Myrtaceous Species Research Articles

Neither lysigenous nor just oil: Demystifying myrtaceous secretory cavities.

Leaf subepidermal secretory cavities are a notable trait in Myrtaceae, but their formation is still controversial because of the lack of consensus on their ontogeny among authors. Knowledge about the compounds present in these cavities has grown over the last few years, demonstrating that terpenoid-rich oils are not their unique content. These two points are the focus of this study on the ontogeny, structure, and contents of secretory cavities in neotropical Myrtaceae. We used histochemical tests and Raman analysis to verify the basic chemical composition of the cavity contents of nine species. We studied the ontogeny of glands in one species, comparing aldehyde-fixed tissues and fresh sections mounted in an inert medium. We observed schizogenous development and appearance of the secretory cavities and found that sample processing may induce cell breakdown, which can be misinterpreted as lysigeny. The content of these cavities contains putative terpenes, resins, carbonyl groups, and flavonoids. Our findings support the hypothesis that the lysigenous appearance of the oil glands is a technical artifact. These tissue distortions must be considered when interpreting the development of this type of secretory structure. Moreover, the basic analyses of chemical constituents show for the first time that the glands of neotropical Myrtaceae are potential reservoirs of some compounds such as flavonoids previously reported as novelties for a few other myrtaceous species. Because some of them are non-lipid compounds, the idea that the glands are just oil repositories is no longer applicable.

In Planta Study Localizes an Effector Candidate from Austropuccinia psidii Strain MF-1 to the Nucleus and Demonstrates In Vitro Cuticular Wax-Dependent Differential Expression.

Austropuccinia psidii is a biotrophic fungus that causes myrtle rust. First described in Brazil, it has since spread to become a globally important pathogen that infects more than 480 myrtaceous species. One of the most important commercial crops affected by A. psidii is eucalypt, a widely grown forestry tree. The A. psidii-Eucalyptus spp. interaction is poorly understood, but pathogenesis is likely driven by pathogen-secreted effector molecules. Here, we identified and characterized a total of 255 virulence effector candidates using a genome assembly of A. psidii strain MF-1, which was recovered from Eucalyptus grandis in Brazil. We show that the expression of seven effector candidate genes is modulated by cell wax from leaves sourced from resistant and susceptible hosts. Two effector candidates with different subcellular localization predictions, and with specific gene expression profiles, were transiently expressed with GFP-fusions in Nicotiana benthamiana leaves. Interestingly, we observed the accumulation of an effector candidate, Ap28303, which was upregulated under cell wax from rust susceptible E. grandis and described as a peptidase inhibitor I9 domain-containing protein in the nucleus. This was in accordance with in silico analyses. Few studies have characterized nuclear effectors. Our findings open new perspectives on the study of A. psidii-Eucalyptus interactions by providing a potential entry point to understand how the pathogen manipulates its hosts in modulating physiology, structure, or function with effector proteins.

Effects of native plants on nitrogen cycling microorganisms in soil

Plants modify the nitrogen (N) cycle in soil through plant N uptake, root exudation, and nitrification inhibition resulting from root exudates and changes to the physicochemical properties of soil. Plants with specific traits can be selected to manage N fluxes in the soil following the land application of N-rich wastes thereby reducing losses of N from these systems into the atmosphere (via nitrous oxide) and waterbodies (via nitrate). Previous work has shown that some New Zealand native myrtaceous species can reduce such losses more than other species, but the underlying mechanisms are unknown. It was hypothesized that lower N losses may result from the inhibition of nitrification and denitrification. We aimed to determine the effect of New Zealand native plant species on the abundance of nitrifying and denitrifying microorganisms in the soil using a pot experiment with five native plant species (Carex secta, Coprosma robusta, Kunzea robusta, Leptospermum scoparium, and Metrosideros umbellata) and exotic pasture (Lolium perenne). Half of the pots received fertilisation with N (urea), phosphorus, potassium, and sulphur, while the remainder were unfertilised controls. We quantified the abundance of bacteria, archaea, and the functional genes encoding nitrite reductase (nirK, nirS), nitrous oxide reductase (nosZ), and bacterial and archaeal ammonia monooxygenase (amoA) in the rhizosphere of these plants. Results indicated that plant species had a significant effect on the abundance of nosZ and bacterial amoA. In fertilised soil, the abundance of bacterial amoA was lower under mono- than dicotyledonous species. Similarly, the chemical properties of the soil differed between these groups. Monocotyledonous species took up more N and had lower concentrations of mineral N in the rhizosphere. This indicates that the increased competition for N likely reduced the abundance of amoA and therefore nitrification and nitrate losses. The results support the utilisation of species selection to reduce N losses. In particular, monocotyledonous species may be planted in high-fertility environments to mitigate N contamination of ground- and surface water. Future work should determine the mechanisms of plant specific interaction with ammonia-oxidising bacteria, although plant uptake can explain some of the observed differences.

