Eucalyptus Polybractea Research Articles

The influence of plant scents on nest box inspection by Eastern Rosella (Platycercus eximius)

ABSTRACT Many cavity nesters add volatile plants with medicinal properties to their nests. In Australia, eucalyptus and tea-trees are highly volatile plants, which have antiparasitic and antimicrobial properties. Here, we tested whether scents of eucalypt (Eucalyptus polybractea) and tea tree (Melaleuca alternifolia) essential oils can attract birds to newly installed nest boxes. Twenty-four nest boxes received three scent treatments (eucalypt, tea tree, control) for 10 days each using a Latin-square design. Bird visitation was recorded using camera traps. Eastern Rosellas (Platycercus eximius) visited the nest boxes the most (1,454 visits) and were therefore the focus of the study. Eastern Rosellas did not change their behaviours in response to the eucalypt scent in nest boxes: there was no difference in visitation, duration of visits or nest box inspection behaviour between nest boxes with eucalypt scent and those with the control scent. However, Eastern Rosellas visited nest boxes with tea tree scent less frequently and spent less time at these boxes than those with the control scent. The mean time that Eastern Rosellas spent inspecting boxes slightly increased over the 10-day period following scent placement at boxes with control and eucalypt scents, while it sharply decreased at boxes with tea tree scent. This is the first study demonstrating that an Australian bird detected and behaved differently in response to plant volatiles. The use of scents may offer opportunities to not only attract, but potentially also deter certain birds from using particular hollows.

Combination of Chemically-Characterized Essential Oils from Eucalyptus polybractea, Ormenis mixta, and Lavandula burnatii: Optimization of a New Complete Antibacterial Formulation Using Simplex-Centroid Mixture Design.

This study aims to identify the volatile profile of three essential oils obtained from Eucalyptus polybractea cryptonifera (EPEO), Ormenis mixta (OMEO), and Lavandula burnatii briquet (LBEO) and to examine their combined antibacterial activity that affords the optimal inhibitory ability against S. aureus and E. coli using simplex-centroid mixture design and checkerboard assay. Essential oils (EOs) were isolated by hydrodistillation and characterized using gas chromatography-mass spectrometry (GC-MS) and gas chromatography coupled with flame-ionization detector (GC-FID). The antibacterial activity was performed using disc diffusion and microdilution assays. The chemical analysis revealed that 1,8-cineole (23.75%), p-cymene (22.47%), and α-pinene (11.20%) and p-menthane-1,8-diol (18.19%), α-pinene (10.81%), and D-germacrene (9.17%) were the main components detected in E. polybractea and O. mixta EOs, respectively. However, L. burnatii EO was mainly represented by linalool (24.40%) and linalyl acetate (18.68%). The EPEO, LBEO, and OMEO had a strong antibacterial effect on S. aureus with minimal inhibitory concentrations (MICs) values ranging from 0.25 to 0.5% (v/v). Furthermore, the combination of 1/2048 MICEPEO + 1/4 MICLBEO showed a synergistic antibacterial effect on S. aureus with a FIC index of 0.25, while the formulation of 1/4 MICEPEO + 1/4 MICOMEO demonstrated an antibacterial synergistic activity on E. coli with a FIC index of 0.5. Moreover, the simplex-centroid mixture design reported that the most effective combinations on E. coli and S. aureus correspond to 32%/28%/40% and 35%/30%/35% of E. polybractea, O. mixta, and L. burnatii, respectively. Presented information highlights the action of antibacterial formulations of these EOs and suggests their potential applications as alternatives to commercialized drugs to contract the development of bacteria causing serious infections and food deterioration.

