Vera Andjic

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.

Kirramyces viscidus sp. nov., a new eucalypt pathogen from tropical Australia closely related to the serious leaf pathogen, Kirramyces destructans

Kirramyces destructans is a serious pathogen causing a leaf, bud and shoot blight disease of Eucalyptus plantations in the subtropics and tropics of South-East Asia. During surveillance of eucalypt taxa trials in northern Queensland, symptoms resembling those of K. destructans were observed on Eucalyptus grandis and E. grandis × E. camaldulensis. Phylogenetic and morphological studies revealed that the Kirramyces sp. associated with these symptoms represents a new taxon described here as K. viscidus sp. nov., which is closely related to K. destructans. Plantation assessments revealed that while E. grandis from the Copperload provenance, collected in northern Queensland, recovered from disease, E. grandis × E. camaldulensis hybrids from South America were highly susceptible to infection by K. viscidus and are not recommended for planting in northern Queensland. Preliminary results suggest the fungus probably originates from Australia. K. viscidus is closely related to K. destructans and causes a disease with similar symptoms, suggesting that it could seriously damage Australian eucalypt plantations, especially those planted off-site.

New Teratosphaeria species occurring on eucalypts in Australia

Although the first Teratosphaeria spp. with colletogloeopsis-like anamorphs were described outside of Australia, recently many new species have been described from Australia. In the present study, several new Teratosphaeria spp. were collected from infected eucalypt leaves in eastern Australia. Phylogenetic and morphological studies revealed five new taxa described here as Teratosphaeria aurantia, T. biformis, T. foliensis, T. micromaculata and T. tinara.

Plants for planting; indirect evidence for the movement of a serious forest pathogen, Teratosphaeria destructans, in Asia

Fungal diseases caused by native pathogens and pathogens introduced with planting stock have a significant impact on exotic plantation forestry in the tropics. Teratosphaeria destructans (formerly Kirramyces destructans) is a serious pathogen causing leaf, bud and shoot blight diseases of Eucalyptus spp. in plantations in the sub-tropics and tropics of south-east Asia. This pathogen was first discovered in Indonesia in 1995 and has subsequently spread to Thailand, China, Vietnam and East Timor. The biology, ecology and genetics of this important pathogen have not been explored yet. The objective of this study was, thus, to determine the genetic diversity and movement of T. destructans throughout south-east Asia using multi-gene phylogenies and microsatellite markers. Out of nine gene regions only two microsatellite markers detected a very low nucleotide polymorphism between isolates; seven other gene regions, ITS, β-tubulin, EF1-α, CHS, ATP6 and two microsatellite loci, reflected genetic uniformity. The two polymorphic molecular markers resolved six haplotypes among isolates from Indonesia and only a single haplotype elsewhere in Asia. The low diversity observed among isolates in the region of the first outbreak is as expected for a small founder population. The spread of a single clone over large distances throughout the region supports the hypothesis of spread via the human-mediated movement of germplasm.

The eucalypt leaf blight pathogen Kirramyces destructans discovered in Australia

Kirramyces destructans is a serious pathogen causing a leaf, bud and shoot blight disease of Eucalyptus species in plantations of the subtropics and tropics of South East Asia. This pathogen was first discovered in Indonesia in 1995 and has subsequently spread to Thailand, China and Vietnam. Kirramyces destructans is not known to occur in Australia and has been considered a major biosecurity threat. During the course of the past four years, surveys have been conducted in existing eucalypt trials in tropical Australia. Several Kirramyces spp. were detected in these surveys, including isolates with morphological and cultural characteristics resembling those of K. destructans. In this study, DNA sequences of three gene regions were used to compare isolates of Kirramyces spp. emerging from the surveys and these were compared with those of K. destructans and the closely related K. eucalypti and K. viscidus. Results have shown, for the first time, that K. destructans is present in northern Australia (Melville Island, Northern Territory and Derby, Western Australia). The observed sequence variation among a small number of isolates also strongly suggests K. destructans is endemic to Northern Australia.

