E. C. Y. Liew

Biogeography and phylogeography of Fusarium: a review

Fusarium is a large, complex genus that causes a wide variety of plant diseases, produces a number of mycotoxins and is becoming increasingly recognized as a significant human pathogen. These fungi occur in ecosystems in all parts of the globe, which makes them useful as a model to better understand biogeographic processes affecting the distribution of fungi. Here we review the information available on the biogeography of different species and clades of Fusarium and some of the likely processes affecting dispersal and speciation.

Fungal Planet description sheets: 107–127

Novel species of microfungi described in the present study include the following from Australia: Phytophthora amnicola from still water, Gnomoniopsis smithogilvyi from Castanea sp., Pseudoplagiostoma corymbiae from Corymbia sp., Diaporthe eucalyptorum from Eucalyptus sp., Sporisorium andrewmitchellii from Enneapogon aff. lindleyanus, Myrmecridium banksiae from Banksia, and Pilidiella wangiensis from Eucalyptus sp. Several species are also described from South Africa, namely: Gondwanamyces wingfieldii from Protea caffra, Montagnula aloes from Aloe sp., Diaporthe canthii from Canthium inerne, Phyllosticta ericarum from Erica gracilis, Coleophoma proteae from Protea caffra, Toxicocladosporium strelitziae from Strelitzia reginae, and Devriesia agapanthi from Agapanthus africanus. Other species include Phytophthora asparagi from Asparagus officinalis (USA), and Diaporthe passiflorae from Passiflora edulis (South America). Furthermore, novel genera of coelomycetes include Chrysocrypta corymbiae from Corymbia sp. (Australia), Trinosporium guianense, isolated as a contaminant (French Guiana), and Xenosonderhenia syzygii, from Syzygium cordatum (South Africa). Pseudopenidiella piceae from Picea abies (Czech Republic), and Phaeocercospora colophospermi from Colophospermum mopane (South Africa) represent novel genera of hyphomycetes. Morphological and culture characteristics along with ITS DNA barcodes are provided for all taxa.

Fusarium species associated with vanilla stem rot in Indonesia

Indonesia is one of the world’s leading producers of vanilla, an important cash crop for smallholders. Stem rot disease is a major constraint to vanilla production in Indonesia and has caused significant economic losses over the last decade. Previous reports of vanilla stem rots in the Asia-Pacific region include those caused by Fusarium, Colletotrichum and Phytophthora species. In this paper, we report Fusarium species associated with the disease. Seven major vanilla-producing provinces were surveyed for disease incidence and 850 samples were collected. Isolates were recovered from diseased stem tissues using a selective medium. Pure cultures on carnation leaf-piece agar and potato dextrose agar were identified based on morphological criteria. Some ambiguous species were verified based on DNA sequences of the translation elongation factor gene.Atotal of 542 Fusarium isolates were recovered, comprising 12 species, namely F. decemcellulare, F. fujikuroi, F. graminearum, F. mangiferae, F. napiforme, F. oxysporum, F. polyphialidicum, F. proliferatum, F. pseudocircinatum, F. semitectum, F. solani and F. subglutinans. F. oxysporum was the most commonly isolated species from all areas surveyed, followed by F. solani and F. semitectum. F. oxysporum, F. solani and F. semitectum were tested for pathogenicity to vanilla but only F. oxysporum was shown to be pathogenic. The vanilla stem rot pathogen in Indonesia is verified to be F. oxysporum f. sp. vanillae.

Fusarium species associated with plants in Australia

Fusarium species associated with plants as pathogens, saprobes and endophytes in Australia are listed with notes on their pathogenicity and toxicity provided. A list of Fusarium species not known to occur in Australia also is provided and their quarantine significance evaluated.

Genealogical concordance phylogenetic species recognition in the Fusarium oxysporum species complex

Fusarium oxysporum is an important plant and human pathogenic ascomycetous group, with near ubiquity in agricultural and non-cultivated ecosystems. Phylogenetic evidence suggests that F. oxysporum is a complex of multiple morphologically cryptic species. Species boundaries and limits of genetic exchange within this complex are poorly defined, largely due to the absence of a sexual state and the paucity of morphological characters. This study determined species boundaries within the F. oxysporum species complex using Genealogical Concordance Phylogenetic Species Recognition (GCPSR) with eight protein coding loci. GCPSR criteria were used firstly to identify independent evolutionary lineages (IEL), which were subsequently collapsed into phylogenetic species. Seventeen IELs were initially identified resulting in the recognition of two phylogenetic species. Further evidence supporting this delineation is discussed.