Cover: Journal of Basic Microbiology. 3‐4/2023

Journal of Basic MicrobiologyVolume 63, Issue 3-4 p. 235-235 COVER PICTUREFree Access Cover: Journal of Basic Microbiology. 3-4/2023 First published: 04 March 2023 https://doi.org/10.1002/jobm.202370005AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Graphical Abstract Cover illustration: Secretion of industrially important amylase on starch agar medium by the salt-tolerant alkaliphilic bacteria isolated from the rhizosphere of medicinal plant Eucalyptus polybractea L., collected from Kharaghoda, near desert Kutch, Gujarat, India. (Photo: Nishtha R. Vaghela, Department of Biosciences, Saurashtra University, Rajkot, Gujarat, India) Volume63, Issue3-4Special Issue: Microbes in action: Ecology to economyMarch-April 2023Pages 235-235 RelatedInformation

Antibacterial interactions between two monofloral honeys and several topical antiseptics, including essential oils

BackgroundHoney has broad spectrum antibacterial activity against clinically important organisms and may be suitable for treating superficial bacterial infections. However, very little data are available describing potential interactions between honey and other topically applied agents such as antiseptics or essential oils.MethodsInteractions between pairs of antibacterial agents were investigated by performing checkerboard assays and determining the fractional inhibitory concentration indices (FICIs). Interactions between the two monofloral honeys marri (from Corymbia calophylla) and manuka, and the antiseptic agents benzalkonium chloride, chlorhexidine digluconate, silver (I) nitrate, tea tree oil, and Eucalyptus polybractea oil were investigated against Staphylococcus aureus ATCC® 43300 and Pseudomonas aeruginosa ATCC® 27853. ResultsAdditive or indifferent interactions (FICI 0.5—2) were observed for all combinations against both organisms tested, with the exception of chlorhexidine and honey. Chlorhexidine and marri honey showed an antagonistic relationship against S. aureus (median FICI 2.00, range 1.25—4.83). Similarly, chlorhexidine and manuka honey showed antagonism against S. aureus (median FICI 2.33, range 2.00—2.67).ConclusionsWith the exception of chlorhexidine, these data indicate that honey does not interfere with the antimicrobial activity of the tested agents, and that honey may be suitable for combination therapy with other topically applied antibacterial agents for treating superficial bacterial infections.

Testing New Provenances of Eucalyptus polybractea: A Eucalypt Oil Mallee Adapted to Semi-Arid Environments

Novel genetic accessions of Eucalyptus polybractea from a previously untested, hotter and drier part of the species’ natural range were tested in a common garden trial at a semi-arid site in NSW, Australia. Eucalyptus polybractea is a mallee eucalypt cultivated for essential oils (1,8-cineole), bioenergy and carbon sequestration on dryland sites in southern Australia (sites receiving about 450 mm mean annual rainfall, MAR). A trial of six previously untested provenances from the relatively hot, dry part of the species’ natural range in South Australia (SA) (250–450 mm MAR) was established alongside seven provenances from New South Wales (NSW) and Victoria within a commercial plantation in NSW. The trial was assessed at age 3.7 years for growth and oil characteristics. While survival was excellent, most of the SA sources were slower growing and of sub-standard oil concentration and quality relative to those from Victoria and NSW. However, a single SA provenance, with the highest oil concentration and 1,8-cineole percentage of all provenances tested, may have potential as a source of selected germplasm. Infusion of SA material into the breeding populations of E. polybractea, which are currently based on NSW and Victorian selections only, may provide more resilience in the face of hotter and drier temperatures expected under projected climate change scenarios, and/or allow the introduction of the species to hotter and drier climates in Australia or other parts of the world with semi-arid climates. However, high-intensity selection of infusions will be required to maintain the growth and oil characteristics in the existing breeding population.

Chemical composition analysis and biological activities of essential oil from Eucalyptus polybractea (L.), growing in plains of Punjab, Northern India, by two different hydro-distillation methods

Eucalyptus essential oil poses various biological activities due to the presence of various bioactive compounds. The objective of this study was to evaluate the effect of direct heat-based hydro distillation (DHBH) and in-direct heat-based hydro-distillation (IDHBH) methods on chemical profile, extraction, and biological activities of essential oils from Eucalyptus polybractea. Eucalyptus Essential Oil (EEO) was extracted from green leaves of eucalyptus plant using DHBH and IDHBH methods. Aroma profile was evaluated by GC-FID technique. Content of phenolics, flavonoids and tannins accompanied by antioxidant activities like iron-chelation and DPPH were studied. Other biological activities like anti-inflammatory and anti-microbial were also analysed. GC-FID chemical profiling revealed a greater number of bioactive compounds in IDHBH extract than DHBH. Relationship between antioxidant activity and chemical composition of extracted oils was investigated. Significant amount of β- pinene, 1,8 cineole, eugenol, Pentadecanoic acid are responsible for antioxidative capacity of both extracts. The concentration of all compounds, especially Pentadecanoic acid and other unique bioactives were higher in IDHBH extract. The level of antioxidants like phenolics, flavonoids and tannins by was high also high in IDHBH extracted oil. This corresponds to higher antioxidant activities like DPPH and iron-chelating activity of IDHBH oil compared with DHBH extract. Similarly, anti-inflammatory, and anti-microbial potential was more in oil extracted with IDHBH than DHBH. The present paper reported that different extraction methods lead to different biochemical composition of essential oils and the choice of a suitable method is extremely important to obtain more preferred compounds with more potent biological activities and this method can be the choice for essential oil-based companies.