Seasonal Variability of a Caryophyllane Chemotype Essential Oil of Eugenia patrisii Vahl Occurring in the Brazilian Amazon.

Eugenia patrisii Vahl is a native and non-endemic myrtaceous species of the Brazilian Amazon. Due to few botanical and phytochemical reports of this species, the objective of the present work was to evaluate the seasonal variability of their leaf essential oils, performed by GC and GC-MS and chemometric analysis. The results indicated that the variation in oil yields (0.7 ± 0.1%) could be correlated with climatic conditions and rainy (R) and dry seasons (D). (E)-caryophyllene (R = 17.1% ± 16.0, D = 20.2% ± 17.7) and caryophyllene oxide (R = 30.1% ± 18.4, D = 14.1% ± 19.3) are the major constituents and did not display significant differences between the two seasons. However, statistically, a potential correlation between the main constituents of E. patrisii essential oil and the climatic parameters is possible. It was observed that the higher temperature and insolation rates and the lower humidity rate, which are characteristics of the dry season, lead to an increase in the (E)-caryophyllene contents, while lower temperature and insolation and higher humidity, which occur in the rainy season, lead to an increase in the caryophyllene oxide content. The knowledge of variations in the E. patrisii essential oil composition could help choose the best plant chemical profile for medicinal purposes.

Austropuccinia psidii, causing myrtle rust, has a gigabase-sized genome shaped by transposable elements.

Austropuccinia psidii, originating in South America, is a globally invasive fungal plant pathogen that causes rust disease on Myrtaceae. Several biotypes are recognized, with the most widely distributed pandemic biotype spreading throughout the Asia-Pacific and Oceania regions over the last decade. Austropuccinia psidii has a broad host range with more than 480 myrtaceous species. Since first detected in Australia in 2010, the pathogen has caused the near extinction of at least three species and negatively affected commercial production of several Myrtaceae. To enable molecular and evolutionary studies into A. psidii pathogenicity, we assembled a highly contiguous genome for the pandemic biotype. With an estimated haploid genome size of just over 1 Gb (gigabases), it is the largest assembled fungal genome to date. The genome has undergone massive expansion via distinct transposable element (TE) bursts. Over 90% of the genome is covered by TEs predominantly belonging to the Gypsy superfamily. These TE bursts have likely been followed by deamination events of methylated cytosines to silence the repetitive elements. This in turn led to the depletion of CpG sites in TEs and a very low overall GC content of 33.8%. Compared to other Pucciniales, the intergenic distances are increased by an order of magnitude indicating a general insertion of TEs between genes. Overall, we show how TEs shaped the genome evolution of A. psidii and provide a greatly needed resource for strategic approaches to combat disease spread.

Resistance of New Zealand Provenance Leptospermum scoparium, Kunzea robusta, Kunzea linearis, and Metrosideros excelsa to Austropuccinia psidii.

