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Manipulation of iron bioavailability in the banana rhizosphere may suppress Fusarium wilt, caused by Fusarium oxysporum f. sp. cubense (Foc). However, iron starvation induced by application of synthetic iron chelators does not effectively suppress Fusarium wilt. It is unclear whether Foc can subvert iron chelators and thereby evade iron starvation through the synthesis of iron-scavenging secondary metabolites, called siderophores. In vitro studies were conducted using iron-deficient growth medium and medium supplemented with a synthetic iron chelator, 2,2'-dipyridyl, to mimic iron starvation in Foc Tropical Race 4 (Foc TR4). Concentration of extracellular siderophores increased three-fold (p lt; 0.05) in the absence of iron. Liquid chromatography-mass spectrometry analysis detected the hydroxamate siderophore, ferrichrome, only in the mycelia of iron-starved cultures. Moreover, iron-starved cultures exhibited a reduction in total cellular protein concentration. In contrast, out of the 20 proteinogenic amino acids, only arginine increased (p lt; 0.05) under iron starvation. Our findings suggest that iron starvation does not cause a remodelling of amino acid metabolism in Foc TR4, except for arginine, which is required for biosynthesis of ornithine, the precursor for siderophore biosynthesis. Collectively, our findings suggest that biosynthesis of siderophores, particularly ferrichrome, could be a counteractive mechanism for Foc TR4 to evade iron starvation.

Fusarium verticillioides causes Fusarium ear rot (FER) of maize and contaminates the grain with mycotoxins called fumonisins. Structural barriers that prevent infection include a closed stylar canal of kernels, which has been suggested to contribute to resistance to FER. In this study, the stylar canal architecture of nine maize inbred lines, characterised for their response to F. verticillioides, was evaluated using scanning electron microscopy. The stylar canal of ovaries, sampled at 1–2 weeks before pollination, and maturing kernels sampled at approximately 1 month after self-pollination, were evaluated. Three inbred lines, CML 390 (highly resistant), RO 544 W (intermediately resistant) and R2565y (susceptible), had ovaries predominantly with closed stylar canals, with 92, 95 and 64.3% of the canals viewed as closed, respectively. Other highly resistant (CML 444, VO 617Y-2 and US 2540 W), intermediately resistant (RO 549 W) and susceptible (R119W and I137tnW) inbred lines displayed a mostly open stylar canal prior to pollination. The stylar canals of all inbred lines were mostly closed 1 month after pollination (90.3–100%). No significant association was found between stylar canal architecture and the FER-resistance status of the maize lines evaluated for ovaries and maturing maize kernels (P > 0.05). The results of the study suggest that the stylar canal architecture may facilitate fungal ingress but does not play a pivotal role in resistance to F. verticillioides.

International audience; Scientific communication is facilitated by a data-driven, scientifically sound taxonomy that considers the end-user's needs and established successful practice. Previously (Geiser et al. 2013; Phytopathology 103:400-408. 2013), the Fusarium community voiced near unanimous support for a concept of Fusarium that represented a clade comprising all agriculturally and clinically important Fusarium species, including the F. solani Species Complex (FSSC). Subsequently, this concept was challenged by one research group (Lombard et al. 2015 Studies in Mycology 80: 189-245) who proposed dividing Fusarium into seven genera, including the FSSC as the genus Neocosmospora, with subsequent justification based on claims that the Geiser et al. (2013) concept of Fusarium is polyphyletic (Sandoval-Denis et al. 2018; Persoonia 41:109-129). Here we test this claim, and provide a phylogeny based on exonic nucleotide sequences of 19 orthologous protein-coding genes that strongly support the monophyly of Fusarium including the FSSC. We reassert the practical and scientific argument in support of a Fusarium that includes the FSSC and several other basal lineages, consistent with the longstanding use of this name among plant pathologists, medical mycologists, quarantine officials, regulatory agencies, students and researchers with a stake in its taxonomy. In recognition of this monophyly, 40 species recently described as Neocosmospora were recombined in Fusarium, and nine others were renamed Fusarium. Here the global Fusarium community voices strong support for the inclusion of the FSSC in Fusarium, as it remains the best scientific, nomenclatural and practical taxonomic option available.

Fusarium verticillioides is the primary fungus that causes Fusarium ear rot (FER) of maize. Infection results in reduced grain yield and quality due to moulding and the contamination of grain with toxic compounds namely fumonisins. Resistance to fungal infection and fumonisin accumulation in maize and maize grain is governed at different levels. In this study, the structural, physico-chemical and genetic basis of resistance to F. verticillioides was investigated in two, replicated field trials at Potchefstroom and Vaalharts in South Africa. Phenotypic data (silk length, husk coverage, pericarp thickness hundred-kernel mass and kernel hardness), physico-chemical data (kernel pH, moisture content, total nitrogen and carbon as well as phenolic acid content) and the expression of pathogenesis-related-5 gene (PR5) and peroxidase gene expression was evaluated in 15 commercial cultivars under artificially inoculated and natural infection conditions. The data were correlated to FER severity, fumonisin accumulation and fungal DNA (referred to as infection indicators). Disease development and fumonisin contamination in Vaalharts was significantly more than in Potchefstroom. There were no significant correlations (r=≥0.60) between phenotypic characteristics and infection indicators. Kernel pH was the most important trait associated with disease development and was negatively correlated (between r=-0.58 and r=-0.75) to all infection indicators. PR5 gene expression had significant positive correlations (r=0.69 and r=0.72) with the fungal and fumonisin levels, respectively. This study presents of the first data demonstrating the use of gene expression in identifying FER/fumonisin-resistant plant material and could aid breeders and growers in selecting resistant material more effectively.

Fusarium head blight (FHB) of wheat occurs commonly in irrigation regions of South Africa and less frequently in dryland regions. Previous surveys of Fusarium species causing FHB identified isolates using morphological characters only. This study reports on a comprehensive characterisation of FHB pathogens conducted in 2008 and 2009. Symptomatic wheat heads were collected from the Northern Cape, KwaZulu-Natal (KZN), Bushveld and eastern Free State (irrigation regions), and from one field in the Western Cape (dryland region). Fusarium isolates were identified with species-specific primers or analysis of partial EF-1α sequences. A representative subset of isolates was characterized morphologically. In total, 1047 Fusarium isolates were collected, comprising 24 species from seven broad species complexes. The F. sambucinum (FSAMSC) and F. incarnatum-equiseti species complexes (FIESC) were most common (83.5% and 13.3% of isolates, respectively). The F. chlamydosporum (FCSC), F. fujikuroi (FFSC), F. oxysporum (FOSC), F. solani (FSSC), and F. tricinctum species complexes (FTSC) were also observed. Within the FSAMSC, 90.7% of isolates belonged to the F. graminearum species complex (FGSC), accounting for 75.7% of isolates. The FGSC was the dominant Fusaria in all four irrigation regions. F. pseudograminearum dominated at the dryland field in the Western Cape. The Northern Cape had the highest species diversity (16 Fusarium species from all seven species complexes). The type B trichothecene chemotype of FGSC and related species was inferred with PCR. Chemotype diversity was limited (15-ADON = 90.1%) and highly structured in relation to species differences. These results expand the known species diversity associated with FHB in South Africa and include first reports of F. acuminatum, F. armeniacum, F. avenaceum, F. temperatum, and F. pseudograminearum from wheat heads in South Africa, and of F. brachygibbosum, F. lunulosporum and F. transvaalense from wheat globally. Potentially novel species were identified within the FCSC, FFSC, FOSC, FSAMSC, FIESC and FTSC.

Fusarium graminearum is ranked among the five most destructive fungal pathogens that affect agroecosystems. It causes floral diseases in small grain cereals including wheat, barley, and oats, as well as maize and rice. We conducted a systematic review of peer-reviewed studies reporting species within the F. graminearum species complex (FGSC) and created two main data tables. The first contained summarized data from the articles including bibliographic, geographic, methodological (ID methods), host of origin and species, while the second data table contains information about the described strains such as publication, isolate code(s), host/substrate, year of isolation, geographical coordinates, species and trichothecene genotype. Analyses of the bibliographic data obtained from 123 publications from 2000 to 2021 by 498 unique authors and published in 40 journals are summarized. We describe the frequency of species and chemotypes for 16,274 strains for which geographical information was available, either provided as raw data or extracted from the publications, and sampled across six continents and 32 countries. The database and interactive interface are publicly available, allowing for searches, summarization, and mapping of strains according to several criteria including article, country, host, species and trichothecene genotype. The database will be updated as new articles are published and should be useful for guiding future surveys and exploring factors associated with species distribution such as climate and land use. Authors are encouraged to submit data at the strain level to the database, which is accessible at https://fgsc.netlify.app .

