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.

Cryptic species, native populations and biological invasions by a eucalypt forest pathogen.

Human-associated introduction of pathogens and consequent invasions is very evident in areas where no related organisms existed before. In areas where related but distinct populations or closely related cryptic species already exist, the invasion process is much harder to unravel. In this study, the population structure of the Eucalyptus leaf pathogen Teratosphaeria nubilosa was studied within its native range in Australia, including both commercial plantations and native forests. A collection of 521 isolates from across its distribution was characterized using eight microsatellite loci, resulting in 112 multilocus haplotypes (MLHs). Multivariate and Bayesian analyses of the population conducted in structure revealed three genetically isolated groups (A, B and C), with no evidence for recombination or hybridization among groups, even when they co-occur in the same plantation. DNA sequence data of the ITS (n = 32), ß-tubulin (n = 32) and 27 anonymous loci (n = 16) were consistent with microsatellite data in suggesting that T. nubilosa should be considered as a species complex. Patterns of genetic diversity provided evidence of biological invasions by the pathogen within Australia in the states of Western Australia and New South Wales and helped unravel the pattern of invasion beyond Australia into New Zealand, Brazil and Uruguay. No significant genetic differences in pathogen populations collected in native forests and commercial plantations were observed. This emphasizes the importance of sanitation in the acquisition of nursery stock for the establishment of commercial plantations.

Ceratocystis species, including two new species associated with nitidulid beetles, on eucalypts in Australia.

The genus Ceratocystis includes important fungal pathogens of trees, including Eucalyptus spp. Ironically, very little is known regarding the diversity or biology of Ceratocystis species on Eucalyptus species in Australia, where most of these trees are native. The aim of this study was to survey for Ceratocystis spp., and their possible insect associates, on eucalypts in Australia and thus to establish a foundation of knowledge regarding these fungi on the continent. Collections were made in three states of Australia from wounds on trees, as well as from nitidulid beetles associated with these wounds. Ceratocystis spp. were identified based on morphology and multigene sequence comparisons. Of the 54 isolates obtained, two previously unknown species of Ceratocystis were found and these are described here as Ceratocystis corymbiicola sp. nov. and Ceratocystis tyalla sp. nov. Furthermore, the distribution of Ceratocystis pirilliformis is expanded to include Eucalyptus spp. in Tasmania.

Draft Genome Sequences for Three Ophiostoma Species Acquired during Revisions of Australian Plant Pathogen Reference Collections.

The fungal genus Ophiostoma contains numerous species that share close associations with wood-boring insects, a relationship with important consequences for global biosecurity. Here, we provide draft genomes for three Ophiostoma species within the well-known Ophiostoma ulmi complex. These resources are valuable for future research efforts related to Ophiostoma and the establishment of biosecurity-focused databases.

Ophiostomatoid fungi associated with pine bark beetles and infested pines in south-eastern Australia, including Graphilbum ipis-grandicollis sp. nov.

The ophiostomatoid fungi are an assemblage of ascomycetes which are arguably best-known for their associations with bark and ambrosia beetles (Curculonidae) and blue stain (sap stain) of many economically important tree species. These fungi are considered a significant threat to coniferous forests, which has resulted in numerous studies characterising the diversity of bark beetles and their ophiostomatoid associates globally. The diversity of ophiostomatoid fungi present in Australian pine plantations, however, remains largely undetermined. The aims of this study were therefore to reconsider the diversity of ophiostomatoid fungi associated with Pinus in Australia, and to establish the baseline of expected taxa found within these plantation ecosystems. To achieve this, we reviewed Australian plant pathogen reference collections, and analysed samples collected during forest health surveillance programs from the major pine growing regions in south-eastern Australia. In total, 135 ophiostomatoid isolates (15 from reference collections and 120 collected during the current study) were assessed using morphological identification and ITS screening which putatively distinguished 15 taxonomic groups. Whole genome sequencing (WGS) of representative isolates from each taxon was performed to obtain high-quality sequence data for multi-locus phylogenetic analysis. Our results revealed a greater than expected diversity, expanding the status of ophiostomatoid fungi associated with Pinus in Australia to include 14 species from six genera in the Ophiostomatales and a single species residing in the Microascales. While most of these were already known to science, our study includes seven first records for Australia and the description of one new species, Graphilbum ipis-grandicollis sp. nov.. This study also provides an early example of whole genome sequencing (WGS) approaches replacing traditional PCR-based methods for taxonomic surveys. This not only allowed for robust multi-locus sequence extraction during taxonomic assessment, but also permitted the rapid establishment of a curated genomic database for ophiostomatoid fungi which will continue to aid in the development of improved diagnostic resources and capabilities for Australian biosecurity.

