that can occur throughout most of the year. [ABSTRACT FROM AUTHOR]

Abstract: Restoration of degraded land has been identified as a top research priority in conservation. Fauna plays a critical role in the re-establishment of a functional ecosystem, yet fauna recolonization of restored areas is less studied than flora. We reviewed the findings of 71 publications on fauna recolonization, through the example of mining rehabilitation in the Australian continent, a global stronghold of large-scale mining. Species densities and richness were frequently lower in rehabilitated compared to undisturbed areas, even more so when only native species were considered. Amongst all criteria used to measure success, recovery of the pre-mining fauna community composition was the hardest to achieve. Introduced species were often found in rehabilitated areas but further research is needed to determine the duration of this association. Meta-analyses of the factors influencing mining rehabilitation success for fauna revealed that fauna groups recolonized heterogeneously. Recolonization was dependent on the methods used to rehabilitate and the number of years since rehabilitation. Notably, methods combining the use of fresh topsoil with the addition of seeds and seedlings were most successful for fauna recolonization, both in term of fauna density and richness. Limitations to this review included strong biases toward certain mining companies, as well as missing data, which decreased the power of meta-analysis. Available publications did not evenly represent all fauna taxa and studies were short when compared to the time needed to re-construct whole ecosystems. We consider the development of comprehensive fauna standards for assessing rehabilitation success critical. This could be the next challenge in restoration ecology. [Copyright &y& Elsevier]

Although birds and mammals play important roles in several mechanisms hypothesized to maintain plant diversity in species-rich habitats, there have been few long-term, community-level tests of their importance. We excluded terrestrial birds and mammals from fourteen 6 x 7.5 m plots in Australian primary tropical rain forest and compared recruitment and survival of tree seedlings annually over the subsequent seven years to that on nearby open plots. We re-censused a subset of the plots after 13 years of vertebrate exclusion to test for longer-term effects. After two years of exclusion, seedling abundance was significantly higher (74%) on exclosure plots and remained so at each subsequent census. Richness was significantly higher on exclosure plots from 1998 to 2003, but in 2009 richness no longer differed, and rarefied species richness was higher in the presence of vertebrates. Shannon's diversity and Pielou's evenness did not differ in any year. Vertebrates marginally increased density-dependent mortality and recruitment limitation, but neither effect was great enough to increase richness or diversity on open plots relative to exclosure plots. Terrestrial vertebrates significantly altered seedling community composition, having particularly strong impacts on members of the Lauraceae. Overall, our results highlight that interactions between terrestrial vertebrates and tropical tree recruitment may not translate into strong community-level effects on diversity, especially over the short term, despite significant impacts on individual species that result in altered species composition. [ABSTRACT FROM AUTHOR]

Abstract: Seeds were collected from a range of citrus rootstock types in China and sent to Australia for evaluation. Before evaluation proceeded, however, the seeds and their seedlings were characterised for uniformity and trueness-to-type. The seeds were cultured in vitro and/or germinated in sand beds to assess whether or not they were mono- or polyembryonic. Seedlings were then rogued on the basis of vigour and morphology before isozyme profiles were developed from leaf extracts to assess seedling uniformity within introductions. Isozyme profiles were also compared to those of the source trees, as well as hybrids generated between some of them in China, to assess and verify trueness-to-type. The degree of variability between the seedlings propagated from the imported seeds and their source trees in China differed between accessions, which highlighted some of the issues that need to be considered when importing citrus germplasm as seeds. Regardless of whether the seedlings could be shown to be identical to their source tree in China, three uniform seedlings of polyembryonic types were established in arboreta as Australian source trees to provide propagules for evaluation and possibly commercial use. [Copyright &y& Elsevier]

Abstract: Although many emergent wetland plants may readily tolerate rapid changes in flooding and drying under freshwater conditions, their tolerance to dynamic water regimes may be compromised by salinity. Melaleuca-dominated woodlands occur naturally in Australia, south-east Asia and New Caledonia. Coastal wetlands dominated by Swamp paperbark (Melaleuca ericifolia) (Myrtaceae), native to south-east Australia, are commonly degraded as a consequence of altered water regime and salinity. This study simulates the release of M. ericifolia seeds from the aerial canopy under a range of water regime and salinity scenarios to determine conditions limiting sexual recruitment. Plant growth and survival were examined following seed release under two static water regimes (moist and flooded sediment) and two dynamic water regimes (simulated drawdown—“flooded-moist” and simulated re-flooding—“moist-flooded”). All water regimes, excluding the continuously flooded regime, were examined at three salinities: 0.1dSm−1 (fresh), 8dSm−1 and 16dSm−1, over a 50-day period commencing 44 days after the seeds were sown. The flooded treatment was examined at 0.1dSm−1 only, to confirm that flooding prohibits establishment of M. ericifolia. Seed and seedlings were positively buoyant and establishment was limited to moist soil. Flotation of seedlings in the flooded-moist treatment, however, did not inhibit subsequent establishment upon moist soil, even at the highest salinity of 16dSm−1. Growth, but not survival, was reduced by salinities of 8dSm−1 and 16dSm−1 in the moist treatment. Flotation of seedlings in saline water in the flooded-moist treatment did not reduce growth or survival compared with fresh water. Survival of seedlings in the moist-flooded treatment was lower in the freshwater and 16dSm−1 treatment compared with the moist treatment, but not at 8dSm−1. These findings suggest that water regime influences establishment of young M. ericifolia plants more strongly than does salinity, at least up to ∼1/3 seawater and in the short term (<2 months). Seedlings are likely to establish during a drawdown where the soil is exposed at salinities of ≤16dSm−1. In contrast, premature re-flooding of seedlings, even with fresh water, will compromise survival. [Copyright &y& Elsevier]

