Puccinia psidii infecting cultivated Eucalyptus and native myrtaceae in Uruguay

Eucalyptus or guava rust caused by Puccinia psidii is a serious disease of Eucalyptus and other Myrtaceae. In Uruguay, it has been previously found on Eucalyptus globulus and Psidium brasiliensis. Almost nothing is known regarding the occurrence of this pathogen on other Eucalyptus species or native Myrtaceae in that country. In this study, we determined the presence of P. psidii on Eucalyptus species and native Myrtaceae trees in Uruguay and evaluated the pathogenicity of specimens from native myrtaceous hosts on E. globulus and E. grandis. Phylogenetic analyses based on the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA operon were used to confirm pathogen identity. Comparisons of ITS sequences confirmed the identity of P. psidii on Eucalyptus globulus, E. grandis, Myrcianthes pungens, and Myrrhinium atropurpureum var. octandrum. This is the first report of P. psidii on M. atropurpureum var. octandrum. Pathogenicity tests showed that isolates from native Myrtaceae could infect both Eucalyptus species tested, indicating a strong biological relationship between both introduced and native Myrtaceae. This study supplies relevant field data, morphological information, molecular phylogenetic analyses and infection studies that contribute to a better understanding of an important and little studied pathogen.     

Histological Comparisons of Fergusobia/Fergusonina-Induced Galls on Different Myrtaceous Hosts

The putative mutualism between different host-specific Fergusobia nematodes and Fergusonina flies is manifested in a variety of gall types involving shoot or inflorescence buds, individual flower buds, stems, or young leaves in the plant family Myrtaceae. Different types of galls in the early-to-middle stages of development, with host-specific species of Fergusobia/Fergusonina, were collected from Australian members of the subfamily Leptospermoideae (six species of Eucalyptus, two species of Corymbia, and seven species of broad-leaved Melaleuca). Galls were sectioned and histologically examined to assess morphological changes induced by nematode/fly mutualism. The different gall forms were characterized into four broad categories: (i) individual flower bud, (ii) terminal and axial bud, (iii) ''basal rosette'' stem, and (iv) flat leaf. Gall morphology in all four types appeared to result from species-specific selection of the oviposition site and timing and number of eggs deposited in a particular plant host. In all cases, early parasitism by Fergusobia/Fergusonina involved several layers of uninucleate, hypertrophied cells lining the lumen of each locule (gall chamber where each fly larva and accompanying nematodes develop). Hypertrophied cells in galls were larger than normal epidermal cells, and each had an enlarged nucleus, nucleolus, and granular cytoplasm that resembled shoot bud gall cells induced by nematodes in the Anguinidae.     

Chemical detoxification vs mechanical removal of host plant toxins in Eucalyptus feeding sawfly larvae (Hymenoptera: Pergidae)

The essential oils that characterize the eucalypts and related Myrtaceae pose a challenge for herbivores. Phytophagous insects that feed on oil-rich Myrtaceae have developed specific mechanisms to deal with these oils, some of which are notoriously toxic (e.g. 1,8-cineole). Some of the eight Australian subfamilies in the sawfly family Pergidae are associated exclusively with Eucalyptus and Melaleuca species that often have high concentrations of essential oils. Unexpectedly, the Perginae and Pterygophorinae use different mechanisms to deal with the same toxic components in their respective host plants. Larvae of the Perginae have the inner surface of their mandibles equipped with soft brush-like structures that are unique among phytophagous insects in general. The proposed role of these ancillary mandibular structures in separating leaf oils from nutritive plant matter could be confirmed in experiments with larvae of two pergine species. The oil sequestration is, however, incomplete and chemical gut content analyses by gas-chromatography (GC) revealed that 1,8-cineole does enter the midgut and is metabolised to hydroxycineole. Although the related Pterygophorinae also feed mainly on oil-rich Myrtaceae, they do not sequester the oil and lack morphological structures on their mandibles. Chemical analysis of the gut content of two pterygophorine species showed that they rely solely on chemical detoxification of the relevant plant compounds, with GC demonstrating that the 1,8-cineole is removed far more rapidly and completely than in the pergine species.     

