A. Maxwell

Mycosphaerella species associated with Eucalyptus in south-western Australia: new species, new records and a key

Mycosphaerella ambiphylla sp. nov. (anamorph: Phaeophleospora) and Mycosphaerella aurantia sp. nov., are described from diseased Eucalyptus globulus leaves. In addition, a new fungal record in Australia, M. mexicana, and two new records for Western Australia, M. gregaria and M. parva, are discussed. A key is provided to Mycosphaerella species on E. globulus in Western Australia.

PCR-identification of Mycosphaerella species associated with leaf diseases of Eucalyptus

A PCR-based technique based on the ITS1-5.8s-ITS2 domain of the rRNA gene for identifying five species associated with Mycosphaerella leaf disease (MLD) of eucalypts was developed. Primer pairs MC2F and MC2R; ML1F and ML1R; MM1F and MM1R; MN1F and MN1R; and MP1F and MP1R amplified a product for DNA extracted from their single target species, those being M. cryptica, M. lateralis, M. marksii, M. nubilosa and M. parva, respectively. The possibility of false positive amplification by each primer pair was tested in reactions with DNA extracts from 16 other Mycosphaerella species associated with eucalypts and against non-infected Eucalyptus globulus leaves. Under the PCR conditions used, there were no false positive amplifications of the 16 non-target Mycosphaerella species, or from non-symptomatic E. globulus leaves for the primer pairs ML1F and ML1R; MM1F and MM1R; MN1F and MN1R; and MP1F and MP1R. The primer pair MC2F and MC2R amplified a 402 nt product from both the target M. crvptica and non-target M. nubilosa. However, these two species were differentiated by digesting the product with the restriction enzyme Sacc II which resulted in a single 402 nt product for M. cryptica, and two products of 78 and 324 nt for M. nubilosa. All of the primers were able to detect their target Mycosphaerella species from Eucalyptus globulus lesions. PCR reactions with these primers on DNA extracted from Mycosphaerella lesions confirmed the presence of all five species from leaf material collected from three plantations in Western Australia.

Infection, hyperparasitism and conidiogenesis of Mycosphaerella lateralis on Eucalyptus globulus in Western Australia

Mycosphaerella lateralis has been isolated from diseased eucalypt foliage in conjunction with the known pathogens M. cryptica and M. nubilosa. This study sought to determine whether Dissoconium dekkeri, the anamorph state of M. lateralis, infects healthy eucalypt leaves or is a hyperparasite of M. cryptica or M. nubilosa. Detached Eucalyptus globulus leaves were inoculated with conidial suspensions of M. lateralis and the progress of leaf infection studied over 6 days. Clearing and staining of the leaves showed that infection occurred via stomata after 3 days. In order to determine whether M. lateralis is a hyperparasite of M. cryptica or M. nubilosa, colonies of these species were grown adjacent to one another on either water agar, 0.2% malt-extract agar (MEA) or 2% MEA. No evidence of M. lateralis parasitising M. cryptica or M. nubilosa was found. This indicates that M. lateralis may be a foliar pathogen, rather than a hyperparasite as was previously suggested. Scanning electron microscopy was used to show that conidiogenesis of M. lateralis is both percurrent and sympodial.

First record of Mycosphaerella nubilosa in Western Australia.

Recent surveys of Eucalyptus globulus plantations in Western Australia have shown Mycosphaerella nubilosa (Cooke) Hansf. to be widespread on juvenile leaves throughout the plantation estate. This is the first report of this economically important pathogen in Western Australia.

First record of Mycosphaerella lateralis on Eucalyptus in Australia.

Mycosphaerella lateralis was isolated from diseased eucalypt leaves in Queensland and Western Australian plantations. This is the first report of the species outside of Africa.

New records of Mycosphaerella leaf disease from Eucalypts in Western Australia

Eight new host records of Mycosphaerella leaf disease (MLD) are described from plantation and endemic eucalypts in Western Australia, extending the host range of Mycosphaerella nubilosa, M. marksii and M. parva.

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 records of Mycosphaerella species from Eucalypts in Queensland

Recent surveys of the Eucalyptus plantation estate in Queensland for Mycosphaerella leaf disease found five new host records and three new records for Queensland.

An advanced slit-type volumetric spore trap for monitoring bioaerosols; new methods for identifying fungal spores

A new slit-type volumetric spore trap (STVS) was developed to be inexpensive, light weight and reliable for sampling fungal diseases in Eucalyptus globulus plantations. It was designed with as few parts as possible to reduce the potential for mechanical failure. A simple toggle switch allowed quick changes in sampling period from 24 h to 7 days (without changing the entire sampling drum mechanism). The sampler was powered either by mains power supply or by a 12 V battery linked to a solar panel. The new STVS trap was validated alongside the industry standard Burkard spore trap. There was a highly significant correlation in spore counts (ρ = 0.992, P <0.001) between the two spore traps and no significant (P < 0.001) differences. The new STVS trap was further tested under field conditions over a 20 month period as part of a larger epidemiological study on Mycosphaerella diseases in E. globulus plantations. During the trial, the spore trap was exposed to harsh weather conditions with temperatures ranging from 2.5 to 39.9°C, wind speeds up to 38 km/h, and monthly rainfall up to 292 mm. A newly developed adhesive for spore collection allowed Mycosphaerella spores to be germinated directly on the matrix. Species were then differentiated using the new germination method.

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.