Sapling and coppice biomass heritabilities and potential gains from Eucalyptus polybractea progeny trials

Eucalyptus polybractea has been planted as a short-rotation coppice crop for bioenergy in Western Australia. Historical breeding selections were based on sapling biomass and despite a long history as a coppice crop, the genetic parameters of coppicing are unknown. Here, we assessed sapling biomass at ages 3 and 6 from three progeny trials across southern Australia. After the second sapling assessment, all trees were harvested. Coppice biomass was assessed 3.5 years later. Mortality following harvest was between 1 and 2%. Additive genetic variance for the 6-sapling estimate at one site was not significant. Sapling heritabilities were between 0.06 and 0.36 at 3 years, and 0.18 and 0.20 at 6 years. The heritability for the coppice biomass was between 0.07 and 0.17. Within-site genetic and phenotypic correlations were strong between all biomass assessments. Cross-site correlations were not different from unity. Selections based on net breeding values revealed positive gains in sapling and coppice biomass. Lower or negative gains were estimated if 3-year sapling selections were applied to the coppice assessments (−7.1% to 3.4%) with useful families culled. Positive gains were obtained if 6-year sapling selections were applied to the coppice assessment (6.4% to 9.3%) but these were lower than those obtained by applying coppice selections to the coppice assessment (8.4% to 14.8%). Removal of poor performing families and families that displayed fast sapling growth rates but under-performed as coppice will benefit potential coppice production. These results indicate that selections should be made using coppice data.

Genetic parameters and potential gains from breeding for biomass and cineole production in three-year-old Eucalyptus polybractea progeny trials

ABSTRACT Eucalyptus polybractea is a mallee eucalypt with potential use as a perennial biomass crop for dryland agriculture in southern Australia, in addition to its established success as a source of eucalyptus oil. Sixty-six indigenous, open-pollinated families from West Wyalong and surrounds in New South Wales were tested in trials at Newdegate, Western Australia; Drummartin, Victoria; and Condobolin, New South Wales. Growth was fastest at Condobolin, followed by Drummartin then Newdegate. The estimated cross-site genetic correlation was rg = 0.85 ± 0.16 between Newdegate and Condobolin, rg = 1.08 ± 0.35 between Newdegate and Drummartin, and rg = 1.03 ± 0.32 between Condobolin and Drummartin. Estimated gains suggest that genotype × environment interaction was not practically significant. Narrow-sense heritability for biomass production was ĥ2 = 0.18 ± 0.07 at Newdegate, ĥ2 = 0.05 ± 0.04 at Drummartin and ĥ2 = 0.32 ± 0.08 at Condobolin. Heritability of leaf cineole concentration at Newdegate was ĥ2 = 0.38 ± 0.09. The genetic correlation between leaf cineole concentration and biomass production was rg = 0.07 ± 0.19 and the phenotypic correlation was rp = −0.12 ± 0.03. Compared to selection on either tree biomass or leaf cineole concentration, index selection incorporating both whole tree biomass and leaf cineole concentration is most effective when looking to maximise both cineole yield and biomass production.

Monoterpene synthases responsible for the terpene profile of anther glands in Eucalyptus polybractea R.T. Baker (Myrtaceae).

