Genetic structure and local adaptation of European wheat yellow rust populations: the role of temperature-specific adaptation

Environmental heterogeneity influences coevolution and local adaptation in host–parasite systems. This also concerns applied issues, because the geographic range of parasites may depend on their capacity to adapt to abiotic conditions. We studied temperature-specific adaptation in the wheat yellow/stripe rust pathogen, Puccinia striiformis f.sp. tritici (PST). Using laboratory experiments, PST isolates from northern and southern France were studied for their ability to germinate and to infect bread and durum wheat cultivars over a temperature gradient. Pathogen origin × temperature interactions for infectivity and germination rate suggest local adaptation to high- versus low-temperature regimes in south and north. Competition experiments in southern and northern field sites showed a general competitive advantage of southern over northern isolates. This advantage was particularly pronounced in the southern ‘home’ site, consistent with a model integrating laboratory infectivity and field temperature variation. The stable PST population structure in France likely reflects adaptation to ecological and genetic factors: persistence of southern PST may be due to adaptation to the warmer Mediterranean climate; and persistence of northern PST can be explained by adaptation to commonly used cultivars, for which southern isolates are lacking the relevant virulence genes. Thus, understanding the role of temperature-specific adaptations may help to improve forecast models or breeding programmes

Tolerance of plant virus disease: Its genetic, physiological, and epidemiological significance

The development and use of tolerance have been proposed as an alternative or complementary method to host resistance in the management of plant diseases, including those caused by viruses. There has been much ambiguity among plant pathologists, plant breeders, and agronomists in the meaning of tolerance and how it can be operationally defined, but a modern consensus seems to have emerged. Tolerance is a relative term that means a limited reduction in host plant fitness (reproduction or survival) in relation to pathogen load throughout or during a defined period of plant development and growth such as the reproductive stage. This emphasizes the need to study reproductive stage disease tolerance. Despite this apparent consensus, there remain questions over the use of model plant systems, the genetic background of tolerance, its physiological expression, and epidemiological consequences of its deployment in crops, in comparison with host resistance. Most examples of tolerance reviewed here are for plant virus systems, although other pathogen taxa are referred to, as is tolerance as a natural phenomenon in wild plants including crop relatives. An argument is made for studying commonalities and interactions in host responses to biotic and abiotic stressors; in particular, whether virus infection can mitigate the impact of heat, cold, drought and salinity stress in plants. Finally, we review the use of mathematical models as a means of evaluating the strategy of using tolerance in disease and crop management

Bases génétiques et fonctionnelles de la durabilité des résistances polygéniques au virus Y de la pomme de terre (PVY) chez le piment (Capsicum annuum)

