Wollemia nobilis is an ancient coniferous tree species that was recently discovered in eastern Australia. This tree is highly threatened due to its limited distribution. No genetic variation has been ...detected within the wild populations of ~100 adult plants. A recent study has revealed that a species of Botryosphaeria is highly pathogenic to W. nobilis . The aim of the present study was to identify this fungus, as well as Botryosphaeria isolates of unknown identity from other Southern Hemisphere coniferous hosts, Araucaria from New Zealand and Widdringtonia from South Africa. To facilitate their identification, sequence data for the ITS rDNA, as well as the β-tubulin and translation elongation factor 1-α genes were combined to determine the phylogenetic relationship of these isolates with those of known Botryosphaeria spp. Isolates from W. nobilis included two Botryosphaeria spp. The first is closely related to B. ribis , but also shares some unique sequence polymorphisms with B. parva. One isolate grouped with B. australis , but also varied slightly from this taxon in the gene regions analysed. Additional isolates will be needed to determine whether these sequence variations represent speciation events or merely variation within populations of B. ribis and B. australis. In addition to this, B. parva was identified from Araucaria in New Zealand, and B. australis was found on Widdringtonia trees in South Africa. All three reports of these fungi are new records for their various hosts and could represent important pathogens of these trees.
Gibberella fujikuroi and Gibberella intermedia (mating populations 'C' and 'D' of the G. fujikuroi species complex) can be distinguished by differences in the spectrum of mycotoxins produced, the ...lack of sexual cross-fertility and diagnostic differences in their DNA sequences. Some isolates from these two biological species, however, can interbreed and complete meiosis to produce viable progeny. Analysis of marker segregation amongst such hybrid progeny can be used to estimate the degree of genomic rearrangement and genetic incompatibility that has accumulated since these sibling species diverged. Recombinant progeny were isolated from crosses of the standard tester strains for these two species and from crosses between these standard testers and a field isolate (KSU X-10626) that was cross-fertile with tester strains of both species. Progeny in all of the crosses segregated for amplified fragment length polymorphisms (AFLPs). Segregation of AFLP loci deviated from 1:1 for two thirds of the loci amongst the progeny of the cross between the 'C' and 'D' mating population tester strains, but <20% of the polymorphic loci in the cross of either tester with KSU X-10626 showed such distortion. It was concluded that G. intermedia and G. fujikuroi are sufficiently interfertile to belong to the same biological species, but that changing the nomenclature to reflect this interfertility requires more evidence for the natural occurrence of a continuum in fertility than is presently available.
Mango malformation (MMD) is an economically significant disease of mango growing regions and a notifiable disease in Australia. Following an incursion of the disease in the Northern Territory (NT) in ...2007, numerous
Fusarium
species were isolated from mango samples during surveillance activities in growing regions within the country between 2007 and 2013, including reported MMD pathogens (
Fusarium mangiferae
,
F. proliferatum
and
F. pseudocircinatum)
, established pathogens of other hosts (e.g.
F. fujikuroi, F. oxysporum, F. parvisorum, F. solani
and
F. verticillioides
) and several undescribed species. In this paper we review the status of all species of
Fusarium
isolated from mango tissue associated with putative malformation symptoms in Australia since 2007, documenting location origins and diagnostic methods and re-assessing their identification based on phylogenetic analysis of available DNA sequences. Their taxonomic affiliations and pathogenicity in particular are discussed with implications for disease management including quarantine, while knowledge gaps are highlighted.
Fusarium
species associated with plants as pathogens, saprobes and endophytes in Australia are listed with notes on their pathogenicity and toxicity provided. A list of
Fusarium
species not known to ...occur in Australia also is provided and their quarantine significance evaluated.
