<Emphasis Type="Italic">Fusarium temperatum</Emphasis> isolated from maize in France

The presence of Fusarium temperatum in France was investigated by analyzing 40 Fusarium strains, previously isolated from infected maize ears in 2011 and formerly identified as Fusarium subglutinans based on morphological characteristics. In this study, 26 strains out of the 40 were identified as F. temperatum and 14 as F. subglutinans based on sequencing of the translation elongation factor 1α gene. The phylogenetic analysis showed that the two species represented two clades strongly supported by bootstrap values. The pathogenicity of F. temperatum strains was confirmed on maize ears. This study provides new information about F. temperatum isolated from maize in France.     

Toxigenic Fusarium Species and Mycotoxins Associated with Maize Ear Rot in Europe

Several Fusarium species occurring worldwide on maize as causal agents of ear rot, are capable of producing mycotoxins in infected kernels, some of which have a notable impact on human and animal health. The main groups of Fusarium toxins commonly found are: trichothecenes, zearalenones, fumonisins, and moniliformin. In addition, beauvericin and fusaproliferin have been found in Fusarium-infected maize ears. Zearalenone and deoxynivalenol are commonly found in maize red ear rot, which is essentially caused by species of the Discolour section, particularly F. graminearum. Moreover, nivalenol and fusarenone-X were often found associated with the occasional occurrence of F. cerealis, and diacetoxyscirpenol and T-2 toxin with the occurrence of F. poae and F. sporotrichioides, respectively. In addition, the occurrence of F. avenaceum and F. subglutinans usually led to the accumulation of moniliformin. In maize pink ear rot, which is mainly caused by F. verticillioides, there is increasing evidence of the wide occurrence of fumonisin B₁. This carcinogenic toxin is usually found in association with moniliformin, beauvericin, and fusaproliferin, both in central Europe due to the co-occurrence of F. subglutinans, and in southern Europe where the spread of F. verticillioides is reinforced by the widespread presence of F. proliferatum capable of producing fumonisin B₁, moniliformin, beauvericin, and fusaproliferin.     

Quantitative detection of Fusarium pathogens and their mycotoxins in South African maize

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.     

Biodiversity of Fusarium species in ears and stalks of maize plants in Belgium

In order to investigate the pre-harvest contamination of maize plants by Fusarium species in Belgium, a three-year survey has been performed in five fields in which three hybrids differing in susceptibility to maize stalk rot were sampled at four different physiological stages. An extensive collection of 5,659 Fusarium isolates characterized at the species level was established during the 2005, 2006, and 2007 growing seasons, with a total of 23 different Fusarium species identified to occur on ears and stalks. A high number of plants was already contaminated by Fusarium spp. at the anthesis stage, although no symptoms were visible on ears or on stalks. As the season progressed, the incidence of Fusarium-infected maize plants reached 100% in several fields. At the end of the growing season, the most frequently isolated species in maize ears were F. graminearum, sometimes associated with F. avenaceum, F. crookwellense, F. culmorum, F. poae, and F. temperatum, a new species recently described on maize. The predominant Fusarium species detected in stalks at the end of the growing season were F. graminearum and F. crookwellense, often associated with F. culmorum and F. temperatum. Year-to-year variability observed for the incidence of F. graminearum can most likely be associated with differences in climatic conditions among the three years.     

<Emphasis Type="Italic">Fusarium</Emphasis> species and mycotoxin profiles on commercial maize hybrids in Germany

High year-to-year variability in the incidence of Fusarium spp. and mycotoxin contamination was observed in a two-year survey investigating the impact of maize ear rot in 84 field samples from Germany. Fusarium verticillioides, F. graminearum, and F. proliferatum were the predominant species infecting maize kernels in 2006, whereas in 2007 the most frequently isolated species were F. graminearum, F. cerealis and F. subglutinans. Fourteen Fusarium-related mycotoxins were detected as contaminants of maize kernels analyzed by a multi-mycotoxin determination method. In 2006, a growth season characterized by high temperature and low rainfall during anthesis and early grain filling, 75% of the maize samples were contaminated with deoxynivalenol, 34% with fumonisins and 27% with zearalenone. In 2007, characterized by moderate temperatures and frequent rainfall during the entire growth season, none of the 40 maize samples had quantifiable levels of fumonisins while deoxynivalenol and zearalenone were detected in 90% and 93% of the fields, respectively. In addition, 3-acetyldeoxynivalenol, 15-acetyldeoxnivalenol, moniliformin, beauvericin, nivalenol and enniatin B were detected as common contaminants produced in both growing seasons. The results demonstrate a significant mycotoxin contamination associated with maize ear rots in Germany and indicate, with regard to anticipated climate change, that fumonisins-producing species already present in German maize production may become more important.     