Les résistances génétiques permettent une lutte efficace contre les maladies des plantes cultivées mais sont limitées par les capacités d évolution des bioagresseurs ciblés. Chez le piment, le fonds génétique peut améliorer la durabilité de la résistance au PVY conférée par le gène majeur pvr23. L objectif de ma thèse était de caractériser les facteurs génétiques de l hôte conditionnant la durabilité du gène majeur en répondant aux questions suivantes : (i) Quels sont leurs actions sur l évolution des populations virales ? (ii) Correspondent-ils aux QTL (quantitative trait loci) de résistance partielle ? (iii) Sont-ils répandus au sein des ressources génétiques du piment ? Différentes expérimentations incluant des tests de résistances, d évolution expérimentale et de compétition entre différents variants viraux, ont montré que les facteurs du fonds génétique augmentant la durabilité de pvr23 agissaient en : (i) diminuant la concentration virale dans la plante, (ii) en réduisant les probabilités de mutations du PVY vers le contournement du gène pvr23 et (iii) en ralentissant la sélection des variants viraux contournants. La détection de QTL et la cartographie des facteurs génétiques affectant la fréquence de contournement de pvr23 (QTL de durabilité) a mis en évidence quatre régions du génome du piment qui, par des effets additifs ou épistatiques, expliquent 70% de la variabilité phénotypique observée. La cartographie comparée montre que trois des quatre QTL de durabilité co-localisent avec des QTL affectant la résistance partielle, suggérant que les QTL de résistance partielle ont un effet pléiotropique sur la durabilité d un gène majeur de résistance. L étude d une collection de 20 accessions de piment, porteuses de pvr23 ou pvr24(allèle très proche de pvr23) dans des fonds génétiques variés, a montré que les fonds génétiques favorables à la durabilité de ces allèles de résistance sont fréquents dans les ressources génétiques du piment. Ces résultats mettent en évidence que la durabilité d un gène majeur de résistance peut-être fortement augmentée lorsqu il est associé à des facteurs génétiques réduisant la multiplication du pathogène. De plus, la fréquence de contournement du gène majeur s est révélée être un caractère très héritable (h =0.87) et la détection de QTL affectant ce caractère est possible. La sélection directe pour de tels QTL est donc envisageable et ouvre de nouvelles perspectives pour préserver la durabilité des gènes majeurs de résistance utilisés en sélection variétale.Genetic resistances provide an efficient control of crop diseases but are limited by pathogen adaptation.In pepper, the durability of the pvr23 allele, conferring resistance to Potato virus Y (PVY), was demonstrated todepend on the plant genetic background. The aim of my PhD thesis was to characterize the host genetic factorsaffecting the durability of the major resistance gene pvr23 and to answer to the following question s: (i) What istheir action on the evolution of the viral population? (ii) Is there identity between the QTLs (quantitative traitloci) controlling the partial resistance and the QTLs affecting the durability of pvr23? (iii) Are these genetic factorswidespread among the genetic resources of pepper? Various experiments including resistance testing,experimental evolution and competition between various PVY variants, enabled to show that the genetic factorsaffecting the durability of pvr23 acted in: (i) decreasing the viral accumulation, (ii) decreasing the probability ofacquisition of resistance breaking (RB) mutations by PVY and (iii) slowing down the selection of RB variants. QTLdetection and mapping of genetic factors affecting the frequency of pvr23 RB showed that four loci actingadditively and in epistatic interactions explained together 70% of the variance of pvr23 breakdown frequency.Comparative mapping between these QTLs and QTLs affecting partial resistance showed that three of the fourQTLs controlling the frequency of pvr23 RB are also involved in quantitative resistance, suggesting that QTLs forquantitative resistance have a pleiotropic effect on the durability of the major resistance gene. Analysis of acollection of 20 pepper accessions, carrying pvr23 or pvr24 (allele closely related to pvr23) in various geneticbackgrounds, showed that genetic backgrounds favorable to the durability of the pvr2-mediated resistance arewidespread in the genetic resources of pepper. These results highlight that the durability of a major resistancegene can be strongly increased when associated with genetic factors decreasing the pathogen multiplication.Moreover, the frequency of a major gene RB is a highly heritable trait and QTLs detection for this trait isachievable. The direct selection for such QTLs opens new prospects to preserve the durability of major resistancegenes used by breeders.AVIGNON-Bib. numérique (840079901) / SudocSudocFranceF

Studies on pathogenicity and host resistance of Exserohilum turcicum and Fusarium spp. on maize (Zea mays L.) cultivated in tropical and temperate climate zones

