Angus J. Carnegie

Unravelling Mycosphaerella: do you believe in genera?

Many fungal genera have been defined based on single characters considered to be informative at the generic level. In addition, many unrelated taxa have been aggregated in genera because they shared apparently similar morphological characters arising from adaptation to similar niches and convergent evolution. This problem is aptly illustrated in Mycosphaerella. In its broadest definition, this genus of mainly leaf infecting fungi incorporates more than 30 form genera that share similar phenotypic characters mostly associated with structures produced on plant tissue or in culture. DNA sequence data derived from the LSU gene in the present study distinguish several clades and families in what has hitherto been considered to represent the Mycosphaerellaceae. In some cases, these clades represent recognisable monophyletic lineages linked to well circumscribed anamorphs. This association is complicated, however, by the fact that morphologically similar form genera are scattered throughout the order (Capnodiales), and for some species more than one morph is expressed depending on cultural conditions and media employed for cultivation. The present study shows that Mycosphaerella s.s. should best be limited to taxa with Ramularia anamorphs, with other well defined clades in the Mycosphaerellaceae representing Cercospora, Cercosporella, Dothistroma, Lecanosticta, Phaeophleospora, Polythrincium, Pseudocercospora, Ramulispora, Septoria and Sonderhenia. The genus Teratosphaeria accommodates taxa with Kirramyces anamorphs, while other clades supported in the Teratosphaeriaceae include Baudoinea, Capnobotryella, Devriesia, Penidiella, Phaeothecoidea, Readeriella, Staninwardia and Stenella. The genus Schizothyrium with Zygophiala anamorphs is supported as belonging to the Schizothyriaceae, while Dissoconium and Ramichloridium appear to represent a distinct family. Several clades remain unresolved due to limited sampling. Mycosphaerella, which has hitherto been used as a term of convenience to describe ascomycetes with solitary ascomata, bitunicate asci and 1-septate ascospores, represents numerous genera and several families yet to be defined in future studies.

Introducing the Consolidated Species Concept to resolve species in the Teratosphaeriaceae

The Teratosphaeriaceae represents a recently established family that includes numerous saprobic, extremophilic, human opportunistic, and plant pathogenic fungi. Partial DNA sequence data of the 28S rRNA and RPB2 genes strongly support a separation of the Mycosphaerellaceae from the Teratosphaeriaceae, and also provide support for the Extremaceae and Neodevriesiaceae, two novel families including many extremophilic fungi that occur on a diversity of substrates. In addition, a multi-locus DNA sequence dataset was generated (ITS, LSU, Btub, Act, RPB2, EF-1α and Cal) to distinguish taxa in Mycosphaerella and Teratosphaeria associated with leaf disease of Eucalyptus, leading to the introduction of 23 novel genera, five species and 48 new combinations. Species are distinguished based on a polyphasic approach, combining morphological, ecological and phylogenetic species concepts, named here as the Consolidated Species Concept (CSC). From the DNA sequence data generated, we show that each one of the five coding genes tested, reliably identify most of the species present in this dataset (except species of Pseudocercospora). The ITS gene serves as a primary barcode locus as it is easily generated and has the most extensive dataset available, while either Btub, EF-1α or RPB2 provide a useful secondary barcode locus.

Further Mycosphaerella species associated with leaf diseases of Eucalyptus

Three new species of Mycosphaerella are described from diseased leaves of Eucalyptus growing in a species trial in south-eastern Australia: Mycosphaerella marksii sp. nov. was associated with circular to irregular, sometimes confluent lesions, bordered by a prominent red-brown margin on several species of Eucalyptus; M. grandis sp. nov. and M. aggregata sp. nov. were associated with lesions confined to the leaf margin, extending from the tip almost back to the petiole, on leaves of E. grandis. It is likely that M. grandis is a primary parasite and M. aggregata a secondary invader. The species are distinguished mainly by their ascospore morphology and germination. Discrepancies between spore dimensions recorded in this and a previous study are explained by differences in the stains used.

Forest health condition in New South Wales, Australia, 1996–2005. II. Fungal damage recorded in eucalypt plantations during forest health surveys and their management