Leaf wax constituents of some myrtaceous species

Eucalyptin and 8-desmethyleucalyptin have been isolated from the leaf wax coatings of several species of Eucalyptus, from Syncarpia glomulifera, Lophostemon confertus and an Angophora hybrid indicating that C-methylated flavones may be fairly distinctive of the family Myrtaceae. Ursolic acid has been isolated from the leaf waxes of E. youmanii, S. glomulifera, Leptospermum petersonii and Melaleuca quinquenervia, friedelin from Lophostemon confertus and 4,6-dimethoxy-2-hydroxyacetophenone from E. michaeliana.     

Diversity and distribution of co-infecting Botryosphaeriaceae from Eucalyptus grandis and Syzygium cordatum in South Africa

Species in the fungal family Botryosphaeriaceae are latent pathogens on woody trees. These fungi often have a wide host range, which can include native and introduced hosts in an area. Multi-locus DNA sequence identification on a recent collection of Botryosphaeriaceae from Eucalyptus grandis and Syzygium cordatum trees in South Africa revealed cross-infectivity of several species, novel host associations and new country reports. Neofusicoccum eucalyptorum, Neofusicoccum kwambonambiense, Neofusicoccum parvum, Neofusicoccum australe and Lasiodiplodia pseudotheobromae were identified from both tree species, with L. pseudotheobromae and N. eucalyptorum isolated for the first time from S. cordatum, similar to N. kwambonambiense from Eucalyptus. This also represents the first report of L. pseudotheobromae from South Africa. Botryosphaeriaceae species on Eucalyptus species and S. cordatum are fairly well known from South Africa. However, this study revealed new associations, indicating that conclusions should not be generalized and that more intensive sampling from different areas and over time is likely to reveal distinct species and host association patterns.     

Foliar Essential Oil Glands of Eucalyptus Subgenus Eucalyptus (Myrtaceae) Are a Rich Source of Flavonoids and Related Non-Volatile Constituents

The sub-dermal secretory cavities (glands) embedded within the leaves of Eucalyptus (Myrtaceae) were once thought to be the exclusive repositories of monoterpene and sesquiterpene oils. Recent research has debunked this theory and shown that abundant non-volatile compounds also occur within foliar glands. In particular, glands of four species in subgenus Eucalyptus contain the biologically active flavanone pinocembrin. Pinocembrin shows great promise as a pharmaceutical and is predominantly plant-sourced, so Eucalyptus could be a potential commercial source of such compounds. To explore this we quantified and assessed the purity of pinocembrin in glands of 11 species of E. subg. Eucalyptus using Electro-Spray Ionisation Liquid Chromatography Mass Spectrometry of acetonitrile extracts and Gas Chromatography Mass Spectrometry analyses of hexane extracts of isolated glands which were free from other leaf tissues. Our results showed that the glands of subgenus Eucalyptus contain numerous flavanones that are structurally related to pinocembrin and often present in much greater abundance. The maximum concentration of pinocembrin was 2 mg g^-1 dry leaf found in E. stellulata, whereas that of dimethylpinocembrin (5,7-dimethoxyflavanone) was 10 mg g^-1 in E. oreades and that of pinostrobin (5-hydroxy-7-methoxyflavanone) was 12 mg g^-1 in E. nitida. We also found that the flavanones are exclusively located within the foliar glands rather than distributed throughout leaf tissues. The flavanones differ from the non-methylated pinocembrin in the degree and positions of methylation. This finding is particularly important given the attractiveness of methylated flavonoids as pharmaceuticals and therapeutics. Another important finding was that glands of some members of the subgenus also contain flavanone O-glucosides and flavanone-β-triketone conjugates. In addition, glands contain free β-triketones, β-triketone heterodimers and chromone C-glucosides. Therefore, the foliar glands of this taxonomically distinct group of plants are a rich source of a range of flavonoids and other biologically active compounds with great commercial potential.     