Research on terpene biosynthesis in the genus Eucalyptus (Myrtaceae) is poorly developed, but recently large numbers of terpene synthase (TPS) genes have been identified. Few of these have been characterized or their expression localized to specific tissues. A prime candidate for detailed examination of TPS gene expression is the bisexual eucalypt flower-composed of male and female reproductive organs, and vegetative tissues that may express different TPS genes. We aimed to characterize and compare the terpene profile and TPS genes expressed in anthers and gynoecia in the high oil-yielding Eucalyptus polybractea R.T. Baker. We hypothesized that gynoecia will produce greater amounts of defensive terpenes, whereas anthers will have a terpene profile that is biased towards a role in pollination. Microscopy of isolated anthers showed them to possess a single, prominent oil gland. Chemical analysis of whole floral structures at different stages of development showed total oil per unit dry mass increased as flower buds expanded, with highest concentrations in mature flower buds just prior to flower opening. The oil profile of gynoecia was dominated by the monoterpene 1,8-cineole, whereas that of isolated anthers were enriched with the monoterpene α-pinene. Through transcriptomic analysis and recombinant protein expression, we were able to identify monoterpene synthases responsible for the different profiles. Synthases for α-pinene and 1,8-cineole were expressed in each tissue type, but the relative expression of the former was higher in anthers. Sequence comparison and site-directed mutagenesis of the α-pinene synthase allowed us to identify amino acids that influence the α-pinene to β-pinene ratio of the product profile. We suggest the terpene constituents of anthers may have multiple roles including attracting pollinators through emission of volatile α-pinene, deterrence of palynivores through emission of volatile 1,8-cineole and adhesion of pollen to pollinators via the release of sticky α-pinene onto the anther surface.

A decadal multi-site study of the effects of frequency and season of harvest on biomass production from mallee eucalypts

Mallee eucalypts are hardy, woody perennials that are being developed as a short-rotation coppice crop in Australia for the production of eucalyptus oil, biofuels and other biomass products. The economic viability of this prospective crop is dependent on its ability to survive and regenerate following repeated harvesting of the above ground component. Here we report on survival and biomass yield of mallee belt plantings of Eucalyptus polybractea, E. loxophleba ssp lissophloia and E. kochii ssp plenissima, at 19 sites, under two harvest-frequencies (3–8 year cycles) and harvest seasons (autumn or spring) over a decade from 2006 to 2015. 16 sites had post-harvest mortality ranging from 1.0% to 12.2% while the remaining three sites with either shallow saline water tables or a silcrete hardpan failed. Average site dry biomass yield across treatments ranged from 2.2 to 32.8 Mg ha−1 yr−1. Higher yielding sites were generally characterised by pH between 3.8 and 8, ECe below 15.0 dS m−1 and high soil fertility. Lower yielding sites were generally near saline valley floors. After 7-years, biomass yield from unharvested treatments exceeded the average cumulative yield of harvest treatments at eight of the 16 sites, including all three E. kochii sites. For E. loxophleba, significant interactions were found between season and frequency of harvest with highest yields in long rotation spring treatments. There were also interactions between site and frequency of harvest, which were mainly driven by the variable performance of the uncut treatment. On average E. loxophleba yielded more biomass following spring harvests whereas E. kochii yielded more following autumn harvests. E. polybractea yield was unaffected by season or frequency of harvest; however, harvest treatments yielded more biomass than uncut treatments. After 10 years, at eight of the nine sites subjected to three 3-year cycles, no decline in biomass yield was observed. The site that declined in production was attributed to depletion of a sandplain aquifer by extensive mallee plantings. Overall, the results from this decadal study indicate that in warm-temperate semi-arid areas, such as the south-west of WA, mallees biomass can be harvested sustainably at most sites even in short (3-year) rotation cycles.

Induction and characterisation of tetraploidy in Eucalyptus polybractea R.T. Baker

