With the Earth’s population expected to reach 11.2 billion by 2100 there is a pressing need to maximize food production at a time when productivity of many crops is reaching a plateau. Minimizing losses to pests and diseases is therefore a crucial means of meeting this challenge and securing food supply. This research topic addresses some of the most important issues in the future sustainability of global crop production. The topic consists of 20 papers, of which 13 describe original research. There are six review papers, plus one hypothesis and theory contribution

Birch

Cooke

Hillocks

Johnson

Moore

Peeters

Frontiers in Plant Science

PubMed

With global populations expected to exceed 9.2 billion by 2050 and available land and water resources devoted to crop production dwindling, we face significant challenges to secure global food security. Only 12 plant species feed 80% of the world’s population, with just three crop species (wheat, rice and maize) accounting for food consumed by 50% of the global population. Annual losses to crop pests and pathogens are significant, thought to be equivalent to that required to feed a billion people, at a time when crop productivity has plateaued. With pesticide applications becoming increasingly unfeasible on cost, efficacy and environmental grounds, there is growing interest in exploiting plant resistance and tolerance traits for crop protection. Indeed, mankind has been selectively breeding plants for desirable traits for thousands of years. However, resistance and tolerance traits have not always been those most desired, and in many cases have been inadvertently lost during the domestication process: crops have been effectively ‘disarmed by domestication’. Moreover, mechanistic understanding of how resistance and tolerance traits operate is often incomplete, which makes identifying the right combination for crop protection difficult. We aimed to address this Research Topic by inviting authors to contribute their knowledge of appropriate resistance and tolerance traits, explore what is known about durability and breakdown of defensive traits and, finally, asking what are the prospects for exploiting these traits for crop protection. The research topic summarised in this book addresses some of the most important issues in the future sustainability of global crop production

Alison J. Karley

Scott N. Johnson

Peter J. Gregory

Rex Brennan

Directory of Open Access Books (DOAB)

Crop Traits for Defense against Pests and Disease: Durability, Breakdown and Future Prospects

Johnson, Scott N.

Karley, Alison J.

Gregory, Peter J.

Brennan, Rex M.

