Control of arable crop pathogens; climate change mitigation, impacts and adaptation

© Springer Science+Business Media New York 2016. This is the accepted manuscript version of an article which has been published in final form at https://doi.org/10.1007/978-1-4939-3536-9_3In the context of threats to global food security from impacts of damaging crop diseases and of climate change, this chapter describes three aspects of the interactions between climate change and diseases that reduce arable crop yields. It considers the role of crop disease control in climate change mitigation, by estimating consequences for greenhouse gas (GHG) emissions of crop management strategies to control diseases, using UK oilseed rape and barley crops as examples. In this chapter we conclude that good control of crop diseases, resulting in more efficient use of nitrogen fertiliser, can decrease UK GHG from crop production by c. 1.6 Mt CO2 eq. each year. Within the chapter we discuss impacts of climate change on incidence of crop diseases and their effects on crop yields, using UK oilseed rape phoma stem canker and wheat fusarium ear blight as examples. For both these diseases, it is estimated that global warming will increase the range and severity of epidemics. To make such estimates, it is emphasised that it is important to estimate impacts of climate on both crop growth and disease development. In response to such projections of impacts of climate change, within this chapter we assess strategies for adaptation to climate change of crop disease management to decrease arable crop losses related to climate change, for both policymakers and farmers.Peer reviewe

Communication is key : Extracellular vesicles as mediators of infection and defence during host-microbe interactions in animals and plants

© The Author(s) 2021. Published by Oxford University Press on behalf of FEMS. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/).Extracellular vesicles (EVs) are now understood to be ubiquitous mediators of cellular communication. In this review, we suggest that EVs have evolved into a highly regulated system of communication with complex functions including export of wastes, toxins and nutrients, targeted delivery of immune effectors, and vectors of RNA silencing. Eukaryotic EVs come in different shapes and sizes and have been classified according to their biogenesis and size distributions. Small EVs (sEVs or exosomes) are released through fusion of endosome-derived multivesicular bodies (MVBs) with the plasma membrane. Medium EVs (mEVs or microvesicles) bud off the plasma membrane as a form of exocytosis. Finally, large EVs (lEVs or apoptotic bodies) are produced as a result of the apoptotic process. This review considers EV secretion and uptake in four eukaryotic kingdoms, three of which produce cell walls. The impact cell walls have on EVs in plants and fungi are discussed, as are roles of fungal EVs in virulence. Contributions of plant EVs to development and innate immunity are presented. Compelling cases are sporophytic self-incompatibility and cellular invasion by haustorium-forming filamentous pathogens. The involvement of EVs in all of these eukaryotic processes is reconciled considering their evolutionary history.Peer reviewe

Trends of pesticide residues in foods imported to the United Kingdom from 2000 to 2020

© 2021 Elsevier Ltd. All rights reserved. This is the accepted manuscript version of an article which has been published in final form at https://doi.org/10.1016/j.foodcont.2021.108616A total of 33,911 samples with determined pesticide residues were collated and analysed in the UK monitoring programme to determine trends in pesticide residue levels in imported foods during the period of 2000–2020. 17,027 of those samples (50.2%) contained detectable residues while 1,126 (3.3%) exceeded maximum residue levels (MRLs). An increased trend and a significant shift before and after 2010 in imported foods containing both detectable residues and exceeding MRLs were found. The main factors responsible for these changes were due to constant amendments in regulations and legal frameworks. With adoption of Regulation EC396/2005, there have been major changes that have affected the operations of the UK food monitoring programme including sampling methods, analysis methods, new MRLs, types of foods, and the accreditation system. The proportion of imported foods with residues and the amounts of residues in imported foods varied from country to country. Foods imported from non-European countries had more non-compliant rates than foods imported from EU. Levels of pesticide residues also varied between processed foods and unprocessed raw agricultural products and between plant-based and animal foods. Fruits and vegetables and cereals had higher occurrences of quantified residues as well as higher MRLs violation rates compared to animal products.Peer reviewe

Genomic evidence for genes encoding leucine-rich repeat receptors linked to resistance against the eukaryotic extra- and intracellular Brassica napus pathogens Leptosphaeria maculans and Plasmodiophora brassicae

