G.E.St.J. Hardy

The future of phosphite as a fungicide to control the soilborne plant pathogen Phytophthora cinnamomi in natural ecosystems

The issues that influence the application of the fungicide phosphite (phosphonate) to natural plant communities affected by Phytophthora cinnamomi Rands are complex. Research has shown significant protective effects that are valued in the preservation of rare and endangered plant species and communities. However, phosphite does have other effects that include phytotoxicity, growth abnormalities, reduced reproductive capacity and large difference in levels of P. cinnamomi control between plant species. Clearly a balanced approach needs to be adopted when using phosphite for the management of P. cinnamomi in natural ecosystems. It is necessary to take into account the beneficial and detrimental effects of phosphite and the possible loss of plant species if the fungicide is not used. Traditional forms of P. cinnamomi management are also outlined to highlight their continued importance in disease management, irrespective of whether phosphite is used or not.

Identification and pathogenicity of Botryosphaeria species associated with grapevine decline in Western Australia

Botryosphaeria species have recently gained importance as pathogens of grapevines worldwide. A survey was conducted of 16 vineyards in three grape-growing regions in Western Australia to determine if Botryosphaeria species were playing a role in grapevine decline. B. australis, B. rhodina, B. obtusa and B. stevensii were isolated from grapevines exhibiting symptoms of decline, and identified based on morphological characteristics and ITS sequence data. These species have all been isolated from grapevines elsewhere in the world. Regional differences between Botryosphaeria species were apparent. B. rhodina was isolated only from the Swan Districts region. B. australis was present in the Margaret River and Pemberton/Manjimup regions, but was never isolated from the Swan Districts region. B. obtusa was isolated from all regions, but most prominently from Manjimup, and B. stevensii was isolated only once from Manjimup. A pathogenicity trial found B. australis, B. rhodina and B. stevensii to be pathogenic to grapevines, whereas B. obtusa did not produce any lesions on the cuttings. In Western Australia, B. australis appears to be the predominant pathogenic Botryosphaeria sp. The role of other species of Botryosphaeria and the interaction between species requires further study.

Phytophthora multivora sp. nov., a new species recovered from declining Eucalyptus, banksia, agonis and other plant species in Western Australia.

A new Phytophthora species, isolated from rhizosphere soil of declining or dead trees of Eucalyptus gomphocephala, E. marginata, Agonis flexuosa, and another 13 plant species, and from fine roots of E. marginata and collar lesions of Banksia attenuata in Western Australia, is described as Phytophthora multivora sp. nov. It is homothallic and produces semipapillate sporangia, smooth-walled oogonia containing thick-walled oospores, and paragynous antheridia. Although morphologically similar to P. citricola, phylogenetic analyses of the ITS and cox1 gene regions demonstrate that P. multivora is unique. Phytophthora multivora is pathogenic to bark and cambium of E. gomphocephala and E. marginata and is believed to be involved in the decline syndrome of both eucalypt species within the tuart woodland in south-west Western Australia.

Plant growth promotion and biological control of Pythium aphanidermatum, a pathogen of cucumber, by endophytic actinomycetes

Aims:  To evaluate the potential of Actinoplanes campanulatus, Micromonospora chalcea and Streptomyces spiralis endophytic in cucumber roots, to promote plant growth and to protect seedlings and mature plants of cucumber from diseases caused by Pythium aphanidermatum, under greenhouse conditions.

False-negative isolations or absence of lesions may cause mis-diagnosis of diseased plants infected with Phytophthora cinnamomi

In a series of growth cabinet, glasshouse and field experiments, tissue samples from living clonal Eucalyptus marginata (jarřah) were incubated immediately after sampling on agar (NARPH) selective for Phytophthora. Phytophthora cinnamomi was recovered 3–6 months after inoculation from 50% of samples with lesions and 30% of symptomless samples. However, up to 11% of samples with and without lesions and from which P. cinnamomi was not initially isolated contained viable pathogen. This was shown by removing tissue which had not produced any growth of P. cinnamomi on NARPH plates, cutting it into smaller sections, washing in sterile deionised water repeatedly for 9 days, and replating. Plating stem or bark tissue directly onto NARPH produced false-negative results for nine P. cinnarnomi isolates and six jarrah clones. The behaviour of the pathogen indicates that it could be present as dormant structures, such as chlamydospores, that need to be induced to germinate. Alternatively, fungistatic compounds in the tissue needed to be removed to allow the pathogen to grow. These results have important implications for disease diagnosis and management, disease-free certification and quarantine clearance.

