Giles E. St. J. Hardy

Seven new species of the Botryosphaeriaceae from baobab and other native trees in Western Australia.

In this study seven new species of the Botryosphaeriaceae are described from baobab (Adansonia gibbosa) and surrounding endemic tree species growing in the Kimberley region of northwestern Australia. Members of the Botryosphaeriaceae were predominantly endophytes isolated from apparently healthy sapwood and bark of endemic trees; others were isolated from dying branches. Phylogenetic analyses of ITS and EF1-α sequence data revealed seven new species: Dothiorella longicollis, Fusicoccum ramosum, Lasiodiplodia margaritacea, Neoscytalidium novaehollandiae, Pseudofusicoccum adansoniae, P. ardesiacum and P. kimberleyense.

Re-evaluation of Phytophthora Species Isolated During 30 Years of Vegetation Health Surveys in Western Australia Using Molecular Techniques

For 30 years, large-scale aerial photography has been used to map the extent of Phytophthora dieback disease in native forests in the southwest of Western Australia, with validation of the observations involving routine testing of soil and root samples for the presence of Phytophthora cinnamomi. In addition to P. cinnamomi, six morpho-species have been identified using this technique: P. citricola, P. megasperma, P. cryptogea, P. drechsleri, P. nicotianae, and P. boehmeriae. In recent years, many new Phytophthora species have been described worldwide, often with similar morphology to existing species; thus, as many of the isolates collected in Western Australia have been difficult to identify based on morphology, molecular identification of the morpho-species is required. Based on amplification of the internal transcribed spacer (ITS) region of the rDNA gene, sequence data of more than 230 isolates were compared with those of existing species and undescribed taxa. P. inundata, P. asparagi, P. taxon PgChlamydo, P. taxon personii, and P. taxon niederhauserii were identified based on sequence data. Phylogenetic analysis revealed that nine potentially new and undescribed taxa can be distinguished. Several of the new taxa are morphologically indistinguishable from species such as P. citricola, P. drechsleri, and P. megasperma. In some cases, the new taxa are closely related to species with similar morphology (e.g., P.sp.4 and P. citricola). However, the DNA sequences of other new taxa such as P.sp.3 and P.sp.9 show that they are not closely related to morphologically similar species P. drechsleri and P. megasperma, respectively. Most of the new taxa have been associated with dying Banksia spp., while P.sp.2 and P.sp.4 have also been isolated from dying Eucalyptus marginata (jarrah). Some taxa (P.sp.3, 6, and 7) appear to have limited distribution, while others like P.sp.4 are widespread.

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.

Botryosphaeria species from Eucalyptus in Australia are pleoanamorphic, producing dichomera synanamorphs in culture.

Species within the genus Botryosphaeria include some of the most widespread and important pathogens of woody plants, and have been the focus of numerous taxonomic studies in recent years. It is currently accepted that anamorphs of Botryosphaeria belong to two distinct genera, Fusicoccum and Diplodia. Species within the genus Fusicoccum commonly produce aseptate, hyaline conidia. In the present study, fungi were isolated from foliage and wood of Eucalyptus in native forests and plantations in Australia. Although these fungi produced Dichomera anamorphs in culture, they clustered within the Fusicoccum clade of Botryosphaeria based on their ITS sequence data. Four species, Botryosphaeria dothidea, B. parva, B. ribis and B. australis produced Dichomera conidia in culture. The Dichomera synanamorphs are described for these four species of Botryosphaeria. In addition, falling within the Fusicoccum clade of Botryosphaeria, two species were found to be distinct from previously described Botryosphaeria spp. based on their ITS sequences, but synonymous with D. versiformis and D. eucalypti. These observations are currently unique to isolates from host trees within the genus Eucalyptus in Australia, and the pleoanamorphic nature of these species is discussed.