Resistance to the pandemic strain of Austropuccinia psidii was identified in New Zealand provenance Leptospermum scoparium, Kunzea robusta, and K. linearis plants. Only 1 Metrosideros excelsa-resistant plant was found (of the 570 tested) and no resistant plants of either Lophomyrtus bullata or L. obcordata were found. Three types of resistance were identified in Leptospermum scoparium. The first two, a putative immune response and a hypersensitive response, are leaf resistance mechanisms found in other myrtaceous species while on the lateral and main stems a putative immune stem resistance was also observed. Both leaf and stem infection were found on K. robusta and K. linearis plants as well as branch tip dieback that developed on almost 50% of the plants. L. scoparium, K. robusta, and K. linearis are the first myrtaceous species where consistent infection of stems has been observed in artificial inoculation trials. This new finding and the first observation of significant branch tip dieback of plants of the two Kunzea spp. resulted in the development of two new myrtle rust disease severity assessment scales. Significant seed family and provenance effects were found in L. scoparium, K. robusta, and K. linearis: some families produced significantly more plants with leaf, stem, and (in Kunzea spp.) branch tip dieback resistance, and provenances provided different percentages of resistant families and plants. The distribution of the disease symptoms on plants from the same seed family, and between plants from different seed families, suggested that the leaf, stem, and branch tip dieback resistances were the result of independent disease resistance mechanisms.

Plant architecture, growth and biomass allocation effects of the invasive pathogen myrtle rust (Austropuccinia psidii) on Australian Myrtaceae species after fire

AbstractIn 2010, the parasitic fungus Austropuccinia psidii (myrtle rust) was detected in Australia. Austropuccinia psidii infects immature growth of myrtaceous species. Many of Australia’s myrtaceous species occur within fire‐prone vegetation communities and have the capacity to resprout after fire. Therefore, it is likely that new post‐fire growth may be vulnerable to A. psidii infection, causing subsequent flow‐on effects to species’ persistence and community dynamics. The aim of this study was to test the impacts of A. psidii on native Australian Myrtaceae species after fire. We grew eight native susceptible species in a glasshouse experiment before burning them and inoculating the resprouting new growth of half the plants with A. psidii. We assessed the effect of A. psidii on the architecture, growth and biomass allocation of our study species. Although general patterns were observed across species, results were found to be species‐specific. Austropuccinia psidii significantly reduced the height of two of the eight species (Callistemon citrinus and Eucalyptus moluccana), but none of the species had increased branching. As expected, specific leaf area was lower (9%) in inoculated plants – although only significant for C. citrinus and E. dalrympleana – and leaf biomass was greater (15%), but significant for Angophora costata only. Finally, biomass allocation did not significantly differ between infection treatments. We can conclude that the effect of A. psidii infection on fire‐damaged plants has significant impacts on plants at the species level, which may have flow‐on effects at the community level, especially after repeated infections. Furthermore, these impacts may be exacerbated in the future under climate change, as the predicted increase in frequency and intensity of fires across Australia will result in more frequent new growth availability, providing more opportunities for A. psidii infection.

Two Myrtaceous species additions to the Flora of Tamil Nadu

Eugenia argentea Bedd. and E. shettyana Murugan & Gopalan are reported here as additions to the Flora of Tamil Nadu. Detailed description and photographic images of herbarium specimens are provided.

Lessons from the Incursion of Myrtle Rust in Australia.

Austropuccinia psidii (myrtle rust) is a globally invasive neotropical rust of the Myrtaceae that came into international prominence following extensive damage to exotic Eucalyptus plantations in Brazil in the 1970s and 1980s. In 2005, myrtle rust established in Hawaii (USA), and over the past 12 years has spread from the Americas into Asia, the Pacific, and South Africa. Myrtle rust was detected in Australia in 2010, and the response and ultimately unsuccessful eradication attempt was a lesson to those concerned about the threat of exotic pests and diseases to Australia's environment. Seven years following establishment, we are already observing the decline of many myrtaceous species and severe impacts to native plant communities. However, the recently developed Myrtle rust in Australia draft action plan identified that there is no nationally coordinated response strategy for the environmental dimensions of this threat. Recent reviews have identified a greater need for involvement from environmental agencies in biosecurity preparedness, response, and resourcing, and we believe this approach needs to extend to the management of invasive environmental pathogens once they establish.