ECM33, a glycosylphosphatidylinositol (GPI)-anchored protein, is important for fungal development and infection through regulating fungal cell wall integrity, however, the functions of its orthologs in pathogenesis have not been characterized in Fusarium oxysporum. Here, we discovered a GPI-anchored protein, FocECM33, which is required for vegetative growth and virulence of Fusasium oxysporum f. sp. cubense tropical race 4 (Foc TR4). FocECM33 was highly upregulated during the early infection process of Foc TR4 in banana roots. The targeted disruption of FocECM33 led to decreased hyphal growth, increased sensitivity to cell wall stresses and reduced virulence on banana plantlets. Furthermore, ΔFocECM33 mutant demonstrated a cell morphology defect, elevated ROS production and increased chitin content. Transcriptome analysis showed that FocECM33 has a significant influence on the production of various secondary metabolites and regulation of many biosynthetic processes in Foc TR4. Taken together, it seems FocECM33 contributes to the virulence of Foc TR4 through regulating the process of hyphal growth, ROS production and chitin synthesis.

Scientific communication is facilitated by a data-driven, scientifically sound taxonomy that considers the end-user's needs and established successful practice. In 2013, the

The identity of the fungi responsible for fruitlet core rot (FCR) disease in pineapple has been the subject of investigation for some time. This study describes the diversity and toxigenic potential of fungal species causing FCR in La Reunion, an island in the Indian Ocean. One-hundred-and-fifty fungal isolates were obtained from infected and healthy fruitlets on Reunion Island and exclusively correspond to two genera of fungi: Fusarium and Talaromyces. The genus Fusarium made up 79% of the isolates, including 108 F. ananatum, 10 F. oxysporum, and one F. proliferatum. The genus Talaromyces accounted for 21% of the isolated fungi, which were all Talaromyces stollii. As the isolated fungal strains are potentially mycotoxigenic, identification and quantification of mycotoxins were carried out on naturally or artificially infected diseased fruits and under in vitro cultures of potential toxigenic isolates. Fumonisins B1 and B2 (FB1-FB2) and beauvericin (BEA) were found in infected fruitlets of pineapple and in the culture media of Fusarium species. Regarding the induction of mycotoxin in vitro, F. proliferatum produced 182 mg kg⁻1 of FB1 and F. oxysporum produced 192 mg kg⁻1 of BEA. These results provide a better understanding of the causal agents of FCR and their potential risk to pineapple consumers.

Banana is an important food crop and source of income in Africa. Sustainable production of banana, however, is at risk because of pests and diseases such as Fusarium wilt, caused by the soil-borne fungus Fusarium oxysporum f. sp. cubense (Foc). Foc can be disseminated from infested to disease-free fields in plant material, water and soil. Early detection of Foc using DNA technologies is thus required to accurately identify the fungus and prevent its further dissemination with plants, soil and water. In this study, quantitative (q)PCR assays were developed for the detection of Foc Lineage VI strains found in central and eastern Africa (Foc races 1 and 2), Foc TR4 (vegetative compatibility groups (VCG) 01213/16) that is present in Mozambique, and Foc STR4 (VCG 0120/15) that occurs in South Africa. A collection of 127 fungal isolates were selected for specificity testing, including endophytic Fusarium isolates from banana pseudostems, non-pathogenic F. oxysporum strains and Foc isolates representing the 24 VCGs in Foc. Primer sets that proved to be specific to Foc Lineage VI, Foc TR4 and Foc STR4 were used to produce standard curves for absolute quantification, and the qPCR assays were evaluated based on the quality of standard curves, repeatability and reproducibility, and limits of quantification (LOQ) and detection (LOD). The qPCR assays for Foc Lineage VI, TR4 and STR4 were repeatable and reproducible, with LOQ values of 10-3-10-4 ng/μL and a LOD of 10-4-10-5 ng/μL. The quantitative detection of Foc strains in Africa could reduce the time and improve the accuracy for identifying the Fusarium wilt pathogen from plants, water and soil on the continent.

Maize production in South Africa is negatively affected by Fusarium verticillioides , an endophytic maize pathogen, as well as by Busseola fusca larval damage. Fusarium verticillioides causes ear, stem and root rot, and also produces fumonisin mycotoxins which are toxic to humans and livestock. The African stem borer ( Busseola fusca ) is a pest of economic importance in maize plants in South Africa. In this study, the interaction between F. verticillioides and B. fusca was investigated to elucidate its effects on Fusarium ear rot and fumonisin production in a Bt hybrid (MON810 event) and its B. fusca -susceptible non- Bt isohybrid. Field trials were conducted over three seasons using a randomised complete block design with six replicates per treatment. The effect of Beta-cyfluthrin (non-systemic, granular) and Benfuracarb (systemic, seed treatment) insecticide applications on the incidence of Fusarium ear rot and fumonisin production in maize was also determined in an unrelated conventional hybrid. For B. fusca infestations, larvae were dispensed into the whorl of each plant at the 12th leaf stage prior to tasselling, while a F. verticillioides MRC826 spore suspension was inoculated through the silks at the silking stage. Maize ears were harvested at physiological maturity and Fusarium ear rot, total fumonisin levels, stem borer damage and target DNA of fumonisin-producing Fusarium spp. quantified. Significantly less Fusarium ear rot and fumonisin were produced in the Bt maize hybrid compared to the non- Bt isohybrid under natural farming conditions, but fungal colonisation and fumonisin production under artificial F. verticillioides inoculation did not differ significantly between the Bt and non- Bt maize. Fumonisin production correlated moderately with the quantity of target DNA of fumonisin-producing Fusarium spp. extracted from maize plants. Benfuracarb application to control stem borer infestation resulted in a significant reduction in Fusarium ear rot and fumonisin production while Beta-cyfluthrin did not. Moreover, B. fusca damage to maize ears significantly increased when both insecticides were not applied to the B. fusca -infested plants. This study indicated that Bt maize and the application of Benfuracarb reduce B. fusca damage to maize ears thereby indirectly reducing Fusarium ear rot and fumonisin production. However, this was not consistent over seasons due to differences in climatic conditions.

Fusarium verticillioides is most frequently associated with maize in South Africa. It colonises maize roots, stems and ears endophytically and causes diseases such as Fusarium ear rot (FER) and stalk rot. Fusarium verticillioides can produce fumonisins, which are toxic secondary metabolites harmful to humans and animals. It is, however, unknown whether endophytic and pathogenic isolates from distinct maize tissues differ in their ability to cause disease and produce fumonisins. In this study, Fusarium spp. were collected from maize roots, stems and kernels for phylogenetic analysis and the F. verticillioides isolates were subjected to pathogenic and toxigenic comparison. The translation elongation 1-α (TEF1) gene of the isolates was sequenced, and a phylogenetic tree constructed with maximum likelihood (ML) and Bayesian interference (BI) inferred. Fumonisin production of F. verticillioides isolates was determined in vitro and in planta by using high performance liquid chromatography, and virulence of the isolates was determined by silk channel inoculation of maize ears under field conditions. F. verticillioides was the species with the highest number of isolates followed by F. temperatum and then F. subglutinans. Phylogenetic analyses clustered the different Fusarium spp. according to species. Fumonisin production by F. verticillioides isolates varied from 0 to 21.3 mg/kg in vitro, and 0–16.2 mg/kg in planta. All the F. verticillioides isolates produced FER symptoms, including isolates from roots and stems. Fusarium verticillioides isolates in South Africa thus presented a species highly diverse in toxigenicity, but not in virulence. This finding has implications for managing mycotoxins in maize, as visible symptoms might be misleading to the actual toxin level present, for example low level of disease severity might represent high fumonisin levels and vice versa. The high numbers of F. temperatum, also a mycotoxin producer highlights the concern that kernels could be contaminated with more than one mycotoxin. Integrated disease management of not only F. verticillioides but all Fusarium spp. should thus focus strongly on reducing fungal contamination of maize and the detoxification of grain with focus on using regionally adapted maize varieties.