Discovery Research Portal

                                                                    University of DundeeCrop Traits for Defense against Pests and DiseaseJohnson, Scott N.; Karley, Alison J.; Gregory, Peter J.; Brennan, Rex M.Published in:Frontiers in Plant ScienceDOI:10.3389/fpls.2017.00209Publication date:2017Licence:CC BYDocument VersionPublisher's PDF, also known as Version of recordLink to publication in Discovery Research PortalCitation for published version (APA):Johnson, S. N., Karley, A. J., Gregory, P. J., & Brennan, R. M. (2017). Crop Traits for Defense against Pests andDisease: Durability, Breakdown and Future Prospects. Frontiers in Plant Science, 8, [209].https://doi.org/10.3389/fpls.2017.00209General rightsCopyright and moral rights for the publications made accessible in Discovery Research Portal are retained by the authors and/or othercopyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated withthese rights. • Users may download and print one copy of any publication from Discovery Research Portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain. • You may freely distribute the URL identifying the publication in the public portal.Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Download date: 16. Aug. 2023EDITORIALpublished: 21 February 2017doi: 10.3389/fpls.2017.00209Frontiers in Plant Science | www.frontiersin.org 1 February 2017 | Volume 8 | Article 209Edited and reviewed by:Diego Rubiales,Instituto de Agricultura Sostenible(CSIC), Spain*Correspondence:Rex M. Brennanrex.brennan@hutton.ac.ukSpecialty section:This article was submitted toCrop Science and Horticulture,a section of the journalFrontiers in Plant ScienceReceived: 30 January 2017Accepted: 03 February 2017Published: 21 February 2017Citation:Johnson SN, Karley AJ, Gregory PJand Brennan RM (2017) Editorial:Crop Traits for Defense against Pestsand Disease: Durability, Breakdownand Future Prospects.Front. Plant Sci. 8:209.doi: 10.3389/fpls.2017.00209Editorial: Crop Traits for Defenseagainst Pests and Disease: Durability,Breakdown and Future ProspectsScott N. Johnson 1, Alison J. Karley 2, Peter J. Gregory 3 and Rex M. Brennan 2*1Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, Australia, 2 The James Hutton Institute,Dundee, UK, 3 School of Agriculture, Policy and Development, University of Reading, Reading, UKKeywords: climate change, crops, food security, pathogens, pests, resistanceEditorial on the Research TopicCropTraits forDefense against Pests andDisease: Durability, Breakdown and Future ProspectsWith the Earth’s population expected to reach 11.2 billion by 2100 there is a pressing need tomaximize food production at a time when productivity of many crops is reaching a plateau.Minimizing losses to pests and diseases is therefore a crucial means of meeting this challengeand securing food supply. This research topic addresses some of the most important issues in thefuture sustainability of global crop production. The topic consists of 20 papers, of which 13 describeoriginal research. There are six review papers, plus one hypothesis and theory contribution.The development of plants with resistance to the most damaging pests and diseases isincreasingly important in the face of growing pressure to reduce synthetic chemical inputs,including pesticides, fungicides, and herbicides used for crop protection. This reduction is partlyunderwritten by legislative directives, consumer demands and indeed an overall reduction inavailable chemical controls for most crops (Hillocks, 2012), especially those outwith the mainarable species. Additionally, losses due to pest and disease attacks represent a major financialcost in crop production and throughout the subsequent supply chain, even before the costs ofcontrol measures are considered. The move toward more sustainable production systems, based onintegrated pest and disease management approaches, is gaining momentum, and the developmentof more resistant cultivars is a major factor contributing to the success of these systems. In addition,there is a recognized need for frameworks (e.g., Birch et al., 2011) which combine natural enemieswith resistant cultivars and other management practices to reduce reliance on crop protectionchemicals and maintain viable and sustainable future crop production.The development of resistant cultivars is crucial to the future of sustainable crop productionpractices, and there is a substantial need for the continued introgression of specific resistancegenes or physical and structural traits, from existing or extended genetic resources. Recentadvances in knowledge can aid this process, even in many minor crop species, where increasedunderstanding of trait heritability and technological advances in genomics and bioinformatics areenabling the identification of genes controlling resistance, providing a framework for improvedselection efficiency. Moreover, the advent of new technologies can provide significant benefits, asexemplified by the opportunities afforded by CRISPR-based tools in understanding plant-pathogeninteractions; these are addressed in the review by Barakate and Stephens. The need for newresistance genes is crucial withinmany pathogen/crop systems, and VanWeymers et al. describe theapplication of a range of “omics” technologies in potato to identify novel resistances to potato blightwithin a large germplasm collection. This approach is one that can be adapted for other speciesand pathogens, as the future role of resistance genes from existing but underexploited geneticJohnson et al. Crop Traits for Pest/Disease Defenseresources is likely to be significant. This is not limited to inherentcrop resistance, however, and Reynolds et al. also highlight therole of “omics” approaches for augmenting plant resistance toinvertebrates using application of silicon.Breeding strategies focused on the identification andincorporation of specific resistance genes, both individually orin effective groups, are being developed and implemented inmany active breeding programmes. The use of marker-assistedbackcross breeding in rice to pyramid resistance genes forbacterial blight and blast diseases is the subject of the paperby Abhilash Kumar et al. An investigation of genes involvedin the infection processes by Phytophthora capsici in Capsicumspp. by Zhang et al. through genome-wide identificationhighlights the role of SQUAMOSA promoter binding protein(SBP)-box genes that can be utilized in future breeding anddevelopment research. Genetic mapping of host plants, suchas Capsicum, was used by Barbary et al. to identify QTLslinked to resistance to Meloidogyne nematode species, andfrom this the underlying genes can eventually be identified andutilized in the breeding of resistant plants. Similarly, wild Vitisgenotypes studied by Wan et al. to find sources of resistanceto Botrytis, based on antioxidant activity linked to resistance,will be deployed in future breeding strategies. Further workon wild Vitis by Wen et al. identified a gene linked to powderymildew resistance and confirmed its effect through ectopicexpression in Arabidopsis; again, this provides a resource forfuture breeding.The effects of pest attacks on host plant metabolism wasinvestigated by Liu et al., using the wild brassica species Barbareavulgaris and the global pest diamondback moth, Plutellaxylostella. By examining changes in glucosinolate biosynthesisinduced by larval infestation, inferences can be made aboutthe mechanisms underpinning defense induction. A quantitativeapproach to the breeding of resistant cultivars is described byMohammed et al. in Sorghum, where the use of diallel progenyenabled the identification of a significant interaction betweenresistance to shoot fly andmorphological traits such as grain yieldand seed size. The information on the quantitative genetics ofSorghum can be used to inform decisions on parental choice forresistance breeding.Many host-pathogen systems are subject to rapid evolution,for example in pathogen race structure or breakdown of hostresistance. The paper by Gómez-Cortecero et al. describes theuse of SNPs and SSRs to study diversity in global populationsof Neonectria ditissima affecting apple trees, and also presentevidence of a relatively simple pattern of host response which isnot influenced by