© 2018 Stotz et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Genes coding for nucleotide-binding leucine-rich repeat (LRR) receptors (NLRs) control resistance against intracellular (cell-penetrating) pathogens. However, evidence for a role of genes coding for proteins with LRR domains in resistance against extracellular (apoplastic) fungal pathogens is limited. Here, the distribution of genes coding for proteins with eLRR domains but lacking kinase domains was determined for the Brassica napus genome. Predictions of signal peptide and transmembrane regions divided these genes into 184 coding for receptor-like proteins (RLPs) and 121 coding for secreted proteins (SPs). Together with previously annotated NLRs, a total of 720 LRR genes were found. Leptosphaeria maculans-induced expression during a compatible interaction with cultivar Topas differed between RLP, SP and NLR gene families; NLR genes were induced relatively late, during the necrotrophic phase of pathogen colonization. Seven RLP, one SP and two NLR genes were found in Rlm1 and Rlm3/Rlm4/Rlm7/Rlm9 loci for resistance against L. maculans on chromosome A07 of B. napus. One NLR gene at the Rlm9 locus was positively selected, as was the RLP gene on chromosome A10 with LepR3 and Rlm2 alleles conferring resistance against L. maculans races with corresponding effectors AvrLm1 and AvrLm2, respectively. Known loci for resistance against L. maculans (extracellular hemi-biotrophic fungus), Sclerotinia sclerotiorum (necrotrophic fungus) and Plasmodiophora brassicae (intracellular, obligate biotrophic protist) were examined for presence of RLPs, SPs and NLRs in these regions. Whereas loci for resistance against P. brassicae were enriched for NLRs, no such signature was observed for the other pathogens. These findings demonstrate involvement of (i) NLR genes in resistance against the intracellular pathogen P. brassicae and a putative NLR gene in Rlm9-mediated resistance against the extracellular pathogen L. maculans.Peer reviewe

Disease management in oilseed rape: insights into the Brassica napus-Pyrenopeziza brassicae pathosystem

Final Published versio

Influence of Elevated Temperatures on Resistance Against Phoma Stem Canker in Oilseed Rape

© 2022 Noel, Qi, Gajula, Padley, Rietz, Huang, Fitt and Stotz. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). https://creativecommons.org/licenses/by/4.0/Cultivar resistance is an important tool in controlling pathogen-related diseases in agricultural crops. As temperatures increase due to global warming, temperatureresilient disease resistance will play an important role in crop protection. However, the mechanisms behind the temperature-sensitivity of the disease resistance response are poorly understood in crop species and little is known about the effect of elevated temperatures on quantitative disease resistance. Here, we investigated the effect of temperature increase on the quantitative resistance of Brassica napus against Leptosphaeria maculans. Field experiments and controlled environment inoculation assays were done to determine the influence of temperature on R gene-mediated and quantitative resistance against L. maculans; of specific interest was the impact of high summer temperatures on the severity of phoma stem canker. Field experiments were run for three consecutive growing seasons at various sites in England and France using twelve winter oilseed rape breeding lines or cultivars with or without R genes and/or quantitative resistance. Stem inoculation assays were done under controlled environment conditions with four cultivars/breeding lines, using avirulent and virulent L. maculans isolates, to determine if an increase in ambient temperature reduces the efficacy of the resistance. High maximum June temperature was found to be related to phoma stem canker severity. No temperature effect on stem canker severity was found for the cultivar ES Astrid (with only quantitative resistance with no known R genes). However, in the controlled environmental conditions, the cultivar ES Astrid had significantly smaller amounts of necrotic tissue at 20 C than at 25 C. This suggests that, under a sustained temperature of 25 C, the efficacy of quantitative resistance is reduced. Findings from this study show that temperature-resilient quantitative resistance is currently available in some oilseed cultivars and that efficacy of quantitative resistance is maintained at increased temperature but not when these elevated temperatures are sustained for a long period.Peer reviewedFinal Published versio

Improved understanding of novel sources of resistance against the light leaf spot pathogen, Pyrenopeziza brassicae