Phosphorus (P) deficiency is a major problem for Australian agriculture. Development of new perennial pasture legumes that acquire or use P more efficiently than the current major perennial pasture legume, lucerne ( Medicago sativa L.), is urgent. A glasshouse experiment compared the response of ten perennial herbaceous legume species to a series of P supplies ranging from 0 to 384 µg g−1 soil, with lucerne as the control. Under low-P conditions, several legumes produced more biomass than lucerne. Four species ( Lotononis bainesii Baker, Kennedia prorepens F.Muell, K. prostrata R.Br, Bituminaria bituminosa (L.) C.H.Stirt) achieved maximum growth at 12 µg P g−1 soil, while other species required 24 µg P g−1. In most tested legumes, biomass production was reduced when P supply was ≥192 µg g−1, due to P toxicity, while L. bainesii and K. prorepens showed reduced biomass when P was ≥24 µg g−1 and K. prostrata at ≥48 µg P g−1 soil. B. bituminosa and Glycine canescens F.J.Herm required less soil P to achieve 0.5 g dry mass than the other species did. Lucerne performed poorly with low P supply and our results suggest that some novel perennial legumes may perform better on low-P soils. [ABSTRACT FROM AUTHOR]

N fertilizer labelled with 15N was used to follow the accumulation and distribution of N applied at different times after planting Eucalyptus grandis W Hill ex Maiden seedlings in south-eastern Queensland, Australia. The first application was made to selected trees at 0.12 y after planting (T0), and treated trees were harvested at intervals after. Further labelled applications were made on different sets of trees 0.50, 0.74, 1.30 and 1.49 years after T0; T0.5, T0.74, T1.30 and T1.49 respectively. After 0.5 y there was no significant difference in growth between T0 trees and unfertilized controls, but after 1 y above-ground biomass and N content of the controls was only 30% and 39% of the fertilized trees respectively ( P <0.05). At later applications controls were not significantly different from fertilized trees up to 1 y later, but after 2 y above-ground biomass and N content was reduced ( P <0.05). Growth reductions occurred after leaves present on the tree at the time of fertilizer application were shed. Leaf biomass and N content increased steadily to age 1.5 y and then stabilized at about 2.5 kg tree-1 and 35 g tree−1 respectively, new growth balanced by litter fall. N content in woody material (stems+branches) increased steadily, equaling that of the leaves at 3.5 y. N derived from fertilizer and the proportion of applied N recovered peaked at 1 y and then decreased. These relationships were not affected by time of application. In T0 trees N in above-ground parts derived from fertilizer increased steadily to 42% of the total 0.5 y after application. It then decreased rapidly after leaf fall commenced while total N content increased. When observations ceased 3.5 y after planting, less than 5% of the N in the trees was derived from fertilizer. N uptake was two-phased. In the first year mineral N from the fertilizer was taken up by the trees. In subsequent years fertilizer contributed to the tree growth but the N taken up came from a different source. [ABSTRACT FROM AUTHOR]

Abstract: We investigated the effects of flooding and drying over 6 months on growth and biomass allocation in seedlings of Muehlenbeckia florulenta Meisn. (tangled lignum), a common and widely distributed shrub of Australia''s desert floodplains. We sought to determine if lignum seedlings respond to flooding or drying by altering traits or allocation patterns or instead display fixed patterns of development. Since desert floodplains are highly unpredictable and heterogeneous environments, we hypothesised that adaptive phenotypic plasticity is unlikely to have developed or be advantageous in seedlings of this species as environmental state changes are highly variable in their timing and duration and plants risk being caught out of kilter with environmental conditions. To test this, we conducted a glasshouse experiment in which lignum seedlings, grown in both clay and sandy sediments, were subjected to a range of hydrological conditions over a period of 6 months. Lignum seedlings exhibited considerable tolerance of both flooding and drying in our experiment and no mortality was observed. Growth was significantly reduced by flooding, however, and seedlings displayed extremely delayed development rather than plasticity in overall biomass allocation or any of the specific morphological variables we measured. Lignum seedlings were considerably more tolerant of drying than flooding and responded plastically by reducing leaf area ratios through reductions in specific leaf areas and leaf production and expansion. Sediment type had little effect on seedling development. Our results indicate that surface water hydrology is likely to be a major determinant of recruitment patterns in this ecologically significant species. [Copyright &y& Elsevier]