Genetic diversity of the myrtle rust pathogen (Austropuccinia psidii) in the Americas and Hawaii: Global implications for invasive threat assessments

SummarySince the myrtle rust pathogen (Austropuccinia psidii) was first reported (as Puccinia psidii) in Brazil on guava (Psidium guajava) in 1884, it has been found infecting diverse myrtaceous species. Because A. psidii has recently spread rapidly worldwide with an extensive host range, genetic and genotypic diversities were evaluated within and among A. psidii populations in its putative native range and other areas of myrtle rust emergence in the Americas and Hawaii. Microsatellite markers revealed several unique multilocus genotypes (MLGs), which grouped isolates into nine distinct genetic clusters [C1–C9 comprising C1: from diverse hosts from Costa Rica, Jamaica, Mexico, Puerto Rico, and USA‐Hawaii, and USA‐California; C2: from eucalypts (Eucalyptus spp.) in Brazil/Uruguay and rose apple (Syzygium jambos) in Brazil; C3: from eucalypts in Brazil; C4: from diverse hosts in USA‐Florida; C5: from Java plum (Syzygium cumini) in Brazil; C6: from guava and Brazilian guava (Psidium guineense) in Brazil; C7: from pitanga (Eugenia uniflora) in Brazil; C8: from allspice (Pimenta dioica) in Jamaica and sweet flower (Myrrhinium atropurpureum) in Uruguay; C9: from jabuticaba (Myrciaria cauliflora) in Brazil]. The C1 cluster, which included a single MLG infecting diverse host in many geographic regions, and the closely related C4 cluster are considered as a “Pandemic biotype,” associated with myrtle rust emergence in Central America, the Caribbean, USA‐Florida, USA‐Hawaii, Australia, China‐Hainan, New Caledonia, Indonesia and Colombia. Based on 19 bioclimatic variables and documented occurrences of A. psidii contrasted with reduced sets of specific genetic clusters (subnetworks, considered as biotypes), maximum entropy bioclimatic modelling was used to predict geographic locations with suitable climate for A. psidii which are at risk from invasion. The genetic diversity of A. psidii throughout the Americas and Hawaii demonstrates the importance of recognizing biotypes when assessing the invasive threats posed by A. psidii around the globe.

A Note on the Distribution of Syzygium neesianum Arn. (Myrtaceae) from India

Syzygium neesianum Arn., a Myrtaceous tree species is reported for the first time for Karnataka from South Canara and Coorg district. A brief description along with photo image of the herbarium specimenis provided herewith for further study.

Parasitoids follow herbivorous insects to a novel host plant, generalist predators less so

AbstractThe ‘enemy‐free space’ hypothesis predicts that herbivorous insects can escape their natural enemies by switching to a novel host plant, with consequences for the evolution of host plant specialisation. However, if natural enemies follow herbivores to their novel host plants, enemy‐free space may only be temporary. We tested this by studying the colonisation of the introduced tree Eucalyptus grandis (Hill) Maiden (Myrtaceae) by insects in Brazil, where various species of herbivores have added eucalyptus to their host plant range, which consists of native myrtaceous species such as guava. Some herbivores, for example, Thyrinteina leucoceraea Ringe (Lepidoptera: Geometridae), cause outbreaks in eucalyptus plantations but not on guava, possibly because eucalyptus offers enemy‐free space. We sampled herbivores (mainly Lepidoptera species) and natural enemies on eucalyptus and guava and assessed parasitism of Lepidoptera larvae on both host plant species during ca. 2 years. Overall, predators were encountered more frequently on guava than on eucalyptus. In contrast, parasitoids were encountered equally and parasitism rates of Lepidoptera larvae were similar on both host plants. This indicates that herbivores may escape some enemies by moving to a novel host plant. However, this escape may be temporary and may vary with time. We argue that studying temporal and spatial patterns of enemy‐free space and the response of natural enemies to host use changes of their herbivorous prey is essential for understanding the role of natural enemies in the evolution of host plant use by herbivorous arthropods.