In the last 60 years, maize production has increased worldwide, reaching 1.14 billion tons in 2018. Maize production in Europe and South America was about 110 and 130 million tons in 2018, respectively. The demand for highly productive maize is observed in both tropical and temperate zones. Thus, the selection of plants from different maturity groups and high yield production are required from breeding programs. Besides highly productive plants, other agronomical traits such as resistance to pest and diseases needs to be considered during selection. Globally, some of the most important diseases affecting maize are northern corn leaf blight (NCLB), and Gibberella and Fusarium ear rot (GER and FER, respectively). Host resistance to E. turcicum is based on qualitative or quantitative sources, while for GER and FER only quantitative resistance is available in commercial hybrids. The quantitative resistance is more durable; however, it is more laborious to introgress into breeding lines. Northern corn leaf blight (NCLB) is an important disease in maize-producing areas worldwide. The symptoms of NCLB, whose causal agent is the ascomycete Exserohilum turcicum (teleomorph Setosphaeria turcica), are characterized by elliptical grey-green lesions. High disease severity can cause yield losses up to 40% (Levy und Pataky 1992). The main control methods applied for NCLB control are fungicide applications and the cultivation of resistant hybrids. Qualitative resistance has been widely used to control NCLB in many countries through the deployment of Ht genes. The race assessment from isolates collected in Argentina and Brazil during 2017, 2018 and 2019 revealed a high frequency of race 0 isolates (83% and 65% in Argentina and Brazil, respectively). In those countries, Ht genes are not being used extensively to control NCLB. This information is important for breeding programs and may help with disease management. Favorable weather conditions for NCLB development are long dewy periods and moderate temperatures. These optimum conditions for disease development can be observed in temperate regions as well as in mid-altitude regions in the tropics. The comparison of E. turcicum isolates in response to temperatures varied in vitro and in vivo between 15 and 30°C demonstrating that the aggressiveness of South American isolates was higher than that of European isolates. The multivariate analysis confirmed that South American isolates are better adapted to higher temperatures by grouping them separately. In conclusion, E. turcicum populations may adapt quickly to environmental changes. The plasticity in adapting to environmental conditions of E. turcicum may decrease the durability of resistance. Studies on the pathogenesis of E. turcicum in the differential maize line B37 with and without the resistance genes Ht1, Ht2, Ht3 and Htn1 were conducted for different stages of infection and disease development from penetration (0-1 dpi), until full symptom expression (14-18 dpi). Symptomological analysis demonstrated that Ht1 expressed necrotic lesions with chlorosis, Ht2 displayed chlorosis and small lesions, Ht3 resulted in chlorotic spots and Htn1 express wilt-type lesions. Histological studies conducted with Chlorazol Black E staining indicated that the pathogen was able to penetrate xylem vessels at 6 dpi in compatible interactions and strongly colonized the mesophyll at 12 dpi, which is considered the crucial process differentiating susceptibility from resistance. Additionally, lower disease levels, low fungal DNA content at 10 and 14 dpi, and the delayed progress of infection in compatible interactions with resistant lines imply that the Ht genes are associated with or confer additional quantitative resistance. Physiological studies showed a reduction in the photosynthetic rate, transpiration, stomatal conductance and instantaneous carboxylation efficiency in the incompatible interaction at 5 dpi. At 14 dpi, the strong necrosis displayed in the resistance reaction by B37Ht1 resulted in the reduction of photosynthesis as observed for B37. However, leaf area, aerial and root dry biomass were not reduced in inoculated plants at 28 dpi. Additionally, high rates of peroxide localization were observed in inoculated plants at 3 and 6 dpi, corroborating data on peroxidase activity. In fact, Ht1, Ht3 and Htn1 reduced pathogen sporulation whereas Ht2 reduced the number and size of lesions. All phenotypical studies demonstrated that Ht genes confer distinct resistance mechanisms. The resistance phenotype expressed by Ht2 may change according to environmental conditions. There are reports on the influence of low post-inoculation temperature (22/18°C) and low light intensity (324 and 162 µmol m-2 s-1) on resistance expressed by this gene. Our objective was to prove that temperature has no influence on the resistance conferred by the Ht2-gene against E. turcicum. Therefore, maize plants were pre-exposed to warm (30/25°C) and moderate (20/15°C) temperature regimes for 10 days before inoculation. There was no influence of pre-inoculation temperature on the expression of resistance by Ht2. The resistance conferred by the Ht2 gene was confirmed by quantifying the fungal DNA in planta at 21 dpi. Changes in resistance phenotypes may be related to pathogen aggressiveness factors. GER and FER can cause qualitative yield losses due to mycotoxin production. GER is mainly caused by Fusarium graminearum and FER by F. verticillioides. GER is more frequent in regions with colder temperatures and high precipitation, and is more prevalent in Germany, while FER occurrence is favored by warm and dry weather conditions and is more prevalent in Brazil. In general, F. graminearum was more aggressive than F. verticillioides, which support affirmations about systemic colonization by F. verticillioides. With regard to tropical and temperate hosts, the German isolates were more aggressive than the Brazilian isolates when inoculated in the tropical lines. Additionally, tropical lines pre-exposed to higher temperatures presented higher disease severity when compared to plants exposed to mild temperatures. In general, the cultivation of resistant hybrids remains a successful strategy for controlling NCLB, GER and FER. The optimization of resistance resources is fundamental for maintaining the durability of resistance.2021-11-1

Terapia fágica na inativação de Pseudomonas syringae pv. actinidiae em plantas de kiwi