Chinthani Shanika Karandeni Dewage, Kavithra Jayani Wijerathna, Henrik U. Stotz, and Bruce D. L. Fitt, 'Improved understanding of novel sources of resistance against the light leaf spot pathogen, Pyrenopeziza brassicae', paper presented at the Association of Applied Biologists Conference Crop Production in Southern Britain 2017, 15 - 16 February 2017, Peterborough, UK. Proceedings available online at: http://www.aab.org.uk/contentok.php?id=501.In this work, the endophytic growth phase of the light leaf spot pathogen Pyrenopeziza brassicae in selected lines from a doubled haploid (DH) population of oilseed rape, which is known to segregate for resistance against P. brassicae, was characterised using controlled environment (CE) experiments. Fungal staining techniques and pathogen-specific quantitative polymerase chain reactions (qPCR) were used to observe and quantify the pathogen biomass, respectively. The qPCR results showed that the resistant lines contained little P. brassicae DNA and there seemed to be little to no change in the amount of DNA over time. In contrast, there was a considerable increase in pathogen DNA in susceptible lines from 0 to 24 days post inoculation (dpi). These results were also reflected in observations made by a fungal staining method. In addition, leaf samples of these DH lines, collected at three different times from winter oilseed rape field experiments, were analysed using qPCR. The resistant lines had a considerably smaller amount of P. brassicae DNA in leaf samples collected later in the cropping season than that in susceptible lines

Transcriptomics of temperature-sensitive R gene-mediated resistance identifies a WAKL10 protein interaction network

© 2024 The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/Understanding temperature-sensitivity of R gene-mediated resistance against apoplastic pathogens is important for sustainable food production in the face of global warming. Here, we show that resistance of Brassica napus cotyledons against Leptosphaeria maculans was temperature-sensitive in introgression line Topas-Rlm7 but temperature-resilient in Topas-Rlm4. A set of 1,646 host genes was differentially expressed in Topas-Rlm4 and Topas-Rlm7 in response to temperature. Amongst these were three WAKL10 genes, including BnaA07g20220D, representing the temperature-sensitive Rlm7-1 allele and Rlm4. Network analysis identified a WAKL10 protein interaction cluster specifically for Topas-Rlm7 at 25 °C. Diffusion analysis of the Topas-Rlm4 network identified WRKY22 as a putative regulatory target of the ESCRT-III complex-associated protein VPS60.1, which belongs to the WAKL10 protein interaction community. Combined enrichment analysis of gene ontology terms considering gene expression and network data linked vesicle-mediated transport to defence. Thus, dysregulation of effector-triggered defence in Topas-Rlm7 disrupts vesicle-associated resistance against the apoplastic pathogen L. maculans.Peer reviewe

Leptosphaeria maculans isolates with variations in AvrLm1 and AvrLm4 effector genes induce differences in defence responses but not in resistance phenotypes in cultivars carrying the Rlm7 gene

© 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. This is an open access article under the terms of the Creative Commons Attribution License, https://creativecommons.org/licenses/by/4.0/BACKGROUND: The phoma stem canker pathogen Leptosphaeria maculans is one of the most widespread and devastating pathogens of oilseed rape (Brassica napus) in the world. Pathogen colonization is stopped by an interaction of a pathogen Avr effector gene with the corresponding host resistance (R) gene. While molecular mechanisms of this gene‐for‐gene interaction are being elucidated, understanding of effector function remains limited. The purpose of this study was to determine the action of L. maculans effector (AvrLm) genes on incompatible interactions triggered by B. napus noncorresponding R (Rlm) genes. Specifically, effects of AvrLm4‐7 and AvrLm1 on Rlm7‐mediated resistance were studied. RESULTS: Although there was no major effect on symptom expression, induction of defence genes (e.g. PR1) and accumulation of reactive oxygen species was reduced when B. napus cv. Excel carrying Rlm7 was challenged with a L. maculans isolate containing AvrLm1 and a point mutation in AvrLm4‐7 (AvrLm1, avrLm4‐AvrLm7) compared to an isolate lacking AvrLm1 (avrLm1, AvrLm4‐AvrLm7). AvrLm7‐containing isolates, isogenic for presence or absence of AvrLm1, elicited similar symptoms on hosts with or without Rlm7, confirming results obtained with more genetically diverse isolates. CONCLUSION: Careful phenotypic examination of isogenic L. maculans isolates and B. napus introgression lines demonstrated a lack of effect of AvrLm1 on Rlm7‐mediated resistance despite an apparent alteration of the Rlm7‐dependent defence response using more diverse fungal isolates with differences in AvrLm1 and AvrLm4. As deployment of Rlm7 resistance in crop cultivars increases, other effectors need to be monitored because they may alter the predominance of AvrLm7. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.Peer reviewe