A Species-Specific PCR Assay Based on the Calmodulin Partial Gene for Identification of Fusarium Verticillioides, F. Proliferatum and F. Subglutinans

Fusarium proliferatum, F. subglutinans and F. verticillioides are the most important Fusarium species occurring on maize world-wide, capable of producing a wide range of mycotoxins which are a potential health hazard for animals and humans. The ribosomal internal transcribed spacer and a portion of the calmodulin gene were sequenced and analysed in order to design species-specific primers useful for diagnosis. The primer pairs were based on a partial calmodulin gene sequence. Three pairs of primers (PRO1/2, SUB1/2 and VER 1/2) produced PCR products of 585, 631 and 578bp for F. proliferatum, F. subglutinans and F. verticillioides, respectively. Primer specificity was confirmed by analyzing DNA of 150 strains of these species, mostly isolated from maize in Europe and USA. The sensitivity of primers was 12.5 pg when the pure total genomic DNA of each species was analyzed. The developed PCR assay should provide a powerful tool for the detection of toxigenic fungi in maize kernels.     

Influence of Climatic Factors on Fusarium Species Pathogenic to Cereals

Fusarium head blight of small-grain cereals, ear rot of maize, seedling blight and foot rot of cereals are important diseases throughout the world. Fusarium graminearum, F. culmorum, F. poae, F. avenaceum and Microdochium nivale (formerly known as F. nivale) predominantly cause Fusarium diseases of small-grain cereals. Maize is predominantly attacked by F. graminearum, F. moniliforme, F. proliferatum and F. subglutinans. These species differ in their climatic distribution and in the optimum climatic conditions required for their persistence. This review deals with the influence of climate on the production and dispersal of inocula, growth, competition, mycotoxin production and pathogenicity. Most species produce inocula, grow best, and are most pathogenic to cereal heads at warm temperatures and under humid conditions. However, the optimal conditions for F. moniliforme and F. proliferatum maize ear rot tend to be hot and dry and M. nivale head blight, seedling blight and foot rot of small-grain cereals tend to occur under cooler conditions. Seedling blight and foot rot caused by other species are favoured by warm dry weather. Between them, these fungi produce four important classes of mycotoxins: trichothecenes, zearalenone, fumonisins and moniliformin. Conditions favourable for in vitro growth are also generally the most favourable for mycotoxin production on cereal grains. These fungi rarely exist in isolation, but occur as a complex with each other and with other Fusaria and other fungal genera. Climatic conditions will influence competition between, and the predominance of, different fungi within this complex.     

Epidemiology of Fusarium Diseases and their Mycotoxins in Maize Ears

Fusarium species cause two distinct diseases on ears of maize, Fusarium ear rot (or pink ear rot) and Gibberella ear rot (or red ear rot), both of which can result in mycotoxin contamination of maize grain. The primary causal agent for Fusarium ear rot is Fusarium verticillioides, but F. subglutinans and F. proliferatum are also important. Gibberella ear rot is caused primarily by F. graminearum, but F. culmorum can also be important, especially in Europe. Aspects of the epidemiology of both diseases have been studied for decades, but only recently have efforts been made to synthesize this information into comprehensive models of disease development. Much of the work on F. graminearum has focused on Fusarium head blight of small-grain crops, but some of the results obtained are also relevant to maize. The primary mycotoxins produced by these fungi, fumonisins and deoxynivalenol, have differing roles in the disease-cycle, and these roles are not completely understood, especially in the case of fumonisins. Progress is being made toward accurate models for risk assessment of both diseases, but key challenges remain in terms of integrating models of pre- and post-infection events, quantifying the roles of insects in these diseases, and characterizing interactions among competing fungi and the environment.     