Pseudomonas syringae (P. syringae) is the causative agent of diseases in a wide variety of plants and includes more than 60 pathovars. Pseudomonas syringae pv. actinidiae (Psa) is one of the pathovars of this species and the causative agent of bacterial cancer in kiwifruit plants. Psa is responsible to high economic losses, seriously affecting the global production of kiwifruit in many countries, including Portugal. The most common treatments for biocontrol of Psa and other infections caused by Pseudomonas syringae pathovars in plants involve copper derivatives and /or antibiotics. However, these treatments should be avoided due to both their high toxicity and development of bacterial resistance. One promising alternative to conventional treatments is the use of phage therapy to control Psa infections in plants. Phages are bacterial viruses and their antibacterial nature through induction of bacterial lysis, their high host specificity and rapid reproduction enable them to control bacterial populations. The use of phages to control bacterial infections has been reported across numerous fields by many researchers. However, there is no report regarding the use of phages to eliminate Psa in kiwifruit plants. Thus, the objective of this work was to evaluate the efficacy of phage therapy to inactivate or reduce Psa in kiwifruit plants. Phage Ф6 (a commercially available and safe phage) was characterized in order to evaluate its potential application in the control of diseases caused by P. syringae, namely caused by Psa. Initially, phage 6 was characterized in terms of host range, latent period, burst size, adsorption to the host and development phage-resistant mutants using its natural host P. syringae pv. syringae. As the kiwifruit plants are exposed to the natural variability of environmental factors, the influence of pH, temperature, solar radiation and UV radiation on phage 6 viability was also evaluated. First, the phage-bacteria interaction was characterized in vitro, using liquid culture medium at MOI of 1 and 100. The results revealed that the phage exhibited a broad lytic spectrum against the tested bacteria, infecting, besides the host P. syringae, the Psa strains CRA-FRU 12.54 and CRA-FRU 14.10. The phage at MOI 1 and 100, can be an effective alternative to control the species P. syringae. However, the MOI of 1 (maximum reduction of 3.9 log CFU/mL) was more effective than MOI of 100 (maximum reduction of 2.6 log CFU/mL). The viability of phage 6 in PBS was primarily affected by UV-B radiation exposure (decrease of 7.3 log PFU/mL after 8 h), solar radiation exposure (decrease of 2.1 PFU/mL after 6 h) and high temperatures (decrease of 8.5 PFU/mL after 6 days at 37 °C). The viability of the phage was not significantly affected by conditions as lower temperatures (decrease 2.0 log PFU/mL after 67 days at 15 °C and 25 °C) and pH (decrease 2.3 log PFU/mL at pH 7 and 7.5 and 2.7 log PFU/mL at pH 6.5). Second, to confirm if this phage can be used to control the Psa strains CRA-FRU 12.54 and CRA-FRU 14.10, in vitro, using liquid culture medium, and ex vivo experiments, using artificially contaminated kiwifruit leaves, were done. In the in vitro assays, a reduction of approximately 2.0 log CFU/mL of both Psa strains was observed after 24 h of incubation. In the ex vivo tests, the decrease was lower after 24 h of incubation, 1.1 log CFU/mL of reduction for Psa CRA-FRU 12.54 and 1.8 log CFU/mL of reduction for Psa CRA-FRU 14.10. Overall, phage therapy showed to be an effective and safe method to inactivate the Psa in kiwifruit plants. In order to exploit the full potential of this therapy, further studies are needed, namely field studies in kiwifruit orchards, applying the phages at the end of the day or during night period in order to avoid phage inactivation by UV radiation and high temperaturePseudomonas syringae é um agente causador de doenças numa ampla variedade de plantas e inclui mais de 60 pathovars. Pseudomonas syringae pv. actinidiae (Psa) é um dos pathovars desta espécie e o agente causal de cancro bacteriano em plantas de kiwi. A Psa é responsável por grandes perdas económicas, afetando seriamente a produção global de kiwis em muitos países, incluindo Portugal. Os tratamentos mais comuns para o biocontrolo de infeções causadas pelos diversos pathovars de Pseudomonas syringae em plantas envolvem derivados de cobre e / ou antibióticos. No entanto, estes tratamentos