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Jasmonic acid (JA) and salicylic acid (SA) phytohormone pathways are important regulators of stress tolerance. Knowledge regarding the diversity, phylogeny and functionality of wheat genes involved in JA and SA response is limited.Using Arabidopsis, rice and wheat genomic and wheat disease transcriptomic data, we deduced the size, phylogenetic diversity and pathogen‐responsiveness of seven hormone‐responsive gene families, and thus selected 14 candidates as potential hormone responsive gene markers. Gene‐specific expression studies assessed the impact of exogenous JA and SA on their transcriptional activation in leaves of two distinct wheat cultivars. RNAseq data were interrogated to assess their disease responsiveness and tissue‐specific expression.This study elucidated the number, phylogeny and pathogen‐responsiveness of wheat genes from seven families, including 12 TaAOS, 6 TaJAMyb, 256 TaWRKY group III, 85 TaPR1, 205 TaPR2, 76 TaPR3 and 124 TaPR5. This included the first description of the wheat AOS, JAMyb, PR2, PR3 and PR5 gene families. Gene expression studies delineated TaAOS1‐5B and TaJAMyb‐4A as JA‐responsive in leaves, but not significantly responsive to SA treatment, while TaWRKY45‐B was a SA‐ but not a JA‐responsive marker. Other candidate genes were either unresponsive or non‐specific to SA or JA.Our findings highlight that all seven gene families are greatly expanded in wheat as compared to other plants (up to 7.6‐fold expansion), and demonstrate disparity in the response to biotic stress between some homoeologous and paralogous sequences within these families. The SA‐ and JA‐responsive marker genes identified herein will prove useful tools to monitor these signalling pathways in wheat. [ABSTRACT FROM AUTHOR]

Septoria tritici blotch (STB) disease of wheat is caused by the fungal pathogen Zymoseptoria tritici. It is the most important foliar disease of wheat in western Europe and affects wheat cultivation worldwide. The combination of intensive fungicide usage, a polycyclic asexual life cycle and an active sexual cycle has led to the emergence of fungal strains resistant/tolerant to all the major classes of fungicides used in its control. The hallmark of this disease is a long, symptomless latent phase that precedes the onset of visible symptoms. Understanding the processes that occur during the symptomless phase of infection is paramount in developing alternative strategies for disease control; however, large gaps in our knowledge of the disease remain. The known unknowns of the latent stage of infection can be summarized in three questions. Does the fungus initiate or manipulate host defences to trigger programmed cell death in order to facilitate nutrient acquisition or is the host acting exclusively? Does the fungus feed during both the latent phase and the necrotrophic phase like a true hemibiotroph? Does the long latent phase serve a beneficial function for the fungus or is it simply an artefact of evolution? This review aims to distil observations made during studies that have directly or indirectly contributed to answering these questions and points towards their most likely answers. [ABSTRACT FROM AUTHOR]

Insight into pathogen population dynamics provides a key input for effective disease management of the potato late blight pathogen Phytophthora infestans. Phytophthora infestans populations vary from genetically complex to more simple with a few clonal lineages. The presence or absence of certain strains of P. infestans may impact the efficacy of fungicides or host resistance. Current evidence indicates that genetically, the Irish populations of P. infestans are relatively simple with a few clonal lineages. In this study, P. infestans populations were genetically characterized based on samples collected at the national centre for potato breeding during the period 2012–16. The dominance of clonal lineages within this P. infestans population was confirmed and the potential selection pressure of fungicide treatment (2013–15) and host resistance (2016) on this clonal P. infestans population was then investigated. It was found that fungicide products did not notably affect the genetic structure of sampled populations relative to samples from untreated control plants. In contrast, samples taken from several resistant potato genotypes were found to be more often of the EU_13_A2 lineage than those taken from control King Edward plants or potato genotypes with low resistance ratings. Resistant potato varieties Sarpo Mira and Bionica, containing characterized R genes, were found to strongly select for EU_13_A2 strains. [ABSTRACT FROM AUTHOR]

