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Fusarium graminearum strains responsible for causing the plant disease Fusarium head blight vary greatly in their ability to cause disease and produce mycotoxins on wheat. With the goal of understanding fungal gene expression related to pathogenicity, three cDNA libraries were created by suppression subtractive hybridization using wheat heads inoculated with a highly aggressive strain and either water or a less aggressive strain of this pathogen. Eighty-four fungal genes expressed during initial disease development were identified. The probable functions of 49 of these genes could be inferred by bioinformatic analysis. Thirty-five ESTs had no known homologues in current databases and were not identified by ab initio gene prediction methods. These ESTs from infected wheat heads probably represent F. graminearum genes that previously were not annotated. Four genes represented in one of these libraries were selected for targeted gene replacement, leading to the characterization of a two-component response regulator homologue involved in pathogenicity of the fungus. The mutants for this gene showed reduced sporulation and delayed spread of Fusarium head blight on wheat.

Introduction: Root rots are a growing concern in edible legumes such as field peas/dry peas and dry beans in north central United States. These crops are commonly grown in rotation [...]

Ascochyta blight of chickpea, caused by the fungal pathogen Ascochyta rabiei, causes significant yield losses in all chickpea growing areas of North America (2, 3). The disease is managed primarily [...]

Ascochyta blight is the most important disease of chickpeas in North Dakota, causing severe yield losses and significantly reducing seed quality. It is caused by the necrotrophic fungal pathogen Ascochyta [...]

North Dakota is the largest producer of dry edible beans (Phaseolus vulgaris L.) in the United States with 660,000 acres planted to this crop in 2008 (USDA-NASS). The ability of [...]

SUMMARY The goal of this study was to develop a tool specifically designed to identify iterative polyketide synthases (iPKSs) from predicted fungal proteomes. A fungi-based PKS prediction model, specifically for fungal iPKSs, was developed using profile hidden Markov models (pHMMs) based on two essential iPKS domains, the β-ketoacyl synthase (KS) domain and acyltransferase (AT) domain, derived from fungal iPKSs. This fungi-based PKS prediction model was initially tested on the well-annotated proteome of Fusarium graminearum, identifying 15 iPKSs that matched previous predictions and gene disruption studies. These fungi-based pHMMs were subsequently applied to the predicted fungal proteomes of Alternaria brassicicola, Fusarium oxysporum f.sp. lycopersici, Verticillium albo-atrum and Verticillium dahliae. The iPKSs predicted were compared against those predicted by the currently available mixed-kingdom PKS models that include both bacterial and fungal sequences. These mixed-kingdom models have been proven previously by others to be better in predicting true iPKSs from non-iPKSs compared with other available models (e.g. Pfam and TIGRFAM). The fungi-based model was found to perform significantly better on fungal proteomes than the mixed-kingdom PKS model in accuracy, sensitivity, specificity and precision. In addition, the model was capable of predicting the reducing nature of fungal iPKSs by comparison of the bit scores obtained from two separate reducing and nonreducing pHMMs for each domain, which was confirmed by phylogenetic analysis of the KS domain. Biological confirmation of the predictions was obtained by polymerase chain reaction (PCR) amplification of the KS and AT domains of predicted iPKSs from V. dahliae using domain-specific primers and genomic DNA, followed by sequencing of the PCR products. It is expected that the fungi-based PKS model will prove to be a useful tool for the identification and annotation of fungal PKSs from predicted proteomes. [ABSTRACT FROM AUTHOR]

The article reports on the spatial dimension of plant disease development which was always neglected by epidemiologists despite its importance. It discusses that methods such as spatial scales, mapping and geostatics to be used for spatial analysis. It infers that the spikelet disease severity is numbered and that the metabolic profiles were recorded using gas chromatography.