Strange Little Flies in the Big City: Exotic Flower-Breeding Drosophilidae (Diptera) in Urban Los Angeles

Urban landscapes are commonly considered too mundane and corrupted to be biotically interesting. Recent insect surveys employing 29 Malaise traps throughout Los Angeles, California, however, have uncovered breeding populations of two unexpected species of one of the most studied and familiar groups of organisms, Drosophila “fruit” flies. Unlike most introduced species of drosophilids, which breed in fresh or decaying fruits, these are specialized flower-breeders. A common species in the survey was Drosophila (Drosophila) gentica Wheeler and Takada, previously collected only once, in El Salvador. It belongs to the flavopilosa species group, all species of which have been known until now from central Chile, Argentina and Uruguay, to Veracruz, Mexico and the Caribbean, breeding in flowers of Cestrum (“jessamine”) and Sessea (Solanaceae). The Los Angeles populations are probably breeding in a native and/or introduced Cestrum; in addition, populations in San Luis Obispo County were visiting ornamental Cestrum. Drosophila gentica occurs as far north as San Francisco, where it was found breeding in Cestrum aurantiacum. D. gentica is redescribed and figured in detail for diagnostic and identification purposes. Specimens from Jamaica previously identified as D. gentica are a distinct species but are not formally described in lieu of complete male specimens. Rare in the Malaise traps was Drosophila (Sophophora) flavohirta Malloch, a common species in Australia on the blossoms of native Myrtaceae, found on introduced Eucalyptus in South Africa and both Eucalyptus and Syzygium in Madagascar; adults feed on myrtaceous pollen and nectar, larvae breed in the flowers. It is also redescribed in detail, including its unusual egg. This is the first New World report of this species; DNA sequences confirm it is a morphologically highly aberrant member of the D. melanogaster species group. This study reveals how intensive field sampling can uncover remarkable biodiversity in even the most urbanized areas.     

混交比例对桉树-乡土树种混交林优势树种叶片资源获取性状的影响

桉树-乡土树种混交林在提高林分生产力和生态系统功能等方面具有较大潜力。该研究以南亚热带4种桉树-乡土树种混交林(桉树与乡土树种混交比例分别为5:5、6:4、7:3、8:2)和桉树纯林为研究对象,研究了3种优势乡土树种华润楠(Machilus chinensis)、阴香(Cinnamomum burmannii)、灰木莲(Manglietia glauca)和速生树种尾叶桉(Eucalyptus urophylla)的叶片生理、结构和化学性状在不同比例混交林中的差异。结果表明,4优势造林树种的叶片性状存在明显的种间差异,其中灰木莲的比叶面积(SLA)、光合磷利用效率(PPUE)、单位质量叶片最大光合速率(A_mass)和蒸腾速率(T_mass)以及叶片养分含量最高,说明灰木莲采取资源获取型的生态策略;尾叶桉的SLA、A_mass、T_mass及叶片养分含量最低,但具有最高的PPUE,说明尾叶桉兼顾了资源获取型和保守型的物种特征。灰木莲与尾叶桉在SLA、A_mass、T_mass     

Plant host relationships of three lineages of the gall-inducing fly <Emphasis Type="Italic">Fergusonina</Emphasis> Malloch (Diptera: Fergusoninidae) on <Emphasis Type="Italic">Eucalyptus</Emphasis> L’Hérit.