any race structure in the pathogen population.Integrated Pest and Disease Management (IPDM) approachesto pest and disease control require the development of resistantvarieties and also monitoring and management strategies thatcan be applied effectively within crops. The paper by Joshi et al.deals with the development of a susceptibility index for codlingmoth on apple, based on oviposition preferences. The review byPeterson et al. considers the wide range of plant defense traitsthat can influence the responses of natural enemies used in IPDMsystems, and also includes the potential impacts of transgeniccrops on trophic levels and arthropod communities.Plant defenses can be exploited to enhance resistance to pestattack and also to confer tolerance of pest infestations. Plantphysical defenses can offer particularly durable resistance to pestsand pathogens (Johnson et al., 2016; Moore and Johnson, 2017);ecological studies, for example, have shown plant physical traitsto be more effective deterrents to insect herbivory than plantsecondary metabolites (Peeters et al., 2007; Cooke and Leishman,2012). As outlined in the review byMitchell et al., plant structuraltraits such as trichomes, spines, and cuticles can provide aphysical barrier to arthropod pest attachment, feeding andoviposition, while plant vigor and altered phenology can increasetolerance of pest damage and reduce the incidence of pestattacks. This paper highlights new avenues for discovery of plantdefensive traits, particularly through research to understand pest-induced changes in plant chemistry and mechanisms of plantdefense “priming”.The effects of a changing climate are likely to alter bothseverity of pest and pathogen attacks, and also the spectrum oforganisms that will cause damage to crop plants (Johnson andJones, 2017). Two papers in this research topic consider changesunder conditions of elevated CO2; the first by McKenzie et al.presents data illustrating the changes in herbivory by two pests ofraspberry, the European large raspberry aphid (Amophorophoaidaei) and the root-feeding vine weevil (Otiorhynchus sulcatus).The second contribution, a review by Sun et al., examines changesin host plant metabolism and water-use efficiency instigatedunder elevated CO2 conditions, and how these changes impacton the outcome of plant-aphid interactions.Host plant resistance can have significant effects on organismsand trophic levels beyond the target pest or pathogen, and thishas implications for integrated management of crop systems.This area is discussed by Peterson et al. in their review, whichalso considers the use of transgenic crops. Genetic modificationtechnology has potential application in the development of pest-resistant cultivars of some arable species, especially where thereare limited sources of resistance within the genus, and this isdiscussed in the context of cotton production systems by Traperoet al. and de Oliveira et al. The identification by the latterauthors of resistances coveringmultiple pestsmay offer particularopportunities.Making use of multiple resistance traits might also offer analternative approach toward pathogen control. The theory paperby Newton suggests that the harmful effects of fungal diseaseoutbreaks in cereal crops could be limited by using mixedgenotype plantings; cultivarmixtures often show higher toleranceof, or resistance to, disease. The impact of this approach on othermicrobial species in the crop environment is also considered.The development of environmentally friendly controlmechanisms for pests is a further aspect of future cropproduction systems, and there are various less damagingingredients under consideration. These can include the useof plant mutualists or manipulation of soil conditions, forexample by application of chemical constituents such as silicon(Johnson et al., 2016). In terms of plant mutualists, arbuscularmycorrhizal fungi can improve crop productivity, as reportedby Robinson-Boyer et al., which may result in better toleranceof pest and disease attack Mitchell et al. and also help plantsFrontiers in Plant Science | www.frontiersin.org 2 February 2017 | Volume 8 | Article 209Johnson et al. Crop Traits for Pest/Disease Defenseresist attack by root herbivores (Johnson et al., 2016). Moreover,the role of silicon application to the soil and resistance toherbivory is considered in the review by Reynolds et al..They present evidence for direct and indirect defenses (e.g.,recruitment of natural enemies of pests via volatile emissions) bysilicon.We hope this research topic will provide a valuable resourcefor workers and researchers in the field of crop protectionby providing a source of information about existing andnovel sources of crop resistance and tolerance traits, theirincorporation into breeding programmes, how they can bedeployed for maximum efficacy under field conditions whenintegrated with other pest and disease control measures, andtheir potential to provide durable and sustainable crop protectionunder a changing environment.TRIBUTE TO ALAIN PALLOIXIt is with sadness that we note the death of Alain Palloix, whosemanuscript on resistance to root-knot nematodes Barbary et al.is included in this research topic. Alain’s work over many yearsmade a significant contribution to the understanding of pepper-pathogen interactions and resistance breeding, and we extend oursympathy to his family and colleagues.AUTHOR CONTRIBUTIONSAll authors listed have made substantial, direct and intellectualcontribution to the work and approved it for publication.ACKNOWLEDGMENTSRB and AK are supported by the Scottish Government throughthe RESAS strategic research programmes in “Crop andGrassland Production and Disease Control” and “Productiveand Sustainable Land Management and Rural Economies”(2016-2021). SJ is supported by grants from the AustralianResearch Council (DP140100363 and DP170102278). We thankthe authors involved in this research topic for their excellent andvaried contributions.REFERENCESBirch, A. N. E., Begg, G. S., and Squire, G. R. (2011). How agro-ecological researchhelps to address food security issues under new IPM and pesticide reductionpolicies for global crop production systems. J. Exp. Bot. 62, 3251–3261.doi: 10.1093/jxb/err064Cooke, J., and Leishman,M. R. (2012). Tradeoffs between foliar silicon and carbon-based defences: evidence from vegetation communities of contrasting soil types.Oikos 121, 2052–2060. doi: 10.1111/j.1600-0706.2012.20057.xHillocks, R. J. (2012). Farming with fewer pesticides: EU pesticide reviewand resulting challenges for UK agriculture. Crop Prot. 31, 85–93.doi: 10.1016/j.cropro.2011.08.008Johnson, S. N., Benefer, C. M., Frew, A., Griffiths, B. S., Hartley, S. E.,Karley, A. J., et al. (2016). New frontiers in belowground ecology forplant protection from root-feeding insects. Appl. Soil Ecol. 108, 96–107.doi: 10.1016/j.apsoil.2016.07.017Johnson, S. N., and Jones, T. H. (2017). Global Climate Change and TerrestrialInvertebrates. Chichester: John Wiley & Son Ltd.Moore, B. D., and Johnson, S. N. (2017). Get tough, get toxic, or get abodyguard: identifying candidate traits conferring belowground resistanceto herbivores in grasses. Front. Plant Sci. 7:1925. doi: 10.3389/fpls.2016.01925Peeters, P. J., Sanson, G., and Read, J. (2007). Leaf biomechanical propertiesand the densities of herbivorous insect guilds. Funct. Ecol. 21, 246–255.doi: 10.1111/j.1365-2435.2006.01223.xConflict of Interest Statement: The authors declare that the research wasconducted in the absence of any commercial or financial relationships that couldbe construed as a potential conflict of interest.Copyright © 2017 Johnson, Karley, Gregory and Brennan. This is an open-accessarticle distributed under the terms of the Creative Commons Attribution License (CCBY). The use, distribution or reproduction in other forums is permitted, provided theoriginal author(s) or licensor are credited and that the original publication in thisjournal is cited, in accordance with accepted academic practice. No use, distributionor reproduction is permitted which does not comply with these terms.Frontiers in Plant Science | www.frontiersin.org 3 February 2017 | Volume 8 | Article 209

English

Crop Traits for Defense against Pests and Disease:Durability, Breakdown and Future Prospects