Successional changes in feeding activity by threatened cockatoos in revegetated mine sites

Context Provision of key habitat resources is essential for effectively managing species that have specific ecological requirements and occur in production landscapes. Threatened black cockatoos in the jarrah (Eucalyptus marginata) forest of Western Australia have a wide range, so their conservation requires support from all land tenures, not just reserves. Mining in the jarrah forest temporarily removes cockatoo feeding habitat, so it is important to understand how cockatoos exploit revegetated areas for food resources. Aims We aimed to determine whether there were successional patterns in cockatoo feeding activity in revegetation aged from 4 to 23 years at three mine sites in the jarrah forest in south-western Australia. Methods We surveyed 232 plots in revegetation to document (1) structural and floristic variation in vegetation across mine sites and revegetation ages, (2) differences in cockatoo feeding activity across mine sites and revegetation ages on the basis of feeding residues and (3) any edge effect reflecting preferential use of vegetation at the interior or exterior of mine pits. We also documented the frequency of occurrence of cockatoo food plants and feeding residues in 480 plots in unmined forest to compare with revegetated areas. Key results Marri (Corymbia calophylla) and jarrah were commonly consumed in unmined forest and Banksia and Hakea species were also fed on to a lesser extent. Revegetated mine pits provided food within 4 years and continued to do so up until the oldest plots studied (23 years). The relative importance of food plants shifted from proteaceous species in young revegetation to myrtaceous species in intermediate to older revegetation. However, extent of feeding on myrtaceous species in older revegetation did not equate to feeding rates in unmined forest, with lower frequencies recorded in revegetation. Conclusions Black cockatoos fed in revegetation at all three mine sites, despite variations in vegetation age, structure and floristics. Feeding on proteaceous and myrtaceous food plants occurred within 4 and 7 years of revegetation being established, respectively, indicating that some food resources are restored quickly after mining disturbance of the jarrah forest. Implications Our results emphasise the importance of monitoring fauna recolonisation over appropriate time scales, to understand how successional processes in revegetation influence fauna population persistence in production landscapes.

The potential in-situ antimicrobial ability of Myrtaceae plant species on pathogens in soil

Concerns that land application of organic waste may introduce microbial contaminants into the environment could be mitigated by growing plants with antiseptic properties in waste-amended soil. We investigated the potential for two myrtaceous plants, manuka (Leptospermum scoparium) and kanuka (Kunzea robusta) with antiseptic properties to reduce numbers of the pathogen indicator Escherichia coli in soil. Pots containing perennial ryegrass (Lolium perenne), manuka and kanuka, were spiked with Escherichia coli and a rainfall event was simulated. Decimal reduction times (DRT) showed E. coli numbers were reduced under kanuka and manuka compared to a pasture control (8, 5 and 93 days respectively). Potentially, these myrtaceous species could mitigate the threat of microbial contamination of soil, while producing valuable biomass for fuel, essential oils or honey.

A Contemporary Introduction to Essential Oils: Chemistry, Bioactivity and Prospects for Australian Agriculture

This review is a comprehensive introduction to pertinent aspects of the extraction methodology, chemistry, analysis and pharmacology of essential oils, whilst providing a background of general organic chemistry concepts to readers from non-chemistry oriented backgrounds. Furthermore, it describes the historical aspects of essential oil research whilst exploring contentious issues of terminology. This follows with an examination of essential oil producing plants in the Australian context with particular attention to Aboriginal custom use, historical successes and contemporary commercial prospects. Due to the harsh dry environment of the Australian landmass, particularly to the cyclical climatic variation attendant upon repeated glaciation/post-glaciation cycles, the arid regions have evolved a rich assortment of unique endemic essential oil yielding plants. Though some of these aromatic plants (particularly myrtaceous species) have given birth to commercially valuable industries, much remains to be discovered. Given the market potential, it is likely that recent discoveries in our laboratory and elsewhere will lead to new product development. This review concludes with an emphasis on the use of chemotaxonomy in selection of commercially viable cultivar chemotypes from the Australian continent. Finally, drawing largely from our own results we propose a list of Australian endemic species with novel commercial potential.