The gall-inducing fly family Fergusoninidae, in association with a mutualist nematode, induces galls on Myrtaceae. Each fly species typically targets a particular site on its host plant, giving rise to a range of gall types, and one plant species may host at least four fly species. While incongruent fly–host evolutionary time scales preclude early cospeciation, it is possible that Fergusoninidae have been diverging with their host plants more recently at correspondingly finer taxonomic levels, such as within host subgenera. To test this possibility, we reduced the scale of our analysis and focussed on a clade of ten Eucalyptus species, sampling intensively and using a phylogenetic approach to compare the relationships between these plant hosts and their associated flies. We also took advantage of the fact that three different gall types, each with its own clade of Fergusonina flies, could be sampled on this focal host clade, in effect giving us three different host/fly association tests on the one set of hosts. The phylogenies of flies from the three different gall types were estimated using Bayesian analysis of mtCOI sequences and compared with an existing phylogeny of the eucalypt host clade. While each gall type showed a different pattern of host relationships, heuristic and quantitative analyses showed that there was little correspondence between plant and fly phylogenies and we conclude that host switching is prevalent in this system. There was more host fidelity in the flower bud gallers on this group of eucalypts, and there was least in the leaf blade gallers, with the shoot bud gallers demonstrating an intermediate level of host fidelity. We discuss the possible factors which may have led to their patterns of host association. This is the first study of Fergusonina to focus on one clade of Eucalyptus L’Hérit. (Myrtaceae) with intensive sampling and shows that each host plant species is commonly used by multiple fergusoninid species. This has provided us with the opportunity to study in detail the host relationships of three separate clades of Fergusonina from different plant tissue types, and has revealed many previously unrecorded host plant/gall site associations.     

Maintenance of a narrow host range by Oxyops vitiosa; a biological control agent of Melaleuca quinquenervia

Host range expansion in insect herbivores is often thought to be mediated by several factors, principal among them are secondary plant metabolites. In weed biological control, the host range of a prospective agent is one of the most important considerations in its implementation. Extensive host testing tests seek to determine the behavioral acceptance and nutritional value of different test plant species to the potential agent. A list of test plants is compiled that comprises species that are close taxonomic relatives of the target weed plus other species of economic or ecologic importance. The host testing of the Melaleuca quinquenervia biological control agent Oxyops vitiosa indicated that larvae would accept and complete development on the Australian target weed M. quinquenervia, two Australian ornamental species, Callistemon citrina, Callistemon viminalis (all Myrtaceae). However, the larvae did not complete development when fed a North American species Myrica cerifera (Myricaceae). The study reported here confirms these results and examines the nutritional and performance differences in O. vitiosa larvae fed leaves of these species. The leaf quality factors, percent moisture, percent nitrogen, toughness, and terpenoid content were related to larval survival, performance and digestive indices. The results indicate that plant quality among the Myrtaceae species was generally similar and correspondingly larval survival, performance and digestive indices differed little when larvae were fed leaves of these species. However, significant differences occurred in the plant quality of the North American M. cerifera compared with the Australian species which had leaves with the lowest percent moisture, lowest leaf toughness, highest percent nitrogen. This species, however, is not a physiological host as none of the neonates survived to pupate. When third instars were switched to M. cerifera from their normal host M. quinquenervia reductions were found in survival, biomass gain, digestive efficiency, and conversion of digested food to insect biomass. The marginal acceptance of this North American native plant in laboratory bioassays appears related to the terpenoid chemistry that has similarities to the taxonomically unrelated host M. quinquenervia. However, the high larval mortality corresponds to several novel terpenoids that are not present in the host. For weed biological control host testing these results indicate that M. cerifera is a poor host for O. vitiosa. Additionally, future test plant lists should include plants with secondary metabolites similar to the target weed as these compounds may constitute behavioral cues that are relevant to these specialized herbivores.     

Diversimorbus metrosiderotis gen. et sp. nov. and three new species of Holocryphia (Cryphonectriaceae) associated with cankers on native Metrosideros angustifolia trees in South Africa