<Emphasis Type="Italic">Fusarium</Emphasis> species complex on maize in Switzerland: occurrence,prevalence, impact and mycotoxins in commercial hybrids under natural infection

The Fusarium species complex of maize kernels and stem pieces as well as mycotoxin contamination of commercial grain maize hybrids for animal feed were evaluated in Switzerland. Throughout 2 years, natural Fusarium infection varied significantly between the years and the locations and it ranged from 0.4% to 49.7% for kernels and from 24.2% to 83.8% for stem pieces. Using the agar plate method, 16 different Fusarium species were isolated from kernels and 15 from stem pieces. The Fusarium species composition, prevalence and impact differed between the north and the south and between kernel and stem piece samples. The dominant species on kernels in the north were F. verticillioides (32.9%), F. graminearum (31.3%), F. proliferatum (7.3%) and F. crookwellense (7.1%), in the south F. verticillioides (57.1%), F. subglutinans (24.6%), F. proliferatum (14.8%) and F. graminearum (1.5%) and on stem pieces F. equiseti (36.0%), F. verticillioides (20.1%), F. graminearum (9.5%), F. crookwellense (6.2%) and F. subglutinans (6.2%). In the south, fumonisin concentration of most hybrids exceeded guidance values for animal feed. Other Fusarium species isolated were F. avenaceum, F. culmorum, F. oxysporum, F. poae, F. sambucinum, F. semitectum, F. sporotrichioides, F. solani, F. tricinctum and F. venenatum. Maize hybrids varied in their susceptibility to Fusarium infection. Because of the high diversity of Fusarium species encountered in Switzerland representing a high toxigenic potential, we propose to screen maize hybrids for resistance against various Fusarium species and examine maize produce for several mycotoxins in order to ensure feed safety.     

Epidemiology of Toxigenic Fungi and their Associated Mycotoxins for Some Mediterranean Crops

Recent data on the epidemiology of the common mycotoxigenic species of Fusarium, Alternaria, Aspergillus and Penicillium in infected or colonized plants, and in stored or processed plant products from the Mediterranean area are reviewed. Emphasis is placed on the toxigenicity of the causal fungal species and the natural occurrence of well known mycotoxins (aflatoxins, ochratoxins, fumonisins, trichothecenes, zearalenone, patulin, Alternaria-toxins and moniliformin), as well as some more recently described compounds (fusaproliferin, beauvericin) whose toxigenic potential is not yet well understood. Several Fusarium species reported from throughout the Mediterranean area are responsible of the formation of mycotoxins in infected plants and in plant products, including: Fusarium graminearum, F. culmorum, F. cerealis, F. avenaceum, F. sporotrichioides and F. poae, which produce deoxynivalenol, nivalenol, fusarenone, zearalenone, moniliformin, and T-2 toxin derivatives in wheat and other small grains affected by head blight or scab, and in maize affected by red ear rot. Moreover, strains of F. verticillioides, F. proliferatum, and F. subglutinans, that form fumonisins, beauvericin, fusaproliferin, and moniliformin, are commonly associated with maize affected by ear rot. Fumonisins, were also associated with Fusarium crown and root rot of asparagus and Fusarium endosepsis of figs, caused primarily by F. proliferatum. Toxigenic A. alternata strains and associated tenuazonic acid and alternariols were commonly found in black mould of tomato, black rot of olive and citrus, black point of small cereals, and black mould of several vegetables. Toxigenic strains of A. carbonarius and ochratoxin A were often found associated with black rot of grapes, whereas toxigenic strains of A. flavus and/or P. verrucosum, forming aflatoxins and ochratoxin A, respectively, were found in moulded plant products from small cereals, peanuts, figs, pea, oilseed rape, sunflower seeds, sesame seeds, pistachios, and almonds. Finally, toxigenic strains of P. expansum and patulin were frequently found in apple, pear and other fresh fruits affected by blue mould rot, as well as in derived juices and jams.     