Eucalyptus polybractea (blue mallee) is the main commercial source of pharmaceutical grade eucalyptus oil in Australia. In foliage, the oil is stored in large sub-dermal foliar glands, which have a diameter that is sometimes comparable to leaf thickness. Given that ploidy increases are often associated with an increase in leaf thickness, it was reasoned that polyploid blue mallee may have larger glands and thus be superior for essential oil production. Our aim was to induce tetraploidy in blue mallee and determine the effect on growth rate, vegetative and reproductive morphology and oil quality and yield under both controlled and field conditions. In vitro cultures of five high-oil-yielding clones were used for the study. Nodal explants were treated with 0.05 to 0.5% colchicine for two to twelve days, resulting in six tetraploid lines from three clones. The most effective concentration of colchicine was 0.5%, but the most effective exposure time and method of nodal explant preparation varied between clones. Tetraploids of one line, and their respective diploid controls, were rooted, acclimatised and transferred to a glasshouse and a field plot for further study. Tetraploids had a significantly slower growth rate in both the glasshouse and field, which may in part be due to a lower root to shoot ratio. Tetraploid leaves from both the glasshouse and field-grown plants were significantly thicker and had larger stomata at a lower density than diploids. Similarly, tetraploid leaves had significantly larger oil glands at a lower density, but the total oil content of tetraploids was significantly lower than that of diploids. Field-grown tetraploids had larger flowers than diploids, but the size differences are unlikely to preclude pollination and fertilization. Successful breeding of diploids and tetraploids will pave the way for the creation of blue mallee triploids and thereby the production of sterile seeds, an attractive possibility for the eucalyptus oil industry.

High marker density GWAS provides novel insights into the genomic architecture of terpene oil yield in Eucalyptus.

Terpenoid-based essential oils are economically important commodities, yet beyond their biosynthetic pathways, little is known about the genetic architecture of terpene oil yield from plants. Transport, storage, evaporative loss, transcriptional regulation and precursor competition may be important contributors to this complex trait. Here, we associate 2.39million single nucleotide polymorphisms derived from shallow whole-genome sequencing of 468 Eucalyptus polybractea individuals with 12 traits related to the overall terpene yield, eight direct measures of terpene concentration and four biomass-related traits. Our results show that in addition to terpene biosynthesis, development of secretory cavities, where terpenes are both synthesized and stored, and transport of terpenes were important components of terpene yield. For sesquiterpene concentrations, the availability of precursors in the cytosol was important. Candidate terpene synthase genes for the production of 1,8-cineole and α-pinene, and β-pinene (which comprised >80% of the total terpenes) were functionally characterized as a 1,8-cineole synthase and a β/α-pinene synthase. Our results provide novel insights into the genomic architecture of terpene yield and we provide candidate genes for breeding or engineering of crops for biofuels or the production of industrially valuable terpenes.

Antimicrobial Activity of Several Cineole-Rich Western Australian Eucalyptus Essential Oils.

Essential oils from the Western Australian (WA) Eucalyptus mallee species Eucalyptus loxophleba, Eucalyptus polybractea, and Eucalyptus kochii subsp. plenissima and subsp. borealis were hydrodistilled from the leaves and then analysed by gas chromatography–mass spectrometry in addition to a commercial Eucalyptus globulus oil and 1,8-cineole. The main component of all oils was 1,8-cineole at 97.32% for E. kochii subsp. borealis, 96.55% for E. kochii subsp. plenissima, 82.95% for E. polybractea, 78.78% for E. loxophleba 2, 77.02% for E. globulus, and 66.93% for E. loxophleba 1. The Eucalyptus oils exhibited variable antimicrobial activity determined by broth microdilution, with E. globulus and E. polybractea oils showing the highest activities. The majority of microorganisms were inhibited or killed at concentrations ranging from 0.25% to 8.0% (v/v). Enterococcus faecalis and Candida albicans were the least susceptible organisms, whilst Acinetobacter baumannii was the most sensitive. In conclusion, all oils from WA Eucalyptus species showed microorganism inhibitory activity, although this varied according to both the Eucalyptus species and the microorganism tested. These data demonstrate that WA Eucalyptus oils show activity against a range of medically important pathogens and therefore have potential as antimicrobial agents.

Accuracy of Genomic Prediction for Foliar Terpene Traits in Eucalyptus polybractea.