The rapid global re-emergence of Fusarium head blight disease of wheat and barley in the last decade along with contamination of grains with mycotoxins attributable to the disease have spurred basic research on the fungal causal agent. As a result, Fusarium graminearum quickly has become one of the most intensively studied fungal plant pathogens. This review briefly summarizes current knowledge on the pathogenicity, population genetics, evolution and genomics of Fusarium graminearum. Taxonomy: Based on the sexual state Gibberella zeae (Schwein.) Petch: Superkingdom Eukaryota; Kingdom Fungi; Phylum Ascomycota; Subphylum Pezizomycotina; Class Sordario- mycetidae; Subclass Hypocreomycetidae; Order Hypocreales; Family Nectriaceae; Genus Gibberella. Host range: The pathogen is capable of causing head blight or `scab' on wheat ( Triticum) , barley ( Hordeum) , rice (Oryza), oats (Avena) and Gibberella stalk and ear rot disease on maize (Zea). The fungus also may infect other plant species without causing disease symptoms. Other host genera cited for Gibberellazeae or F. graminearum sensu lato are Agropyron, Agrostis, Bromus, Calamagrostis, Cenchrus, Cortaderia, Cucumis, Echinochloa, Glycine, Hierochloe, Lolium, Lycopersicon, Medicago, Phleum, Poa, Schizachyrium, Secale, Setaria, Sorghum, Spartina and Trifolium. Disease symptoms and signs: For wheat, brown, dark purple to black necrotic lesions form on the exterior surface of the florets and glume. Although these lesion symptoms sometimes are referred to as scab, they are not formally related to the hyperplasia and hypertrophic epidermal growth associated with other scab diseases such as apple scab. Peduncles immediately below the inflorescence may become discoloured brown/purple. With time, tissue of the inflorescence often becomes blighted, appearing bleached and tan, while the grain within atrophies. Awns often become deformed, twisted and curved downward. In barley, infections are not always readily apparent in the field. Infected spikelets may show a browning or water-soaked appearance. Infected barley kernels show a tan to dark brown discolouration that can be similar to that caused by other kernel blighting organisms. During prolonged wet periods, pink to salmon-orange spore masses of the fungus are often seen on infected spikelets, glumes and kernels in both wheat and barley. For maize ear rot, infection occurs by way of colonizing silk and thus symptoms first appear at the ear apex. White mycelium, turning pink to red with time, colonizes kernels and may progress basipetally, covering the entire ear. [ABSTRACT FROM AUTHOR]

Targeted gene replacement is one of the primary strategies for functional characterization of fungal genes and several methods have been developed for this purpose over the years. The increased availability of genome sequence information in the present times has enabled wider adoption of protocols based on the knowledge of the gene sequence and its surrounding region. Among such targeted gene replacement approaches, the spilt-marker method has gained popularity in filamentous fungi. This method involves only two rounds of PCR and does not require any subcloning. It is based on the availability of a marker gene (e.g., the hygromycin gene) and sequences of the gene of interest, as well as around 1 kb long regions flanking the gene on either side. The technique includes PCR amplification of the flanking regions of the gene of interest and the marker gene followed by a fusion PCR which leads to the creation of two molecular cassettes, each containing a part of the marker gene fused to one flanking region. These molecular cassettes are then simultaneously used for transformation of protoplasts. Three homologous recombination events, one within each flanking region and one in the marker gene, lead to the replacement of the gene of interest with a functional marker gene. The transformants are then grown on selective media and emerging colonies can be screened for presence of the marker and absence of the gene being replaced using various methods.

Gene cloning is the first step of targeted gene replacement for functional studies, discovery of gene alleles, and gene expression among other applications. In this chapter, we will describe a cloning technique suitable for fungal species where the genomic information and sequences available are limited. This strategy involves obtaining protein sequences of the gene of interest from various organisms to identify at least two conserved regions. Degenerate primers are designed from these two conserved regions and the resulting PCR products are sequenced. The sequence of the PCR products can be analyzed using suitable databases to determine their similarity to the gene/protein of interest. In cases where the entire gene cannot be cloned directly using these primers, this initial nucleotide sequence can be used as a template for further primer design and genome walking in both directions for either the cloning of a longer fragment or even the cloning of the complete gene. Here, we describe the partial cloning of a reducing polyketide synthase gene from the fungal plant pathogen Ascochyta rabiei using this strategy.