Forests New South Wales (NSW) manages over 26 000 ha of young eucalypt (Eucalyptus and Corymbia) plantations, established since 1994, in NSW, Australia. Forest health surveillance of these plantations was initiated in late 1995: results for damage from fungal diseases, including foliar, stem and root fungi, are summarised for surveys from 1996 to 2005. The main pathogen in Corymbia spp. plantations was Quambalaria shoot blight, caused by Quambalaria pitereka, which caused shoot death, affecting growth and form. Kirramyces (=Phaeophleospora) epicoccoides caused significant defoliation (>75% severity) of Eucalyptus grandis and E. grandis×Eucalyptus camaldulensis clones in several locations from 2000 onwards, often resulting in infection by stem fungi leading to top-death and tree mortality. Kirramyces eucalypti caused significant defoliation (>95% severity) of Eucalyptus nitens over several years in two plantations, which also resulted in infection by stem fungi and top-death and tree mortality of many trees. Other leaf fungi (e.g. Mycosphaerella cryptica, Mycosphaerella marksii, Aulographina eucalypti and Pilidiella eucalyptorum) were common on several host species, but rarely reached a level of serious concern. Holocryphia eucalypti was associated with elongated perennial cankers, top-death and tree mortality of Eucalyptus dunnii in plantations severely defoliated by insects and fungi or that had experienced severe windstorms. Botryosphaeria spp. were associated with twig cankers and shoot dieback of Eucalyptus pilularis on stressed sites, but also with root-bole damage and scattered mortality of several hosts during drought. Caliciopsis sp. pleomorpha was associated with localised branch and stem cankers, mostly of stressed trees, on a range of hosts from 2003 onwards, and severe cankers leading to tree mortality of E. nitens. Phytophthora cinnamomi was associated with mortality of several hosts in years following episodes of high rainfall. Mortality from Armillaria luteobubalina was rare. Management options for these diseases are discussed, and include: (1) risk-site mapping to assist in targeting management options; (2) increasing tree resistance via tree breeding; and (3) increasing tree tolerance to damage, and recovery after damage, via silvicultural regimes such as fertiliser application and improved site-species matching.

Retracing the routes of introduction of invasive species: the case of the Sirex noctilio woodwasp

Understanding the evolutionary histories of invasive species is critical to adopt appropriate management strategies, but this process can be exceedingly complex to unravel. As illustrated in this study of the worldwide invasion of the woodwasp Sirex noctilio, population genetic analyses using coalescent‐based scenario testing together with Bayesian clustering and historical records provide opportunities to address this problem. The pest spread from its native Eurasian range to the Southern Hemisphere in the 1900s and recently to Northern America, where it poses economic and potentially ecological threats to planted and native Pinus spp. To investigate the origins and pathways of invasion, samples from five continents were analysed using microsatellite and sequence data. The results of clustering analysis and scenario testing suggest that the invasion history is much more complex than previously believed, with most of the populations being admixtures resulting from independent introductions from Europe and subsequent spread among the invaded areas. Clustering analyses revealed two major source gene pools, one of which the scenario testing suggests is an as yet unsampled source. Results also shed light on the microevolutionary processes occurring during introductions, and showed that only few specimens gave rise to some of the populations. Analyses of microsatellites using clustering and scenario testing considered against historical data drastically altered our understanding of the invasion history of S. noctilio and will have important implications for the strategies employed to fight its spread. This study illustrates the value of combining clustering and ABC methods in a comprehensive framework to dissect the complex patterns of spread of global invaders.

Fungal Planet description sheets: 69–91

Novel species of microfungi described in the present study include the following from Australia: Bagadiella victoriae and Bagadiella koalae on Eucalyptus spp., Catenulostroma eucalyptorum on Eucalyptus laevopinea, Cercospora eremochloae on Eremochloa bimaculata, Devriesia queenslandica on Scaevola taccada, Diaporthe musigena on Musa sp., Diaporthe acaciigena on Acacia retinodes, Leptoxyphium kurandae on Eucalyptus sp., Neofusicoccum grevilleae on Grevillea aurea, Phytophthora fluvialis from water in native bushland, Pseudocercospora cyathicola on Cyathea australis, and Teratosphaeria mareebensis on Eucalyptus sp. Other species include Passalora leptophlebiae on Eucalyptus leptophlebia (Brazil), Exophiala tremulae on Populus tremuloides and Dictyosporium stellatum from submerged wood (Canada), Mycosphaerella valgourgensis on Yucca sp. (France), Sclerostagonospora cycadis on Cycas revoluta (Japan), Rachicladosporium pini on Pinus monophylla (Netherlands), Mycosphaerella wachendorfiae on Wachendorfia thyrsifolia and Diaporthe rhusicola on Rhus pendulina (South Africa). Novel genera of hyphomycetes include Noosia banksiae on Banksia aemula (Australia), Utrechtiana cibiessia on Phragmites australis (Netherlands), and Funbolia dimorpha on blackened stem bark of an unidentified tree (USA). Morphological and culture characteristics along with ITS DNA barcodes are provided for all taxa.