Unlike agricultural crops, most forest species have not had millennia of improvement through phenotypic selection, but can contribute energy and material resources and possibly help alleviate climate change. Yield gains similar to those achieved in agricultural crops over millennia could be made in forestry species with the use of genomic methods in a much shorter time frame. Here we compare various methods of genomic prediction for eight traits related to foliar terpene yield in Eucalyptus polybractea, a tree grown predominantly for the production of Eucalyptus oil. The genomic markers used in this study are derived from shallow whole genome sequencing of a population of 480 trees. We compare the traditional pedigree-based additive best linear unbiased predictors (ABLUP), genomic BLUP (GBLUP), BayesB genomic prediction model, and a form of GBLUP based on weighting markers according to their influence on traits (BLUP|GA). Predictive ability is assessed under varying marker densities of 10,000, 100,000 and 500,000 SNPs. Our results show that BayesB and BLUP|GA perform best across the eight traits. Predictive ability was higher for individual terpene traits, such as foliar α-pinene and 1,8-cineole concentration (0.59 and 0.73, respectively), than aggregate traits such as total foliar oil concentration (0.38). This is likely a function of the trait architecture and markers used. BLUP|GA was the best model for the two biomass related traits, height and 1 year change in height (0.25 and 0.19, respectively). Predictive ability increased with marker density for most traits, but with diminishing returns. The results of this study are a solid foundation for yield improvement of essential oil producing eucalypts. New markets such as biopolymers and terpene-derived biofuels could benefit from rapid yield increases in undomesticated oil-producing species.

Impact of biochar application on the productivity of a temperate vegetable cropping system

ABSTRACTFew studies have investigated the potential of biochar in supporting cool temperate horticultural systems with fertile soils. We examined the effects of applying 10 t ha−1 of blue mallee (Eucalyptus polybractea) biochar in combination with fertiliser rate treatments (either full or half the regional recommended rate) on crop yield, yield parameters and soil properties of a cool temperate vegetable cropping system on a red Ferrosol. Biochar amendment did not improve crop yield or other yield parameters of cauliflower, peas and broccoli crops. Similarly, soil parameters including nitrate and ammonium were unaffected by biochar treatment. We suggest the lack of biochar effect on crop and soil parameters was related to the inherent chemical fertility and structural robustness of Ferrosols, which may have mitigated any potential benefits from biochar amendment. Our results demonstrate that biochar application may not bring significant soil quality and crop productivity improvements to high-input agricultural systems.

Ovicidal, larvicidal, and behavioural effects of some plant essential oils on diamondback moth (Lepidoptera: Plutellidae)

AbstractAlternatives to synthetic insecticides are desirable for management of diamondback moth, Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae), an insect pest of global importance. Many essential oils derived from aromatic plants have demonstrated toxicity and behaviour altering effects on insect pests, and are considered low-risk alternatives to synthetic insecticides. We conducted laboratory experiments to determine the biological activity of several low-cost, commercially available essential oils against P. xylostella. Experiments testing ovicidal effects, larvicidal effects, larval feeding deterrence, and adult oviposition deterrence were done with essential oils derived from Artemisia abrotanum Linnaeus (Asteraceae), balsam fir (Abies balsamea Linnaeus (Pinaceae)), black pepper (Piper nigrum Linnaeus (Piperaceae)), eucalyptus (Eucalyptus polybractea (Baker) (Myrtaceae)), garlic (Allium sativum Linnaeus (Amaryllidaceae)), rosewood (a blend of different oil constituents), tansy (Tanacetum vulgare Linnaeus (Asteraceae)), and thyme (Thymus zygis Linnaeus (Lamiaceae)), using concentrations of 1, 2.5, and 5% v/v. Although all essential oils had some level of bioactivity against certain P. xylostella life stages, essential oils from garlic, rosewood, and thyme were most effective overall, demonstrating significant ovicidal and larvicidal activity, as well as deterrent effects on larval feeding and settling behaviour, and adult oviposition. Although variable phytotoxicity was observed with essential oils at 2.5% and 5% v/v concentrations, the results suggest that rosewood, garlic, and thyme essential oils have potential in management of P. xylostella.