Central Archive at the University of Reading

Editorial: crop traits for defense against pests and disease: durability, breakdown and future prospects Article Published Version Creative Commons: Attribution 4.0 (CC­BY) Open Access Johnson, S. N., Karley, A. J., Gregory, P. J. and Brennan, R. M. (2017) Editorial: crop traits for defense against pests and disease: durability, breakdown and future prospects. Frontiers in Plant Science, 8. 209. ISSN 1664­462X doi: https://doi.org/10.3389/fpls.2017.00209 Available at http://centaur.reading.ac.uk/69750/ It is advisable to refer to the publisher’s version if you intend to cite from the work. To link to this article DOI: http://dx.doi.org/10.3389/fpls.2017.00209 Publisher: Frontiers All outputs in CentAUR are protected by Intellectual Property Rights law, including copyright law. Copyright and IPR is retained by the creators or other copyright holders. Terms and conditions for use of this material are defined in the End User Agreement . www.reading.ac.uk/centaur CentAUR Central Archive at the University of Reading Reading’s research outputs onlineEDITORIALpublished: 21 February 2017doi: 10.3389/fpls.2017.00209Frontiers in Plant Science | www.frontiersin.org 1 February 2017 | Volume 8 | Article 209Edited and reviewed by:Diego Rubiales,Instituto de Agricultura Sostenible(CSIC), Spain*Correspondence:Rex M. Brennanrex.brennan@hutton.ac.ukSpecialty section:This article was submitted toCrop Science and Horticulture,a section of the journalFrontiers in Plant ScienceReceived: 30 January 2017Accepted: 03 February 2017Published: 21 February 2017Citation:Johnson SN, Karley AJ, Gregory PJand Brennan RM (2017) Editorial:Crop Traits for Defense against Pestsand Disease: Durability, Breakdownand Future Prospects.Front. Plant Sci. 8:209.doi: 10.3389/fpls.2017.00209Editorial: Crop Traits for Defenseagainst Pests and Disease: Durability,Breakdown and Future ProspectsScott N. Johnson 1, Alison J. Karley 2, Peter J. Gregory 3 and Rex M. Brennan 2*1Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, Australia, 2 The James Hutton Institute,Dundee, UK, 3 School of Agriculture, Policy and Development, University of Reading, Reading, UKKeywords: climate change, crops, food security, pathogens, pests, resistanceEditorial on the Research TopicCropTraits forDefense against Pests andDisease: Durability, Breakdown and Future ProspectsWith the Earth’s population expected to reach 11.2 billion by 2100 there is a pressing need tomaximize food production at a time when productivity of many crops is reaching a plateau.Minimizing losses to pests and diseases is therefore a crucial means of meeting this challengeand securing food supply. This research topic addresses some of the most important issues in thefuture sustainability of global crop production. The topic consists of 20 papers, of which 13 describeoriginal research. There are six review papers, plus one hypothesis and theory contribution.The development of plants with resistance to the most damaging pests and diseases isincreasingly important in the face of growing pressure to reduce synthetic chemical inputs,including pesticides, fungicides, and herbicides used for crop protection. This reduction is partlyunderwritten by legislative directives, consumer demands and indeed an overall reduction inavailable chemical controls for most crops (Hillocks, 2012), especially those outwith the mainarable species. Additionally, losses due to pest and disease attacks represent a major financialcost in crop production and throughout the subsequent supply chain, even before the costs ofcontrol measures are considered. The move toward more sustainable production systems, based onintegrated pest and disease management approaches, is gaining momentum, and the developmentof more resistant cultivars is a major factor contributing to the success of these systems. In addition,there is a recognized need for frameworks (e.g., Birch et al., 2011) which combine natural enemieswith resistant cultivars and other management practices to reduce reliance on crop protectionchemicals and maintain viable and sustainable future crop production.The development of resistant cultivars is crucial to the future of sustainable crop productionpractices, and there is a substantial need for the continued introgression of specific resistancegenes or physical and structural traits, from existing or extended genetic resources. Recentadvances in knowledge can aid this process, even in many minor crop species, where increasedunderstanding of trait heritability and technological advances in genomics and bioinformatics areenabling the identification of genes controlling resistance, providing a framework for improvedselection efficiency. Moreover, the advent of new technologies can provide significant benefits, asexemplified by the opportunities afforded by CRISPR-based tools in understanding plant-pathogeninteractions; these are addressed in the review by Barakate and Stephens. The need for newresistance genes is crucial withinmany pathogen/crop systems, and VanWeymers et al. describe theapplication of a range of “omics” technologies in potato to identify novel resistances to potato blightwithin a large germplasm collection. This approach is one that can be adapted for other speciesand pathogens, as the future role of resistance genes from existing but underexploited geneticJohnson et al. Crop Traits for Pest/Disease Defenseresources is likely to be significant. This is not limited to inherentcrop resistance, however, and Reynolds et al. also highlight therole of “omics” approaches for augmenting plant resistance toinvertebrates using application of silicon.Breeding strategies focused on the identification andincorporation of specific resistance genes, both individually orin effective groups, are being developed and implemented inmany active breeding programmes. The use of marker-assistedbackcross breeding in rice to pyramid resistance genes forbacterial blight and blast diseases is the subject of the paperby Abhilash Kumar et al. An investigation of genes involvedin the infection processes by Phytophthora capsici in Capsicumspp. by Zhang et al. through genome-wide identificationhighlights the role of SQUAMOSA promoter binding protein(SBP)-box genes that can be utilized in future breeding anddevelopment research. Genetic mapping of host plants, suchas Capsicum, was used by Barbary et al. to identify QTLslinked to resistance to Meloidogyne nematode species, andfrom this the underlying genes can eventually be identified andutilized in the breeding of resistant plants. Similarly, wild Vitisgenotypes studied by Wan et al. to find sources of resistanceto Botrytis, based on antioxidant activity linked to resistance,will be deployed in future breeding strategies. Further workon wild Vitis by Wen et al. identified a gene linked to powderymildew resistance and confirmed its effect through ectopicexpression in Arabidopsis; again, this provides a resource forfuture breeding.The effects of pest attacks on host plant metabolism wasinvestigated by Liu et al., using the wild brassica species Barbareavulgaris and the global pest diamondback moth, Plutellaxylostella. By examining changes in glucosinolate biosynthesisinduced by larval infestation, inferences can be made aboutthe mechanisms underpinning defense induction. A quantitativeapproach to the breeding of resistant cultivars is described byMohammed et al. in Sorghum, where the use of diallel progenyenabled the identification of a significant interaction betweenresistance to shoot fly andmorphological traits such as grain yieldand seed size. The information on the quantitative genetics ofSorghum can be used to inform decisions on parental choice forresistance breeding.Many host-pathogen systems are subject to rapid evolution,for example in pathogen race structure or breakdown of hostresistance. The paper by Gómez-Cortecero et al. describes theuse of SNPs and SSRs to study diversity in global populationsof Neonectria ditissima affecting apple trees, and also presentevidence of a relatively simple pattern of host response which isnot influenced by any race structure in the pathogen population.Integrated Pest and Disease Management (IPDM) approachesto pest and disease control require the development of resistantvarieties and also monitoring and management strategies thatcan be applied effectively within crops. The paper by Joshi et al.deals with the development of a susceptibility index for codlingmoth on apple, based on oviposition preferences. The review byPeterson et al. considers the wide range of plant defense traitsthat can influence the responses of natural enemies used in IPDMsystems, and also includes the potential impacts of transgeniccrops on trophic levels and arthropod communities.Plant defenses can be exploited to enhance resistance to pestattack and also to confer tolerance of pest infestations. Plantphysical defenses can offer particularly durable resistance to pestsand pathogens (Johnson et al., 2016; Moore and Johnson, 2017);ecological studies, for example, have shown plant physical traitsto be more effective deterrents to insect herbivory than plantsecondary metabolites (Peeters et al., 2007; Cooke and Leishman,2012). As outlined in the review byMitchell et al., plant structuraltraits such as trichomes, spines, and cuticles can provide aphysical barrier to arthropod pest attachment, feeding andoviposition, while plant vigor and altered phenology can increasetolerance of pest damage and reduce the incidence of pestattacks. This paper highlights new avenues for discovery of plantdefensive traits, particularly through research to understand pest-induced changes in plant chemistry and mechanisms of plantdefense “priming”.The effects of a changing climate are likely to alter bothseverity of pest and pathogen attacks, and also the spectrum oforganisms that will cause damage to crop plants (Johnson andJones, 2017). Two papers in this research topic consider changesunder conditions of elevated CO2; the first by McKenzie et al.presents data illustrating the changes in herbivory by two pests ofraspberry, the European large raspberry aphid (Amophorophoaidaei) and the root-feeding vine weevil (Otiorhynchus sulcatus).The second contribution, a review by Sun et al., examines changesin host plant metabolism and water-use efficiency instigatedunder elevated CO2 conditions, and how these changes impacton the outcome of plant-aphid interactions.Host plant resistance can have significant effects on organismsand trophic levels beyond the target pest or pathogen, and thishas implications for integrated management of crop systems.This area is discussed by Peterson et al. in their review, whichalso considers the use of transgenic crops. Genetic modificationtechnology has potential application in the development of pest-resistant cultivars of some arable species, especially where thereare limited sources of resistance within the genus, and this isdiscussed in the context of cotton production systems by Traperoet al. and de Oliveira et al. The identification by the latterauthors of resistances coveringmultiple pestsmay offer particularopportunities.Making use of multiple resistance traits might also offer analternative approach toward pathogen control. The theory paperby Newton suggests that the harmful effects of fungal diseaseoutbreaks in cereal crops could be limited by using mixedgenotype plantings; cultivarmixtures often show higher toleranceof, or resistance to, disease. The impact of this approach on othermicrobial species in the crop environment is also considered.The development of environmentally friendly controlmechanisms for pests is a further aspect of future cropproduction systems, and there are various less damagingingredients under consideration. These can include the useof plant mutualists or manipulation of soil conditions, forexample by application of chemical constituents such as silicon(Johnson et al., 2016). In terms of plant mutualists, arbuscularmycorrhizal fungi can improve crop productivity, as reportedby Robinson-Boyer et al., which may result in better toleranceof pest and disease attack Mitchell et al. and also help plantsFrontiers in Plant Science | www.frontiersin.org 2 February 2017 | Volume 8 | Article 209Johnson et al. Crop Traits for Pest/Disease Defenseresist attack by root herbivores (Johnson et al., 2016). Moreover,the role of silicon application to the soil and resistance toherbivory is considered in the review by Reynolds et al..They present evidence for direct and indirect defenses (e.g.,recruitment of natural enemies of pests via volatile emissions) bysilicon.We hope this research topic will provide a valuable resourcefor workers and researchers in the field of crop protectionby providing a source of information about existing andnovel sources of crop resistance and tolerance traits, theirincorporation into breeding programmes, how they can bedeployed for maximum efficacy under field conditions whenintegrated with other pest and disease control measures, andtheir potential to provide durable and sustainable crop protectionunder a changing environment.TRIBUTE TO ALAIN PALLOIXIt is with sadness that we note the death of Alain Palloix, whosemanuscript on resistance to root-knot nematodes Barbary et al.is included in this research topic. Alain’s work over many yearsmade a significant contribution to the understanding of pepper-pathogen interactions and resistance breeding, and we extend oursympathy to his family and colleagues.AUTHOR CONTRIBUTIONSAll authors listed have made substantial, direct and intellectualcontribution to the work and approved it for publication.ACKNOWLEDGMENTSRB and AK are supported by the Scottish Government throughthe RESAS strategic research programmes in “Crop andGrassland Production and Disease Control” and “Productiveand Sustainable Land Management and Rural Economies”(2016-2021). SJ is supported by grants from the AustralianResearch Council (DP140100363 and DP170102278). We thankthe authors involved in this research topic for their excellent andvaried contributions.REFERENCESBirch, A. N. E., Begg, G. S., and Squire, G. R. (2011). How agro-ecological researchhelps to address food security issues under new IPM and pesticide reductionpolicies for global crop production systems. J. Exp. Bot. 62, 3251–3261.doi: 10.1093/jxb/err064Cooke, J., and Leishman,M. R. (2012). Tradeoffs between foliar silicon and carbon-based defences: evidence from vegetation communities of contrasting soil types.Oikos 121, 2052–2060. doi: 10.1111/j.1600-0706.2012.20057.xHillocks, R. J. (2012). Farming with fewer pesticides: EU pesticide reviewand resulting challenges for UK agriculture. Crop Prot. 31, 85–93.doi: 10.1016/j.cropro.2011.08.008Johnson, S. N., Benefer, C. M., Frew, A., Griffiths, B. S., Hartley, S. E.,Karley, A. J., et al. (2016). New frontiers in belowground ecology forplant protection from root-feeding insects. Appl. Soil Ecol. 108, 96–107.doi: 10.1016/j.apsoil.2016.07.017Johnson, S. N., and Jones, T. H. (2017). Global Climate Change and TerrestrialInvertebrates. Chichester: John Wiley & Son Ltd.Moore, B. D., and Johnson, S. N. (2017). Get tough, get toxic, or get abodyguard: identifying candidate traits conferring belowground resistanceto herbivores in grasses. Front. Plant Sci. 7:1925. doi: 10.3389/fpls.2016.01925Peeters, P. J., Sanson, G., and Read, J. (2007). Leaf biomechanical propertiesand the densities of herbivorous insect guilds. Funct. Ecol. 21, 246–255.doi: 10.1111/j.1365-2435.2006.01223.xConflict of Interest Statement: The authors declare that the research wasconducted in the absence of any commercial or financial relationships that couldbe construed as a potential conflict of interest.Copyright © 2017 Johnson, Karley, Gregory and Brennan. This is an open-accessarticle distributed under the terms of the Creative Commons Attribution License (CCBY). The use, distribution or reproduction in other forums is permitted, provided theoriginal author(s) or licensor are credited and that the original publication in thisjournal is cited, in accordance with accepted academic practice. No use, distributionor reproduction is permitted which does not comply with these terms.Frontiers in Plant Science | www.frontiersin.org 3 February 2017 | Volume 8 | Article 209

