G. A. Kile’s research while affiliated with The Commonwealth Scientific and Industrial Research Organisation and other places

Nuclear and mitochondrial markers were used to examine variation within three closely related species of tree pathogens with differing reproductive strategies. Ceratocystis eucalypti is obligately outcrossing; Ceratocystis virescens is capable of selfing due to unidirectional mating type switching; and Chalara australis is an asexual species, comprised of a single mating type. When the nuclear DNA fingerprinting markers (CAT)5 and (CAG)5 were used as probes against Pst I-restricted DNA, isolates of C. eucalypti were found to be highly polymorphic, and Ch. australis showed very little polymorphism. The selfing C. virescens showed an intermediate level of variation in the nuclear fingerprint markers, and much of the variation appeared to be due to differences between two forms of the species, one pathogenic to Acer and Liriodendron and another less-pathogenic form on Fagus and other hardwoods. Mitochondrial DNA (mtDNA) polymorphisms were examined by digesting total DNA with Hae III or CfoI, and C. eucalypti showed somewhat more variation in mtDNA than did C. virescens. The only polymorphism seen in the mtDNA of Ch. australis was associated with a plasmid. Selfing in C. virescens may be common and could explain an intermediate level of diversity when compared to the obligately outcrossing C. eucalypti and the asexual Ch. australis.

Armillaria species cause Armillaria root rot on a wide range of plant species throughout the world. Based on morphology and sexual compatibility, various species of Armillaria have been reported from Australia and New Zealand. These include A. hinnulea, A. fumosa, A. pallidula, A. novae-zelandiae and A. luteobubalina from Australia. In New Zealand, A. limonea, A. novae-zelandiae, A. hinnulea and a fourth undescribed but morphologically distinct species are recognized. To determine the phylogenetic relationships between Armillaria spp. from Australia and New Zealand, the ITS region (ITS 1, 5.8S rRNA gene and ITS2) of the rRNA operon was amplified and the DNA sequences determined for a collection of isolates. The ITS sequences of A. ostoyae (from USA) and A. sinapina (from USA) were included for comparison. Phylogenetic trees were generated using parsimony analysis. Armillaria hinnulea was found to be more closely related to Armillaria spp. occurring in the Northern Hemisphere than it was to the other Australian and New Zealand species. The remainder of the Australian and New Zealand Armillaria spp. included in this study formed a monophyletic clade and confirmed separation of species based on morphology and sexual compatibility.

included in this study formed a monophyletic clade and confirmed separation of species based on morphology and sexual compatibility. Armillaria species cause Armillaria root rot on a wide range of plant species throughout the world. Based on morphology and sexual compatibility, various species of Armillaria have been reported from Australia and New Zealand. These include A. hinnulea, A. fumosa, A. pallidula, A. novae-zelandiae and A. luteobubalina from Australia. In New Zealand, A. limonea, A. novae-zelandiae, A. hinnulea and a fourth undescribed but morphologically distinct species are recognized. To determine the phylogenetic relationships between Armillaria spp. from Australia and New Zealand, the ITS region (ITS 1, 5.8S rRNA gene and ITS2) of the rRNA operon was amplified and the DNA sequences determined for a collection of isolates. The ITS sequences of A. ostoyae (from USA) and A. sinapina (from USA) were included for comparison. Phylogenetic trees were generated using parsimony analysis. Armillaria hinnulea was found to be more closely related to Armillaria spp. occurring in the Northern Hemisphere than it was to the other Australian and New Zealand species. The remainder of the Australian and New Zealand Armillaria spp.

Very few disease of eucalypts have been associated with viruses, phytoplasmas, bacteria or nematodes. In most cases the causal role of viruses and phytoplasmas associated with disorders of eucalypts has not been proven conclusively. Only bacteria diseases caused by Ralstonia solanacearum in Brazil is an important disease for which the causal agent has been clearly established. This disease killed up to 17% of eucalypt seedlings within six months of planting in certain areas. The particular biotypes of Ralstonia solanacearum pathogenic on eucalypts in Brazil is not known to be present in Australia. Very few nematodes associated with eucalypts have been shown to cause serious damage. Nematodes of the genus Fergusobi, together with the fly Fergusonina are associated with diseases of the above-ground parts of eucalypts.

Isolations from stem wounds in living Eucalyptus spp. trees in native forest in eastern Victoria, Australia regularly yielded a Chalara sp. that was morphologically similar to Chalara australis. Unlike Ch. australis, however, sexually compatible isolates were detected, and the teleomorph was formed in culture and also observed occurring on naturally infected wood. A single isolation of the same fungus was also made from a stem wound on E. regnans in Tasmania. The fungus is described as Ceratocystis eucalypti sp. nov. characterized by exceptionally long ascospores which appear to be sheathed. Its anamorph Chalara eucalypti sp. nov., is also described. Mating studies indicate that the fungus is heterothallic with a single locus, bi-allelic mating system. Two mating types were evident among ten field isolates and hermaphrodite and male-only isolates were detected within both mating types. Inoculations of eucalypt seedlings in the greenhouse, saplings in the field and billets cut from cool temperate rainforest species showed that although the fungus can produce a vascular stain, and small cankers in eucalypts, it is only weakly pathogenic.

Nineteen electrophoretic phenotypes (unique combinations of electromorphs) were found among 98 isolates of Ceratocystis coerulescens and morphologically similar species using 10 isozymes. Analysis of the isozyme data and morphological comparisons suggested that there are five variants of C. coerulescens found on conifers: three are associated with blue-stain of Picea or Pinus, one (C. coerulescens f. douglasii) with blue-stain of Pseudotsuga, and one associated with the bark beetle Dendroctonus rufipennis on Picea. Ceratocystis polonica and C. laricicola, associated with bark beetle species in the genus Ips on Picea and Larix, respectively, had similar isozymes, are morphologically indistinguishable from each other, and should probably be synonymized. Ceratocystis virescens, cause of stain of hardwoods and sapstreak disease of Acer saccharum, is distinct from the conifer species of Ceratocystis in isozyme electromorphs and anamorph morphology. Isozymes of C. virescens show some similarity to those of two Australian species, an undescribed species of Ceratocystis from Eucalyptus and Chalara australis. The Chalara states of these three hardwood species and Chalara neocaledoniae are morphologically similar.

Nineteen electrophoretic phenotypes (unique combinations of electromorphs) were found among 98 isolates of Ceratocystis coerulescens and morphologically similar species using 10 isozymes. Analysis of the isozyme data and morphological comparisons suggested that there are five variants of C. coerulescens found on conifers: three are associated with blue-stain of Picea or Pinus, one (C. coerulescens f. douglasii) with blue-stain of Pseudotsuga, and one associated with the bark beetle Dendroctonus rufipennis on Picea. Ceratocystis polonica and C. laricicola, associated with bark beetle species in the genus Ips on Picea and Larix, respectively, had similar isozymes, are morphologically in-distinguishable from each other, and should probably be synonymized. Ceratocystis virescens, cause of stain of hardwoods and sapstreak disease of Acer saccharum, is distinct from the conifer species of Ceratocystis in isozyme electromorphs and anamorph morphology. Isozymes of C. virescens show some similarity to those of two Australian species, an undescribed species of Ceratocystis from Eucalyptus and Chalara australis. The Chalara states of these three hardwood species and Chalara neocaledoniae are morphologically similar.