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Austropuccinia psidii is a rust fungus that has expanded its known geographic distribution and host range on Myrtaceae. Invasions by rust fungi are often caused by asexual urediniospores that give rise to populations with low genotypic diversity. Recently it was shown that basidiospores, the gametic spores of A. psidii, were able to infect species of Myrtaceae under controlled conditions. The present study tested the hypothesis that sexual reproduction occurs through infection of Myrtaceae by basidiospores of A. psidii in recently invasive populations from New Zealand and South Africa. We provided three lines of evidence to test this hypothesis: i) presence of a sexual stage, ii) high genotypic diversity within an invasive population, and iii) no genetic linkage between microsatellite markers in multilocus genotypes. Our results provide evidence that invasions of A. psidii are caused by both urediniospores that spread clonal genotypes, and teliospores that produce recombinant basidiospores, which infect Myrtaceae. We reject the hypothesis that field infections of A. psidii are only caused by asexual urediniospores, and support that sexual reproduction occurs in invasive populations and may accelerate adaptation to environmental change. [ABSTRACT FROM AUTHOR]

The myrtle rust pathogen, Austropuccinia psidii, was recently detected in New Zealand and Singapore. We used microsatellite markers to identify the strain of A. psidii that caused these incursions. Our results show that the pandemic strain of the pathogen caused outbreaks in both New Zealand and Singapore. [ABSTRACT FROM AUTHOR]

The article discusses the relation of plant family Myrtaceae to the sexual life cycle of the rust fungus Austropuccinia psidii. Topics include the infection of the Myrtaceae species Syzygium jambos by A. psidii basidiospores, testing of badiospores for recombination, and the separation of basidiospores from teliospores and urediniospores.

The rust fungus Austropuccinia psidii was recently reported from ornamental Corymbia citriodora and plantations of Eucalyptus in Colombia. It is unknown whether the genotypic diversity of the pathogen in Colombia reflects that of other countries in South America or if unique genotypes occur. Multilocus genotypes (MLG) were determined for collections of A. psidii from four host genera, Corymbia, Eucalyptus, Psidium and Syzygium in Colombia and compared to collections from Australia, Brazil, Indonesia, Paraguay and South Africa. The genotypic diversity of 58 samples on 15 genera of Myrtaceae was determined using seven microsatellite markers. Two lineages of A. psidii were detected among Colombian samples. These included a previously unknown genotype on Psidium guajava, different to those sampled from Brazil, as well as the pandemic biotype, which has spread to Pacific countries such as Australia, Hawaii and Indonesia. This is the first time the pandemic biotype of A. psidii has been found in South America where the rust is believed to be native. These findings raise questions with regard to the origin of the pandemic biotype of A. psidii and emphasise the threat that this biotype poses to forestry. [ABSTRACT FROM AUTHOR]

Over the past decade, Puccinia psidii, which causes rust on species of Myrtaceae, has spread rapidly to new areas and is now widespread. Quarantine has done little to prevent its movement through the Americas, the Pacific, Africa, and in this report, South-East Asia. Puccinia psidii is reported for the first time from Indonesia on two genera of Myrtaceae, namely Eucalyptus and Melaleuca. Its identity was confirmed using morphology, a molecular barcode comparison to an epitype specimen, and with a molecular phylogenetic approach. Comparison of seven microsatellite markers indicates that the rust genotype in Indonesia and Australia is identical. The potential impacts of P. psidii in South-East Asia to the natural environment and plantation forestry are discussed in light of this first report from the region. [ABSTRACT FROM AUTHOR]

Rust fungi are obligate plant parasites belonging to the order Pucciniales; they comprise about 7,800 species throughout the world. Some species seriously damage crops, vegetables, fruits and trees. Of these species, wheat stem rust ( Puccinia graminis f. sp. tritici), Asian soybean rust ( Phakopsora pachyrhizi) and myrtle rust ( Puccinia psidii) have recently become major concerns worldwide, and this review, discusses recent rust disease outbreaks of Asian soybean rust and myrtle rust. Both rusts have very wide host ranges. Asian soybean rust has spread from its original region of distribution (eastern Asia) to many areas of soybean cultivation around the world. Myrtle rust is a new disease in areas where host plants were first introduced and has spread to other parts of the world including the areas where the host plants are indigenous. New diseases of economically important plants can occur by host shifts from wild host plants or host jumps from phylogenetically unrelated plant species. Recent advances in molecular phylogenetic studies have contributed to a revision of rust taxonomy. Molecular phylogenetic analyses, together with precise morphological observations and inoculation experiments, have identified taxonomic groups among populations that are morphologically very similar. Systematic, ecological and other basic biological studies of rust fungi in both cultivated and wild host plants are very important for developing methods to control rust diseases. Recent changes in the International Code of Botanical Nomenclature will surely affect the systematics of rust fungi. [ABSTRACT FROM AUTHOR]