Botryosphaeriaceae from tuart (Eucalyptus gomphocephala) woodland, including descriptions of four new species

Eucalyptus gomphocephala (tuart) is a tree native to the southwest coast of Western Australia, where, in some areas, there is a significant decline in the health of tuart. Botryosphaeriaceous taxa have been isolated as endophytes and canker pathogens from numerous hosts in many parts of the world and have been implicated in the decline of E. gomphocephala. In the present study, endophytic fungi were isolated from a wide variety of native woody plant species (Acacia cochlearis, A. rostellifera, Allocasuarina fraseriana, Agonis flexuosa, Banksia grandis, E. gomphocephala, E. marginata and Santalum acuminatum), at two locations in native E. gomphocephala woodland; a site in decline at Yalgorup National Park and a healthy site at Woodman Point Regional Park. Of the 226 isolates obtained, 154 were botryosphaeriaceous taxa, 80% of which were found to be Neofusicoccum australe, isolated from all hosts at both collection sites. Four new species are described, Dothiorella moneti, Dothiorella santali, Neofusicoccum pennatisporum, and a species belonging to a genus only recently included in the Botryosphaeriaceae, Aplosporella yalgorensis. The other species isolated were Botryosphaeria dothidea on the new hosts A. rostellifera, A. cochlearis and E. marginata and Dichomera eucalypti, on the new host E. marginata. None of the new species formed lesions on excised stems of their host species, E. gomphocephala, or a common plantation species, E. globulus. However, Neofusicoccum australe formed lesions on excised stems of E. globulus and E. gomphocephala.

Landscape-scale assessment of tree crown dieback following extreme drought and heat in a Mediterranean eucalypt forest ecosystem

Mediterranean regions are under increasing pressure from global climate changes. Many have experienced more frequent extreme weather events such as droughts and heatwaves, which have severe implications for the persistence of forest ecosystems. This study reports on a landscape-scale assessment investigating potential associated factors of crown dieback in dominant tree species following an extreme dry and hot year/summer of 2010/11 in the Northern Jarrah Forest of Western Australia. Analyses focussed on the influence of (i) geology, (ii) topography, (iii) climate, and (iv) fire history. The results showed that trees on specific soils were more likely to show canopy dieback. Generally, trees on rocky soils with low water holding capacity were found to be affected more frequently. Other explanatory factors identified that dieback occurred (i) on sites that were close to rock outcrops, (ii) in areas that received a slightly higher amount of annual rainfall compared to the surrounding landscape, (iii) on sites at high elevations and (vi) on steep slopes, and (v) in areas that were generally slightly warmer than their surroundings. These results expand our understanding of how landscape-scale factors contribute to the effects of an extreme drought and heating event in Mediterranean forest ecosystems, and give indications of where changes are likely to occur within the landscape in the future. The analogues with other Mediterranean climate regions make the results of this study transferable and a starting point for further investigations.

Microbiological differences between limed and unlimed soils and their relationship with cavity spot disease of carrots (Daucus carota L.) caused by Pythium coloratum in Western Australia

Application of lime (4000 kg ha-1) to a soil used for commercial carrot production (pH 6.9) significantly (p<0.05) reduced the incidence of cavity spot disease of carrots compared to unlimed soil (pH 5.1). It significantly (p<0.01) increased soil microbial activity as measured by the hydrolysis of fluorescein diacetate and arginine ammonification. The application of lime resulted in a significant (p<0.01) increase in the total numbers of colony forming units (efu) of aerobic bacteria, fluorescent pseudomonads, Gram negative bacteria, actinomycetes and a significant (p<0.01) decrease in the cfu of filamentous fungi and yeasts compared to unlimed soil. Liming also increased the cfu of non-streptomycete actinomycetes rarely reported in similar studies. These non-streptomycete actinomycetes were estimated and isolated using polyvalent Streptomyces phages and the dry heat technique to reduce the dominance of streptomycetes on isolation plates. The non-streptomycete actinomycetes isolated included species of Actinoplanes, Micromonospora, Streptoverticillium, Nocardia, Rhodococcus, Microbispora, Actinomadura, Dactylosporangium and Streptosporangium. The numbers of actinomycetes antagonistic to Pythium coloratum, a causal agent of cavity spot disease of carrots increased in soil amended with lime. Application of lime also reduced the isolation frequency of P. coloratum from asymptomatic carrot roots grown in soil artificially infested with the pathogen, 3, 4 and 5 weeks after sowing.