The aim of this project was to investigate the ability of artificially applied smoke and heat stimuli to simulate field responses of soil seed banks to fire. The ability to simulate field responses to fire would allow- managers to better understand the effects that fire might have on a community before actually burning it. This knowledge is greatly lacking for many Australian ecosystems at present, such that fire is avoided as a management tool for fear of negative ecological impacts. The composition and density of seedlings was compared between soil samples subjected to fire in the field and soil samples treated with a range of heat and smoke stimuli in 4 different Australian ecosystems along a rainfall gradient from subtropical to arid. The treatments used were: no treatment; smoke for 1 hour; heat at 80°C; heat at 80°C and smoke for 1 hour; heat at 105°C; heat at 105°C and smoke for 1 hour. The results vary greatly between ecosystems with no one treatment closely simulating the effects of fire. In addition, there was no significant difference between the control and the fire treatment in terms of the number of species or the abundance of seedlings that emerged from the seed bank. Thus the role of fire and fire related cues in stimulating seed banks is discussed. The results also revealed a relationship between seed bank response and the likely "natural" fire frequency of an ecosystem which may be useful to identify optimal fire intervals when managing for biodiversity. However, this needs further investigation. [ABSTRACT FROM AUTHOR]

Hymenoscyphus fraxineus was isolated from four leaf rachises with necrotic lesions of flowering ash ( Fraxinus ornus) seedlings, which had been planted on a forest site in Austria where they were exposed to a massive natural infection pressure. This represents the first definite report of natural infection of this ash species by the ash dieback pathogen. [ABSTRACT FROM AUTHOR]

Effects of soil type, time, depth of seed burial and rainfall pattern were investigated on the longevity of glyphosate resistant annual ryegrass ( Lolium rigidum Gaudin) in the northern summer rainfall dominant grain region of Australia in a 16 month experiment conducted under polyhouse conditions. Lolium rigidum seeds placed in nylon bags were buried in pots at 5 and 10 cm depth in either Laureldale (clay) or Kirby (sandy loam) soil receiving simulated rainfall representing a Tamworth (summer) and Hamilton (winter) rainfall environment of Australia. The bags were exhumed every four months and tested for percent viable, germinable, dormant and dead seeds. In the short term (several months), factors such as soil type, rainfall and depth of burial affected the fate and condition of L. rigidum seeds and emergence pattern of seedlings. However, irrespective of treatment, all seeds lost their viability after 16 months of burial. Hence, in the longer term, L. rigidum behaviour in this summer dominant rainfall environment with different soils is likely to be similar to that where the weed occurs more commonly in the southern Mediterranean regions of Australia. Maximum emergence in the polyhouse occurred during mid autumn similar to that in the field. The results from this experiment will allow for the development of management strategies which may enhance the depletion of the soil seedbank of viable L. rigidum seeds in the shortest possible time. [ABSTRACT FROM AUTHOR]

While the influence of elevated CO2 on the production, mass and quality of plant seeds has been well studied, the effect of warming on these characters is largely unknown; and there is practically no information on possible interactions between warming and elevated CO2, despite the importance of these characters in population maintenance and recovery. Here, we present the impacts of elevated CO2 and warming, both in isolation and combination, on seed production, mass, quality, germination success and subsequent seedling growth of Austrodanthonia caespitosa, a dominant temperate C3 grass from Australia, using seeds collected from the TasFACE experiment. Mean seed production and mass were not significantly affected by either elevated CO2 or warming, but elevated CO2 more than doubled the proportion of very light, inviable seeds ( P < 0.05) and halved mean seed N concentration ( P < 0.04) and N content ( P < 0.03). The dependence of seed germination success on seed mass was affected by an elevated CO2× warming interaction ( P < 0.004), such that maternal exposure to elevated CO2 or warming reduced germination if applied in isolation, but not when applied in combination. Maternal effects were retained when seedlings were grown in a common environment for 6 weeks, with seedlings descended from warmed plants 20% smaller ( P < 0.008) with a higher root : shoot ratio ( P < 0.001) than those from unwarmed plants. Given that both elevated CO2 and warming reduced seed mass, quality, germinability or seedling growth, it is likely that global change will reduce population growth or distribution of this dominant species. [ABSTRACT FROM AUTHOR]

