Colletogloeopsis zuluensis, previously known as Coniothyrium zuluense, causes a serious stem canker disease on Eucalyptus spp. grown as non-natives in many tropical and sub-tropical countries. This stem canker disease was first reported from South Africa and it has subsequently been found on various species and hybrids of Eucalyptus in other African countries as well as in countries of South America and South-East Asia. In previous studies, phylogenetic analyses based on DNA sequence data of the ITS region suggested that all material of C. zuluensis was monophyletic. However, the occurrence of the fungus in a greater number of countries, and analyses of DNA sequences with additional isolates has challenged the notion that a single species is involved with Coniothyrium canker. The aim of this study was to consider the phylogenetic relationships amongst C. zuluensis isolates from all available locations and to support these analyses with phenotypic and morphological comparisons. Individual and combined phylogenies were constructed using DNA sequences from the ITS region, exons 3 through 6 of the β-tubulin gene, the intron of the translation elongation factor 1-α gene, and a partial sequence of the mitochondrial ATPase 6 gene. Both phylogenetic data and morphological characteristics showed clearly that isolates of C. zuluensis represent at least two taxa. One of these is C. zuluensis as it was originally described from South Africa, and we provide an epitype for it. The second species occurs in Argentina and Uruguay, and is newly described as C. gauchensis. Both fungi are serious pathogens resulting in identical symptoms. Recognising them as different species has important quarantine consequences.

No abstract

Twelve microsatellite markers were developed for population analyses of the fungal pathogen, Dothistroma septosporum. Intersimple sequence repeat polymerase chain reaction (ISSR-PCR) and an enrichment protocol (fast isolation by amplified fragment length polymorphism of sequences containing repeats [FIASCO]) were both used to identify 28 unique microsatellite regions in the genome. From 22 primer pairs designed, 12 were polymorphic. These markers, screened on two populations representing 42 isolates, produced 40 alleles across all loci with an allelic diversity of 0.09-0.76 per locus. Cross-species amplification showed variable success with Dothistroma rhabdoclinis and Mycosphaerella dearnessi and some sequence variation within isolates of Dothistroma pini. These markers will be used to further study the population structure and diversity of D. septosporum.

No abstract

Teratosphaeria gauchensis causes a serious canker disease on Eucalyptus spp. in plantations in South America and Africa. The pathogen is closely related to, but distinct from T. zuluensis that causes a similar stem canker disease on Eucalyptus. The objective of this study was to use 10 previously developed polymorphic microsatellite markers to study the population diversity of T. gauchensis, based on collections of the fungus made in Argentina and Uruguay. The alleles were size -analyzed to determine population genetic parameters of the T. gauchensis populations. The results showed that isolates from the two collection sites represent the same population. Overall, the genetic diversity amongst isolates was higher than expected and inconsistent with the notion that the pathogen represents a recent introduction into South America.Additional keywords: ascomycete, Eucalyptus stem canker, forest pathogen, Teratosphaeria gauchensis, Teratosphaeria zuluensis, microsatellites, population structure. known as Coniothyrium canker on Eucalyptus spp. Teratosphaeria zuluensis was the first of these fungi to be described after it was discovered causing serious damage to the stems of clonally propagated Eucalyptus grandis in the Kwa-Zulu Natal province of South Africa (Wingfield et al. 1997). The disease spread rapidly in the 1990's and became one of the most serious impediments to Eucalyptus plantation forestry in that country (Old et al. 2003).Due to the serious economic impact of Coniothyrium canker on plantations in South Africa, there were various studies undertaken to better understand the relevance and biology of T. zuluensis (van Zyl, 1999, van Zyl et al. 2002. Some years later, a very similar disease was discovered on E grandis clones in Argentina and Uruguay and surprisingly, the causal agent was found to be different to T. zuluense (Cortinas et al. 2006b). The causal agent of the disease was described as Teratosphaeria gauchensis. Teratosphaeria gauchensis and T. zuluensis are morphologically almost indistinguishable and they give rise to the same symptoms after infection. Thus, the only reliable means to distinguish between the two fungi is via DNA sequence comparisons. Both fungi were initially described as mitotic species and residing in the teleomorph genus Mycosphaerella based on phylogenetic inference (Cortinas et al. 2006b; Andjic et al. 2007) but recent taxonomic re-evaluation has relegated them to anamorphs of Teratosphaeria in the Teratosphaeriaceae (Crous et al. 2007; Crous et al. 2009).Teratosphaeria gauchensis causes cankers on young branches and tree trunks although it has also been isolated from leaf spots on E. maidenii and E. tereticornis in Uruguay (Pérez et al. 2009a).The typical stem and trunk lesions caused by this fungus are necrotic and have a characteristic dark oval shape (Cortinas et al. 2006b). The extent of the lesions varies depending on the susceptibility of the infected trees. Severe infections arise from small cankers that merge to cover large areas of the trunk. Both the sof...