Fusarium verticillioides and Busseola fusca are among the most significant biotic constraints to maize production in South Africa. In this study, the effect of B. fusca damage and mechanical wounding to maize ears on Fusarium ear rot development and fumonisin production was investigated. The effect of the interaction on Fusarium ear rot and B. fusca damage was studied by inoculating maize ears with F. verticillioides isolate MRC826 and infesting plant whorls with aliquots of 10–15 neonate larvae at the 12th leaf stage prior to tasselling. To simulate hail damage, maize ears were mechanically wounded at the blister stage with cork borers of different sizes and number of wounds, with and without F. verticillioides inoculation. Uninoculated, uninfested and undamaged control treatments were included. Field trials were conducted over three seasons using a randomised complete block design with six replicates per treatment. In all seasons, most Fusarium ear rot developed on ears inoculated with F. verticillioides. This study indicated that B. fusca infestation was not associated with higher Fusarium ear rot incidence in two of the three seasons. Moreover, B. fusca infestation was not associated with high fumonisin production in any season. This indicates that the presence of B. fusca was not highly associated with Fusarium ear rot or fumonisin production, possibly due to its characteristic feeding nature that causes sporadic wounds on maize ears, but also the strong impact of weather variability. Fusarium ear rot development and fumonisin production by F. verticillioides inoculum varied seasonally indicating the importance of environmental conditions on Fusarium ear rot and fumonisin production. Fusarium ear rot and fumonisin production significantly increased with the severity of cork borer wounding in both naturally infected and artificially inoculated maize ears. Therefore, the prevention of severe injuries to kernels, whether by mechanical damage or insects, should be considered as important in reducing Fusarium ear rot and fumonisin production in maize.

Busseola fusca and Fusarium verticillioides are considered the most important pest and pathogen, respectively, of maize in South Africa. Busseola fusca tunnels into stems and ears of maize plants, whereas F. verticillioides causes Fusarium ear rot and deposits fumonisins in maize kernels. Frass (excreta) deposited by B. fusca larvae in maize stems and ears during feeding could potentially be contaminated with pathogens such as F. verticillioides, thereby indirectly and passively contributing to plant diseases. The mycoflora present in frass of B. fusca larvae was thus investigated in this study, and the dissemination of fumonisin-producing Fusarium spp. by B. fusca larvae in maize stems determined. Busseola fusca frass was collected from plants with visible insect damage in three maize-growing districts in South Africa. The mycoflora in the frass was isolated and identified morphologically to genus level, followed by the sequencing of target genes for species identification. Species of Acremonium, Aspergillus, Fusarium, Mucor, Rhizopus and Talaromyces were associated with the B. fusca frass. The role of B. fusca larvae in disseminating fumonisin-producing Fusarium spp. was then determined in greenhouse and field trials. Maize whorls were inoculated with F. verticillioides MRC826 spores 4 weeks after plant emergence, and infested with B. fusca larvae 2 days later. The stems were split open after 3 weeks and frass collected from feeding channels, thereafter, target DNA of fumonisin-producing Fusarium spp. was quantified using real-time PCR. Target DNA of fumonisin-producing Fusarium spp. was significantly higher in frass collected from greenhouse plants inoculated with F. verticillioides than in frass collected from the uninoculated control, indicating that the inoculation was successful in the absence of soil-borne inoculum. Nevertheless, the field trial showed no significant differences in target DNA in frass from inoculated and non-inoculated plants. This is possibly due to natural F. verticillioides infection of maize plants in the field. This study further indicated that B. fusca frass also contained maize pathogens such as Aspergillus spp. and Fusarium spp., which could cause ear rot diseases. The occurrence of Acremonium zeae in frass has potential implications for the biological control of F. verticillioides, as the fungus produces pyrrocidines A and B antibiotics which are known to be antagonistic to F. verticillioides. The occurrence of Aspergillus niger in frass requires further investigation in order to clarify its role in fumonisin contamination of maize in South Africa.

Summary Fusaric acid (FSA) is a phytotoxin produced by several Fusarium species and has been associated with plant disease development, although its role is still not well understood.Mutation of key genes in the FSA biosynthetic gene (FUB) cluster in Fusarium oxysporum f. sp. cubense tropical race 4 (Foc TR4) reduced the FSA production, and resulted in decreased disease symptoms and reduced fungal biomass in the host banana plants.When pretreated with FSA, both banana leaves and pseudostems exhibited increased sensitivity to Foc TR4 invasion. Banana embryogenic cell suspensions (ECSs) treated with FSA exhibited a lower rate of O2 uptake, loss of mitochondrial membrane potential, increased reactive oxygen species (ROS) accumulation, and greater nuclear condensation and cell death. Consistently, transcriptomic analysis of FSA‐treated ECSs showed that FSA may induce plant cell death through regulating the expression of genes involved in mitochondrial functions.The results herein demonstrated that the FSA from Foc TR4 functions as a positive virulence factor and acts at the early stage of the disease development before the appearance of the fungal hyphae in the infected tissues.

Fusarium wilt (Panama disease) of bananas is well established in two of the five banana production regions in South Africa: Kiepersol (near Hazyview) and southern KwaZulu-Natal. The disease is caused by a soilborne fungus, Fusarium oxysporumSchlechtend.: Fr. f. sp. cubense (E.F. Sm.) W.C. Snyd. & H.N. Hans., which is most commonly introduced into an area by infected plant material or in contaminated soil attached to vehicles, farm machinery, or footwear. In September 2000, banana plants were observed dying at an experimental site in a commercial Cavendish plantation in the Tzaneen area of the Northern Province of South Africa. Symptoms included wilting of leaves (starting from the oldest foliage) and yellow-brown discoloration of vascular tissue in the rhizome and pseudostem. These symptoms are typical of those described for Panama disease of bananas (2). Similar symptoms were observed at another experimental site in a banana plantation in the Komatipoort region of the Mpumalanga Province in November 2000. Komatipoort is currently the largest banana production region in South Africa. Panama disease has not previously been reported in the Tzaneen and Komatipoort regions. Both are at least 200 km away from the other banana production areas in South Africa. Fungal isolations were made from four diseased plants in both Tzaneen and Komatipoort, and the discolored tissue of the pseudostem was placed on potato dextrose agar amended with novobiocin (0.2 g/liter). Single-spore cultures made from developing colonies were identified as F. oxysporum based on morphological characteristics. Isolates were sent to the Cooperative Research Centre for Tropical Plant Protection (CRCTPP) in Australia for identification by means of DNA amplification fingerprinting (DAF) analysis (1). Based on DAF analysis, isolates from Tzaneen and Komatipoort were identical to those in vegetative compatibility group 0120 of F. oxysporum f. sp. cubense (“subtropical” race 4), the causal agent of Panama disease in Kiepersol and southern KwaZulu-Natal. Pathogenicity studies were performed in the greenhouse by inoculating 5-cm Cavendish banana plants with two isolates of F. oxysporum f. sp. cubense from Tzaneen and two isolates from Komatipoort. Ten plants per isolate were inoculated by submerging their roots in a suspension of microconidia (105 spores/ml). Roots of control plants were submerged in sterile distilled water. Within 6 weeks, wilting symptoms developed on the lower leaves of inoculated banana plants, and the central cylinder of the rhizomes turned reddish brown. F. oxysporum f. sp. cubense was reisolated from the diseased tissue to complete Koch's postulates. The outbreaks of Panama disease in Komatipoort and Tzaneen do not appear to have spread further. Both of the infected fields were placed under quarantine, and symptomatic plants were destroyed. References: (1) S. Bentley et al. Phytopathology 88:1283, 1998. (2) R. H. Stover. Fusarial Wilt (Panama Disease) of Bananas and Other Musa Species. CMI, Kew, Surrey, UK, 1962.

Fusarium oxysporum f. sp. cepae causes Fusarium basal rot of onion, a disease of worldwide importance. Limited information is available on the phylogenetic diversity, vegetative compatibility groups (VCGs), mating type idiomorphs, and virulence of F. oxysporum isolates associated with onion. Therefore, these characteristics were investigated in 19 F. oxysporum f. sp. cepae isolates from Colorado, 27 F. oxysporum f. sp. cepae and 33 F. oxysporum isolates nonpathogenic to onion from South Africa. Six F. oxysporum f. sp. cepae VCGs (0421 to 0426) were identified, of which three were new. The dominant VCGs in Colorado and South Africa were VCG 0421 (47% of isolates) and VCG 0425 (74%), respectively. VCG 0423 was the only VCG that was shared between the two regions. Molecular phylogenies (intergenic spacer region of the rDNA, elongation factor 1α, and mitochondrial small-subunit) confirmed the polyphyletic nature of F. oxysporum f. sp. cepae and showed that some F. oxysporum f. sp. cepae and nonpathogenic F. oxysporum isolates were genetically related. Most F. oxysporum f. sp. cepae isolates clustered into two distinct, well-supported clades. The largest clade only contained highly virulent isolates, including the two main VCGs (0421 and 0425), whereas the basal clade mostly contained moderately virulent isolates. These groupings along with the VCG data provide an important basis for selection of isolates for use in breeding programs, and for the development of molecular makers to identify VCGs. Mating type genotyping revealed the distribution of both mating type (MAT1-1 and MAT1-2) idiomorphs across phylogenetic clades, and the fact that several isolates contained both idiomorphs.