Eucalyptus globulus is the most commonly planted hardwood species in industrial plantations in Australia. It is typically planted well out of its natural range and may therefore present a significant risk of exotic pollen-mediated gene flow into native eucalypt populations. This risk was assessed by documenting levels of flowering within plantations, frequencies at which reproductively compatible native species are found adjacent to plantations, levels of F1 hybridisation with native populations, and the existence of F1 hybrid seedling recruitment. We surveyed over 300 plantations across southern Australia over two years. Flower abundance was found to be low with an average of 3% of trees found to flower on an inside row and 7% on the outside edge row of mature plantations. Considerable variation in flowering was found between locations (0–20% of trees reproductive) and 52% of plantations did not have compatible native species growing adjacent. Consequently, 65% of reproductive age plantations presented minimal or low risk of hybridisation due to lack of flowering and/or lack of adjacent compatible native species. Only three out of 10 surveyed high risk plantations were found to hybridise with native eucalypts (Eucalyptus camaldulensis, 0–3% hybrids in open-pollinated seed; Eucalyptus ovata, 0–2%). Established exotic E. ovata × globulus F1 hybrid seedlings were also identified at just one site, in response to disturbance from fire. The potential for gene flow from E. globulus plantations into native eucalypt populations does exist, however, the implementation of an outlined risk management framework would greatly reduce the likelihood. [Copyright &y& Elsevier]

We examined growth of Eucalyptus microcarpa seedlings in soil collected from four sites in southeastern Australia, in which retired pasture land has been revegetated with mixed plantings of Eucalyptus and Acacia species. Revegetation of farm land in southeastern Australia is an area of major investment. The focus of the study was to examine the influence of soil biota on seedling growth and its possible interaction with soil enrichment from a legume ( Acacia) and decomposition rates. We used a soil freezing treatment (−80°C for 3 days) to retard the soil biota, with the expectation that invertebrates in particular would be killed. Soil freezing did not cause a nutrient pulse, but did reduce the level of ammonium in soil. Nitrate levels increased with time in pots, regardless of the soil treatment. Decomposition rates measured using cellulose substrate were significantly reduced by the freeze treatment, but only for approximately 90 days. Eucalyptus microcarpa seedlings grown in freeze-treated soil were approximately 40% smaller (total biomass), had marginally lower LAR (leaf area ratio), and significantly lower LMA (leaf mass per area). Low LMA indicates that leaves are either thinner in cross-section or less dense. We hypothesise that both the poor growth of seedlings and production of less robust leaves are consequences of reduced availability of soil nutrients due to the diminished soil biota after freeze treatment. Litter under Acacia was richer in nitrogen than litter under Eucalyptus but there was no difference in nitrogen content of soil, and consequently no soil source effects on plant growth or decomposition. We suggest that variation in the soil biota has the potential to greatly enhance or hinder the success of revegetation on retired agricultural land, but enrichment of soil by decomposition of nitrogen rich litter in these sites requires longer than the 8–15 years since they were revegetated. [ABSTRACT FROM AUTHOR]

The majority of Eucalyptus species are native to Australia, but worldwide there are over 3 million ha of exotic plantations, especially in the tropics and subtropics. Of the numerous known leaf diseases, three species of Phaeophleospora can cause severe defoliation of young Eucalyptus; Phaeophleospora destructans, Phaeophleospora eucalypti and Phaeophleospora epicoccoides. Phaeophleospora destructans has a major impact on seedling survival in Asia and has not, as yet, been found in Australia where it is considered a serious threat to the biosecurity of native eucalypts. It can be difficult to distinguish Phaeophleospora species based on symptoms and micromorphology and an unequivocal diagnostic tool for quarantine purposes would be useful. In this study, a multiple gene genealogy of these Phaeophleospora species and designed specific primers has been constructed to detect their presence from leaf samples. The phylogenetic position of these Phaeophleospora species within Mycosphaerella was established. They are closely related to each other and to other important Eucalyptus pathogens, Mycosphaerella nubilosa, Mycosphaerella cryptica and Colletogloeopsis zuluensis. The specific primers developed can now be used for diagnostic and screening purposes within Australia. [ABSTRACT FROM AUTHOR]