Systematics of key phytopathogenic Fusarium species: current status and future challenges

This review is intended to provide plant pathologists and other scientists with a current overview of the most important Fusarium phytopathogens and mycotoxin producers. Knowledge of Fusarium species diversity and their evolutionary relationships has increased dramatically due to the application of multilocus molecular phylogenetics and genealogical concordance phylogenetic species recognition over the past 15 years. Currently Fusarium is estimated to comprise at least 300 genealogically exclusive phylogenetic species; however, fewer than half have been formally described. The most important plant pathogens reside in the following four groups: the F. fujikuroi species complex noted for Bakanae of rice, ear rot of maize, pitch canker of pine and several species that contaminate corn and other cereals with fumonisin mycotoxins; the F. graminearum species complex including the primary agents causing Fusarium head blight of wheat and barley that contaminate grain with trichothecene mycotoxins; the F. oxysporum species complex including vascular wilt agents of over 100 agronomically important crops; and the F. solani species complex, which includes many economically destructive foot and root rot pathogens of diverse hosts. Several other Fusarium phytopathogens reported from Japan and nested within other species complexes are reviewed briefly. With the abandonment of dual nomenclature, a broad consensus within the global community of Fusarium researchers has strongly supported the unitary use of the name Fusarium instead of several teleomorph names linked to it. Plant pathologists and other scientists needing accurate identifications of Fusarium isolates are encouraged to use Fusarium-ID and Fusarium MLST, Internet accessible websites dedicated to the molecular identification of Fusarium species.     

Morphological and molecular identification and PCR amplification to determine the toxigenic potential of Fusarium spp. isolated from maize ears in southern Poland

The average amount of precipitation in spring and summer 2010 and 2011 coupled with relatively high temperatures caused massive Fusarium spp. infection of maize and yield losses in southern Poland. In order to examine the cause of this disease outbreak, Fusarium spp. were isolated and fungal strains were identified based on morphological characters and species-specific PCR assays. A total of 200 maize samples were processed, resulting in the obtention of 71 strains, which belonged to five Fusarium species, F. poae being the predominant one (74.56%). Other isolates were identified as F. graminearum, F. oxysporum, F. verticillioides and F. proliferatum. PCR-based detection of mycotoxin-synthesis-pathway genes was also used to determine the potential of the analyzed strains to produce trichothecenes (DON and NIV) and fumonisins (FUM). Only 14 isolates revealed the potential to produce DON (11 strains) and FUM (3 strains). HPLC analyses of grain samples revealed the presence of DON only – other mycotoxins were not detected. Moreover, 57.1% of potentially mycotoxin-producing isolates indicated the toxicity in a biological test.     

Occurrence of Fusarium species in maize kernels grown in northwestern Spain

Fusarium poses food and feed safety problems because most species produce mycotoxins. To understand the epidemiology of the Fusarium disease, efforts must focus more precisely on how environmental variables affect disease presence. The objectives of the present study were to monitor the occurrence of Fusarium species in maize kernels in northwestern Spain to determine the risk of mycotoxin contamination and to identify environmental traits affecting the composition of the Fusarium species identified. A combination of 24 environments was evaluated. The percentage of kernels infected by F. verticillioides ranged from 33 to 99%, supporting the idea that fumonisin contamination is the main maize‐based feed and food safety concern in this area. In this region, temperature and humidity primarily affected Fusarium spp. occurrence. Warmer temperatures during the later stages of kernel development and during kernel drying increased the frequency of F. verticillioides in maize kernels, while the presence of F. subglutinans was increased by higher relative humidity during the silking stage and cooler temperatures during kernel drying.     