The Cryphonectriaceae includes important tree pathogens, especially on the Myrtales. During a routine disease survey in the Western Cape Province of South Africa, a fungus resembling the Eucalyptus pathogen Holocryphia eucalypti was observed on native Metrosideros angustifolia (Myrtales). The aims of this study were to identify the fungus and to expand surveys for fungi in the Cryphonectriaceae on M. angustifolia. Fungi were identified based on DNA sequence comparisons and morphological features, and their pathogenicity was tested on M. angustifolia under field conditions. Based on morphology and multigene phylogenetic analyses of DNA sequence data from six gene regions, we describe a new genus including a single species and three new species of Holocryphia (Cryphonectriaceae) from M. angustifolia. These fungi are provided with the names Diversimorbus metrosiderotis gen. et sp. nov., Holocryphia capensis sp. nov., Holocryphia gleniana sp. nov., and Holocryphia mzansi sp. nov. We also revise H. eucalypti, the type of the genus, to include only isolates from Eucalyptus in South Africa. Research results indicated that H. mzansi may undergo host shifts between different tree genera in the Myrtaceae. Inoculation tests showed that isolates of all the newly described species can cause lesions on the branches of M. angustifolia, indicating that they are all pathogens of this tree.     

Multiple introductions from multiple sources: invasion patterns for an important Eucalyptus leaf pathogen

Many population studies on invasive plant pathogens are undertaken without knowing the center of origin of the pathogen. Most leaf pathogens of Eucalyptus originate in Australia and consequently with indigenous populations available, and it is possible to study the pathways of invasion. Teratosphaeria suttonii is a commonly occurring leaf pathogen of Eucalyptus species, naturally distributed in tropical and subtropical regions of eastern Australia where it is regarded as a minor pathogen infecting older leaves; however, repeated infections, especially in exotic plantations, can result in severe defoliation and tree deaths. Nine polymorphic microsatellite markers were used to assess the genetic structure of 11 populations of T. suttonii of which four where from within its native range in eastern Australia and the remaining seven from exotic Eucalyptus plantations. Indigenous populations exhibited high allele and haplotype diversity, predominantly clonal reproduction, high population differentiation, and low gene flow. The diversity of the invasive populations varied widely, but in general, the younger the plantation industry in a country or region, the lower the diversity of T. suttonii. Historical gene flow was from Australia, and while self‐recruitment was dominant in all populations, there was evidence for contemporary gene flow, with South Africa being the most common source and Uruguay the most common sink population. This points distinctly to human activities underlying long‐distance spread of this pathogen, and it highlights lessons to be learned regarding quarantine.     

Biological control reduces herbivore’s host range

The enemy release hypothesis predicts that alien populations are more vigorous and grow faster in introduced areas than within their natural range due to lack of natural enemies. An extension of this theory would be that the lack of natural enemies on an herbivore species will indirectly increase the number of host plant species that it can infest. The eucalyptus gall wasp Ophelimus maskelli is a recent introduction to the Mediterranean basin. Its arrival was followed after about two years by its parasitoid, Closterocerus chamaeleon. We evaluated the range of hosts used by the gall wasp by surveying 50 Eucalyptus species, 37 Eucalyptus hybrids and 18 E. globulus half-sibling families, before and after the establishment of the parasitoid. We found a consistent reduction in the observed host range of the gall wasp after the establishment of the parasitoid with a reduction of 83% on Eucalyptus species, 84% on hybrids, and 94% on E. globulus half-siblings. Host range narrowed down from 18 to three closely-related host species, all in the section Exsertaria, series Exsertae, E. camaldulensis, E. tereticornis and E. rudis, which are probably the standard hosts of O. maskelli. In the remaining affected species the intensity of attack decreased significantly in all studied regions. These findings show that, besides the direct gains from classical biological control, there may be indirect benefits through a natural-enemy-induced reduction in the range of host plants used by herbivorous insect pests.     

Ellagitannins of the casuarinaceae,stachyuraceae and myrtaceae

Eight ellagitannins and related polyphenols, found in Casuarina stricta and Stachyurus praecox, were detected in the leaf of Psidium species. Five of them and a new polyphenol, named isostrictinin, were isolated from Psidium guajava. Most of these compounds were detected in several species of Myrtaceae, and 2, 3-hexahydroxydiphenoylglucose and 4, 6-hexahydroxydiphenoylglucose were found in some.     