Fusarium verticillioides causes Fusarium ear rot (FER) of maize and produces fumonisins, which affects grain quality. Host-plant resistance can reduce both FER and fumonisins in maize. In this study, 18 maize inbred lines were evaluated for resistance to F. verticillioides and fumonisin accumulation at five localities in South Africa. Additive main effects and multiplicative interaction analyses revealed significant environment × genotype interactions, with inbred lines CML 390, US 2540W, RO 424W, and VO 617y-2 consistently exhibiting low FER severity (≤5.4%), fungal target DNA (≤0.1 ng μl−1), and fumonisin levels (≤5.6 ppm). Genotype main effect and genotype × environment biplots showed that inbred lines CML 390, US 2540W, and RO 424W were most resistant to FER, fungal colonization, and fumonisin accumulation, respectively, while inbred line RO 424W was most stable in its resistance response over environments. These inbred lines also demonstrated broad adaptability by consistently exhibiting resistance to FER, fungal colonization, and fumonisins across localities. The identified lines could serve as valuable sources of resistance against F. verticillioides and its fumonisins in local breeding programs.

Banana Fusarium wilt is a major production constraint globally and a significant threat to the livelihoods of millions of people in East and Central Africa (ECA). A proper understanding of the diversity and population dynamics of the causal agent, Fusarium oxysporum f. sp. cubense (Foc), could be useful for the development of sustainable disease management strategies for the pathogen. The current study investigated the diversity of Foc in ECA using vegetative compatibility group (VCG) analysis, PCR-RFLPs of the ribosomal DNA's intergenic spacer region, as well as phylogenetic analysis of the elongation factor-1α gene. Six VCGs (0124, 0125, 0128, 01212, 01220, and 01222), which all belong to one lineage (Foc lineage VI), were widely distributed throughout the region. VCGs 0128 and 01220 are reported for the first time in Burundi, the Democratic Republic of Congo (DRC), Rwanda, Tanzania, and Uganda, while VCG 01212 is reported in the DRC and Rwanda. Isolates that did not belong to any of the known VCGs were identified as Foc lineage VI members by phylogenetic analysis and may represent novel VCGs. CAV 2734, a banana pathogen collected in Rwanda, clustered with nonpathogenic F. oxysporum isolates in lineage VIII. Results from this study will contribute significantly toward the implementation of banana Fusarium wilt disease management practices in the region, such as the restricted movement of infected planting material and the selective planting of resistant banana varieties.

Fusarium ear rot (FER) and fumonisin accumulation in maize, caused by Fusarium verticillioides, can lead to lower grain quality, crop yield reduction and mycotoxicosis of humans and livestock. The best approach to control this fungus is through the development of resistant maize varieties, however, no immune cultivars are available with commercial cultivars ranging from susceptible to moderately resistant. Therefore, this study evaluated F1 maize hybrids, generated from inbred lines resistant to FER/fumonisins and Aspergillus flavus/aflatoxins, for improved resistance to F. verticillioides infection and fumonisin contamination. Diallel analysis was performed to understand the inheritance of resistance to F. verticillioides/fumonisins. Consequently, maize inbred lines resistant to F. verticillioides/fumonisins under South African conditions and lines resistant to Aspergillus flavus under Kenyan conditions were crossed to produce 18 hybrids. Hybrids and parental lines were planted in replicated field trials at three localities in South Africa. Artificially inoculated trials were conducted with disease severity, F. verticillioides target DNA and total fumonisin concentrations determined by visual assessment, quantitative PCR and liquid chromatography tandem mass spectrometry, respectively. Hybrids R119W × CKL05015, CML 495 × CKL05015 and CKL05015 × R119W were the most resistant to FER severity, F. verticillioides colonisation and fumonisin contamination, respectively. The resistance levels of hybrids did not differ significantly from their parental inbred lines, except for specific hybrids in certain test environments. General combining ability and specific combining ability were significant (P ≤ 0.05) for all three parameters evaluated. Kenyan inbred lines CKL05015 and CML 495 were good general combiners for resistance to fumonisin contamination. Specific combinability estimates showed that CKL05015 × R119W was the best hybrid combination for resistance to FER severity, F. verticillioides colonisation and fumonisin contamination. Additive gene effects were predominant in the inheritance of resistance in this set of hybrids. Parental inbred line performance was indicative of F1 hybrids performance. This study provided fundamental information on the maize lines evaluated that would be useful to breeders in the development of F. verticillioides/fumonisin-resistant cultivars.

Our objective was to develop an explicit AFLP-marker to quantify the abundance of Fusarium oxysporum f.sp. strigae (Fos), an effective soil-borne biocontrol agent (BCA) against the parasitic weed Striga hermonthica, in tropical soils. The specificity of the AFLP-marker to Fos was confirmed on basis of comparison of Fusarium isolates of differing relatedness to Fos. These consisted of 40 Fos, 17 Fusarium spp. and 68 F. oxysporum isolates retrieved from tropical and temperate ecosystems. The robustness of the AFLP-marker for monitoring Fos was validated in a controlled incubation experiment. In this experiment, we inoculated the known Fos-BCA “Foxy-2” as model organism via seed coating (1.15 * 105 colony forming units per seed) of a tropical maize (Zea mays L.) variety to a tropical clayey (Humic Nitisol) and a sandy (Ferric Alisol) soil, both with no indigenous Fos infestation. The proliferation of “Foxy-2” was followed at 14, 28 and 42 days after start of experiment by Fos-specific quantitative PCR using the AFLP-marker. Moreover, the experimental set-up considered two additional factors: (1) presence of S. hermonthica, and (2) application of Tithonia diversifolia residues as nitrogen-rich resource for supporting “Foxy-2” proliferation. The explicit AFLP-marker was appropriate to reveal that soil type and organic resource availability exhibited distinct effects on abundance of inoculated “Foxy-2”. Negative PCR signals, which confirmed the Fos-specificity of the developed AFLP-marker, were retrieved from control soils not inoculated with “Foxy-2”. Hence, we verified the applicability of the explicit AFLP-marker for Fos in two soils, but recommend additional broad scale field studies to approve its suitability as Fos monitoring tool for differently managed soils in contrasting tropical agro-ecological zones.

Fusarium basal rot of onion, caused by Fusarium oxysporum f.sp. cepae, is one of the leading causes of post-harvest and storage losses within the Western Cape region in South Africa. Several vegetative compatibility groups (VCGs) of F. oxysporum f.sp. cepae have been associated with bulb rot in mature onions in South Africa, of which VCG 0425 predominates. Our study investigated seed and seedling transplants as potential sources of inoculum of F. oxysporum f.sp. cepae, and whether VCG 0425 is associated with these materials. Fusarium isolation studies from 13 seed lots showed that seven of the seed lots were infected with either moderately or highly virulent F. oxysporum f.sp. cepae isolates. The infection frequency of seed lots was between 0.17 and 0.50%, and only two of the seed lots were infected with VCG 0425. The seedborne nature of F. oxysporum f.sp. cepae was confirmed by showing that a green fluorescent protein (GFP)-labelled F. oxysporum f.sp. cepae VCG 0425 transformant could be transmitted from infected soil to bulbs, and from there to the seed stalks and seeds. Onion seedling transplants from nurseries were also implicated as a source of inoculum. The incidence of F. oxysporum f.sp. cepae in nurseries increased as the season progressed from 2.7% at the 6-week-old growth stage to 5.7% at the 14-week-old stage. The F. oxysporum f.sp. cepae isolates from transplants were highly to moderately virulent. However, none of the isolates proved to be VCG 0425. Most (>86%) of the F. oxysporum isolates from seed and seedlings were not F. oxysporum f.sp. cepae and were not pathogenic to onion. Altogether, the results indicate that onion seed and seedlings are inoculum sources of F. oxysporum f.sp. cepae in the Western Cape Province, but that VCG 0425 is rarely associated with these sources.