Editorial: crop traits for defense against pests and disease: durability, breakdown and future prospects

                                                                    University of DundeeCrop Traits for Defense against Pests and DiseaseJohnson, Scott N.; Karley, Alison J.; Gregory, Peter J.; Brennan, Rex M.Published in:Frontiers in Plant ScienceDOI:10.3389/fpls.2017.00209Publication date:2017Licence:CC BYDocument VersionPublisher's PDF, also known as Version of recordLink to publication in Discovery Research PortalCitation for published version (APA):Johnson, S. N., Karley, A. J., Gregory, P. J., & Brennan, R. M. (2017). Crop Traits for Defense against Pests andDisease: Durability, Breakdown and Future Prospects. Frontiers in Plant Science, 8, Article 209.https://doi.org/10.3389/fpls.2017.00209General rightsCopyright and moral rights for the publications made accessible in Discovery Research Portal are retained by the authors and/or othercopyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated withthese rights.Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Download date: 24. Sep. 2025EDITORIALpublished: 21 February 2017doi: 10.3389/fpls.2017.00209Frontiers in Plant Science | www.frontiersin.org 1 February 2017 | Volume 8 | Article 209Edited and reviewed by:Diego Rubiales,Instituto de Agricultura Sostenible(CSIC), Spain*Correspondence:Rex M. Brennanrex.brennan@hutton.ac.ukSpecialty section:This article was submitted toCrop Science and Horticulture,a section of the journalFrontiers in Plant ScienceReceived: 30 January 2017Accepted: 03 February 2017Published: 21 February 2017Citation:Johnson SN, Karley AJ, Gregory PJand Brennan RM (2017) Editorial:Crop Traits for Defense against Pestsand Disease: Durability, Breakdownand Future Prospects.Front. Plant Sci. 8:209.doi: 10.3389/fpls.2017.00209Editorial: Crop Traits for Defenseagainst Pests and Disease: Durability,Breakdown and Future ProspectsScott N. Johnson 1, Alison J. Karley 2, Peter J. Gregory 3 and Rex M. Brennan 2*1Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, Australia, 2 The James Hutton Institute,Dundee, UK, 3 School of Agriculture, Policy and Development, University of Reading, Reading, UKKeywords: climate change, crops, food security, pathogens, pests, resistanceEditorial on the Research TopicCropTraits forDefense against Pests andDisease: Durability, Breakdown and Future ProspectsWith the Earth’s population expected to reach 11.2 billion by 2100 there is a pressing need tomaximize food production at a time when productivity of many crops is reaching a plateau.Minimizing losses to pests and diseases is therefore a crucial means of meeting this challengeand securing food supply. This research topic addresses some of the most important issues in thefuture sustainability of global crop production. The topic consists of 20 papers, of which 13 describeoriginal research. There are six review papers, plus one hypothesis and theory contribution.The development of plants with resistance to the most damaging pests and diseases isincreasingly important in the face of growing pressure to reduce synthetic chemical inputs,including pesticides, fungicides, and herbicides used for crop protection. This reduction is partlyunderwritten by legislative directives, consumer demands and indeed an overall reduction inavailable chemical controls for most crops (Hillocks, 2012), especially those outwith the mainarable species. Additionally, losses due to pest and disease attacks represent a major financialcost in crop production and throughout the subsequent supply chain, even before the costs ofcontrol measures are considered. The move toward more sustainable production systems, based onintegrated pest and disease management approaches, is gaining momentum, and the developmentof more resistant cultivars is a major factor contributing to the success of these systems. In addition,there is a recognized need for frameworks (e.g., Birch et al., 2011) which combine natural enemieswith resistant cultivars and other management practices to reduce reliance on crop protectionchemicals and maintain viable and sustainable future crop production.The development of resistant cultivars is crucial to the future of sustainable crop productionpractices, and there is a substantial need for the continued introgression of specific resistancegenes or physical and structural traits, from existing or extended genetic resources. Recentadvances in knowledge can aid this process, even in many minor crop species, where increasedunderstanding of trait heritability and technological advances in genomics and bioinformatics areenabling the identification of genes controlling resistance, providing a framework for improvedselection efficiency. Moreover, the advent of new technologies can provide significant benefits, asexemplified by the opportunities afforded by CRISPR-based tools in understanding plant-pathogeninteractions; these are addressed in the review by Barakate and Stephens. The need for newresistance genes is crucial withinmany pathogen/crop systems, and VanWeymers et al. describe theapplication of a range of “omics” technologies in potato to identify novel resistances to potato blightwithin a large germplasm collection. This approach is one that can be adapted for other speciesand pathogens, as the future role of resistance genes from existing but underexploited geneticJohnson et al. Crop Traits for Pest/Disease Defenseresources is likely to be significant. This is not limited to inherentcrop resistance, however, and Reynolds et al. also highlight therole of “omics” approaches for augmenting plant resistance toinvertebrates using application of silicon.Breeding strategies focused on the identification andincorporation of specific resistance genes, both individually orin effective groups, are being developed and implemented inmany active breeding programmes. The use of marker-assistedbackcross breeding in rice to pyramid resistance genes forbacterial blight and blast diseases is the subject of the paperby Abhilash Kumar et al. An investigation of genes involvedin the infection processes by Phytophthora capsici in Capsicumspp. by Zhang et al. through genome-wide identificationhighlights the role of SQUAMOSA promoter binding protein(SBP)-box genes that can be utilized in future breeding anddevelopment research. Genetic mapping of host plants, suchas Capsicum, was used by Barbary et al. to identify QTLslinked to resistance to Meloidogyne nematode species, andfrom this the underlying genes can eventually be identified andutilized in the breeding of resistant plants. Similarly, wild Vitisgenotypes studied by Wan et al. to find sources of resistanceto Botrytis, based on antioxidant activity linked to resistance,will be deployed in future breeding strategies. Further workon wild Vitis by Wen et al. identified a gene linked to powderymildew resistance and confirmed its effect through ectopicexpression in Arabidopsis; again, this provides a resource forfuture breeding.The effects of pest attacks on host plant metabolism wasinvestigated by Liu et al., using the wild brassica species Barbareavulgaris and the global pest diamondback moth, Plutellaxylostella. By examining changes in glucosinolate biosynthesisinduced by larval infestation, inferences can be made aboutthe mechanisms underpinning defense induction. A quantitativeapproach to the breeding of resistant cultivars is described byMohammed et al. in Sorghum, where the use of diallel progenyenabled the identification of a significant interaction betweenresistance to shoot fly andmorphological traits such as grain yieldand seed size. The information on the quantitative genetics ofSorghum can be used to inform decisions on parental choice forresistance breeding.Many host-pathogen systems are subject to rapid evolution,for example in pathogen race structure or breakdown of hostresistance. The paper by Gómez-Cortecero et al. describes theuse of SNPs and SSRs to study diversity in global populationsof Neonectria ditissima affecting apple trees, and also presentevidence of a relatively simple pattern of host response which isnot influenced by any race structure in the pathogen population.Integrated Pest and Disease Management (IPDM) approachesto pest and disease control require the development of resistantvarieties and also monitoring and management strategies thatcan be applied effectively within crops. The paper by Joshi et al.deals with the development of a susceptibility index for codlingmoth on apple, based on oviposition preferences. The review byPeterson et al. considers the wide range of plant defense traitsthat can influence the responses of natural enemies used in IPDMsystems, and also includes the potential impacts of transgeniccrops on trophic levels and arthropod communities.Plant defenses can be exploited to enhance resistance to pestattack and also to confer tolerance of pest infestations. Plantphysical defenses can offer particularly durable resistance to pestsand pathogens (Johnson et al., 2016; Moore and Johnson, 2017);ecological studies, for example, have shown plant physical traitsto be more effective deterrents to insect herbivory than plantsecondary metabolites (Peeters et al., 2007; Cooke and Leishman,2012). As outlined in the review byMitchell et al., plant structuraltraits such as trichomes, spines, and cuticles can provide aphysical barrier to arthropod pest attachment, feeding andoviposition, while plant vigor and altered phenology can increasetolerance of pest damage and reduce the incidence of pestattacks. This paper highlights new avenues for discovery of plantdefensive traits, particularly through research to understand pest-induced changes in plant chemistry and mechanisms of plantdefense “priming”.The effects of a changing climate are likely to alter bothseverity of pest and pathogen attacks, and also the spectrum oforganisms that will cause damage to crop plants (Johnson andJones, 2017). Two papers in this research topic consider changesunder conditions of elevated CO2; the first by McKenzie et al.presents data illustrating the changes in herbivory by two pests ofraspberry, the European large raspberry aphid (Amophorophoaidaei) and the root-feeding vine weevil (Otiorhynchus sulcatus).The second contribution, a review by Sun et al., examines changesin host plant metabolism and water-use efficiency instigatedunder elevated CO2 conditions, and how these changes impacton the outcome of plant-aphid interactions.Host plant resistance can have significant effects on organismsand trophic levels beyond the target pest or pathogen, and thishas implications for integrated management of crop systems.This area is discussed by Peterson et al. in their review, whichalso considers the use of transgenic crops. Genetic modificationtechnology has potential application in the development of pest-resistant cultivars of some arable species, especially where thereare limited sources of resistance within the genus, and this isdiscussed in the context of cotton production systems by Traperoet al. and de Oliveira et al. The identification by the latterauthors of resistances coveringmultiple pestsmay offer particularopportunities.Making use of multiple resistance traits might also offer analternative approach toward pathogen control. The theory paperby Newton suggests that the harmful effects of fungal diseaseoutbreaks in cereal crops could be limited by using mixedgenotype plantings; cultivarmixtures often show higher toleranceof, or resistance to, disease. The impact of this approach on othermicrobial species in the crop environment is also considered.The development of environmentally friendly controlmechanisms for pests is a further aspect of future cropproduction systems, and there are various less damagingingredients under consideration. These can include the useof plant mutualists or manipulation of soil conditions, forexample by application of chemical constituents such as silicon(Johnson et al., 2016). In terms of plant mutualists, arbuscularmycorrhizal fungi can improve crop productivity, as reportedby Robinson-Boyer et al., which may result in better toleranceof pest and disease attack Mitchell et al. and also help plantsFrontiers in Plant Science | www.frontiersin.org 2 February 2017 | Volume 8 | Article 209Johnson et al. Crop Traits for Pest/Disease Defenseresist attack by root herbivores (Johnson et al., 2016). Moreover,the role of silicon application to the soil and resistance toherbivory is considered in the review by Reynolds et al..They present evidence for direct and indirect defenses (e.g.,recruitment of natural enemies of pests via volatile emissions) bysilicon.We hope this research topic will provide a valuable resourcefor workers and researchers in the field of crop protectionby providing a source of information about existing andnovel sources of crop resistance and tolerance traits, theirincorporation into breeding programmes, how they can bedeployed for maximum efficacy under field conditions whenintegrated with other pest and disease control measures, andtheir potential to provide durable and sustainable crop protectionunder a changing environment.TRIBUTE TO ALAIN PALLOIXIt is with sadness that we note the death of Alain Palloix, whosemanuscript on resistance to root-knot nematodes Barbary et al.is included in this research topic. Alain’s work over many yearsmade a significant contribution to the understanding of pepper-pathogen interactions and resistance breeding, and we extend oursympathy to his family and colleagues.AUTHOR CONTRIBUTIONSAll authors listed have made substantial, direct and intellectualcontribution to the work and approved it for publication.ACKNOWLEDGMENTSRB and AK are supported by the Scottish Government throughthe RESAS strategic research programmes in “Crop andGrassland Production and Disease Control” and “Productiveand Sustainable Land Management and Rural Economies”(2016-2021). SJ is supported by grants from the AustralianResearch Council (DP140100363 and DP170102278). We thankthe authors involved in this research topic for their excellent andvaried contributions.REFERENCESBirch, A. N. E., Begg, G. S., and Squire, G. R. (2011). How agro-ecological researchhelps to address food security issues under new IPM and pesticide reductionpolicies for global crop production systems. J. Exp. Bot. 62, 3251–3261.doi: 10.1093/jxb/err064Cooke, J., and Leishman,M. R. (2012). Tradeoffs between foliar silicon and carbon-based defences: evidence from vegetation communities of contrasting soil types.Oikos 121, 2052–2060. doi: 10.1111/j.1600-0706.2012.20057.xHillocks, R. J. (2012). Farming with fewer pesticides: EU pesticide reviewand resulting challenges for UK agriculture. Crop Prot. 31, 85–93.doi: 10.1016/j.cropro.2011.08.008Johnson, S. N., Benefer, C. M., Frew, A., Griffiths, B. S., Hartley, S. E.,Karley, A. J., et al. (2016). New frontiers in belowground ecology forplant protection from root-feeding insects. Appl. Soil Ecol. 108, 96–107.doi: 10.1016/j.apsoil.2016.07.017Johnson, S. N., and Jones, T. H. (2017). Global Climate Change and TerrestrialInvertebrates. Chichester: John Wiley & Son Ltd.Moore, B. D., and Johnson, S. N. (2017). Get tough, get toxic, or get abodyguard: identifying candidate traits conferring belowground resistanceto herbivores in grasses. Front. Plant Sci. 7:1925. doi: 10.3389/fpls.2016.01925Peeters, P. J., Sanson, G., and Read, J. (2007). Leaf biomechanical propertiesand the densities of herbivorous insect guilds. Funct. Ecol. 21, 246–255.doi: 10.1111/j.1365-2435.2006.01223.xConflict of Interest Statement: The authors declare that the research wasconducted in the absence of any commercial or financial relationships that couldbe construed as a potential conflict of interest.Copyright © 2017 Johnson, Karley, Gregory and Brennan. This is an open-accessarticle distributed under the terms of the Creative Commons Attribution License (CCBY). The use, distribution or reproduction in other forums is permitted, provided theoriginal author(s) or licensor are credited and that the original publication in thisjournal is cited, in accordance with accepted academic practice. No use, distributionor reproduction is permitted which does not comply with these terms.Frontiers in Plant Science | www.frontiersin.org 3 February 2017 | Volume 8 | Article 209