First Report of Rust Caused by Puccinia psidii on Eucalyptus dunnii in Uruguay.

Eucalypt rust caused by Puccinia psidii Winter represents a major disease affecting eucalypt production in South America, and is threatening myrtaceous hosts worldwide. In Uruguay, it was first detected infecting Eucalyptus globulus in 2001 (4) and later on E. grandis, Myrrhinium atropurpureum, and Myrcianthes pungens, two myrtaceae hosts native to Uruguay (3). Over the summer 2013, bright orange-yellowish pustules were detected on stock plants of E. dunnii in a nursery located in western Uruguay, province of Paysandú. A severe and explosive epidemic was readily observed. Affected leaves were taken to the laboratory and examined under the microscope. Uredinia and urediniospores were similar with those described previously in Uruguay on other hosts (3,4). Uredioniospores were 18 to 25 × 15 to 21 μm, yellow, unicellular, spherical to elliptical, base truncate, finely and uniformly echinulate with spines up to 1 μm long, with an evident bald patch without spines. To confirm identity of this fungus, genomic DNA was extracted from single-pustule urediniospores, and ITS region was amplified using primers PR1 and PR2 (1) with PCR conditions previously described (3). Forward and reverse sequences from three single pustules were obtained, assembled, and compared with those available in GenBank using BLAST searches. Obtained sequences showed to be identical to those analyzed by Pérez et al. (2011) collected from E. grandis and E. globulus, with no variation found in the analyzed region. A 100% identity was found with isolates UY1374 and UY1375 obtained from E. globulus, and with isolate UY1731 obtained from E. grandis (FJ710805, FJ710806, and FJ710807, respectively). Sequences were deposited in GenBank with accession numbers KM083129, KM083130, and KM083131. Even though this pathogen is known to occur in a wide variety of myrtaceous species, to our knowledge, this is the first natural infection record of P. psidii on E. dunnii in Uruguay and worldwide. This report confirms previous studies that indicated the susceptibility of E. dunnii when inoculated under controlled conditions (2,5). E. dunnii is being widely planted in Uruguay, eastern Argentina, and southern Brazil, with increasing significance to the pulp industry. Although the consequences of this finding have yet to be realized, scouting plantations is essential to estimate the real impact of this pathogen on this tree species. Our study contributes to expand the host range known for this globally important pathogen.

Essential oil composition and antimicrobial interactions of understudied tea tree species

The essential oil composition of three Myrtaceous species (Leptospermum petersonii, Leptospermum scoparium and Kunzea ericoides) belonging to the tea tree group were analysed using gas chromatography coupled to mass spectrometry (GC–MS). The major compounds determined from the mean±SD of the monthly samples collected for one calendar year in L. petersonii are citronellal (11.4±4.3%), citronellol (17.5±7.1%), neral (19.7±1.6%) and geranial (34.7±3.3%). The major compounds in L. scoparium are eudesma-4(14)-11-diene (11.6±2.4%), α-selinene (10.4±2.3%) and (E)-methyl cinnamate (12.6±3.8%). The major compounds in K. ericoides are α-pinene (37.6±6.3%) and p-cymene (13.5±4.1%). The essential oils show some promising antimicrobial activity against selected micro-organisms when investigated using the minimum inhibitory concentration assay. Highest sensitivities were noted for the Brevibacteria (lowest MIC value of 0.06mg/ml), a genus associated with foot odour. When the different essential oils were combined in various ratios and tested against Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans, a predominantly additive effect was noted.

First Report of Puccinia psidii Caused Rust Disease Epiphytotic on the Invasive Shrub Rhodomyrtus tomentosa in Florida.