The use of chemicals to fertilize crops incurs economic and environmental costs and it is widely recognized that the current level of chemical fertilizer use is unsustainable in many intensive farming systems. Any methods that can reduce fertilizer input and still maintain acceptable yields would be of great benefit to both the farmer and the environment. The use of beneficial endophytes as crop inoculants may go some way towards improving crop yields beyond that achievable using fertilizer increases alone. Field trials were conducted over two seasons on three contrasting field sites to test the effects of fungal endophytes from a wild barley relative on three barley cultivars (Mickle, Planet and Propino). Seeds were either untreated or dressed with a consortium of four endophyte strains, and three levels of nitrogen (N) were applied to both treatments: full N, 50% N and 0 N. On the field site with the lowest overall N input, the endophyte treatment with 50% N restored yield for ‘Planet’ to that associated with untreated plants receiving the full N input. On the same site and with the same cultivar, endophyte treatment increased yield by 15% under full N, and by a mean 12% for all three cultivars with 50% N input. Over both seasons and all three sites, the endophyte treatment increased yield for the cultivar Planet by a mean of 9%. For the endophyte-associated increase in the variety Planet grain yield over the untreated trials strong correlations were found between increased yield and each of low rainfall, greater evaporation and greater number of degree days above the base. Furthermore, the efficacy of the endophytes was not removed by regular foliar fungicidal treatment. These results suggest that fungal endophytes can contribute to improving barley yield grown in low rainfall areas and under a range of fertilizer input regimes, provided that endophyte treatments are applied to compatible crop cultivars and sites. [ABSTRACT FROM PUBLISHER]

Crops often face severe and damaging local drought events, and in some regions, these episodes are predicted to become more frequent due to climate change. Some micro-organisms have been shown to improve drought tolerance and improve yield in crop plants. Here, we show that fungal root endophytes isolated from a wild barley species ( Hordeum murinum subsp. murinum) induced significant improvements in agronomic traits for a severely drought-stressed barley cultivar grown in a controlled environment, including number of tillers, grain yield and shoot biomass. Five endophyte strains were tested, and the trait that showed the greatest significant difference in the drought-stressed plants was the number of tillers, where all of the endophyte treatments induced a greater number of tillers per plant. However, except in one case, the mean dry root weight for all plants was greater in the control plants, indicating preferential allocation of resources to aboveground parts in the endophyte treatments. Results were not consistent across all endophyte treatments, with some endophytes performing much better than others. As these growth studies were conducted using soil-based compost, the results may translate to the field and suggest that some of these endophytes have potential as barley inoculants in arid growing conditions. [ABSTRACT FROM AUTHOR]

Fungal infections of barley have tremendous agricultural significance, and can be detrimental or beneficial. Beneficial root infections often involve endophytic fungi, but endophytic associations do not always confer benefits on their hosts. Endophyte infection can be negative, positive or neutral for the host. Benefits to barley and other plants infected with endophytic root fungi include an increase in seed yield, enhanced resistance to pathogens and improved stress tolerance. Even if an endophyte is never pathogenic, it is not always beneficial. The most important factors that determine the nature of the relationship are the specific combination of partner genotypes and developmental stage, and the ecological and environmental setting. The nutrient status of the plant and the availability of soil nutrients may have little effect on the degree of beneficial endophyte colonization and, unlike mycorrhizae, there is no apparent increase in endophyte-associated phosphorous transfer. There are indications of an association between successful endophyte colonization and high soil pH and clay content. The greatest benefits to the barley plant resulting from the associations seem to be obtained in abiotically stressed environments. Fungal infection may give the plant a greater ability to cope with the stress if the partners are in a balanced relationship. Each new study reveals an increasing diversity of beneficial fungal root endophytes and the full potential of these organisms is still to be determined. Further studies are urgently required to develop specific beneficial root–endophyte associations, or combination of them, that are tailored to individual barley varieties for maximum impact in agriculture. [ABSTRACT FROM PUBLISHER]