Aim To explore: (1) the relative influences of site conditions, especially moisture relations, on pathways and rates of monsoon rain forest seedling and sapling regeneration, especially of canopy dominants, in northern Australia; and (2) contrasts between regeneration syndromes of dominant woody taxa in savannas and monsoon rain forest. Location Four monsoon rain forest sites, representative of regional major habitat and vegetation types, in Kakadu National Park, northern Australia. Methods A decadal study involved: (1) initial assessment over 2.5 years to explore within-year variability in seed rain, dormant seed banks and seedling (< 50 cm height) dynamics; and (2) thereafter, monitoring of seedling and sapling (50 cm height to 5 cm d.b.h.) dynamics undertaken annually in the late dry season. On the basis of observations from this and other studies, regeneration syndromes of dominant monsoon rain forest taxa are contrasted with comparable information for dominant woody savanna taxa, Eucalyptus and Corymbia especially. Results Key observations from the monsoon rain forest regeneration dynamics study component are that: (1) peak seed rain inputs of rain forest taxa were observed in the wet season at perennially moist sites, whereas inputs at seasonally dry sites extended into, or peaked in, the dry season; (2) dormant soil seed banks of woody rain forest taxa were dominated by pioneer taxa, especially figs; (3) longevity of dormant seed banks of woody monsoon rain forest taxa, including figs, was expended within 3 years; (4) seedling recruitment of monsoon rain forest woody taxa was derived mostly from wet season seed rain with limited inputs from soil seed banks; (5) at all sites rain forest seedling mortality occurred mostly in the dry season; (6) rain forest seedling and sapling densities were consistently greater at moist sites; (7) recruitment from clonal reproduction was negligible, even following unplanned low intensity fires. Main conclusions By comparison with dominant savanna eucalypts, dominant monsoon rain forest taxa recruit substantially greater stocks of seedlings, but exhibit slower aerial growth and development of resprouting capacity in early years, lack lignotubers in mesic species, and lack capacity for clonal reproduction. The reliance on sexual as opposed to vegetative reproduction places monsoon rain forest taxa at significant disadvantage, especially slower growing species on seasonally dry sites, given annual–biennial fires in many north Australian savannas. [ABSTRACT FROM AUTHOR]

Drought is an increasingly common climatic event that can devastate ecosystems, as well as surrounding agricultural and forestry industries. Few places face this challenge more than Australia, where millennia of droughts linked to geography and climatic drivers, such as El Niño, have shaped the flora and fauna into forms predicated on resilience and economy. How an organism responds to these cyclic challenges is a combination of the inherent tolerance mechanisms encoded in their genome and outside influences, such as the effect of nutrients and symbiotic interactions. In this issue of Physiologia Plantarum, Tariq et al. (2019) describes how the presence of the element phosphorus can bolster the physiological and biochemical response of eucalypt seedlings to severe drought conditions. [ABSTRACT FROM AUTHOR]

Crown rot, caused by Fusarium pseudograminearum, is an important disease of wheat in Australia and elsewhere. In order to identify molecular markers associated with partial seedling resistance to this disease, bulked segregant analysis and quantitative trait loci (QTL) mapping approaches were undertaken using a population of 145 doubled haploid lines constructed from ‘2-49’ (partially resistant) × ‘Janz’ (susceptible) parents. Phenotypic data indicated that the trait is quantitatively inherited. The largest QTLs were located on chromosomes 1D and 1A, and explained 21% and 9% of the phenotypic variance, respectively. Using the best markers associated with five QTLs identified by composite interval mapping, the combined effect of the QTLs explained 40.6% of the phenotypic variance. All resistance alleles were inherited from ‘2-49’ with the exception of a QTL on 2B, which was inherited from ‘Janz’. A minor QTL on 4B was loosely linked (19.8 cM) to the Rht1 locus in repulsion. None of the QTLs identified in this study were located in the same region as resistance QTLs identified in other populations segregating for Fusarium head blight, caused by Fusarium graminearum. [ABSTRACT FROM AUTHOR]

The role a small marsupial, the woylie Bettongia penicillata, might play in the recruitment and regeneration of Western Australian sandalwood Santalum spicatum through its seed caching behaviour was investigated in this study. To determine the fate of the seeds, cotton thread was attached to the seeds and the trail followed. A total of 25 seed caches were located. All of the seeds were found in separate caches, which was consistent with scatter-hoarding behaviour. The average distance from the source of the seeds to the cache was 43.1 m ± 5.8 m at Dryandra woodland and 29.1 m ± 3.8 m at Karakamia sanctuary. The mean cache depth was 4.3 cm ± 0.2 cm at Dryandra woodland compared with 4.6 cm ± 0.3 cm at Karakamia sanctuary. Significantly more seedlings and saplings grew away from sandalwood trees at sites where woylies were present than at sites with no woylies. In contrast, significantly more seedlings and saplings grew under adult sandalwood trees at the site without woylies than where they were present, although there were significantly lower rates of recruitment and sandalwood regeneration at these sites. In addition, significantly more whole, undisturbed sandalwood seeds were found under the parent trees at the woylie-free site than at the site with woylies. These findings strongly suggest that little seed dispersal or regeneration of sandalwood occurs in the absence of woylies. Through scatter-hoarding, woylies have the potential to disperse and cache sandalwood seeds away from the source and significantly alter the subsequent regeneration of sandalwood. Furthermore, by caching seeds large distances away from a source, woylies could modify the distribution of sandalwood in an area. [ABSTRACT FROM AUTHOR]