Assessment of a non-destructive method to predict oil yield in Eucalyptus polybractea (blue mallee)

Eucalyptus oil is produced from a number of “oil mallee” species with high concentration of foliar essential oils, high proportion of 1,8-cineole and the ability to re-sprout with multiple stems from lignotubers after coppicing. Eucalyptus polybractea is one of the most planted mallees in Australia, but few efforts have been made to improve crop yields through selection or breeding programs, with the exception of seed collection from trees with high oil and 1,8-cineole concentration. The yield of essential oil from commercial eucalypt plantations is subject to several quantitative traits that interact, both positively and negatively. Using non-destructive methods we assessed traits relating to oil yield (quantitative and qualitative variation of foliar essential oils and biomass-related parameters) for their variability, heritability as well as phenotypic and genetic interactions in an open-pollinated progeny trial with 40 families and 480 individuals of E. polybractea. From this we built models to predict family yield performance and compared our predictions to commercial scale harvests of the same trial.Our models show that relying on oil concentration and 1,8-cineole proportion alone is not ideal for selection of top performing families. Rather a mixture of biomass related traits, foliar oil concentration, 1,8-cineole proportion and leaf architecture contribute to the top performing families in varying ways.

Genome-wide analysis of essential oil yield variation in Eucalyptus polybractea

Genome-wide analysis of essential oil yield variation in Eucalyptus polybractea

Biochar Field Study: Greenhouse Gas Emissions, Productivity, and Nutrients in Two Soils

Application of biochar to soil has potential to reduce greenhouse gas (GHG) emissions, store C for long‐term and provide agronomic benefits. However, the extent of these benefits are dependent on the type of biochar used and the environmental system in which it has been placed. While there are a large number of laboratory and glasshouse experiments, the number of biochar field studies is still limited. We conducted a 2‐yr field study to evaluate the effect of a wood‐based (blue mallee; Eucalyptus polybractea) biochar on GHG fluxes, pasture biomass, soil nutrient leaching, and nutrient uptake under different fertilizer rates in two soils (Arenosol and Cambisol) under a perennial pasture. Three rates of biochar were used in full factorial combination with 50 and 100% of the recommended fertilizer rate. Greenhouse gas fluxes (CO2, CH4, and N2O) were measured using static gas chambers on a monthly basis during the first year, then a bimonthly basis during the second year. Pasture biomass, nutrient uptake, and soil solution chemistry were determined on a regular basis over the 2‐yr period. The biochar induced no or minimal effects on GHG fluxes, pasture biomass, nutrient uptake or soil solution chemistry. In most instances, the significant differences between treatments were due to soil type. Fertilizer significantly increased pasture biomass for the first 8 mo, but thereafter there was no effect. There were also no adverse effects from the biochar. This biochar would be most suitable for enhancing soil C storage, as opposed to improving grassland production.Core Ideas A wood‐based biochar was added to two soil types in a 2‐yr field study. Biochar had minimal effect on soil greenhouse gas emissions. Biochar had no effect on plant biomass or soil leachate nutrient concentration.

Roles of biochar in improving phosphorus availability in soils: A phosphate adsorbent and a source of available phosphorus

In this study, the amounts of phosphorus (P) in nine types of biochar (one natural woody biochar and eight manufactured plant derived biochars) extractable by deionized water, 0.5N NaHCO3 (pH=8.5) and 0.5N H2SO4, respectively, and P adsorption on single biochar or soil/biochar mixtures were examined to investigate the potential effect and role of biochar in improving P availability in soils. Results indicated that biochars were able to bring available P into soils, but the amount and form of available P was dependent on biochar types. The results from P adsorption experiments (in phosphate solutions of 100 and 200mgPL−1, respectively) revealed that not all the biochars showed favourable P retention abilities and the amount of P retained by each biochar varied with the P concentration in the solution used. Among the nine biochars studied, only biochar derived from Mallee (Eucalyptus polybractea) at 720°C with a solid residence time of 20min showed a high P retention ability. Soils amended with Mallee biochar (5% w/w) showed an increase in the P retention ability by 16% after treatment with 200mgPL−1 phosphate solution. 55% of the retained P on Mallee biochar was still available for plant uptake. Results from the kinetic study of P adsorption on Mallee biochar indicated that there were two stages in P adsorption on Mallee biochar, a rapid chemisorption stage followed by a surface-diffusion-controlled stage when the surface adsorption sites were saturated. Scanning electron microscopy coupled with energy dispersive X-ray spectroscopy and attenuated total reflectance-Fourier transform infrared spectroscopy revealed that calcium carbonate was mainly responsible for P chemisorption on Mallee biochar.