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The oomycete genus Phytophthora includes plant pathogens that pose significant threats to agricultural systems, natural ecosystems and urban forests. Urban forests are increasingly recognized for their role in mitigating climate change impacts and urban greening initiatives are underway worldwide. However, research suggests that the urban forest is also a reservoir of Phytophthora diversity, acting as bridgeheads for the introduction of these pathogens into production and natural ecosystems. The source of Phytophthora in urban forests is linked to anthropogenic factors, with the live plant trade the primary pathway. This study focused on the incidence and diversity of Phytophthora in amenity tree nursery stock in eastern Australia, primarily New South Wales, with one nursery from Victoria. The findings revealed a high incidence of Phytophthora in nursery stock destined for urban greening projects, having an overall positive rate of 22.1%, with incidence in individual nurseries ranging from 2.5% to 32%. The study detected 13 described Phytophthora species that are considered polyphagous on woody hosts and three lineages that potentially represent novel species. In addition, the detection of P. mediterranea and P. heterospora represent first reports for Australia, with P. mediterranea considered a biosecurity concern. The study highlights the substantial risk associated with the live plant trade as a source of Phytophthora introduction into urban forests and beyond. These findings underscore the urgent need to strictly implement clean nursery management practices to reduce the economic and environmental risks associated with Phytophthora in urban greening programmes. [ABSTRACT FROM AUTHOR]

As part of the International Plant Sentinel Network program monitoring high priority plant species from the United Kingdom, soil samples were collected from an asymptomatic Quercus robur (English Oak) at the Blue Mountains Botanic Garden, Mount Tomah (NSW). The soil samples were baited for Phytophthora with detection based on a Phytophthora genus specific Taqman™ assay. Species were identified using Sanger sequencing and phylogenetic analysis of the mitochondrial DNA subunit cytochrome c oxidase subunit 1 (COI) and the nuclear ribosomal DNA internal transcribed spacer 1, 5.8S, ITS2 and partial 28S regions (ITS). Isolates of Phytophthora that were recovered were identical to the Phytophthora plurivora ex-type strain based on phylogenetic inference. This is the first identification of Phytophthora plurivora in Australia. [ABSTRACT FROM AUTHOR]

Ascochyta koolunga (Didymellaceae, Pleosporales) was first described in 2009 (as Phoma koolunga) and identified as the causal agent of Ascochyta blight of Pisum sativum (field pea) in South Australia. Since then A. koolunga has not been reported anywhere else in the world, and its origins and occurrence on other legume (Fabaceae) species remains unknown. Blight and leaf spot diseases of Australian native, pasture and naturalised legumes were studied to investigate a possible native origin of A. koolunga. Ascochyta koolunga was not detected on native, naturalised or pasture legumes that had leaf spot symptoms, in any of the studied regions in southern Australia, and only one isolate was recovered from P. sativum. However, we isolated five novel species in the Didymellaceae from leaf spots of Australian native legumes from commercial field pea regions throughout southern Australia. The novel species were classified on the basis of morphology and phylogenetic analyses of the internal transcribed spacer region and part of the RNA polymerase II subunit B gene region. Three of these species, Nothophoma garlbiwalawarda sp. nov., Nothophoma naiawu sp. nov. and Nothophoma ngayawang sp. nov., were isolated from Senna artemisioides. The other species described here are Epicoccum djirangnandiri sp. nov. from Swainsona galegifolia and Neodidymelliopsis tinkyukuku sp. nov. from Hardenbergia violaceae. In addition, we report three new host-pathogen associations in Australia, namely Didymella pinodes on S. artemisioides and Vicia cracca, and D. lethalis on Lathyrus tingitanus. This is also the first report of Didymella prosopidis in Australia. [ABSTRACT FROM AUTHOR]

Abstract: The Fusarium oxysporum species complex (FOSC) is a ubiquitous ascomycetous group that includes both pathogenic and non-pathogenic strains, the former being responsible for disease in over 100 cultivated plant species. Previous phylogenetic studies have uncovered at least four major clades within the FOSC, with Clade 1 hypothesised as being ancestral. However, the origin of these clades and pathogenic strains is poorly understood. Due to an emphasis on agricultural isolates in previous studies, the underlying diversity of this species complex in non-cultivated soils is largely unknown. To address this imbalance an extensive survey of isolates associated with native vegetation geographically isolated from cultivation throughout the Australian continent was conducted. A multi-gene phylogenetic analysis of the translation elongation factor (EF-1α) and the mitochondrial small subunit (mtSSU) rDNA loci did not recover any novel clades. However, the Australian isolates had high levels of intra-Clade diversity based on EF-1α sequence type (ST) comparison with a global dataset. The ST diversity was not equally distributed across the four clades, with the majority of novel STs recovered from Clade 1. Implications on the origin of the FOSC are discussed. [Copyright &y& Elsevier]

Fusarium goolgardi, isolated from the grass tree Xanthorrhoea glauca in natural ecosystems of Australia, is closely related to fusaria that produce a subgroup of trichothecene (type A) mycotoxins that lack a carbonyl group at carbon atom 8 (C-8). Mass spectrometric analysis revealed that F. goolgardi isolates produce type A trichothecenes, but exhibited one of two chemotypes. Some isolates (50%) produced multiple type A trichothecenes, including 4,15-diacetoxyscirpenol (DAS), neosolaniol (NEO), 8-acetylneosolaniol (Ac-NEO) and T-2 toxin (DAS-NEO-T2 chemotype). Other isolates (50%) produced only DAS (DAS chemotype). In the phylogenies inferred from DNA sequences of genes encoding the RNA polymerase II largest (RPB1) and second largest (RPB2) subunits as well as the trichothecene biosynthetic genes (TRI), F. goolgardi isolates were resolved as a monophyletic clade, distinct from other type A trichothecene-producing species. However, the relationships of F. goolgardi to the other species varied depending on whether phylogenies were inferred from RPB1 and RPB2, the 12-gene TRI cluster, the two-gene TRI1-TRI16 locus, or the single-gene TRI101 locus. Phylogenies based on different TRI loci resolved isolates with different chemotypes into distinct clades, even though only the TRI1-TRI16 locus is responsible for structural variation at C-8. Sequence analysis indicated that TRI1 and TRI16 are functional in F. goolgardi isolates with the DAS-NEO-T2 chemotype, but non-functional in isolates with DAS chemotype due to the presence of premature stop codons caused by a point mutation.