Seedling emergence in a eucalypt savanna of north-eastern Australia was documented over a 12-month period, between May 1999 and May 2000. Seedling emergence for grasses, forbs and subshrubs was found to mainly occur in a brief pulse at the start of the wet season following fire or the removal of grass biomass. Only a minor number of tree and shrub seedlings were detected overall. Burning, or cutting away the grass layer in unburnt savanna, in both the early (i.e. May) and the late (i.e. October) dry seasons significantly increased seedling emergence over undisturbed savanna that had been unburnt for 3 years. Removing the grass layer in unburnt savanna, during either the early or the late dry season, triggered similar seedling densities to savanna burnt in the early dry season. Late dry season fires promoted the greatest seedling density. We attribute this to the higher intensity, late dry season fires releasing a greater proportion of seed from dormancy, coupled with the higher density of soil seed reserves present in the late dry season. [ABSTRACT FROM AUTHOR]

Emergence and persistence characteristics ofPhalaris paradoxaseeds in no- and minimum-till situations and at different burial depths were studied in a sub-tropical environment. Three experiments were carried out using naturally shed seeds. In the first experiment, seedlings emerged from May through to September each year, although the majority of seedlings emerged in July. In the second experiment with greater seed density, cultivation in March of each year stimulated seedling emergence, altered the periodicity of emergence and accelerated the decline of seeds in the seedbank compared with plots that received no cultivation. The majority of seedlings in the cultivated plots emerged in May whereas the majority of seedlings in the undisturbed plots emerged in July. Emergence accounted for only 4–19% of the seedbank in both experiments over 2 years. Seed persistence was short in both field experiments, with less than 1% remaining 2 years after seed shed. In the third experiment, burial depth and soil disturbance significantly influenced seedling emergence and persistence of seed. Seedlings emerged most from seed mixed in the top 10 cm when subjected to annual soil disturbance, and from seed buried at 2.5 and 5.0 cm depths in undisturbed soil. Emergence was least from seed on the soil surface, and buried at 10 and 15 cm depths in undisturbed soil. Seeds persisted longest when shed onto the soil surface and persisted least when the soil was tilled. These results suggest that strategic cultivation may be a useful management tool, as it will alter the periodicity of emergence allowing use of more effective control options and will deplete the soil seedbank more rapidly. [ABSTRACT FROM AUTHOR]

Recruitment in many shrub and tree species in arid Australia is limited by domestic and feral animal grazing. The outbreak of Rabbit Calicivirus Disease (RCD or RHD) in late 1995 at Kinchega National Park (NP) in arid western NSW, Australia, coincided with intensified warren ripping and other rabbit (Oryctolagus cuniculus) control efforts. We monitored changes in rabbit numbers in response to these factors using spotlight counts and dung-pellet counts. Rabbit populations declined initially, and were low for the remainder of the study. To assess the impact of rabbit control on vegetation, we examined whether recruitment of seedlings or vegetative suckers was occurring at Kinchega NP, following the arrival of RCD; how long such recruits were likely to survive under current grazing pressures; and whether the magnitude of current seedling and vegetative sucker recruitment and survival is greater than available data prior to RCD and extensive warren control. We followed the survival of individual seedlings and newly emerged suckers of six shrub or tree species, most of which are considered to be at risk of local decline. Three levels of caging were used to exclude all mammalian grazers; all mammalian grazers except rabbits; and no mammalian grazers. Pooled cohorts of seedlings and suckers were analysed using failure-time analyses. During the course of the study, suckering was observed in four species (Acacia carneorum,Alectryon oleifolius,Casuarina pauperandSantalum acuminatum), with seedlings observed in the other two species (Dodonaea viscosaandAcacia ligulata). Survival of suckers of some species was slightly greater than pre-RCD estimates, but in general, a pattern of little or nil recruitment is likely in suckers exposed to rabbits or to all grazing mammals. Seedling survival was particularly low regardless of the level of exclusion, largely due to desiccation. Reduction of grazing impacts may only allow recruitment into populations of species reliant on seedlings under more favourable climatic circumstances than experienced in this study, while the probability of successful recruitment into populations of suckering species in western NSW continues to be low even at very low rabbit densities. [ABSTRACT FROM AUTHOR]