Taxonomic identity of the Sterile Red Fungus inferred using nuclear rDNA ITS 1 sequences

The taxonomic position and properties of an unidentified fungus isolated from wheat roots was investigated. The Sterile Red Fungus (SRF) is characterised by its fast growing habit, red pigmentation, non-sporing nature and mycelial form resembling some Laetisaria and Limonomyces species. rDNA variation was used to study the relationship of the SRF to Laetisaria spp. and Limonomyces spp. Nucleotide sequence obtained from eight Laetisaria and three Limonomyces species representing the ITS 1 region, were analysed by PCR and direct sequencing. Plant growth promoting properties of the five taxa were also determined. The SRF had closest identity (98 %) to British material of Limonomyces roseipellis. UPGMA analysis of ITS 1 DNA sequence support a close relationship between SRF and L. roseipellis. The relationship inferred by nucleotide sequence data was supported by phenotypic analysis; both L. roseipellis and the SRF were shown to promote the growth of wheat plants. Unexpectedly, Laetisaria arvalis and material named as Limonomyces roseipellis from New Zealand appeared to be closely related with 98 % rDNA sequence identity, suggesting the misidentification of the New Zealand collection.

New species of Teratosphaeria associated with leaf diseases on Corymbia calophylla (Marri)

Corymbia calophylla is an important eucalypt species endemic to the south-west of Western Australia. It is currently in decline across its native habitat for unknown reasons but perhaps due to climate change or to the presence of a recently described canker disease caused by Quambalaria coyrecup. Few fungal leaf pathogens have been described from C. calophylla. The following paper describes two new species of Teratosphaeria from C. calophylla, Teratosphaeria calophylla sp. nov and T. rubidae sp. nov. In addition, a new epitype was designated for T. australiensis.

Pathways to false-positive diagnoses using molecular genetic detection methods; Phytophthora cinnamomi a case study

Abstract Phytophthora cinnamomi is one of the worlds most invasive plant pathogens affecting ornamental plants, horticultural crops and natural ecosystems. Accurate diagnosis is very important to determine the presence or absence of this pathogen in diseased and asymptomatic plants. In previous studies, P. cinnamomi species‐specific primers were designed and tested using various polymerase chain reaction (PCR) techniques including conventional PCR, nested PCR and quantitative real‐time PCR. In all cases, the primers were stated to be highly specific and sensitive to P. cinnamomi. However, few of these studies tested their primers against closely related Phytophthora species (Phytophthora clade 7). In this study, we tested these purported P. cinnamomi‐specific primer sets against 11 other species from clade 7 and determined their specificity; of the eight tested primer sets only three were specific to P. cinnamomi. This study demonstrated the importance of testing primers against closely related species within the same clade, and not just other species within the same genus. The findings of this study are relevant to all species‐specific microbial diagnosis.

Colletotrichum species in Australia

Forty-four species of Colletotrichum are confirmed as present in Australia based on DNA sequencing analyses. Many of these species were identified directly as a result of two workshops organised by the Subcommittee on Plant Health Diagnostics in Australia in 2015 that covered morphological and molecular approaches to identification of Colletotrichum. There are several other species of Colletotrichum reported from Australia that remain to be substantiated by DNA sequence-based methods. This body of work aims to provide a basis from which to critically examine a number of isolates of Colletotrichum deposited in Australian culture collections.

New cryptic species of Teratosphaeria on Eucalyptus in Australia

Teratosphaeria destructans and T. viscida are serious pathogens causing leaf, bud and shoot blight diseases of Eucalyptus plantations in the subtropics and tropics of South-East Asia (T. destructans) and North Queensland, Australia (T. viscida). During disease surveys in northern Western Australia and the Northern Territory of Australia, symptoms resembling those of T. destructans were observed on young and adult leaves of native and plantation Eucalyptus spp. and its hybrids. Phylogenetic studies revealed Teratosphaeria species associated with these symptoms are new taxonomic novelties described here as T. novaehollandiae and T. tiwiana spp. nov. Isolates from previous records of T. destructans recorded in Australia were re-examined and based upon the phylogenetic evidence are reassigned to these new taxa. We conclude that T. destructans is absent from Australia.