Previous studies have evaluated the overall structure of populations of Fusarium pseudograminearum (teleomorph, Gibberella coronicola), causal agent of cereal crown rot, but there is no information ...available on spatial relationships of genetic variation in field populations. Three 1-m-row sections in crown-rot-affected wheat fields in the Australian grain belt were intensively sampled to estimate population genetic parameters and the spatial aggregation, or clustering, of disease aggregates and genotypes. Estimates of population genetic parameters based on amplified fragment length polymorphisms (AFLPs) indicated that the genetic diversity in isolates from the 1-m-row populations described a significant portion of the diversity recorded for corresponding field and regional populations. In point pattern analysis, there was physical clustering and aggregation of F. pseudograminearum isolates from two of the three sites. Analysis of the spatial distribution of clonal haplotypes (DICE similarity greater-than-or-equal 97%) indicated significant aggregation of clones in all three 1-m-row populations. Based on matrix comparison tests, both mating types and genetic distances had significant spatial aggregation for at least two of the three 1-m-row populations. This is consistent with the presence of non-random spatial genetic structure due to clonal aggregation. High levels of genetic diversity and spatial structuring of disease and genotypes in at least two of the three 1-m-row populations is consistent with the hypothesis that stubble is a primary inoculum source in no-tillage farming systems, resulting in aggregated patterns of disease and allowing for haplotypes to be maintained in the field over a number of annual cropping cycles.
Eight histopathologists, based at different hospitals, who had previously examined 100 consecutive colposcopic cervical biopsies were circulated with the results of the initial study. The slides were ...then 'reblinded' and re-examined by the pathologists who, as before, assigned them into one of six diagnostic categories. The degree of interpathologist agreement for the seven observers who returned usable responses was characterized by kappa statistics and compared to the corresponding figures for the same observers from the previous study. Although some of the observers showed significant alterations in their diagnostic practices there was persistent poor agreement for CIN 1 and 2, mediocre agreement for CIN 3 and excellent agreement for invasive carcinoma. Intra-observer agreement was consistently better than inter-observer agreement for each of the diagnostic categories. Significant differences were found among observers in the degree of intra-observer variability. The 20 cases in which there was most disagreement were re-examined by one of the authors who compared these with 20 biopsies which caused little disagreement. Disagreement was considered to be associated with florid papilloma-virus changes, basal cell hyperplasia and severe inflammation in varying combinations. On the basis of these findings we suggest changes in the terminology of CIN lesions.
Two new species of
Fusarium
associated with Australian indigenous grasses in natural ecosystems are described as
F. lyarnte
and
F. werrikimbe
on the basis of morphology, DNA fingerprinting and ...phylogenetic analysis of EF-1α and β-tubulin sequence data. Isolates of these species were initially recovered from soil in the McGraths Creek area of central Australia and subsequently recovered from soil and stems of the indigenous grass
Sorghum interjectum
from Litchfield National Park in the Northern Territory, and from
Sorghum leiocladum
from Werrikimbe National Park in New South Wales. The common feature of both of these species is the production of large globose microconidia in false heads on polyphialides. Attempts to apply the biological species concept were unsuccessful.
Fusarium torulosum was isolated consistently from the leaves of kikuyu plants collected from a pasture near Maitland, NSW, on which grazing cattle had been affected by kikuyu poisoning. This fungus ...is known to produce the toxins wortmannin and butenolide, both of which can produce clinical signs and pathological changes similar to those exhibited by cattle with kikuyu poisoning. The available evidence suggests that F. torulosum might be the casual agent of kikuyu poisoning in Australia.
Clove decline is the most serious of clove diseases in North Sulawesi, Indonesia. Despite its devastating impact on one of the most important cash crops in this region, the aetiology of this disease ...has yet been established until recently. Infected trees show symptoms of wilt and defoliation, which often lead to the death of whole trees. In a recent disease survey of 17 sites and more than 100 farms throughout North Sulawesi, clove decline was observed on all sites, with disease incidence of greater than 90%. A fungus, closely resembling the wilt pathogen, Ceratocystis fimbriata, was consistently isolated from wood tissues of infected trees. This fungus appears to be associated with a wood-boring beetle, Hexamitodera semivelutina. The larvae bore into trees forming extensive galleries within the trunks. All isolates of this fungus were obtained from stained wood tissue adjacent to these wood-borer galleries. Multiple pathogenicity tests confirmed the pathogenicity of this fungus on both seedlings and mature clove trees. Molecular studies are being conducted on these isolates to confirm their identity.
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