Natural occurrence of <Emphasis Type="Italic">Fusarium</Emphasis> species and fumonisin on maize grains in Ethiopia

Fusarium species causing maize kernel rot are major threats to maize production, due to reduction in yield as well as contamination of kernels by mycotoxins that poses a health risk to humans and animals. Two-hundred maize kernel samples, collected from 20 major maize growing areas in Ethiopia were analyzed for the identity, species composition and prevalence of Fusarium species and fumonisin contamination. On average, 38 % (range: 16 to 68 %) of maize kernels were found to be contaminated by different fungal species. Total of eleven Fusarium spp. were identified based on morphological characteristics and by sequencing the partial region of translation elongation factor 1-alpha (EF-1α) gene. Fusarium verticillioides was the dominant species associated with maize kernels (42 %), followed by F. graminearum species complex (22.5 %) and F. pseudoanthophilium (13.4 %). The species composition and prevalence of Fusarium species differed among the areas investigated. Fusarium species composition was as many as eight and as few as four in some growing area. The majority of the maize samples (77 %) were found positive for fumonisin, with concentrations ranging from 25 μg kg^?1 to 4500 μg kg^?1 (mean: 348 μg kg^?1 and median: 258 μg kg^?1). Slight variation in fumonisin concentration was also observed among areas. Overall results indicate widespread occurrence of several Fusarium species and contamination by fumonisin mycotoxins. These findings are useful for intervention measures to reduce the impact of the main fungal species and their associated mycotoxins, by creating awareness and implementation of good agricultural practices.     

Genetic Analysis of the Role of Trichothecene and Fumonisin Mycotoxins in the Virulence of Fusarium

The phytotoxicity of the Fusarium trichothecene and fumonisin mycotoxins has led to speculation that both toxins are involved in plant pathogenesis. This subject has been addressed by examining virulence of trichothecene and fumonisin-nonproducing mutants of Fusarium in field tests. Mutants were generated by transformation-mediated disruption of genes encoding enzymes that catalyze early steps in the biosynthesis of each toxin. Two economically important species of Fusarium were selected for these studies: the trichothecene-producing species Fusarium graminearum, which causes wheat head blight and maize ear rot, and the fumonisin-producing species F. verticillioides, which causes maize ear rot. Trichothecene-non-producing mutants of F. graminearum caused less disease than the wild-type strain from which they were derived on both wheat and maize, although differences in virulence on maize were not observed under hot and dry environmental conditions. Genetic analyses of the mutants demonstrated that the reduced virulence on wheat was caused by the loss of trichothecene production rather than by a non-target mutation induced by the gene disruption procedure. Although the analyses of virulence of fumonisin-non-producing mutants of F. verticillioides are not complete, to date, the mutants have been as virulent on maize ears as their wild-type progenitor strains. The finding that trichothecene production contributes to the virulence of F. graminearum suggests that it may be possible to generate plants that are resistant to this fungus by increasing their resistance to trichothecenes. As a result, several researchers are trying to identify trichothecene resistance genes and transfer them to crop species.     

Ear Rot Susceptibility and Mycotoxin Contamination of Maize Hybrids Inoculated with Fusarium Species Under Field Conditions

The development of new maize hybrids with resistance to Fusarium infection is an effective means of minimizing the risk of mycotoxin contamination. Several maize hybrids have been investigated for Fusarium ear rot and accumulation of fumonisin B₁ (FB₁), fumonisin B₂ (FB₂), beauvericin (BEA) and fusaproliferin (FP) after artificial inoculation in the field with toxigenic strains of Fusarium verticillioides and Fusarium proliferatum. The year of inoculation had a significant influence on the disease severity and mycotoxin accumulation in maize kernels. Of all the hybrids tested, only Mona exhibited resistance to ear rot caused by F. verticillioides and produced low levels of fumonisins during three years of experiments. In Fusarium-damaged kernels (FDK), fumonisin B₁, fumonisin B₂, beauvericin and fusaproliferin were detected at concentrations much higher (up to 10–20 times) than in healthy-looking kernels (HLK). Animal and human exposure to these mycotoxins can be drastically reduced by removing mouldy and visibly damaged kernels from the commodity.     