Rex M. Brennan

Frontiers - Publisher Connector

EDITORIAL
published: 21 February 2017
doi: 10.3389/fpls.2017.00209
Frontiers in Plant Science | www.frontiersin.org 1 February 2017 | Volume 8 | Article 209
Edited and reviewed by:
Diego Rubiales,
Instituto de Agricultura Sostenible
(CSIC), Spain
*Correspondence:
Rex M. Brennan
rex.brennan@hutton.ac.uk
Specialty section:
This article was submitted to
Crop Science and Horticulture,
a section of the journal
Frontiers in Plant Science
Received: 30 January 2017
Accepted: 03 February 2017
Published: 21 February 2017
Citation:
Johnson SN, Karley AJ, Gregory PJ
and Brennan RM (2017) Editorial:
Crop Traits for Defense against Pests
and Disease: Durability, Breakdown
and Future Prospects.
Front. Plant Sci. 8:209.
doi: 10.3389/fpls.2017.00209
Editorial: Crop Traits for Defense
against Pests and Disease: Durability,
Breakdown and Future Prospects
Scott N. Johnson 1, Alison J. Karley 2, Peter J. Gregory 3 and Rex M. Brennan 2*
1Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, Australia, 2 The James Hutton Institute,
Dundee, UK, 3 School of Agriculture, Policy and Development, University of Reading, Reading, UK
Keywords: climate change, crops, food security, pathogens, pests, resistance
Editorial on the Research Topic
CropTraits forDefense against Pests andDisease: Durability, Breakdown and Future Prospects
With the Earth’s population expected to reach 11.2 billion by 2100 there is a pressing need to
maximize food production at a time when productivity of many crops is reaching a plateau.
Minimizing losses to pests and diseases is therefore a crucial means of meeting this challenge
and securing food supply. This research topic addresses some of the most important issues in the
future sustainability of global crop production. The topic consists of 20 papers, of which 13 describe
original research. There are six review papers, plus one hypothesis and theory contribution.
The development of plants with resistance to the most damaging pests and diseases is
increasingly important in the face of growing pressure to reduce synthetic chemical inputs,
including pesticides, fungicides, and herbicides used for crop protection. This reduction is partly
underwritten by legislative directives, consumer demands and indeed an overall reduction in
available chemical controls for most crops (Hillocks, 2012), especially those outwith the main
arable species. Additionally, losses due to pest and disease attacks represent a major financial
cost in crop production and throughout the subsequent supply chain, even before the costs of
control measures are considered. The move toward more sustainable production systems, based on
integrated pest and disease management approaches, is gaining momentum, and the development
of more resistant cultivars is a major factor contributing to the success of these systems. In addition,
there is a recognized need for frameworks (e.g., Birch et al., 2011) which combine natural enemies
with resistant cultivars and other management practices to reduce reliance on crop protection
chemicals and maintain viable and sustainable future crop production.
The development of resistant cultivars is crucial to the future of sustainable crop production
practices, and there is a substantial need for the continued introgression of specific resistance
genes or physical and structural traits, from existing or extended genetic resources. Recent
advances in knowledge can aid this process, even in many minor crop species, where increased
understanding of trait heritability and technological advances in genomics and bioinformatics are
enabling the identification of genes controlling resistance, providing a framework for improved
selection efficiency. Moreover, the advent of new technologies can provide significant benefits, as
exemplified by the opportunities afforded by CRISPR-based tools in understanding plant-pathogen
interactions; these are addressed in the review by Barakate and Stephens. The need for new
resistance genes is crucial withinmany pathogen/crop systems, and VanWeymers et al. describe the
application of a range of “omics” technologies in potato to identify novel resistances to potato blight
within a large germplasm collection. This approach is one that can be adapted for other species
and pathogens, as the future role of resistance genes from existing but underexploited genetic
Johnson et al. Crop Traits for Pest/Disease Defense
resources is likely to be significant. This is not limited to inherent
crop resistance, however, and Reynolds et al. also highlight the
role of “omics” approaches for augmenting plant resistance to
invertebrates using application of silicon.
Breeding strategies focused on the identification and
incorporation of specific resistance genes, both individually or
in effective groups, are being developed and implemented in
many active breeding programmes. The use of marker-assisted
backcross breeding in rice to pyramid resistance genes for
bacterial blight and blast diseases is the subject of the paper
by Abhilash Kumar et al. An investigation of genes involved
in the infection processes by Phytophthora capsici in Capsicum
spp. by Zhang et al. through genome-wide identification
highlights the role of SQUAMOSA promoter binding protein
(SBP)-box genes that can be utilized in future breeding and
development research. Genetic mapping of host plants, such
as Capsicum, was used by Barbary et al. to identify QTLs
linked to resistance to Meloidogyne nematode species, and
from this the underlying genes can eventually be identified and
utilized in the breeding of resistant plants. Similarly, wild Vitis
genotypes studied by Wan et al. to find sources of resistance
to Botrytis, based on antioxidant activity linked to resistance,
will be deployed in future breeding strategies. Further work
on wild Vitis by Wen et al. identified a gene linked to powdery
mildew resistance and confirmed its effect through ectopic
expression in Arabidopsis; again, this provides a resource for
future breeding.
The effects of pest attacks on host plant metabolism was
investigated by Liu et al., using the wild brassica species Barbarea
vulgaris and the global pest diamondback moth, Plutella
xylostella. By examining changes in glucosinolate biosynthesis
induced by larval infestation, inferences can be made about
the mechanisms underpinning defense induction. A quantitative
approach to the breeding of resistant cultivars is described by
Mohammed et al. in Sorghum, where the use of diallel progeny
enabled the identification of a significant interaction between
resistance to shoot fly andmorphological traits such as grain yield
and seed size. The information on the quantitative genetics of
Sorghum can be used to inform decisions on parental choice for
resistance breeding.
Many host-pathogen systems are subject to rapid evolution,
for example in pathogen race structure or breakdown of host
resistance. The paper by Gómez-Cortecero et al. describes the
use of SNPs and SSRs to study diversity in global populations
of Neonectria ditissima affecting apple trees, and also present
evidence of a relatively simple pattern of host response which is
not influenced by any race structure in the pathogen population.
Integrated Pest and Disease Management (IPDM) approaches
to pest and disease control require the development of resistant
varieties and also monitoring and management strategies that
can be applied effectively within crops. The paper by Joshi et al.
deals with the development of a susceptibility index for codling
moth on apple, based on oviposition preferences. The review by
Peterson et al. considers the wide range of plant defense traits
that can influence the responses of natural enemies used in IPDM
systems, and also includes the potential impacts of transgenic
crops on trophic levels and arthropod communities.
Plant defenses can be exploited to enhance resistance to pest
attack and also to confer tolerance of pest infestations. Plant
physical defenses can offer particularly durable resistance to pests
and pathogens (Johnson et al., 2016; Moore and Johnson, 2017);
ecological studies, for example, have shown plant physical traits
to be more effective deterrents to insect herbivory than plant
secondary metabolites (Peeters et al., 2007; Cooke and Leishman,
2012). As outlined in the review byMitchell et al., plant structural
traits such as trichomes, spines, and cuticles can provide a
physical barrier to arthropod pest attachment, feeding and
oviposition, while plant vigor and altered phenology can increase
tolerance of pest damage and reduce the incidence of pest
attacks. This paper highlights new avenues for discovery of plant
defensive traits, particularly through research to understand pest-
induced changes in plant chemistry and mechanisms of plant
defense “priming”.
The effects of a changing climate are likely to alter both
severity of pest and pathogen attacks, and also the spectrum of
organisms that will cause damage to crop plants (Johnson and
Jones, 2017). Two papers in this research topic consider changes
under conditions of elevated CO2; the first by McKenzie et al.
presents data illustrating the changes in herbivory by two pests of
raspberry, the European large raspberry aphid (Amophorophoa
idaei) and the root-feeding vine weevil (Otiorhynchus sulcatus).
The second contribution, a review by Sun et al., examines changes
in host plant metabolism and water-use efficiency instigated
under elevated CO2 conditions, and how these changes impact
on the outcome of plant-aphid interactions.
Host plant resistance can have significant effects on organisms
and trophic levels beyond the target pest or pathogen, and this
has implications for integrated management of crop systems.
This area is discussed by Peterson et al. in their review, which
also considers the use of transgenic crops. Genetic modification
technology has potential application in the development of pest-
resistant cultivars of some arable species, especially where there
are limited sources of resistance within the genus, and this is
discussed in the context of cotton production systems by Trapero
et al. and de Oliveira et al. The identification by the latter
authors of resistances coveringmultiple pestsmay offer particular
opportunities.
Making use of multiple resistance traits might also offer an
alternative approach toward pathogen control. The theory paper
by Newton suggests that the harmful effects of fungal disease
outbreaks in cereal crops could be limited by using mixed
genotype plantings; cultivarmixtures often show higher tolerance
of, or resistance to, disease. The impact of this approach on other
microbial species in the crop environment is also considered.
The development of environmentally friendly control
mechanisms for pests is a further aspect of future crop
production systems, and there are various less damaging
ingredients under consideration. These can include the use
of plant mutualists or manipulation of soil conditions, for
example by application of chemical constituents such as silicon
(Johnson et al., 2016). In terms of plant mutualists, arbuscular
mycorrhizal fungi can improve crop productivity, as reported
by Robinson-Boyer et al., which may result in better tolerance
of pest and disease attack Mitchell et al. and also help plants
Frontiers in Plant Science | www.frontiersin.org 2 February 2017 | Volume 8 | Article 209
Johnson et al. Crop Traits for Pest/Disease Defense
resist attack by root herbivores (Johnson et al., 2016). Moreover,
the role of silicon application to the soil and resistance to
herbivory is considered in the review by Reynolds et al..
They present evidence for direct and indirect defenses (e.g.,
recruitment of natural enemies of pests via volatile emissions) by
silicon.
We hope this research topic will provide a valuable resource
for workers and researchers in the field of crop protection
by providing a source of information about existing and
novel sources of crop resistance and tolerance traits, their
incorporation into breeding programmes, how they can be
deployed for maximum efficacy under field conditions when
integrated with other pest and disease control measures, and
their potential to provide durable and sustainable crop protection
under a changing environment.
TRIBUTE TO ALAIN PALLOIX
It is with sadness that we note the death of Alain Palloix, whose
manuscript on resistance to root-knot nematodes Barbary et al.
is included in this research topic. Alain’s work over many years
made a significant contribution to the understanding of pepper-
pathogen interactions and resistance breeding, and we extend our
sympathy to his family and colleagues.
AUTHOR CONTRIBUTIONS
All authors listed have made substantial, direct and intellectual
contribution to the work and approved it for publication.
ACKNOWLEDGMENTS
RB and AK are supported by the Scottish Government through
the RESAS strategic research programmes in “Crop and
Grassland Production and Disease Control” and “Productive
and Sustainable Land Management and Rural Economies”
(2016-2021). SJ is supported by grants from the Australian
Research Council (DP140100363 and DP170102278). We thank
the authors involved in this research topic for their excellent and
varied contributions.
REFERENCES
Birch, A. N. E., Begg, G. S., and Squire, G. R. (2011). How agro-ecological research
helps to address food security issues under new IPM and pesticide reduction
policies for global crop production systems. J. Exp. Bot. 62, 3251–3261.
doi: 10.1093/jxb/err064
Cooke, J., and Leishman,M. R. (2012). Tradeoffs between foliar silicon and carbon-
based defences: evidence from vegetation communities of contrasting soil types.
Oikos 121, 2052–2060. doi: 10.1111/j.1600-0706.2012.20057.x
Hillocks, R. J. (2012). Farming with fewer pesticides: EU pesticide review
and resulting challenges for UK agriculture. Crop Prot. 31, 85–93.
doi: 10.1016/j.cropro.2011.08.008
Johnson, S. N., Benefer, C. M., Frew, A., Griffiths, B. S., Hartley, S. E.,
Karley, A. J., et al. (2016). New frontiers in belowground ecology for
plant protection from root-feeding insects. Appl. Soil Ecol. 108, 96–107.
doi: 10.1016/j.apsoil.2016.07.017
Johnson, S. N., and Jones, T. H. (2017). Global Climate Change and Terrestrial
Invertebrates. Chichester: John Wiley & Son Ltd.
Moore, B. D., and Johnson, S. N. (2017). Get tough, get toxic, or get a
bodyguard: identifying candidate traits conferring belowground resistance
to herbivores in grasses. Front. Plant Sci. 7:1925. doi: 10.3389/fpls.2016.
01925
Peeters, P. J., Sanson, G., and Read, J. (2007). Leaf biomechanical properties
and the densities of herbivorous insect guilds. Funct. Ecol. 21, 246–255.
doi: 10.1111/j.1365-2435.2006.01223.x
Conflict of Interest Statement: The authors declare that the research was
conducted in the absence of any commercial or financial relationships that could
be construed as a potential conflict of interest.
Copyright © 2017 Johnson, Karley, Gregory and Brennan. This is an open-access
article distributed under the terms of the Creative Commons Attribution License (CC
BY). The use, distribution or reproduction in other forums is permitted, provided the
original author(s) or licensor are credited and that the original publication in this
journal is cited, in accordance with accepted academic practice. No use, distribution
or reproduction is permitted which does not comply with these terms.
Frontiers in Plant Science | www.frontiersin.org 3 February 2017 | Volume 8 | Article 209


