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Pathogenic and putatively nonpathogenic isolates of Fusarium oxysporum are ubiquitously present in soils. Pathogenic isolates designated as formae speciales are very host specific. The genes that determine host‐specific pathogenicity may be expected to be similar between strains within a forma specialis. Three different pathways were used for mining putative effectors from 85 assembled genome sequences representing isolates from the agricultural and natural ecosystems. A total of 436 putative effectors were identified, of which 115 were present in all the isolates. The presence–absence phylogeny showed some clustering of isolates based on the ecosystems, while some clustered with isolates from different ecosystems. Isolates from the agricultural and natural ecosystems shared 358 putative effectors. Agricultural isolates had 78 unique putative effectors, while isolates from the natural ecosystems had no unique effectors. Isolates from the natural ecosystems had effectors that have previously been confirmed with virulence functions in other filamentous fungi, suggesting that the natural ecosystems may be acting as a reservoir for pathogenic isolates awaiting compatible hosts. They also possessed putative effectors with domains involved in polysaccharide degradation. The putative effectors in the natural ecosystem isolates may be important for both parasitic and ecological fitness. Further analysis of the three characterized ff. sp.—lycopersici, niveum, and pisi—revealed high conservation in the pathogenicity mechanism in F. oxysporum. However, each strain had unique putative effectors, which may be responsible for host specificity. [ABSTRACT FROM AUTHOR]

Pathogenicity and genetic diversity of Fusarium oxysporum from geographically widespread native Gossypium populations, including a cotton growing area believed to be the center of origin of VCG 01111 and VCG 01112 of F. oxysporum f. sp. vasinfectum ( Fov) in Australia, was determined using glasshouse bioassays and AFLPs. Five lineages (A-E) were identified among 856 isolates. Of these, 12% were strongly pathogenic on cotton, 10% were weakly pathogenic and designated wild Fov, while 78% were nonpathogenic. In contrast to the occurrence of pathogenic isolates in all five lineages in soils associated with wild Gossypium, in cotton growing areas only three lineages (A, B, E) occurred and all pathogenic isolates belonged to two subgroups in lineage A. One of these contained VCG 01111 isolates while the other contained VCG 01112 isolates. Sequence analyses of translation elongation factor-1α, mitochondrial small subunit rDNA, nitrate reductase and phosphate permease confirmed that Australian Fov isolates were more closely related to lineage A isolates of native F. oxysporum than to Fov races 1-8 found overseas. These results strongly support a local evolutionary origin for Fov in Australian cotton growing regions. [ABSTRACT FROM AUTHOR]

Royal National Park, Australia's oldest national park, is a significant reserve for conservation of the flora and fauna that are characteristic of the Hawkesbury Sandstone in New South Wales. Since at least 1974, Phytophthora Root Rot (caused by Phytophthora cinnamomi) has been known to occur in the Park, but there is no knowledge of the extent of infestation or the potential impacts of the disease within the Park. This study investigated the distribution of the pathogen within Royal National Park at two scales: a systematic survey by vegetation type, and a targeted survey of populations of Waratah and Spear Grass-tree. These two species are known to be susceptible to Phytophthora Root Rot and are therefore potential indicators of the impact of the pathogen on vegetation in Royal National Park. Phytophthora cinnamomi was recovered from all vegetation types sampled but most commonly in heathland/open scrub vegetation. The pathogen was easily recovered from sites containing Spear Grass-tree, but was not isolated from any sites containing Waratah. Because of the widespread distribution of P. cinnamomi, we conclude that hygiene measures will be of little use to prevent the spread of the pathogen within Royal National Park. Monitoring of the occurrence and spread of disease symptoms in plants and applying phosphite to protect susceptible rare or threatened flora may be the most appropriate management options. [ABSTRACT FROM AUTHOR]

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]