Imminent Extinction of Australian Myrtaceae by Fungal Disease.

Myrtle rust is a fungal disease that has spread rapidly across the globe, arriving in Australia in 2010. The tree species Rhodomyrtus psidioides is nearly extinct in the wild as a result of the disease, leading to potential disruption of ecosystem function. Many other Myrtaceae may also be threatened and unprecedented impacts of the disease are predicted.

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.

New species of Mycosphaerella from Myrtaceae in plantations and native forests in eastern Australia.

The majority of Mycosphaerella species from eucalypts (Eucalyptus, Corymbia and Angophora) in Australia have been recorded only from trees growing in plantations. This illustrates a bias in research in the past two decades toward commercial enterprise, and it emphasises a lack of understanding of the occurrence of these important fungi under natural conditions. Surveys of foliar fungi in native forests in eastern Australia, as well as adjacent plantations, thus have been initiated in recent years. In this study we describe four new species of Mycosphaerella from Eucalyptus spp. as well as other Myrtaceae. Mycosphaerella tumulosa sp. nov. (anamorph: Pseudocercospora sp.) was found on more than seven species of Eucalyptus and Corymbia in native forests and plantations in northeastern New South Wales and southeastern Queensland and appears to be relatively common, although not damaging to these trees. Mycosphaerella multiseptata sp. nov. was recorded from several locations on species of Angophora in native forests and amenity plantings. Mycosphaerella pseudovespa sp. nov. was found in one location in native forest on E. biturbinata. The first species of Mycosphaerella to be described from Syncarpia, M. syncarpiae sp. nov., was found in native forests in numerous locations from Sydney through to northeastern New South Wales and appears to be relatively common.

EF-1α DNA Sequences Indicate Multiple Origins of Introduced Populations of Essigella californica (Hemiptera: Aphididae).

Aphids in the pine-feeding Nearctic genus Essigella (Sternorrhyncha, Aphididae, Lachninae) have been introduced in Europe, North Africa, Oceania, and South America. Mitochondrial, nuclear, and endosymbiont DNA sequences of 12 introduced populations from three continents confirm they all belong to Essigella californica (Essig, 1909). Intron sequence variation of the nuclear gene EF-1α has revealed the existence of four distinct groups. Group I gathers one population from China, where the species is newly reported, and several from Europe (France and Italy); Group II is represented by one population from Argentina; Group III includes two populations from Southern Australia with one from New Zealand; and Group IV corresponds to five populations from Eastern and South-Eastern Australia. These results indicate that introduced populations of E. californica have at least four source populations. They also show that intron variation of EF-1α can be a method to discriminate populations of asexually reproducing aphids.

The bark beetle, Ips grandicollis, disrupts biological control of the woodwasp, Sirex noctilio, via fungal symbiont interactions.

The corticoid fungus, Amylostereum areolatum, is deposited in pine trees by the woodwasp, Sirex noctilio, at the time of oviposition. This fungus is essential in S. noctilio larval growth and it is also a food source for Beddingia siricidicola, the nematode used for S. noctilio biological control. In recent years, the historically successful biological control programme has been disrupted in Australia by the bark beetle, Ips grandicollis. This study investigated whether the mechanism of this disruption involves a fungus, Ophiostoma ips, which I. grandicollis introduces into trees. In artificial and wood media, A. areolatum was unable to grow in areas occupied by O. ips. The latter fungus was faster growing, especially at 25 °C rather than 20 °C. Larval galleries of S. noctilio in field-collected samples were strongly associated with wood infested by A. areolatum and absent from areas affected by O. ips. The nematode failed to survive and reproduce on O. ips as it can on A. areolatum. Competitive interactions between O. ips and A. areolatum within the trap trees are demonstrated to be key factors in the negative effect of I. grandicollis on S. noctilio biological control programmes.