Fusarium: two endophytic novel species from tropical grasses of northern Australia

Two new species of Fusarium associated with Australian indigenous grasses in natural ecosystems are described as F. lyarnte and F. werrikimbe on the basis of morphology, DNA fingerprinting and phylogenetic analysis of EF-1α and β-tubulin sequence data. Isolates of these species were initially recovered from soil in the McGraths Creek area of central Australia and subsequently recovered from soil and stems of the indigenous grass Sorghum interjectum from Litchfield National Park in the Northern Territory, and from Sorghum leiocladum from Werrikimbe National Park in New South Wales. The common feature of both of these species is the production of large globose microconidia in false heads on polyphialides. Attempts to apply the biological species concept were unsuccessful.

High levels of diversity in Fusarium oxysporum from non-cultivated ecosystems in Australia

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.

Genetic Structure of Fusarium pseudograminearum Populations from the Australian Grain Belt

Crown rot, caused by the fungus Fusarium pseudograminearum (teleomorph Gibberella coronicola) is a major disease of wheat in the Australian grain belt. However, there is little information available on the population structure of this pathogen. We measured genetic diversity as assessed with amplified fragment length polymorphism (AFLP) analysis within and between populations of F. pseudograminearum from northeastern, south central, and southwestern regions of the Australian grain belt. Amongst the 217 isolates, 176 haplotypes were identified and grouped into two main clusters. One cluster contained isolates from populations in northeastern Australia, and the other cluster contained isolates from populations in south central and southwestern Australia. The southern populations were distinguished from the northeastern populations by higher levels of population differentiation (Gst) between them and genetic identity amongst the regional populations. We hypothesize that the F. pseudograminearum populations from northeastern and southern Australia are independent, which could result from different founding events or from geographic isolation and the accumulation of genetic differences due to genetic drift and/or selection.

An emended description of Fusarium brevicatenulatum and F. pseudoanthophilum based on isolates recovered from millet in Kenya

Cultures morphologically similar to F. brevicatenulatum and F. pseudoanthophilum were recovered from millet collected in Kenya. Morphological characterisation showed that the production of pyriform microconidia and chlamydospores, key characters separating these species from each other and from other Fusarium species, was variable in these cultures. Sexual compatibility studies of these isolates and holotype cultures of F. brevicatenulatum and F. pseudoanthophilum revealed that they belonged to the same biological species. No fertile crosses were observed between putative isolates of F. brevicatenulatum from millet and tester strains of F. verticillioides, F. sacchari, F. proliferatum, F. subglutinans, F. thapsinum, and F. konzum. Neither were fertile crosses obtained from any self-cross tests, indicating that the cultures were heterothallic. Further studies using AFLP, and sequencing of the β-tubulin, calmodulin, and translation elongation factor 1-α genes revealed that the isolates from the millets and those of the ex-holotype cultures of F. brevicatenulatum and F. pseudoanthophilum belonged to the same species. The species epithet F. brevicatenulatum is preferred on the basis of priority.

Prevalence and aetiology of Phytophthora foot rot of black pepper in Vietnam

Black pepper is a high value export crop in Vietnam. The production of black pepper, however, is reduced remarkably by Phytophthora foot rot disease. Although the disease was first reported in 1952, the identity of the causal organism has never been conclusively determined. Hence, the aim of this study was to identify the causal agent associated with Phytophthora foot rot epidemics in black pepper. A national survey of the disease and collection of samples were conducted in four major black pepper growing provinces. Phytophthora isolates obtained from the diseased roots, collars and leaves as well as the root-zone soil were identified by morphological characteristics and verified by ITS-RFLP analysis. Phytophthora capsici was determined as the main pathogen causing Phytophthora foot rot of black pepper in Vietnam based on disease symptoms, morphological characteristics, pathogenicity and ITS-RFLP analysis.