The potential of small Eucalyptus plantations in farmscapes to foster native woody plant diversity: local and landscape constraints

The major focus of ecological restorations has been on understanding local factors. However, landscape factors such as dispersal limitation of individuals or propagules across the surrounding matrix can also constrain the restoration progress. We investigated to what extent native woody species colonize and thrive in plantations, focusing on both the role of local factors such as grazing and canopy cover as well as on landscape factors. We recorded all native tree and shrub species in 60 small Eucalyptus plantations embedded in an open agricultural landscape at 0.1–12 km from a remnant continuous forest in central Ethiopia. We found a total of 1,571 individuals of native woody plants belonging to 55 species. Number of such species in a plantation increased significantly with the height of the grass sword indicating their sensitivity to grazing. Moreover, the number of woody species in the patches decreased significantly with distance to the forest. Our results illustrate the need for regulating the grazing pressure for a successful regeneration of native species in Eucalyptus plantations. In addition, sowing or planting native trees will be necessary in most plantations, as only few remnant natural forests that could act as seed sources occur across the Ethiopian highlands. Another main obstacle might be the prohibition of selling timber of native trees, which indirectly discourage farmers from letting native trees regenerate. Thus, the increasing cover of Eucalyptus seen across the country will not automatically foster a recovery of native woody plant biodiversity, even if managed to optimize local environmental conditions.     

Variation in the ability of larvae of phytophagous insects to develop on evolutionarily unfamiliar plants: a study with gypsy moth Lymantria dispar and Eucalyptus

• 1 By examining variation in the abilities of polyphagous insects to develop on host plants with secondary metabolites that they have never encountered previously, we may be able to gain some insights into the nature of evolution of biochemical mechanisms to process plant secondary metabolites by phytophagous insects.
• 2 The present study aimed to examine variation in the ability of gypsy moth larvae Lymantria dispar (Lymantriidae) to complete development on different species of the plant genus Eucalyptus (Myrtaceae). Leaves of at least some Eucalyptus species contain formylated phloroglucinol derivatives. These are secondary metabolites that are evolutionarily unfamiliar to the gypsy moth.
• 3 Larvae of gypsy moth showed extremely variable responses in larval performance between Eucalyptus species, between individual trees within host plant species, between moth populations, and between individuals within moth populations.
• 4 Larval survivorship was in the range 0–94%, depending on the host. Failure of at least some larvae to complete development on some Eucalyptus species indicates that gypsy moth larvae have a limited ability to process secondary metabolites in eucalypt leaves.
• 5 At least some individuals, however, appear to already possess biochemical mechanisms that process the secondary metabolites in leaves of Eucalyptus species, and therefore the abilities of larvae to complete development on phylogenetically and chemically unfamiliar hosts are already present before the gypsy moth encounters these potential hosts.

     

Botryosphaeriaceae species overlap on four unrelated,native South African hosts

Botryosphaeriaceae represents an important and diverse family of latent fungal pathogens of woody plants. We address the question of host range of these fungi by sampling leaves and branches of four native South African trees, including Acacia karroo (Fabaceae), Celtis africana (Cannabaceae), Searsia lancea (Anacardiaceae), and Gymnosporia buxifolia (Celastraceae). Two new species of the Botryosphaeriaceae, namely Tiarosporella africana sp. nov. and Aplosporella javeedii sp. nov. were identified, together with five known species, including Neofusicoccum parvum, Neofusicoccum kwambonambiense, Spencermartinsia viticola, Diplodia pseudoseriata, and Botryosphaeria dothidea. Most Botryosphaeriaceae occurred on more than one host. With the exception of S. lancea, which was infected by A. javeedii all the hosts were infected by more than one Botryosphaeriaceae species. Collectively, the results suggest that some intrinsic host factors, possibly combined with local environmental conditions, affect the distribution and co-infectivity of various hosts by the Botryosphaeriaceae. This would counteract the general ability of a species in the Botryosphaeriaceae to infect a broad range of plants. The combination of host and environmental factors might also explain why some Botryosphaeriaceae with apparently broad host ranges, are found on different suites of hosts in different areas of the world.