Editorial: Crop Traits for Defense against Pests and Disease: Durability, Breakdown and Future Prospects

Crossref

Johnson, Scott N. (R16889)

Western Sydney ResearchDirect

Editorial : crop traits for defense against pests and disease : durability, breakdown and future prospects

                                                              University of DundeeCrop Traits for Defense against Pests and DiseaseJohnson, Scott N.; Karley, Alison J.; Gregory, Peter J.; Brennan, Rex M.Published in:Frontiers in Plant ScienceDOI:10.3389/fpls.2017.00209Publication date:2017Document VersionFinal published versionLink to publication in Discovery Research PortalCitation for published version (APA):Johnson, S. N., Karley, A. J., Gregory, P. J., & Brennan, R. M. (2017). Crop Traits for Defense against Pests andDisease: Durability, Breakdown and Future Prospects. Frontiers in Plant Science, 8, [209]. DOI:10.3389/fpls.2017.00209General rightsCopyright and moral rights for the publications made accessible in Discovery Research Portal are retained by the authors and/or othercopyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated withthese rights. • Users may download and print one copy of any publication from Discovery Research Portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain. • You may freely distribute the URL identifying the publication in the public portal.Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Download date: 28. Apr. 2017EDITORIALpublished: 21 February 2017doi: 10.3389/fpls.2017.00209Frontiers in Plant Science | www.frontiersin.org 1 February 2017 | Volume 8 | Article 209Edited and reviewed by:Diego Rubiales,Instituto de Agricultura Sostenible(CSIC), Spain*Correspondence:Rex M. Brennanrex.brennan@hutton.ac.ukSpecialty section:This article was submitted toCrop Science and Horticulture,a section of the journalFrontiers in Plant ScienceReceived: 30 January 2017Accepted: 03 February 2017Published: 21 February 2017Citation:Johnson SN, Karley AJ, Gregory PJand Brennan RM (2017) Editorial:Crop Traits for Defense against Pestsand Disease: Durability, Breakdownand Future Prospects.Front. Plant Sci. 8:209.doi: 10.3389/fpls.2017.00209Editorial: Crop Traits for Defenseagainst Pests and Disease: Durability,Breakdown and Future ProspectsScott N. Johnson 1, Alison J. Karley 2, Peter J. Gregory 3 and Rex M. Brennan 2*1Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, Australia, 2 The James Hutton Institute,Dundee, UK, 3 School of Agriculture, Policy and Development, University of Reading, Reading, UKKeywords: climate change, crops, food security, pathogens, pests, resistanceEditorial on the Research TopicCropTraits forDefense against Pests andDisease: Durability, Breakdown and Future ProspectsWith the Earth’s population expected to reach 11.2 billion by 2100 there is a pressing need tomaximize food production at a time when productivity of many crops is reaching a plateau.Minimizing losses to pests and diseases is therefore a crucial means of meeting this challengeand securing food supply. This research topic addresses some of the most important issues in thefuture sustainability of global crop production. The topic consists of 20 papers, of which 13 describeoriginal research. There are six review papers, plus one hypothesis and theory contribution.The development of plants with resistance to the most damaging pests and diseases isincreasingly important in the face of growing pressure to reduce synthetic chemical inputs,including pesticides, fungicides, and herbicides used for crop protection. This reduction is partlyunderwritten by legislative directives, consumer demands and indeed an overall reduction inavailable chemical controls for most crops (Hillocks, 2012), especially those outwith the mainarable species. Additionally, losses due to pest and disease attacks represent a major financialcost in crop production and throughout the subsequent supply chain, even before the costs ofcontrol measures are considered. The move toward more sustainable production systems, based onintegrated pest and disease management approaches, is gaining momentum, and the developmentof more resistant cultivars is a major factor contributing to the success of these systems. In addition,there is a recognized need for frameworks (e.g., Birch et al., 2011) which combine natural enemieswith resistant cultivars and other management practices to reduce reliance on crop protectionchemicals and maintain viable and sustainable future crop production.The development of resistant cultivars is crucial to the future of sustainable crop productionpractices, and there is a substantial need for the continued introgression of specific resistancegenes or physical and structural traits, from existing or extended genetic resources. Recentadvances in knowledge can aid this process, even in many minor crop species, where increasedunderstanding of trait heritability and technological advances in genomics and bioinformatics areenabling the identification of genes controlling resistance, providing a framework for improvedselection efficiency. Moreover, the advent of new technologies can provide significant benefits, asexemplified by the opportunities afforded by CRISPR-based tools in understanding plant-pathogeninteractions; these are addressed in the review by Barakate and Stephens. The need for newresistance genes is crucial withinmany pathogen/crop systems, and VanWeymers et al. describe theapplication of a range of “omics” technologies in potato to identify novel resistances to potato blightwithin a large germplasm collection. This approach is one that can be adapted for other speciesand pathogens, as the future role of resistance genes from existing but underexploited geneticJohnson et al. Crop Traits for Pest/Disease Defenseresources is likely to be significant. This is not limited to inherentcrop resistance, however, and Reynolds et al. also highlight therole of “omics” approaches for augmenting plant resistance toinvertebrates using application of silicon.Breeding strategies focused on the identification andincorporation of specific resistance genes, both individually orin effective groups, are being developed and implemented inmany active breeding programmes. The use of marker-assistedbackcross breeding in rice to pyramid resistance genes forbacterial blight and blast diseases is the subject of the paperby Abhilash Kumar et al. An investigation of genes involvedin the infection processes by Phytophthora capsici in Capsicumspp. by Zhang et al. through genome-wide identificationhighlights the role of SQUAMOSA promoter binding protein(SBP)-box genes that can be utilized in future breeding anddevelopment research. Genetic mapping of host plants, suchas Capsicum, was used by Barbary et al. to identify QTLslinked to resistance to Meloidogyne nematode species, andfrom this the underlying genes can eventually be identified andutilized in the breeding of resistant plants. Similarly, wild Vitisgenotypes studied by Wan et al. to find sources of resistanceto Botrytis, based on antioxidant activity linked to resistance,will be deployed in future breeding strategies. Further workon wild Vitis by Wen et al. identified a gene linked to powderymildew resistance and confirmed its effect through ectopicexpression in Arabidopsis; again, this provides a resource forfuture breeding.The effects of pest attacks on host plant metabolism wasinvestigated by Liu et al., using the wild brassica species Barbareavulgaris and the global pest diamondback moth, Plutellaxylostella. By examining changes in glucosinolate biosynthesisinduced by larval infestation, inferences can be made aboutthe mechanisms underpinning defense induction. A quantitativeapproach to the breeding of resistant cultivars is described byMohammed et al. in Sorghum, where the use of diallel progenyenabled the identification of a significant interaction betweenresistance to shoot fly andmorphological traits such as grain yieldand seed size. The information on the quantitative genetics ofSorghum can be used to inform decisions on parental choice forresistance breeding.Many host-pathogen systems are subject to rapid evolution,for example in pathogen race structure or breakdown of hostresistance. The paper by Gómez-Cortecero et al. describes theuse of SNPs and SSRs to study diversity in global populationsof Neonectria ditissima affecting apple trees, and also presentevidence of a relatively simple pattern of host response which isnot influenced by any race structure in the pathogen population.Integrated Pest and Disease Management (IPDM) approachesto pest and