Fusarium oxysporum formae specialis cubense (Foc) is a soil-borne fungus that causes Fusarium wilt, which is considered to be the most destructive disease of bananas. The fungus is believed to have evolved with its host in the Indo-Malayan region, and from there it was spread to other banana-growing areas with infected planting material. The diversity and distribution of Foc in Asia was investigated. A total of 594 F. oxysporum isolates collected in ten Asian countries were identified by vegetative compatibility groups (VCGs) analysis. To simplify the identification process, the isolates were first divided into DNA lineages using PCR-RFLP analysis. Six lineages and 14 VCGs, representing three Foc races, were identified in this study. The VCG complex 0124/5 was most common in the Indian subcontinent, Vietnam and Cambodia; whereas the VCG complex 01213/16 dominated in the rest of Asia. Sixty-nine F. oxysporum isolates in this study did not match any of the known VCG tester strains. In this study, Foc VCG diversity in Bangladesh, Cambodia and Sri Lanka was determined for the first time and VCGs 01221 and 01222 were first reported from Cambodia and Vietnam. New associations of Foc VCGs and banana cultivars were recorded in all the countries where the fungus was collected. Information obtained in this study could help Asian countries to develop and implement regulatory measures to prevent the incursion of Foc into areas where it does not yet occur. It could also facilitate the deployment of disease resistant banana varieties in infested areas.

Cereal grains include some of the most important crops grown in South Africa and play a major role in the local economy. Maize, wheat and sorghum are extensively consumed by humans and farm animals, and are also utilised in industrial processes. Grain crops that are grown commercially contribute up to 33% of the country’s total gross agricultural production, whereas subsistence farmers grow grains mainly to sustain their families. In rural communities an average intake of maize grain of more than 300 g dry weight per person per day is not uncommon. The production of grains is often constrained by pests and diseases that may reduce their yields and quality. In South Africa, 33 mycotoxin-producing Fusarium species have been associated with grain crops. Mycotoxins, such as fumonisins and deoxynivalenol, have been found in levels exceeding the maximum levels imposed by the US Food and Drug Administration and the European Union and therefore pose a serious public health concern. We provide an extensive overview of mycotoxigenic Fusarium species associated with grain crops in South Africa, with particular reference to maize, wheat and sorghum. Significance: Mycotoxigenic Fusarium species negatively affect the most important staple food crops grown in South Africa. Mycotoxin contamination has a direct impact on food safety and security. The genus Fusarium includes some of the most important mycotoxin-producing species.

Fusarium verticillioides is the causal agent of Fusarium ear rot (FER), an economically important disease of maize worldwide. The fungus also produces fumonisins in maize grain, which poses a food safety concern. To better understand the molecular interactions between maize and F. verticillioides during infection, genes expressed in infected and healthy maize kernels have been investigated. The expression of fungal genes in grain during infection has, however, received little attention. This is because fungal RNA forms only a fraction of the total RNA present in maize kernels, making transcriptome sequencing thereof difficult. The aim of this study, thus, was to study the expression of two F. verticillioides fumonisin biosynthetic (FUM) genes in maize kernels by reverse-transcription quantitative PCR (RT-qPCR). The ears of a susceptible maize inbred line were artificially inoculated with F. verticillioides, and maize kernels harvested 0, 7 and 14 days after inoculation (dai). The relative expression of the FUM1 and FUM19 genes was then quantified using RT-qPCR, and correlated to fumonisin levels in the kernels. Both genes were up-regulated in the fungus-inoculated plants 7 dpi, when fumonisin levels and F. verticillioides DNA concentration in the infected kernels increased. After 14 days with increasing fumonisin levels, the relative expression of FUM1 was further increased, but not that of FUM19. There was no significant correlation between in planta FUM gene expression and fumonisin concentration in maize kernels (P > 0.05). The optimization of a RT-qPCR protocol has provided a targeted approach to study fungal genes that play a role in pathogenesis and fumonisin production in planta and can further provide insights into the F. verticillioides-maize pathosystem.

In this letter, we advocate recognizing the genus Fusarium as the sole name for a group that includes virtually all Fusarium species of importance in plant pathology, mycotoxicology, medicine, and basic research. This phylogenetically guided circumscription will free scientists from any obligation to use other genus names, including teleomorphs, for species nested within this clade, and preserve the application of the name Fusarium in the way it has been used for almost a century. Due to recent changes in the International Code of Nomenclature for algae, fungi, and plants, this is an urgent matter that requires community attention. The alternative is to break the longstanding concept of Fusarium into nine or more genera, and remove important taxa such as those in the F. solani species complex from the genus, a move we believe is unnecessary. Here we present taxonomic and nomenclatural proposals that will preserve established research connections and facilitate communication within and between research communities, and at the same time support strong scientific principles and good taxonomic practice Fil: Geiser, David M.. State University of Pennsylvania; Estados Unidos Fil: Aoki, Takayuki. National Institute of Agrobiological Sciences; Japón Fil: Bacon, Charles W.. Toxicology and Mycotoxin Research; Grecia Fil: Baker, Scott E.. Pacific Northwest National Laboratory; Estados Unidos Fil: Bhattacharyya, Madan K.. University of Iowa; Estados Unidos Fil: Chulze, Sofia Noemi. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Fisicoquímicas y Naturales. Departamento de Microbiología e Inmunología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Scandiani, María Mercedes. Laboratorio Agrícola Río Paraná. San Pedro; Argentina Fil: Ploetz, Randy C.. University of Florida; Estados Unidos Fil: Proctor, Robert H.. NCAUR-ARS-USDA; Estados Unidos Fil: Rehner, Stephen A.. United States Department of Agriculture; Estados Unidos Fil: Robert, Vincent A. R. G.. Fungal Biodiversity Center; Países Bajos Fil: Rooney, Alejandro P.. NCAUR-ARS-USDA; Estados Unidos Fil: Salleh, Baharuddin bin. University of Malaysia; Malasia Fil: Scauflaire, Jonathan. Université Catholique de Louvain; Bélgica Fil: Short, Dylan P. G.. University of California; Estados Unidos Fil: Steenkamp, Emma. University of Pretoria; Sudáfrica Fil: Suga, Haruhisa. Gifu University; Japón Fil: Summerell, Brett A.. The Royal Botanic Garden Sydney; Australia Fil: Sutton, Deanna A.. University of Texas; Estados Unidos Fil: Thrane, Ulf. Technical University of Denmark; Dinamarca Fil: Trail, Francis. Michigan State University; Estados Unidos Fil: Van Diepeningen, Anne. Fungal Biodiversity Center; Países Bajos Fil: VanEtten, Hans D.. University of Arizona; Estados Unidos Fil: Viljoen, Altus. University of Stellenbosch; Sudáfrica Fil: Waalwijk, Cees. Wageningen University; Países Bajos Fil: Ward, Todd J.. NCAUR-ARS-USDA. Pretoria; Sudáfrica Fil: Wingfield, Michael J.. University of Pretoria; Sudáfrica Fil: Xu, Jin-Rong. Purdue University; Estados Unidos Fil: Yang, Xiao-Bing. University of Iowa; Estados Unidos Fil: Yli-Mattila, Tapani. University of Turku; Finlandia Fil: Zhang, Ning. Rutgers University; Estados Unidos

Fusarium ear rot of maize, caused by Fusarium verticillioides, reduces grain yield and quality and contaminates it with mycotoxins (fumonisin). As maize cultivars with complete resistance to Fusarium ear rot and fumonisin contamination have not been identified, and since the disease is difficult to control by conventional means, novel strategies for disease control and fumonisin reduction are required. One such strategy could involve the use of chemical elicitors that induce resistance in plants against a broad spectrum of pathogens, insects and abiotic stresses. In this study the ability of resistance elicitors to reduce infection by F. verticillioides and prevent fumonisin contamination in maize was investigated, and their impact on yield assessed. Five elicitors were selected based on their ability to activate different pathways in plant defence systems. The elicitors included β-amino butyric acid (BABA), benzothiadiazole (BTH), harpin protein, 2,6-dichloroisonicotinic acid (INA), and methyl jasmonate (MeJA). A fungicide containing difenoconazole (triazole) and azoxystrobin (strobilurin) as active ingredients and that has known fungicidal activity in other plant-pathogen interactions, but not specifically Fusarium ear rot, was also included. The plant resistance elicitors and fungicide were evaluated in multi-site field trials. Following artificial inoculation with F. verticillioides isolate MRC 826, a high fumonisin producer, visual rating of Fusarium ear rot severity was performed and fumonisin B1, B2 and B3 content of the grain quantified with high performance liquid chromatography. None of the five elicitors or the fungicide consistently reduced Fusarium ear rot and/or fumonisin contamination significantly. Treatment of maize with BTH resulted in a significant reduction in ear filling and yield in field trials. Treatment effects on fumonisin content were influenced by maize genotype and trial location, since significant interactions were observed between treatment, maize genotype and trial location. While the evaluated elicitors might be useful for prevention of maize foliar diseases, they were not effective at reducing Fusarium ear rot or fumonisin contamination. However, optimisation of elicitor application method, dose, frequency and timing could possibly yield improved results.