Use of the Genealogical Sorting Index (GSI) to delineate species boundaries in the Neofusicoccum parvum–Neofusicoccum ribis species complex

Neofusicoccum is a recently described genus of common endophytes and pathogens of woody hosts, previously placed in the genus Botryosphaeria. Many morphological characteristics routinely used to describe species overlap in Neofusicoccum, and prior to the use of molecular phylogenetics, isolates from different hosts and locations were often misidentified. Two cryptic species Neofusicoccum ribis and Neofusicoccum parvum were initially described from different continents and recently another four species within this complex were described using fixed nucleotide polymorphisms for differentiation. In a survey of eucalypt cankers in eastern Australia, a collection of morphologically similar Neofusicoccum isolates were obtained. This collection was analysed within the framework of the morphological (MSRC), ecological (ESRC) and phylogenetic (PSRC) species recognition concepts. Morphological data based on spore measurements (MSRC), together with pathogenicity trials (ESRC) were considered alongside molecular analysis (PSRC), which included multiple gene phylogenies constructed from four nuclear gene regions. We also used the Genealogical Sorting Index method to provide objective evidence for the status of terminal taxa in the phylogenetic analysis. The isolates examined exhibited overlapping morphological and culture characteristics, similar pathogenicity to excised stems and shared hosts within the same locations. Phylogenetic analysis separated isolates into 8 clades corresponding to six described species: N. ribis, N. parvum, Neofusicoccum kwambonambiense, Neofusicoccum cordaticola, Neofusicoccum umdonicola, Neofusicoccum batangarum, and two new species. GSI support indicated combined phylogenetic data were monophyletic for all clades and all p-values were significant allowing us to reject the null hypothesis that all groups were from a single mixed group. Consequently the description of Neofusicoccum occulatum is presented.

Pathogenic Botryosphaeriaceae associated with Mangifera indica in the Kimberley Region of Western Australia

Members of the Botryosphaeriaceae, in particular Lasiodiplodia theobromae, Neofusicoccum parvum, N. mangiferum and Botryosphaeria dothidea, commonly cause stem cankers, dieback and stem end rot of mangoes worldwide. In the current study, eight taxa of Botryosphaeriaceae were identified as canker-associated fungi, pathogens, potential pathogens or endophytes of mangoes in the Kimberley, Australia. These include Neoscytalidium novaehollandiae, Ne. dimidiatum, Pseudofusicoccum adansoniae, P. ardesiacum, P. kimberleyense, Lasiodiplodia sp. 1, L. iraniensis and L. pseudotheobromae. The pathogenicity of a selection of these species toward fruit and branches was tested. All were pathogenic to mango in comparison to the control, with Lasiodiplodia spp. being the most pathogenic. It appears that either geographic isolation or the unique growing conditions in the Kimberley may have provided an effective barrier to the acquisition or establishment of known botryosphaeriaceous pathogens. Wounds caused by mechanical pruning may provide an entry point for infection, whilst severe pruning may increase plant stress.

Climate and landscape drivers of tree decline in a Mediterranean ecoregion

Climate change and anthropogenic land use are increasingly affecting the resilience of natural ecosystems. In Mediterranean ecoregions, forests and woodlands have shown progressive declines in health. This study focuses on the decline of an endemic woodland tree species, Eucalyptus wandoo (wandoo), occurring in the biodiversity hotspot of southwest Western Australia. We determined the change in health of wandoo stands between 2002 and 2008 across its geographic and climatic range, and associated this change in health with non-biotic variables focusing on: (1) fragment metrics; (2) topography; (3) soil characteristics; and (4) climate. Only fragment metrics and climate variables were found to be significantly related to the observed change in health. Stands that were small with high perimeter/area ratios were found to be most sensitive to health declines. Recent increases in autumn temperatures and decreases in annual rainfall were negatively affecting health of wandoo most prominently in the low rainfall zone of its climatic range. Together, these results suggest the onset of range contraction for this ecologically important species, which is likely to be exacerbated by projected future changes in climate. Our results emphasize the importance of establishing monitoring programs to identify changes in health and decline trends early to inform management strategies, particularly in the sensitive Mediterranean ecoregions.