Teratosphaeria nubilosa, a serious leaf disease pathogen of Eucalyptus spp. in native and introduced areas.

BACKGROUND: Teratosphaeria nubilosa is a serious leaf pathogen of several Eucalyptus spp. This review considers the taxonomic history, epidemiology, host associations and molecular biology of T. nubilosa. TAXONOMY: Kingdom Fungi; Phylum Ascomycota; Class Dothideomycetes; Order Capnodiales; Family Teratosphaeriaceae; genus Teratosphaeria; species nubilosa. IDENTIFICATION: Pseudothecia hypophyllous, less so amphigenous, ascomata black, globose becoming erumpent, asci aparaphysate, fasciculate, bitunicate, obovoid to ellipsoid, straight or incurved, eight-spored, ascospores hyaline, non-guttulate, thin walled, straight to slightly curved, obovoid with obtuse ends, medially one-septate, slightly constricted at the median septum, tapering to both ends, ascospore germination type F, germinating from both ends, germ tubes growing parallel to the long axis of the spore with distortion of the primary ascospore cell. HOST RANGE: Teratosphaeria nubilosa is a primary pathogen of several Eucalyptus spp., including E. botryoides, E. bicostata, E. bridgesiana, E. cypellocarpa, E. dunnii, E. globulus ssp. bicostata, E. globulus ssp. globulus, E. globulus ssp. maidenii, E. globulus ssp. pseudoglobulus, E. grandis, E. gunnii, E. nitens, E. pilularis, E. quadrangulata, E. viminalis, E. grandis x E. resinifera and E. urophylla x E. globulus. DISEASE SYMPTOMS: Leaf spots predominantly occur on juvenile Eucalyptus foliage; however, T. nubilosa has also recently been found on mature Eucalyptus foliage. Leaf spots are amphigenous, varying in size from small spots that are round to irregular. Lesions enlarge and coalesce to form larger blotches over the leaf surface. Initial lesions appear as pale-green spots surrounded by purple margins and, once mature, are generally yellow to pale brown with dark-brown raised borders. USEFUL WEBSITES: Mycobank, http://www.mycobank.org; Mycosphaerella identification website, http://www.cbs.knaw.nl/mycosphaerella/BioloMICS.aspx.

Phylogenetic reassessment supports accommodation of Phaeophleospora and Colletogloeopsis from eucalypts in Kirramyces.

Species of Phaeophleospora are anamorphs of Mycosphaerella and they include some of the most serious foliar pathogens of Eucalyptus spp. grown in plantations worldwide. Pathogens assigned to this genus and occurring on Eucalyptus spp. were previously treated in Kirramyces and they are also phylogenetically closely related to other anamorphs of Mycosphaerella residing in the genus Colletogloeopsis. The primary aim of this study was to consider the appropriate taxonomic placement of these species. To achieve this goal, morphological characteristics and DNA sequence data from the ITS and translation EF1-alpha gene regions were used to compare the type species P. eugeniae, Phaeophleospora spp. and Colletogloeopsis spp. occurring on eucalypts, using ex-type cultures and herbarium specimens. Phylogenetic data and morphological comparisons supported the separation of P. eugeniae from Phaeophleospora species occurring on eucalypts. The name Phaeophleospora is retained for P. eugeniae and the name Kirramyces is resurrected for the species occurring on eucalypts (genera Eucalyptus, Corymbia, and Angophora). Sequence data from the type specimens of two previously described species of Kirramyces, K. lilianiae and K. delegatensis, show they reside in a clade with other Kirramyces spp. Morphological and DNA sequence comparisons also showed that there is considerable overlap between species of Phaeophleospora and Colletogloeopsis from eucalypts. Based on these findings, Colletogloeopsis is reduced to synonymy with the older Kirramyces and the description of Kirramyces is emended to include species with aseptate, as well as multiseptate, conidia produced in acervuli or pycnidia. Two new species of Kirramyces, K. angophorae and K. corymbiae, are also described.