The effect of small temperature differentials (16 vs. 20°C) on the pathogenicity of deoxynivalenol producing single isolates ofFusarium culmorumandF. graminearumand on the fusarium head blight (FHB) response of eight wheat cultivars was examined.Fusarium culmoruminoculation caused greater visual disease symptoms at 20°C than at 16°C, both overall and on an individual cultivar basis (overall AUDPC = 13·5 and 9·6, respectively) (P < 0·05). In contrast,F. graminearuminoculation caused greater overall visual disease symptoms at 16°C than at 20°C, both overall and at the individual cultivar level (overall AUDPC = 12·8 and 10·9, respectively) (P < 0·05). Results showed bothF. culmorumandF. graminearuminoculations caused a greater loss in yield at 20°C (54·3 and 46·9% relative 1000-grain weight, respectively) compared with 16°C (73·3 and 66·9% relative 1000-grain weight, respectively) (P < 0·05).Fusarium culmorum-inoculated heads contained similar amounts of fungal DNA at both 16 and 20°C (1·9 and 1·7 ng mg−1 of plant material, respectively) (not significant), while forF. graminearuminoculation, plants contained higher amounts of fungal DNA at 20°C (2·0 and 1·0 ng mg−1 of plant material, respectively) (P < 0·05). Overall, there was a significant negative correlation between AUDPC and percentage relative 1000-grain weight at both 16 and 20°C (r =−0·693 and−0·794, respectively,P < 0·01). [ABSTRACT FROM AUTHOR]

The major products of the trichothecene mycotoxin biosynthetic pathway produced in a species– and sometimes isolate–specific manner by cereal–pathogenic Fusarium fungi include T–2 toxin, diacetoxyscirpenol, deoxynivalenol and nivalenol. This paper briefly reviews the major effects of such trichothecenes on the gross morphology, cytology and molecular signalling within eukaryotic cells. The gross toxic effects of select trichothecenes on animals include growth retardation, reduced ovarian function and reproductive disorders, immuno–compromization, feed refusal and vomiting. The phytotoxic effects of deoxynivalenol on plants can be summarized as growth retardation, inhibition of seedling and green plant regeneration. Trichothecenes are now recognized as having multiple inhibitory effects on eukaryote cells, including inhibition of protein, DNA and RNA synthesis, inhibition of mitochondrial function, effects on cell division and membrane effects. In animal cells, they induce apoptosis, a programmed cell death response. Current knowledge about the eukaryotic signal transduction cascades and downstream gene products activated by trichothecenes is limited, especially in plants. In mammalian cells, certain trichothecenes trigger a ribotoxic stress response and activate mitogen–activated protein kinases. DON mediates the inflammatory response by modulating the binding activities of specific transcription factors and subsequently inducing cytokine gene expression. Several genes are up–regulated in wheat in response to trichothecene mycotoxins; the significance, if any, of these genes in the host response to trichothecenes has yet to be elucidated. [ABSTRACT FROM AUTHOR]

The pathogenic and genetic diversity ofColletotrichum lindemuthianumisolates collected from a total of 10 Central and South American, European and African countries were characterized using common bean differential cultivar pathogenicity tests and amplified fragment length polymorphism (AFLP) analysis. On the basis of pathogenicity tests, 74 isolates were attributed to 30 different pathogenic races using the CIAT-defined binary race-classification system. Twenty-one races were restricted geographically, being exclusive to different countries. Race 9 was the most widespread, being detected in four different countries. Cluster analysis of consensus AFLP data generated using three selective AFLP primer combinations grouped 86 isolates (including the 74 subjected to pathogenicity tests) into three clusters (with one isolate as an outlier). This analysis showed that the majority of South and Central American isolates were divided among two clusters, and that the limited number of European and African isolates used in this study were genetically most similar to Central American isolates. Overall, the results of this research showed some associations between the genetic diversity of the isolates and their country of origin, but not between genetic diversity and race classification of isolates. [ABSTRACT FROM AUTHOR]