Rapidly expanding host range for Puccinia psidii sensu lato in Australia

A rust affecting Myrtaceae was recently detected in New South Wales, Australia. Based on urediniospore morphology and host range, it was identified as Uredo rangelii, a taxon regarded as a member of the eucalyptus/guava rust (Puccinia psidii sensu lato) complex, although confusion currently surrounds its taxonomy. The exotic rust was given the common name of myrtle rust to distinguish it from eucalyptus/guava rust. The more recent discovery of teliospores in NSW that match those of P. psidii sensu stricto indicates the rust in Australia is a strain (with tonsured urediniospores) of P. psidii s.l. Outside Australia, P. psidii has a wide host range within Myrtaceae, being reported from 129 species in 33 genera, and is very damaging in South and Central America–including in eucalypt plantations in Brazil–the Caribbean and in Florida and Hawaii. To ascertain the potential threat to forestry in Australia posed by the introduced rust, we tested key forestry species, as well as key known hosts of eucalyptus/guava rust, in artificial inoculation experiments. We showed that several species of Eucalyptus are susceptible (viz. E. pilularis, E. cloeziana, E. agglomerata and E. grandis), as is Melaleuca quinquenervia. Observations during testing revealed a lengthened latent period (from inoculation until pustule formation and eruption) of four to five weeks during winter. Here we also report on observations on new hosts from surveys in NSW under the emergency response that followed the detection of the exotic rust, and surveys in NSW and Queensland following the cessation of the emergency response. In Australia, P. psidii s.l. has currently been found on 107 host species in 30 genera during surveys, including species in Angophora, Asteromyrtus, Austromyrtus, Backhousia, Callistemon, Chamelaucium, Choricarpia, Decaspermum, Eucalyptus, Eugenia, Gossia, Lenwebbia, Leptospermum, Lophomyrtus, Melaleuca, Metrosideros, Myrtus, Pilidiostigma, Rhodamnia, Rhodomyrtus, Ristantia, Stockwellia, Syncarpia, Syzygium, Tristania, Tristaniopsis, Ugni, Uromyrtus and Xanthostemon. Species under cultivation (in nurseries and gardens) that are severely affected include Gossiainophloia, Agonis flexuosa, Syzygium jambos and S. anisatum while species that are severely damaged in native bushland include Rhodamnia rubescens, Rhodomyrtus psidioides, Choricarpia leptopetala and Melaleuca quinquenervia.

novel species of Mycosphaerellaceae and Teratosphaeriaceae

Recent phylogenetic studies based on multi-gene data have provided compelling evidence that the Mycosphaerellaceae and Teratosphaeriaceae represent numerous genera, many of which can be distinguished based on their anamorph morphology. The present study represents the second contribution in a series describing several novel species in different capnodealean genera defined in a previous study. Novelties on Eucalyptus from Australia include: Penidiella pseudotasmaniensis, P. tenuiramis, Phaeothecoidea intermedia, P. minutispora, Pseudocercospora tereticornis, Readeriella angustia, R. eucalyptigena, R. menaiensis, R. pseudocallista, R. tasmanica, Teratosphaeria alboconidia, T. complicata, T. majorizuluensis, T. miniata, T. profusa, Zasmidium aerohyalinosporum and Z. nabiacense, while Teratosphaeria xenocryptica is described on Eucalyptus from Chile. Novelties on other hosts include Phaeophleospora eugeniicola on Eugenia from Brazil, and Zasmidium nocoxi on twig litter from the USA.

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.

Mycosphaerella leaf disease reduces growth of plantation-grown Eucalyptus globulus

Summary Species of Mycosphaerella cause significant leaf damage and defoliation in young eucalypt plantations in southern Australia and overseas. The effects on growth, however, have not been adequately quantified, although over 310 000 ha of Eucalyptus globulus had been planted in Australia by the end of 2000. In a replicated field experiment (2-y-old E. globulus family trial) exposed to natural infection by species of Mycosphaerella, we periodically sprayed fungicides (benomyl and chlorothalonil) on half of the trees and not the other half. Quantitative assessments of disease (both severity of leaf spots and defoliation) and measurements of tree height and diameter were conducted periodically over the following 17 mo. The fungicides effectively controlled the disease caused by the species of Mycosphaerella present in the trial (M. cryptica and M. nubilosa). Even at low levels of infection by the Mycosphaerella spp. (less than 10% leaf area affected), the unsprayed trees had significantly poorer growth, with height increment reduced by 13% and diameter increment by 4%. Defoliation of unsprayed trees (61 %) was double that of sprayed trees (32%). Severity of leaf spots was positively correlated with defoliation (r = 0.36, P < 0.001), and defoliation was negatively correlated with both height increment (r = -0.37, P < 0.001) and diameter increment (r = -0.29, P < 0.001) — evidence that disease was reducing growth. While spraying controls disease, it is time-consuming and may not be commercially viable. Breeding for resistance to reduce the impact of Mycosphaerella leaf disease may be the most economic control strategy.