Summary 1. Australia's savannas typically are burnt every 1–3 years. Although there are concerns about the effect of frequent fire on recruitment of Australian savanna species, there is a lack of information. This research aimed to determine whether seed or microsite availability limits seedling recruitment of the overstorey tree Eucalyptus miniata and the midstorey shrub Acacia oncinocarpa , whether seed or microsite availability is affected by frequent fire, and the consequent effect on seedling recruitment. 2. Quadrats were established in unburnt areas. Experimental manipulations were addition of seed and/or disturbance of the soil surface to increase the number of microsites suitable for germination. In a second experiment, seed was added to quadrats established in three fire regimes after the annual burning event (unburnt, burnt early in the dry season, burnt late in the dry season). 3. In unburnt areas, seedling regeneration was limited by both seed supply and microsite availability. Both burning regimes reduced seedling emergence, possibly because the reduced canopy cover caused unfavourable microclimate, the increased grass and forb ground cover increased competition for resources, and there was increased loss of seed to seed harvesters. 4. The results indicate that sexual regeneration of these common species is disadvantaged by current burning practices because both seed supply and the number of microsites are reduced. Thus, long-term changes in savanna floristic structure seem likely unless fire managers aim to increase the fire-free intervals. The relative abundance of species able to reproduce vegetatively may increase under frequent fire regimes. Such a change may take a long time to detect given the fire-resistant and long-lived nature of overstorey species, and the capacity for vegetative regeneration in many savanna species. The impacts of fire on limiting seedling regeneration will require savanna managers to consider fire-free intervals... [ABSTRACT FROM AUTHOR]

Discusses the use of local seeds of native plant species for revegetation in Australia. Background on surveys conducted on seed banks; Reasons for selecting local seeds; Demand and supply for local seed; Discussion on the shortage of seed and seedlings.

The growth and survival of Eucalyptus obliqua seedlings from twenty-two provenances throughout the range of the species in south-eastern Australia were studied in three field trials in Tasmania and Victoria. Early results indicated significant variation among provenances for several growth parameters and for survival. Ranking for height was consistent on the two low-altitude planting sites and similar to that in previously reported glasshouse studies. Within provenances there were also significant differences between families for growth and survival. These results suggest that genetic improvement of the species is possible, not only by selection of the most suitable provenances for particular sites, but also by the selection of superior individual trees within a provenance. [ABSTRACT FROM AUTHOR]

Focuses on mistletoe seedling establishment on eucalypt hosts in Australia. Germination and early seedling development of mistletoes; Factors that cause early seedling mortality.

(1) Causes of seedling mortality in Diplachne fusca were investigated, and the flooding tolerance of seedlings was examined in field and glasshouse experiments in temperate New South Wales, Australia. (2) Seedlings growing under non-flooded conditions in rice crops sown in unflooded soils, were susceptible to water stress, with up to 65% dying. Seedlings emerging in autumn after rain also became water stressed. Those surviving were stunted by cold temperatures or killed by frost or site disturbance. (3) Under controlled flooding conditions, continuous submergence resulted in greater germination than brief irrigations. Delaying permanent flooding gave less germination but fewer deaths after the onset of flooding compared with flooding for the duration of the experiment. Significantly more seedlings established in 4 cm deep permanent floodwater than in 12 cm. (4) In the glasshouse, single-leaved seedlings could establish in 20 cm deep water with no mortality. Submerged seedlings emerged above water level by rapid elongation of the fourth and fifth leaves. (5) A strategy for the control of D. fusca in rice fields is described, using the results of this and previous studies. [ABSTRACT FROM AUTHOR]

(1) The native grass Diplachne fusca has become an important weed in rice fields in temperate Australia since rice cultivation began there in 1922. Field and glasshouse experiments were conducted to examine the population dynamics of D. fusca in rice fields and to develop strategies for its control. (2) D. fusca can develop a persistent seed bank, with 48 000 seeds m-2 (0-6 cm depth) measured at one site 18 months after the last seed input. No seedlings emerged from depths > 10 mm whereas 60% of seedlings arose from seed lying on the soil surface. Emergence was strongly inhibited by the presence of litter or living pasture plants. The highest seedling density was on bare ground (1480 m-2), but this represented < 5% of the seed bank. (3) The patterns of seedling emergence were similar to those observed after experimentally storing seeds for 7.5 months in a range of semi-natural and artificial storage conditions. High dormancy levels were found in seed which had been stored dry and exposed to natural weather conditions. Storage in water gave the highest germination, but a single drying cycle reduced germination from 44% to 10%. Darkness inhibited germination of non-dormant seed. (4) The development of dormant seed reserves in the soil and the dependence on open areas for regeneration are features that D. fusca shares with many arable weeds and colonizing species. These features, as well as the loss of seed dormancy with prolonged flooding, are interpreted as adaptations to intermittent wetlands, the natural habitat of D. fusca prior to its invasion of rice fields. [ABSTRACT FROM AUTHOR]