Fusarium ear rot of maize, caused by Fusarium verticillioides, is an important disease affecting maize production worldwide. Apart from reducing yield and grain quality, F. verticillioides produces fumonisins which have been associated with mycotoxicoses of animals and humans. Currently, no maize breeding lines are known with resistance to F. verticillioides in South Africa. The objective of this study, therefore, was to evaluate 24 genetically diverse maize inbred lines as potential sources of resistance to Fusarium ear rot and fumonisin accumulation in field trials at Potchefstroom and Vaalharts in South Africa. After artificial silk channel inoculation with F. verticillioides, Fusarium ear rot development was determined at harvest and fumonisins B1, B2, and B3 quantified. A significant inbred line by location effect was observed for Fusarium ear rot severity (P ≤ 0.001), although certain lines proved to be consistently resistant across both locations. The individual inbred lines also differed considerably in fumonisin accumulation between Potchefstroom and Vaalharts, with differentiation between susceptible and potentially resistant inbred lines only being possible at Vaalharts. A greenhouse inoculation trial was then also performed on a subset of potentially resistant and highly susceptible lines. The inbred lines CML 390, CML 444, CML 182, VO 617Y-2, and RO 549 W consistently showed a low Fusarium ear rot (–1. These lines could potentially act as sources of resistance for use within a maize breeding program.

Fusarium oxysporum f. sp. cepae, which causes basal rot of onion, consists of seven vegetative compatibility groups (VCGs 0420 to 0426) and several single-member VCGs (SMVs). F. oxysporum f. sp. cepae populations in South Africa and Colorado each consist of one main VCG (namely, VCG 0425 and 0421, respectively). The aim of this study was to develop sequence-characterized amplified region (SCAR) markers for the identification of VCGs 0425 and 0421, using 79 previously characterized F. oxysporum isolates. A second aim was to investigate the prevalence of VCG 0425 among 88 uncharacterized South African onion F. oxysporum isolates using (i) the developed SCAR markers and (ii) inter-retrotransposon (IR)- and random amplified polymorphic DNA (RAPD) fingerprinting. Only two RAPD primers provided informative fingerprints for VCG 0425 isolates but these could not be developed into SCAR markers, although they provided diagnostic fragments for differentiation of VCG 0425 from VCG 0421. IR fingerprinting data were used to develop a multiplex IR-SCAR polymerase chain reaction method for the identification of VCG 0421, VCG 0425, and SMV 4 isolates as a group. Molecular identification of the uncharacterized collection of 88 F. oxysporum isolates (65 F. oxysporum f. sp. cepae and 23 F. oxysporum isolates nonpathogenic to onion) confirmed that VCG 0425 is the main VCG in South Africa, with all but 3 of the 65 F. oxysporum f. sp. cepae isolates having the molecular characteristics of this VCG. Genotyping and VCG testing showed that two of the three aforementioned isolates were new SMVs (SMV 6 and SMV 7), whereas the third (previously known as SMV 3) now belongs to VGC 0247.

The distribution and co-occurrence of four Fusarium species and their mycotoxins were investigated in maize samples from two susceptible cultivars collected at 14 localities in South Africa during 2008 and 2009. Real-time PCR was used to quantify the respective Fusarium species in maize grain, and mycotoxins were quantified by multi-toxin analysis using HPLC-MS. In 2008, F. graminearum was the predominant species associated with maize ear rot in the eastern Free State, Mpumalanga and KwaZulu-Natal provinces, while F. verticillioides was predominant in the Northwest, the western Free State and the Northern Cape provinces. In 2009, maize ear rot infection was higher and F. graminearum became the predominant species found in the Northwest province. Fusarium subglutinans was associated with maize ear rot in both years at most of the localities, while F. proliferatum was not detected from any of the localities. Type B trichothecenes, especially deoxynivalenol, and zearalenone were well correlated with the amount of F. graminearum, fumonisins with F. verticillioides, and moniliformin and beauvericin with F. subglutinans. This information is of great importance to aid understanding of the distribution and epidemiology of Fusarium species in South Africa, and for predicting mycotoxin contamination risks and implementing preventative disease management strategies.

Species identity and trichothecene toxin potential of 560 members of the Fusarium graminearum species complex (FGSC) collected from diseased wheat, barley and maize in South Africa was determined using a microsphere-based multilocus genotyping assay. Although three trichothecene types (3-ADON, 15-ADON and NIV) were represented among these isolates, strains with the 15-ADON type predominated on all three hosts. A significant difference, however, was identified in the composition of FGSC pathogens associated with Gibberella ear rot (GER) of maize as compared to Fusarium head blight (FHB) of wheat or barley (P

Fusarium wilt of banana, caused by the soil-borne fungus Fusarium oxysporum f. sp. cubense (Foc), is a major constraint to banana production worldwide. A strain of the fungus that affects Cavendish and other dessert bananas in the tropics, called Foc tropical race 4 (TR4; VCG 01213/16), has been confined to five Asian countries (Indonesia, Malaysia, Philippines, mainland China, and Taiwan) for more than three decades. Cavendish production is now being expanded in Asia to Laos, Myanmar, and Vietnam, where local varieties still dominate the market. This is owing to an increase in Cavendish banana consumption and a decline in areas of production caused by Foc TR4 in China. The expansion of Cavendish production in Southeast Asia, however, has increased the risk of Foc TR4 being introduced into new countries. Leaf-yellowing symptoms typical of banana Fusarium wilt were observed in three provinces in northern Vietnam along the Red River that originates in the Yunnan province of China, namely Hanoi (October 2014), Hung Yen (October 2015), and Lao Cai (October 2015). When cut open, pseudostems displayed a dark-red to brown discoloration of vascular tissue, and the inner rhizome revealed a ring of yellow-brown staining. Samples of symptomatic strands from pseudostems were collected to identify the causal agent by morphological, molecular, and vegetative compatibility group (VCG) identification. The samples were first plated onto potato dextrose agar (PDA) containing streptomycin for fungal isolation. The cultures were then purified, single-spored, and maintained at the culture collection of the Department of Plant Pathology at Stellenbosch University in South Africa. Eight Fusarium isolates obtained were identified to species level on PDA and carnation leaf agar plates according to their cultural and spore morphology (Nelson et al. 1983). For molecular identification, total DNA was extracted and amplified with Foc TR4-specific primers (Dita et al. 2010) and Foc race 4-specific primers (Lin et al. 2009). VCG testing was performed according to the method of Puhalla (1985) by pairing nit-1 and nit-3 mutants of the isolates from Vietnam with nit-M testers of VCGs 01213, 01216, and 01213/16. Pathogenicity testing was performed by replanting Cavendish tissue culture plantlets at the six-leaf stage in sand mixed with corn powder, which was colonized by the individual Fusarium isolates from Vietnam, at a ratio of 19:1. Control plants were treated with sterile distilled water. The identity of the Vietnamese isolates was confirmed as F. oxysporum, whereas PCR and VCG analysis characterized six of them as VCG 01213/16 strains. After 6 weeks, plants inoculated with the VCG 01213/16 isolates produced typical symptoms of Fusarium wilt, so Koch's postulates were completed. The occurrence of Foc TR4 in Vietnam can have a significant economic impact to agricultural production, because investments were made to replace citrus, longan, and corn fields with Cavendish plantations. Foc TR4 also poses a threat to local banana varieties, and these varieties should therefore be evaluated for resistance to the fungus. The potential spread of Foc TR4 in Vietnam should be minimized by surveillance, public awareness campaigns, risk assessment, and containment efforts.