Rhodomyrtus tomentosa (Aiton) Hassk. (downy-rose myrtle, family: Myrtaceae), of South Asian origin, is an invasive shrub that has formed monotypic stands in Florida (3). During the winter and spring of 2010 through 2012, a rust disease of epiphytotic proportion was observed on young foliage, stem terminals, and immature fruits of this shrub in natural areas of Martin and Lee counties, Florida. Expanding leaves and succulent stems developed chlorotic flecks on the surface that developed into pustules and ruptured to discharge urediniospores. Symptomatic leaves and stems developed severe necrotic spots and resulted in tissue distortion, defoliation, and stem dieback. Based on symptoms and urediniospore morphology and dimensions (17.7 to 26.1 [22.1 ± 0.3] × 14.7 to 21.1 [17.7 ± 0.2] μm; n = 51) (4), the causal agent was identified as Puccinia psidii Winter; teliospores were not observed in samples since it does not produce these spore stages below 20°C ambient temperature (1). This identification was confirmed by a GenBank BLAST of internal transcribed spacer (ITS) sequences (Accession Nos. KC607876 and KC607877) that showed 99% identity with 42 sequences of P. psidii from diverse host species and locations. P. psidii is believed to be of neotropical origin and has a host range of 129 species in 33 genera within Myrtaceae (2). However, P. psidii caused disease of downy-rose myrtle has not been previously reported in Florida, even though severe infections occurred on another invasive tree, Melaleuca quinquenervia (Cav.) S.F. Blake (3), growing in adjacent areas. In December 2011, urediniospores were collected from downy-rose myrtle, established in aqueous suspension (45,000 spores/ml), and spray inoculated on potted downy-rose myrtle plants (n = 3), which were maintained in 100% ambient humidity, at 20°C, with a 12-h light cycle for 72 h. Plants mock-inoculated with water served as the negative control. Disease symptoms, including chlorotic flecks and raised surfaces, appeared on leaf lamina in 3 to 6 days on P. psidii-inoculated plants, while control plants remained symptomless. Raised surfaces developed into distinct pustules and eventually erupted to discharge urediniospores within 6 to 12 days of inoculation. Tests were repeated once during March and April of 2012 with the same results. The latent and incubation periods reported herein are within the previously reported range for P. psidii (2,4). To our knowledge, this is the first confirmed report of P. psidii epiphytotic on downy-rose myrtle populations in Florida. The recent occurrence of P. psidii epiphytotic on downy-rose myrtle raises critical questions as to why this myrtle rust disease is so severe and widespread on this host after decades of presumed exposure to P. psidii in Florida. Because this rust pathogen has emerged as a major invasive threat to many myrtaceous species around the world, further genotyping and cross-inoculation studies are needed to determine the host specificity and potential origin of the P. psidii isolates derived from downy-rose myrtle (2).

Strategies of a small nectarivorous marsupial, the western pygmy-possum, in response to seasonal variation in food availability

The foraging behavior of the western pygmy-possum (Cercartetus concinnus) was investigated at Innes National Park (INP), South Australia, in the context of understanding survival strategies in a variable environment. Individual C. concinnus were radiotracked continuously for periods of up to 9 days over a 1-year period. Movements, timing of activity, and use of food trees were recorded, as well as information on availability of floral resources. Nectar feeding was the most common feeding behavior when the nectar of Eucalyptus spp. was available. Eucalyptus rugosa was the preferred food source; other myrtaceous species were used when flowers of E. rugosa were unavailable and possums switched to sap and lerp when nectar was scarce. Movement patterns of C. concinnus varied seasonally and among individual animals. C. concinnus was capable of traveling long distances of up to 4.7 km in a single night in search of resources. Areas of use tended to be larger when E. rugosa was flowering (up to 300 ha), but possums also undertook long-distance travel to reach resources when nectar was rare. These long-distance movements suggest that the home ranges of C. concinnus can be several hundred hectares in size. C. concinnus at INP rely on long-distance movements, diet-switching, floristically and structurally diverse habitats, and torpor to cope with temporal and spatial fluctuations in resource availability.

Syzygium Megacarpum (Craib) Rathakr. & N.C. Nair (Myrtaceae) –A New Record for Andaman – Nicobar Islands

Syzygium megacarpum (Craib) Rathakr. & N.C. Nair, a wild myrtaceous tree species, is described along with photographs as a new distributional record for Andaman-Nicobar Islands.