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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]

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]

Susceptibility of eight commercial European wheat cultivars to fusarium head blight (FHB) disease caused by Fusarium graminearum, F. culmorum, F. poae and Microdochium nivale (formerly known as Fusarium nivale) was compared under controlled environment conditions (16°C). FHB did not differentially affect cultivars in terms of disease symptoms, fungal DNA content of grain or deoxynivalenol (DON) contamination. However, the Hungarian-grown cultivars GK-Othalom and Fatima 2 (of Romanian origin) showed greater type V resistance (yield tolerance) to FHB than did the others. Also, nivalenol was produced by F. poae in these two cultivars and in Italian cultivar Norba, but not in other cultivars. Overall, significant relationships were found between the FHB and seedling blight resistance in vitro of these eight cultivars, but such relationships were generally highly dependent on cultivar, and therefore it is likely that the in vitro test is at best measuring components of FHB resistance and/or genotype-specific resistance components. [ABSTRACT FROM AUTHOR]

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 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]