Fusarium wilt, caused by Fusarium oxysporum f. sp. cubense (Foc), is an important disease of banana in almost all banana-producing countries of the world. The recent occurrence of a highly virulent form of Foc in Asia, known as ‘tropical race 4’ (TR4), presents an imminent threat to the region’s Cavendish-based banana industries. Foc-TR4 has caused severe damage to the Cavendish banana industry of Taiwan since 1967, destroyed new plantations of Cavendish banana in Indonesia and Malaysia since the early 1990s and caused field epidemics in the Northern Territory of Australia between 1997 and 1999. In 2004, severe Foc infection in banana plantations in Guangdong province, South China, heightened the TR4 threat. All outbreaks are associated with the vegetative compatibility group (VCG) complex 1213/16. Historical field observations of Foc in Cavendish banana cultivars in the Philippines since 1970 are described. More than 30,000 individual reports of infection were officially recorded in the Philippines from 1974 to 1991. These infections were tested and identified as VCG 0122, 0123 and 0126, which are believed to be less virulent than the VCG 01213/16 complex. In September 2006, 30 infected plant samples were collected from highland and lowland Cavendish banana farms in Davao. These samples confirmed that the recent outbreaks of Fusarium wilt in Cavendish in the Philippines were caused by the VCG 01213/16 complex. The Philippine government, private banana companies and Bioversity International are collaborating to manage the disease and to try to contain further spread of Foc-TR4. INTRODUCTION Fusarium wilt, caused by Fusarium oxysporum f. sp. cubense (Foc), is a major concern of the global banana industry. The devastating disease destroyed ‘Gros Michel’ (AAA genome) plantations in the Central American/Caribbean region in the 1950s and lead to the disappearance of the cultivar as the traditional export banana. Cavendish cultivars (AAA genome), which are resistant to Foc race 1 that attacks ‘Gros Michel’, were used as replacements. Today, Cavendish cultivars are the mainstay of the world’s banana export industries. The recent occurrence of a virulent form of Foc in Asia that affects Cavendish banana cultivars in the tropics presents a serious new threat. This new form of Foc belongs to the vegetative compatibility group (VCG) 01213/16 and has been associated with severe field epidemics in Indonesia and Malaysia. Referred to as ‘tropical race 4’ (TR4), this pathogen has been observed in several countries in Asia where Cavendish banana cultivars are important for local consumption and export. In addition, all banana cultivars that are susceptible to Foc races 1 and 2 also succumb to TR4. It is believed that Foc has co-evolved with banana in Asia and that Foc-TR4 is endemic in this part of the world. This paper will review the historical occurrences of Proc. IS on Banana Crop Prot., Sust. Prod.

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; One of the most serious diseases of banana is fusarium wilt, caused by Fusarium oxysporum f.sp. cubense (Foc). The objectives of this study were to isolate and identify nonpathogenic F. oxysporum strains from soils suppressive to banana wilt, and to determine the diversity of these isolates. More than 100 Fusarium strains were isolated from the rhizosphere of banana plants and identified to species level. Pathogenicity testing was carried out to confirm that these isolates were nonpathogens of banana. A PCR-based RFLP analysis of the intergenic spacer region of the ribosomal RNA operon was used to characterize the nonpathogens. The isolates were also compared with isolates of Foc from South Africa and the known biological control isolate of F. oxysporum, Fo47. The species-specific primers FOF1 and FOR1, in addition to morphological features, were used to confirm the identity of F. oxysporum isolates included in the PCR-RFLP analysis. Twelve different genotypes could be distinguished, identified by a six-letter code allocated to each isolate following digestion with the restriction enzymes HaeIII, HhaI, HinfI, MspI, RsaI and ScrfI. Eleven of these included nonpathogenic F. oxysporum isolates, and these groups could all be distinguished from the genotype that included Foc. Fo47 was included in one of the genotype groups consisting of nonpathogenic F. oxysporum isolates from South Africa.

Fusarium oxysporum f. sp. cubense (Foc) is one of the most important threats to global banana production. Strategies to control the pathogen are lacking, with plant resistance offering the only long-term solution, if sources of resistance are available. Prevention of introduction of Foc into disease-free areas thus remains a key strategy to continue sustainable banana production. In recent years, strains of Foc affecting Cavendish bananas have destroyed plantations in a number of countries in Asia and in the Middle East, and one African country. One vegetative compatibility group (VCG), 01213/16, is considered the major threat to bananas in tropical and subtropical climatic conditions. However, other genetically related VCGs, such as 0121, may potentially jeopardize banana cultures if they were introduced into disease-free areas. To prevent the introduction of these VCGs into disease-free Cavendish banana-growing countries, a real-time PCR test was developed to accurately detect both VCGs. A previously described putative virulence gene was used to develop a specific combination of hydrolysis probe/primers for the detection of tropical Foc race 4 strains. The real-time PCR parameters were optimized by following a statistical approach relying on orthogonal arrays and the Taguchi method in an attempt to enhance sensitivity and ensure high specificity of the assay. This study also assessed critical performance criteria, such as repeatability, reproducibility, robustness, and specificity, with a large including set of 136 F. oxysporum isolates, including 73 Foc pathogenic strains representing 24 VCGs. The validation data demonstrated that the new assay could be used for regulatory testing applications on banana plant material and can contribute to preventing the introduction and spread of Foc strains affecting Cavendish bananas in the tropics.

BACKGROUND: Fusarium wilt, caused by the fungal pathogen Fusarium oxysporum f. sp. cubense (Foc), is one of the most destructive diseases of banana. Toxins produced by Foc have been proposed to play an important role during the pathogenic process. The objectives of this study were to investigate the contamination of banana with toxins produced by Foc, and to elucidate their role in pathogenesis. METHODOLOGY/PRINCIPAL FINDINGS: Twenty isolates of Foc representing races 1 and 4 were isolated from diseased bananas in five Chinese provinces. Two toxins were consistently associated with Foc, fusaric acid (FA) and beauvericin (BEA). Cytotoxicity of the two toxins on banana protoplast was determined using the Alamar Blue assay. The virulence of 20 Foc isolates was further tested by inoculating tissue culture banana plantlets, and the contents of toxins determined in banana roots, pseudostems and leaves. Virulence of Foc isolates correlated well with toxin deposition in the host plant. To determine the natural occurrence of the two toxins in banana plants with Fusarium wilt symptoms, samples were collected before harvest from the pseudostems, fruit and leaves from 10 Pisang Awak 'Guangfen #1' and 10 Cavendish 'Brazilian' plants. Fusaric acid and BEA were detected in all the tissues, including the fruits. CONCLUSIONS/SIGNFICANCE: The current study provides the first investigation of toxins produced by Foc in banana. The toxins produced by Foc, and their levels of contamination of banana fruits, however, were too low to be of concern to human and animal health. Rather, these toxins appear to contribute to the pathogenicity of the fungus during infection of banana plants.

Fusarium oxysporum f. sp. cubense (Foc) causes Fusarium wilt, a lethal disease that results in devastating economic losses to banana production worldwide. The pathogen originates from Asia where it evolved with its host, the wild banana plant Musa acuminata. Foc consists of three races, eight lineages and 24 Vegetative Compatibility Groups (VCGs). Most damage is caused by Foc tropical race 4 (TR4), which occurs exclusively in Asia. China is the biggest producer of Cavendish bananas (AAA) in the world, with plantations covering approximately 372.4677×103 hectares constituting up 90% of banana production, with the rest made up of Pisang Awak (ABB) and Dajiao or Plantain (AAB) bananas. In this study, 80 Foc isolates from six production areas were collected from diseased banana cultivars in China. These isolates were all single-spored and characterized to lineage level using five restriction enzymes while VCG identity was determined by generating nit-mutants, and pairing these mutants with a VCG tester set for Foc. To determine the occurrence of Foc TR4 in China, all isolates were screened with a newly developed Foc TR4-specific primer set. All the Foc isolates were also inoculated on Cavendish, Pisang Awak and Dajiao bananas for pathogenicity testing. Our results showed that Foc in China was highly diverse, as five of the eight lineages and 11 of the 24 known VCGs could be determined. The Foc TR4-specific primer set was highly specific for detecting VCG 01213/16, and could be used in diversity studies to rapidly identify this VCG complex. The majority of the isolates from China were identified as Foc TR4 (VCG 01213/16), and this VCG was found in four of the five production areas. Species of Fusarium other than F. oxysporum were non-pathogenic to banana. The selection of Foc-resistant banana clones, and the development of appropriate disease management strategies for Fusarium wilt of banana in China, is urgently required