disease control require the development of resistantvarieties and also monitoring and management strategies thatcan be applied effectively within crops. The paper by Joshi et al.deals with the development of a susceptibility index for codlingmoth on apple, based on oviposition preferences. The review byPeterson et al. considers the wide range of plant defense traitsthat can influence the responses of natural enemies used in IPDMsystems, and also includes the potential impacts of transgeniccrops on trophic levels and arthropod communities.Plant defenses can be exploited to enhance resistance to pestattack and also to confer tolerance of pest infestations. Plantphysical defenses can offer particularly durable resistance to pestsand pathogens (Johnson et al., 2016; Moore and Johnson, 2017);ecological studies, for example, have shown plant physical traitsto be more effective deterrents to insect herbivory than plantsecondary metabolites (Peeters et al., 2007; Cooke and Leishman,2012). As outlined in the review byMitchell et al., plant structuraltraits such as trichomes, spines, and cuticles can provide aphysical barrier to arthropod pest attachment, feeding andoviposition, while plant vigor and altered phenology can increasetolerance of pest damage and reduce the incidence of pestattacks. This paper highlights new avenues for discovery of plantdefensive traits, particularly through research to understand pest-induced changes in plant chemistry and mechanisms of plantdefense “priming”.The effects of a changing climate are likely to alter bothseverity of pest and pathogen attacks, and also the spectrum oforganisms that will cause damage to crop plants (Johnson andJones, 2017). Two papers in this research topic consider changesunder conditions of elevated CO2; the first by McKenzie et al.presents data illustrating the changes in herbivory by two pests ofraspberry, the European large raspberry aphid (Amophorophoaidaei) and the root-feeding vine weevil (Otiorhynchus sulcatus).The second contribution, a review by Sun et al., examines changesin host plant metabolism and water-use efficiency instigatedunder elevated CO2 conditions, and how these changes impacton the outcome of plant-aphid interactions.Host plant resistance can have significant effects on organismsand trophic levels beyond the target pest or pathogen, and thishas implications for integrated management of crop systems.This area is discussed by Peterson et al. in their review, whichalso considers the use of transgenic crops. Genetic modificationtechnology has potential application in the development of pest-resistant cultivars of some arable species, especially where thereare limited sources of resistance within the genus, and this isdiscussed in the context of cotton production systems by Traperoet al. and de Oliveira et al. The identification by the latterauthors of resistances coveringmultiple pestsmay offer particularopportunities.Making use of multiple resistance traits might also offer analternative approach toward pathogen control. The theory paperby Newton suggests that the harmful effects of fungal diseaseoutbreaks in cereal crops could be limited by using mixedgenotype plantings; cultivarmixtures often show higher toleranceof, or resistance to, disease. The impact of this approach on othermicrobial species in the crop environment is also considered.The development of environmentally friendly controlmechanisms for pests is a further aspect of future cropproduction systems, and there are various less damagingingredients under consideration. These can include the useof plant mutualists or manipulation of soil conditions, forexample by application of chemical constituents such as silicon(Johnson et al., 2016). In terms of plant mutualists, arbuscularmycorrhizal fungi can improve crop productivity, as reportedby Robinson-Boyer et al., which may result in better toleranceof pest and disease attack Mitchell et al. and also help plantsFrontiers in Plant Science | www.frontiersin.org 2 February 2017 | Volume 8 | Article 209Johnson et al. Crop Traits for Pest/Disease Defenseresist attack by root herbivores (Johnson et al., 2016). Moreover,the role of silicon application to the soil and resistance toherbivory is considered in the review by Reynolds et al..They present evidence for direct and indirect defenses (e.g.,recruitment of natural enemies of pests via volatile emissions) bysilicon.We hope this research topic will provide a valuable resourcefor workers and researchers in the field of crop protectionby providing a source of information about existing andnovel sources of crop resistance and tolerance traits, theirincorporation into breeding programmes, how they can bedeployed for maximum efficacy under field conditions whenintegrated with other pest and disease control measures, andtheir potential to provide durable and sustainable crop protectionunder a changing environment.TRIBUTE TO ALAIN PALLOIXIt is with sadness that we note the death of Alain Palloix, whosemanuscript on resistance to root-knot nematodes Barbary et al.is included in this research topic. Alain’s work over many yearsmade a significant contribution to the understanding of pepper-pathogen interactions and resistance breeding, and we extend oursympathy to his family and colleagues.AUTHOR CONTRIBUTIONSAll authors listed have made substantial, direct and intellectualcontribution to the work and approved it for publication.ACKNOWLEDGMENTSRB and AK are supported by the Scottish Government throughthe RESAS strategic research programmes in “Crop andGrassland Production and Disease Control” and “Productiveand Sustainable Land Management and Rural Economies”(2016-2021). SJ is supported by grants from the AustralianResearch Council (DP140100363 and DP170102278). We thankthe authors involved in this research topic for their excellent andvaried contributions.REFERENCESBirch, A. N. E., Begg, G. S., and Squire, G. R. (2011). How agro-ecological researchhelps to address food security issues under new IPM and pesticide reductionpolicies for global crop production systems. J. Exp. Bot. 62, 3251–3261.doi: 10.1093/jxb/err064Cooke, J., and Leishman,M. R. (2012). Tradeoffs between foliar silicon and carbon-based defences: evidence from vegetation communities of contrasting soil types.Oikos 121, 2052–2060. doi: 10.1111/j.1600-0706.2012.20057.xHillocks, R. J. (2012). Farming with fewer pesticides: EU pesticide reviewand resulting challenges for UK agriculture. Crop Prot. 31, 85–93.doi: 10.1016/j.cropro.2011.08.008Johnson, S. N., Benefer, C. M., Frew, A., Griffiths, B. S., Hartley, S. E.,Karley, A. J., et al. (2016). New frontiers in belowground ecology forplant protection from root-feeding insects. Appl. Soil Ecol. 108, 96–107.doi: 10.1016/j.apsoil.2016.07.017Johnson, S. N., and Jones, T. H. (2017). Global Climate Change and TerrestrialInvertebrates. Chichester: John Wiley & Son Ltd.Moore, B. D., and Johnson, S. N. (2017). Get tough, get toxic, or get abodyguard: identifying candidate traits conferring belowground resistanceto herbivores in grasses. Front. Plant Sci. 7:1925. doi: 10.3389/fpls.2016.01925Peeters, P. J., Sanson, G., and Read, J. (2007). Leaf biomechanical propertiesand the densities of herbivorous insect guilds. Funct. Ecol. 21, 246–255.doi: 10.1111/j.1365-2435.2006.01223.xConflict of Interest Statement: The authors declare that the research wasconducted in the absence of any commercial or financial relationships that couldbe construed as a potential conflict of interest.Copyright © 2017 Johnson, Karley, Gregory and Brennan. This is an open-accessarticle distributed under the terms of the Creative Commons Attribution License (CCBY). The use, distribution or reproduction in other forums is permitted, provided theoriginal author(s) or licensor are credited and that the original publication in thisjournal is cited, in accordance with accepted academic practice. No use, distributionor reproduction is permitted which does not comply with these terms.Frontiers in Plant Science | www.frontiersin.org 3 February 2017 | Volume 8 | Article 209

http://www.frontiersin.org/books/Crop_Traits_for_Defense_against_Pests_and_Disease_Durability_Breakdown_and_Future_Prospects/1187#nogo

Editorial: crop traits for defense against pests and disease: durability, breakdown and future prospects

Abstract

Similar works

Full text

Available Versions

Directory of Open Access Books (DOAB)

Discovery Research Portal

Central Archive at the University of Reading

Discovery Research Portal

Frontiers - Publisher Connector

Crossref

Western Sydney ResearchDirect

Discovery Research Portal