(1) Seed production and release by Banksia tricuspis, a small tree restricted to a 50 ² area in south-western Australia, were assessed. Most plants in the study population lowered in the nineteenth year after fire and on average 16500 ovules per adult were (2) Most flower heads were destroyed by moth larvae and larval-seeking cockatoos. Of the 115 young seeds produced on average per adult, almost half aborted, apparently due to the constraints of the breeding system and limited supply of mineral nutrients. Beetle larvae destroyed a further 15% of mature seeds. (3) There was winked senescence and spontaneous release of seeds in the fourth and subsequent years. The mean value of eighty-four canopy-stored viable seeds per adult that remained were almost entirely accounted for by the size of the crops for the last 3 years. (4) All viable seeds were released in response to an autumn wildfire. Seedling establishment only occurred immediately after the fire. (5) Low seed production and rapid depletion of the canopy-stored seed bank are not sufficient in themselves to account for the rarity of B. tricuspis. Management in the wild should include conservation of cockatoos and other animals which consume the granivorous moth larvae and control of the fire regime. [ABSTRACT FROM AUTHOR]

Isolates of Pythium attributable to thirteen named species and to species group F (sensu van der Plaats­Niterink) were isolated from roots of field-grown rice seedlings showing poor root development and lack of vigour. P. arrhenomanes and group F were the most commonly isolated species. The roots of 15-week-old rice plants yielded only P. flevoense, P. vanterpoolii, P. rostratum and Pythium group G of which the latter two were not obtained from seedling roots. In pot tests with representative Pythium isolates, P. arrhenomanes was most pathogenic to rice seedlings, causing pre- and post-emergence death and average reductions in shoot and root growth in surviving seedlings of 48 and 70%, respectively. P. irregulare killed seedlings before but not after emergence, whilst the response of rice seedlings to P. myriotylum apparently depended on the length and timing of a cold shock treatment. P. pyrilobum did not reduce seedling number or shoot growth but reduced root growth. P. vanterpoolii and group F were not pathogenic in the tests. P. coloratum, P. echinulatum, P. flevoense, P. oedochilum, P. oligandrum, P. periilum, P. pyrilobum and P. rostratum were isolated infrequently and had no adverse effects on seedlings in pathogenicity tests, although P. myriotylum, P. oligandrum, and P. periilum were associated with significant increases in shoot growth. P. tracheiphilum was isolated from one site but its pathogenicity was not tested, This is the first record of P. coloratura, P. echinulatum. P. flevoense, P. irregulare, P. oedochilum, P. oligandrum, P. periilum, P. pyrilobum and P. tracheiphilum from rice roots. [ABSTRACT FROM AUTHOR]

When cucumber seedlings were dusted with tobacco streak ilarvirus (TSV)-infected pollen and infested with 5-10 thrips (adults and larvae mixed), Thrips tabaci transmitted all three Australian strains of TSV. In similar work, Microcephalothrips abdominalis transmitted both and Frankliniella schultzei one strain, respectively, of two TSV strains tested. Transmission of the Ageratum strain (TSV-Ag) infecting pollen of Ageratum houstonianum was very efficient (100%) by all three thrips species. However, transmission rates of only 0-28% were achieved using the Ajuga strain (TSV-A) and the strawberry strain (TSV- S) in pollen of other hosts. A fourth thrips species, T. parvispinus, transmitted TSV-Ag from infected tomato pollen to Chenopodium amaranticolor seedlings. There was, therefore, little or no vector specificity in the thrips transmission of the three strains of TSV, but factors associated with the virus-infected pollen affected the efficiency of transmission. This is the first report of F. schultzei and T. parvispinus as vectors of TSV. [ABSTRACT FROM AUTHOR]

Double-stranded RNA analysis indicated that widespread latent infection by citrus tristeza virus (CTV) occurs naturally in a citrus variety collection at Merbein, Australia. Detection was based on the presence of the putative replicative form (RF) of the virus (ca 19.5 kilobase pairs) and the presence or absence of three previously known putative subgenomic dsRNAs with molecular sizes of ca 3.1, 1.7 and 0.8 kilobase pairs. With the exception of some citrus relatives normally used as rootstocks, the dsRNAs were readily detectable in all the trees tested. Variability was noticed among the dsRNAs profiles of individual seedling trees of Microcitrus australasica var. sanguinea. By contrast, dsRNA patterns of trees of open-pollinated Ellendale tangor were indistinguishable. A number of dsRNA bands found in West Indian lime infected with CTV were not detected when this isolate was graft-inoculated to healthy sweet orange seedlings. A simple method for enhancing the sensitivity of detection of the CTV dsRNA bands by silver staining is described which involves incubating the gels in RNase A prior to staining; this allowed detection of the putative CTV RT m only 40 mg of green bark material. [ABSTRACT FROM AUTHOR]