Abstract Between 1986 and 1998, isolates of Erwinia amylovora were obtained from rosaceous plant species throughout Ireland. Sixty five of these isolates have been compared with 10 E. amylovora isolates from Bulgaria, the Czech Republic and Greece, seven other Erwinia isolates and one Pseudomonas isolate (83 isolates in total). Their identity was confirmed by the pear test and by chromosome and plasmid-specific polymerase chain reaction (PCR) analyses. Random amplified polymorphic DNA (RAPD) analysis was used to study the genetic variability of the 65 Irish isolates. Six random primers (CUGEA 1, 2, 3, 4, 5 and 6) were used for random amplified RAPD analysis; the degree of amplification differed with the primers, but all produced at least 13 (CUGEA 1) and at most 27 (CUGEA 5) different RAPD profiles. Phylogenetic analysis of the RAPD profiles showed that 44 of the 65 Irish isolates showed genetic homogenicity (s ≥0.92), but the remaining 21 isolates were more genetically diverse than the other Irish isolates and the foreign E. amylovora isolates. There was no significant relationship between the genetic variability of the Irish E. amylovora isolates (based on RAPD analysis) and the host species, year of isolation or their geographical origin. [ABSTRACT FROM AUTHOR]

Over 4 years, the environmental conditions and the causal agents of Fusarium head blight (FHB) disease of wheat were determined in field sites in four European countries: Hungary, Ireland, Italy, and the United Kingdom. Polymerase chain reaction-based methods were used to detect each species causing FHB and quantify its DNA (as a measurement of fungal abundance) in the samples. Canonical correspondence analysis (CCA) was used to determine the relationship of the incidence and abundance of each species with weather variables. CCA indicated that little variability in the species prevalence data was explained by the weather variables. In contrast, a greater proportion of variability in abundance data was accounted for by the weather variables. Most samples contained two or more species and statistical analysis suggested that these species tended to coexist at field sites. CCA also indicated that there were differences in the relationships of the prevalence and abundance of the six FHB species with environmental variables. Fusarium poae was associated with relatively drier and warmer conditions, whereas F. graminearum was associated with warmer/humid conditions. F. avenaceum and F. culmorum were both associated with niches of cooler/wet/humid conditions. Two Microdochium species were associated with regions of relatively cool/moderate temperatures and frequent rainfalls of short duration. The results also suggested that environmental conditions differentially affect the infection and colonization processes, and the comparative abundance of the six species. [ABSTRACT FROM AUTHOR]

ABSTRACT This study investigated antifungal activity in soluble extracts from seed of a range of wheat cultivars differing in susceptibility to Fusarium head blight. Antifungal activity was assessed in terms of beta-D-glucuronidase (GUS) activity of a Fusarium culmorum GUS transformant using a sensitive laboratory assay. Significant antifungal activity was detected in seed extracts from WEK0609, CM 820036, and Arina. Initial characterization of the Arina seed extract indicated that it contained antifungal proteinaceous compounds. The Arina extract yielded two (60 and 80%) ammonium sulfate fractions containing inhibitory compounds. Gel filtration chromatography and subsequent sodium dodecyl sulfate-polyacrylamide gel electrophoresis of antifungal fractions showed that the antifungal activities detected in the Arina 60 and 80% ammonium sulfate fractions were associated with putative proteinaceous compounds with apparent molecular masses of approximately 60 and 28 kDa, respectively.

The Tri5 gene encodes trichodiene synthase, which catalyzes the first reaction in the trichothecene biosynthetic pathway. In vitro, a direct relationship was observed between Tri5 expression and the increase in deoxynivalenol production over time. We developed a reverse transcription (RT)-PCR assay to quantify Tri5 gene expression in trichothecene-producing strains of Fusarium species. We observed an increase in Tri5 expression following treatment of Fusarium culmorum with fungicides, and we also observed an inverse relationship between Tri5 expression and biomass, as measured by beta-D-glucuronidase activity, during colonization of wheat (cv. Avalon) seedlings by F. culmorum. RT-PCR analysis also showed that for ears of wheat cv. Avalon inoculated with F. culmorum, there were different levels of Tri5 expression in grain and chaff at later growth stages. We used the Tri5-specific primers to develop a PCR assay to detect trichothecene-producing Fusarium species in infected plant material.