Early PCR-based detection of Fusarium culmorum,F. graminearum,F. sporotrichioides and F. poae on stem bases of winter wheat throughout Poland

Foot rot and crown rot are fungal diseases of wheat caused by a complex of Fusarium species. They have a huge economic impact mainly due to yield reduction. A survey was conducted to identify four Fusarium species, occurring on wheat stem bases, using species-specific PCR assays in samples collected during spring of 2012. The dominant species was F. graminearum, which was identified in above 64 % of samples. F. culmorum was detected in 15.71 %, F. poae in 15.71 % and F. sporotrichioides in 5.71 % wheat fields. Most of the wheat fields in the eastern Poland were infected with at least one or two of Fusarium species, while in central Poland no Fusarium species were identified in most of the fields. The presence of F. graminearum tends to favor the presence of F. culmorum and this effect was visible also for F. poae and F. sporotrichioides. The frequency of F. graminearum and F. culmorum detections were highest where wheat crops were preceded by maize and in the samples from late sown fields. The opposite observation was made for F. poae and F. sporotrichioides, where the number of detections of these species was higher in samples from early sown fields. The number of detected Fusarium species was significantly lower in samples collected from fields protected with autumn herbicide in comparison to unprotected fields. The rate of autumn N fertilization did not affect the number of Fusarium detections.     

Fusarium miscanthi and other Fusarium species as causal agents of Miscanthus × giganteus rhizome rot

In 2010, Miscanthus × giganteus rhizomes were collected from Belgian fields showing emergence reduction and were analyzed for detection and identification of fungal species. All rhizomes were infected by at least one Fusarium species, of which F. culmorum, F. miscanthi, F. crookwellense and F. graminearum were the most abundant. Results of the pathogenicity tests by soil inoculation demonstrate the ability of F. miscanthi, F. culmorum and F. avenaceum to cause rhizome rot disease under greenhouse conditions. This is the first report of F. miscanthi and other Fusarium species isolated from M. × giganteus rhizomes in Belgium.     

Detection of Fusarium langsethiae on wheat in Belgium

In 2010, the populations of Fusarium sp. and Microdochium sp. were monitored in Belgium and 16 strains were identified as Fusarium langsethiae on wheat in Belgium. The other species identified from the sampling were F. poae, F. tritinctum, F. graminearum, F. avenaceum and Microdochium nivale. The pathogenicity potential of the F. langsethiae strains was assessed via an in vitro coleoptile growth rate test on wheat seedlings and compared with strains of F. poae, F. tritinctum, F. graminearum and F. avenaceum known to cause Fusarium head blight. The results showed the ability of F. langsethiae to cause retardation in the wheat coleoptile growth rate, but at a lower rate than F. graminearum, F. avenaceum, F. poae and F. tricinctum. A test for mycotoxin production in vitro showed the ability of the four strains tested to produce T-2 and HT-2 toxins at a rate of up to 290 mg kg^?1. This is the first report on the potential pathogenicity of F. langsethiae on wheat in Belgium, a species known to produce T-2 and HT-2 toxins, which are highly toxic for humans and animals.     

Characterization of Fusarium diseases on commercially grown orchids in Hawaii

A decline of unknown aetiology has become a major problem for commercial orchid production in Hawaii, one of the primary orchid‐producing states in the USA. The major symptoms of decline include root degradation, foliar blight, pseudobulb rot and sheath rot. It was unclear whether all these symptoms are caused by the same or different pathogens, but preliminary research indicated that Fusarium species may be involved. In this study, the incidence of Fusarium species was examined across 186 plants, from 29 orchid genera and intergeneric hybrids across three islands in the state of Hawaii. The main five species associated with diseased orchids were F. proliferatum (38% of samples), F. solani (16%), F. oxysporum (16%) and two previously undescribed species (8% for both species combined). The two undescribed species were similar in appearance to F. subglutinans, and were designated FS‐A and FS‐B. Pathogenicity tests established that both F. proliferatum and FS‐B caused foliar spots, foliar blight and pseudostem rot on Dendrobium orchids, and that F. proliferatum isolates from diseased tissue of several genera could also induce symptoms on Dendrobium orchids. Although orchids have increasing importance in floriculture, relatively little is known about orchid pathogens, and previous studies focused primarily on Cymbidium and Phalaenopsis. This study provides new information concerning Dendrobium orchid pathogens and suggests a much wider host range than previously recognized for the five Fusarium species recovered from tissue with symptoms. These findings can contribute to better management of Fusarium diseases, which represent a significant challenge to orchid production in Hawaii.