Background Fusarium wilt, caused by the fungal pathogen Fusarium oxysporum f. sp. cubense tropical race 4 (Foc TR4), is considered the most lethal disease of Cavendish bananas in the world. The disease can be managed in the field by planting resistant Cavendish plants generated by somaclonal variation. However, little information is available on the genetic basis of plant resistance to Foc TR4. To a better understand the defense response of resistant banana plants to the Fusarium wilt pathogen, the transcriptome profiles in roots of resistant and susceptible Cavendish banana challenged with Foc TR4 were compared. Results RNA-seq analysis generated more than 103 million 90-bp clean pair end (PE) reads, which were assembled into 88,161 unigenes (mean size = 554 bp). Based on sequence similarity searches, 61,706 (69.99%) genes were identified, among which 21,273 and 50,410 unigenes were assigned to gene ontology (GO) categories and clusters of orthologous groups (COG), respectively. Searches in the Kyoto Encyclopedia of Genes and Genomes Pathway database (KEGG) mapped 33,243 (37.71%) unigenes to 119 KEGG pathways. A total of 5,008 genes were assigned to plant-pathogen interactions, including disease defense and signal transduction. Digital gene expression (DGE) analysis revealed large differences in the transcriptome profiles of the Foc TR4-resistant somaclonal variant and its susceptible wild-type. Expression patterns of genes involved in pathogen-associated molecular pattern (PAMP) recognition, activation of effector-triggered immunity (ETI), ion influx, and biosynthesis of hormones as well as pathogenesis-related (PR) genes, transcription factors, signaling/regulatory genes, cell wall modification genes and genes with other functions were analyzed and compared. The results indicated that basal defense mechanisms are involved in the recognition of PAMPs, and that high levels of defense-related transcripts may contribute to Foc TR4 resistance in banana. Conclusions This study generated a substantial amount of banana transcript sequences and compared the defense responses against Foc TR4 between resistant and susceptible Cavendish bananas. The results contribute to the identification of candidate genes related to plant resistance in a non-model organism, banana, and help to improve the current understanding of host-pathogen interactions.

Fusarium spp. produce fumonisins – mycotoxins that are of importance to maize production in South Africa. Fumonisins have been associated with human oesophageal cancer and cause various diseases in animals that are of concern to the animal feed industry. Maize samples, collected from subsistence farm fields in the Eastern Cape, KwaZulu-Natal, Limpopo and Mpumalanga provinces of South Africa during the 2006 and 2007 growing seasons, were analysed for Fusarium spp. and contamination with fumonisins. Fusarium verticillioides was the most common Fusarium species in maize followed by F. subglutinans and F. proliferatum . Levels of contamination with fumonisins ranged from 0 μg/g to 21.8 μg/g, depending on the region where samples were collected. Levels of fumonisins were highest in northern KwaZulu-Natal (Zululand) where 52% and 17% of samples collected in 2006 and 2007, respectively, exceeded 2 μg/g. Regression analyses showed a positive correlation between fumonisin-producing Fusarium spp. determined by real-time polymerase chain reaction and concentration of fumonisins ( r = 0.93). Many samples from Zululand, and some from Mokopane (Limpopo) and Lusikisiki (Eastern Cape), contained fumonisins at levels well above the maximum levels of 2 μg/g set by the Food and Drug administration (USA) and therefore also the limit of 1 μg/g set by the European Union for food intended for direct human consumption. Regulations governing contamination of grain with fumonisins are not yet implemented in South Africa. The high incidence of fumonisins in subsistence farming systems indicates the need for awareness programmes and further research.

Fusarium oxysporumf. sp.cubense, the causal agent of fusarium wilt of banana (Musaspp.), is one of the most destructive strains of the vascular wilt fungusF. oxysporum. Genetic relatedness among and within vegetative compatibility groups (VCGs) ofF. oxysporumf. sp.cubensewas studied by sequencing two nuclear and two mitochondrial DNA regions in a collection of 70F. oxysporumisolates that include representatives of 20 VCGs ofF. oxysporumf. sp.cubense, other formae speciales, and nonpathogens. To determine the ability ofF. oxysporumf. sp.cubenseto sexually recombine, crosses were made between isolates of opposite mating types. Phylogenetic analysis separated theF. oxysporumisolates into two clades and eight lineages. Phylogenetic relationships betweenF. oxysporumf. sp.cubenseand other formae speciales ofF. oxysporumand the relationships among VCGs and races ofF. oxysporumf. sp.cubenseclearly showed thatF. oxysporumf. sp.cubense's ability to cause disease on banana has emerged multiple times, independently, and that the ability to cause disease to a specific banana cultivar is also a polyphyletic trait. These analyses further suggest that both coevolution with the host and horizontal gene transfer may have played important roles in the evolutionary history of the pathogen. All examined isolates harbored one of the two mating-type idiomorphs, but never both, which suggests a heterothallic mating system should sexual reproduction occur. Although, no sexual structures were observed, some lineages ofF. oxysporumf. sp.cubenseharboredMAT-1andMAT-2isolates, suggesting a potential that these lineages have a sexual origin that might be more recent than initially anticipated.

Fusarium oxysporum f. sp. cubense (Foc) is responsible for fusarium wilt of bananas. The pathogen consists of several variants that are divided into three races and 21 vegetative compatibility groups (VCGs). Several DNA-based techniques have previously been used to analyse the worldwide population of Foc, sometimes yielding results that were not always consistent. In this study, the high-resolution genotyping method of AFLP is introduced as a potentially effective molecular tool to investigate diversity in Foc at a genome-wide level. The population selected for this study included Foc isolates representing different VCGs and races, isolates of F. oxysporum f. sp. dianthi, a putatively non-pathogenic biological control strain F. oxysporum (Fo47), and F. circinatum. High-throughput AFLP analysis was attained using five different infrared dye-labelled primer combinations using a two-dye model 4200s LI-COR automated DNA analyser. An average of approx. 100 polymorphic loci were scored for each primer pair using the SAGAMX automated AFLP analysis software. Data generated from five primer pair combinations were combined and subjected to distance analysis, which included the use of neighbour-joining and a bootstrap of 1000 replicates. A tree inferred from AFLP distance analysis revealed the polyphyletic nature of the Foc isolates, and seven genotypic groups could be identified. The results indicate that AFLP is a powerful tool to perform detailed analysis of genetic diversity in the banana pathogen Foc.

Fusarium subglutinans is a well-known pathogen of many crops. The fungus causes a serious disease of pines known as pitch canker. A proposal has been made to designate isolates from pines E subglutinans f. sp. pini (F. s. f. sp. pini). An enigma regarding the nomenclature is that some F. s. f. sp. pini isolates have been reported to induce decay of gladiolus corms whereas certain isolates of F. subglutinans from gladiolus corms were also found to be weakly to moderately pathogenic to pine seedlings. In this study we re-examined three previously studied isolates from gladiolus in the United States that had been referred to as F. subglutinans ( = F. moniliforme var. subglutinans) or F. moniliforme in the literature. We found that these isolates were typical of F. proliferatum. They were mildly pathogenic on pine seedlings and significantly less virulent than an isolate of F. s. f. sp. pini. Inoculation of gladiolus corms with these isolates of F. proliferatum from gladiolus, F. oxysporum from pine seedlings, and E subglutinans from pines (F. s. f. sp. pini), corn, mango, and pineapple indicated that only isolates of E proliferatum were moderately pathogenic to gladiolus corms. This study therefore supports the proposal that isolates of F. subglutinans from pines represent a specific forma specialis within the species.

Viljoen. A., Wingfield, M. J., and Marasas. W. F. 0.1994. First report of Fusarium subglurinans f. sp. pini on pine seedlings in South Africa. Plant Dis. 78:309-312. A study of fungi responsible for root rot of Pinus parula seedlings in a forest nursery yielded Fusarium subglutinans f. sp. pini and F. oxysporum. F. s. pini was isolated most frequently from diseased seedlings and proved to be the most virulent fungus in pathogenicity tests conducted on germinated seed and 2-mo-old seedlings. Inoculation of 3-yr-old trees with F. s. pini yielded symptoms reminiscent of pitch canker. This is the first report of F. s. pini causing root disease of pine seedlings and is also the first record of the fungus in the Southern Hemisphere.