Veratryl alcohol as an inducer of laccase by an ascomycete, Botryosphaeria sp., when screened on the polymeric dye Poly R-478

A.M. BARBOSA, R.F.H. DEKKER AND G.E. ST HARDY. 1996. Forty fungi isolated from diverse environments in Western Australia were screened for ligninolytic activity based on in‐vivo decolorization of the polymeric dye Poly R‐478. Three isolates identified as Aspergillus, Botryosphaeria and Coniochaeta species were selected for further studies. The Botryosphaeria and Coniochaeta isolates were found to produce laccase constitutively in submerged culture when grown on glucose, or on ryegrass seed by solid state fermentation. A comparison of the three isolates grown on glucose in the presence of 3,4‐dimethoxybenzyl (veratryl) alcohol (40 mmol 1−1) showed that only the Botryosphaeria isolate produced laccase, with laccase activities 115‐fold higher than when grown on glucose alone.

Multiple new Phytophthora species from ITS Clade 6 associated with natural ecosystems in Australia: evolutionary and ecological implications

During surveys of dying vegetation in natural ecosystems and associated waterways in Australia many new taxa have been identified from Phytophthora ITS Clade 6. For representative isolates, the region spanning the internal transcribed spacer region of the ribosomal DNA, the nuclear gene encoding heat shock protein 90 and the mitochondrial cox1 gene were PCR amplified and sequenced. Based on phylogenetic analysis and morphological and physiological comparison, four species and one informally designated taxon have been described; Phytophthora gibbosa, P. gregata, P. litoralis, P. thermophila and P. taxon paludosa. Phytophthora gibbosa, P. gregata and P. taxon paludosa form a new cluster and share a common ancestor; they are homothallic and generally associated with dying vegetation in swampy or water-logged areas. Phytophthora thermophila and P. litoralis are sister species to each other and more distantly to P. gonapodyides. Both new species are common in waterways and cause scattered mortality within native vegetation. They are self-sterile and appear well adapted for survival in an aquatic environment and inundated soils, filling the niche occupied by P. gonapodyides and P. taxon salixsoil in the northern hemisphere. Currently the origin of these new taxa, their pathogenicity and their role in natural ecosystems are unknown. Following the precautionary principle, they should be regarded as a potential threat to native ecosystems and managed to minimise their further spread.

Fungal Planet description sheets: 107–127

Novel species of microfungi described in the present study include the following from Australia: Phytophthora amnicola from still water, Gnomoniopsis smithogilvyi from Castanea sp., Pseudoplagiostoma corymbiae from Corymbia sp., Diaporthe eucalyptorum from Eucalyptus sp., Sporisorium andrewmitchellii from Enneapogon aff. lindleyanus, Myrmecridium banksiae from Banksia, and Pilidiella wangiensis from Eucalyptus sp. Several species are also described from South Africa, namely: Gondwanamyces wingfieldii from Protea caffra, Montagnula aloes from Aloe sp., Diaporthe canthii from Canthium inerne, Phyllosticta ericarum from Erica gracilis, Coleophoma proteae from Protea caffra, Toxicocladosporium strelitziae from Strelitzia reginae, and Devriesia agapanthi from Agapanthus africanus. Other species include Phytophthora asparagi from Asparagus officinalis (USA), and Diaporthe passiflorae from Passiflora edulis (South America). Furthermore, novel genera of coelomycetes include Chrysocrypta corymbiae from Corymbia sp. (Australia), Trinosporium guianense, isolated as a contaminant (French Guiana), and Xenosonderhenia syzygii, from Syzygium cordatum (South Africa). Pseudopenidiella piceae from Picea abies (Czech Republic), and Phaeocercospora colophospermi from Colophospermum mopane (South Africa) represent novel genera of hyphomycetes. Morphological and culture characteristics along with ITS DNA barcodes are provided for all taxa.

Phosphite concentration: its effect on phytotoxicity symptoms and colonisation by Phytophthora cinnamomi in three understorey species of Eucalyptus marginata forest

Pre-treatment of plants with foliar sprays of 0.2, 0.5 and 2% phosphite restricted colonisation by Phytophthora cinnamomi in inoculated stems of Adenanthos barbiger and Daviesia decurrens, and led to a reduction in the isolation of P. cinnamomi from these stems in comparison with unsprayed plants. In plants treated with 2% phosphite, P. cinnamomi was not isolated from D. decurrens but was isolated from 22% of the stems of A. barbiger. In Xanthorrhoea preissii, colonisation by, and isolation of, P. cinnamomi from inoculated roots was not significantly affected by pre-treatment of the foliage with 0.2, 0.5 and 2% phosphite. Very low concentrations of phosphite were detected in the roots of X. preissii (maximum mean of 2.2 μg/g dry weight), in comparison with the phosphite concentrations measured in the foliage of A. barbiger and D. decurrens plants treated with phosphite (maximum means of 80 and 871 μg/g dry weight, respectively). Treatment with 0.2% phosphite resulted in minimal phytotoxicity in each of the three species, whereas treatment with 2% phosphite led to the development of severe phytotoxicity symptoms. This study indicates that phosphite has potential for the management of P. cinnamomi in native plant communities.

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.