devem ser evitados devido à sua elevada toxicidade e ao desenvolvimento de resistências a estes químicos nas bactérias. Uma alternativa promissora aos tratamentos convencionais é o uso da terapia fágica. Os fagos são vírus que infetam bactérias, sendo considerados antibacterianos por serem capazes de causar lise bacteriana, apresentar especificidade e replicação rápida. O uso de fagos para controlar infeções bacterianas tem sido relatado por vários investigadores em diversas áreas. No entanto, não há nenhum estudo sobre o uso de fagos para eliminar Psa em plantas de kiwi. Assim, o objetivo deste trabalho foi avaliar a eficácia da terapia fágica para controlar infeções causadas por P. syringae em plantas. O fago 6 (fago seguro e disponível comercialmente) foi caracterizado de forma a avaliar a sua potencial aplicação no controlo de doenças causadas por P. syringae, nomeadamente as causadas por Psa, e também causadas pelo seu hospedeiro natural P. syringae pv. syringae. Inicialmente, o fago 6 foi caracterizado em termos de gama de hospedeiros, período latente, número de explosão, adsorção ao hospedeiro e desenvolvimento de mutantes resistentes aos fagos utilizando o seu hospedeiro natural P. syringae pv. syringae. Tendo em conta que, as plantas de kiwi estão expostas à variação natural dos fatores ambientais, a influência do pH, temperatura, radiação solar e radiação UV na viabilidade do fago 6 também foi avaliada. Inicialmente, a interação fago-bactéria foi caracterizada in vitro, utilizando meio de cultura líquido, à MOI de 1 e 100. Os resultados monstraram que o fago exibe um amplo espectro lítico, infectando além do hospedeiro P. syringae, as estirpes de Psa CRA-FRU 12.54 e CRA-FRU 14.10. Os ensaios in vitro de mostraram que o uso do fago 6 na MOI de 1 e 100, pode ser uma alternativa eficaz ao controle de P. syringae. No entanto, a MOI de 1 (redução máxima de 3,9 log UFC / mL) foi mais eficaz que a MOI de 10 e 100 (redução máxima de 2,6 log UFC / mL). A viabilidade do fago 6 foi principalmente afetada pela exposição à radiação UV-B (diminuição de 7,3 log UFP / mL após 8 horas), exposição à radiação solar (diminuição de 2,1 PFU / mL após 6 horas) e altas temperaturas (diminuição de 8,5 UFP / mL após 6 dias a 37 °C e decréscimo de apenas 2,0 log UFP / mL após 67 dias a 15 °C e 25 °C ). A viabilidade do fago não foi significativamente afetada a temperaturas mais baixas (diminuição de 2,0 log PFU / mL após 67 dias a 15 °C e 25 °C) e pH na gama 6,5-7,0 (diminuição de 2,3 log PFU / mL em pH 7 e 7,5 e 2,7 log PFU / mL a pH 6,5). Numa segunda fase, para confirmar que este fago pode ser utilizado para controlar as estirpes de Psa CRA-FRU 12.54 e CRA-FRU 14.10, realizaram-se ensaios in vitro, em meio de cultura líquido, e ex vivo, utilizando folhas de kiwis artificialmente contaminadas. Nos ensaios in vitro, foi observada uma redução de aproximadamente 2,0 log UFC/ mL para as duas estirpes de Psa após 24 h de incubação. Nos testes ex vivo, a redução foi menor após 24 h de incubação (1,1 log UFC/mL no caso da estirpe Psa CRA-FRUA 12.54 e 1,8 log UFC/mL no caso da estirpe Psa CRA-FRU 14.10). A terapia fágica mostrou ser um método eficaz e seguro para inativar a Psa nas plantas de kiwi. A fim de explorar todo o potencial desta terapia, são necessários mais estudos, nomeadamente estudos no campo, em pomares de kiwis, aplicando os fagos no final do dia ou durante o período noturno para evitar a inativação do fago pela radiação UV e pela temperatura altaMestrado em Microbiologi

Investigating causes of mortality in live export cattle

This research project was initiated to provide industry with current, credible, scientific data on causes of death and risk factors for mortality in Australian live export cattle on long-haul voyages. Animal data and necropsy samples were collected from animals that died on 20 research voyages during the study period March 2010 to September 2012. The average voyage mortality percentage was 0.37%. Respiratory disease was the most commonly diagnosed cause of death, accounting for 107/215 (49.8%) of deaths overall, and 107/181 (59.1%) of deaths for which a diagnosis could be made. In addition, pneumonia was identified in 33% of animals for which respiratory disease was not considered the primary cause of death. Other common causes of death included lameness (n = 22/181, 12.2%), ketosis (n = 12, 6.6%), septicemia (n = 11, 6.1%), and enteric disease (n = 10, 5.5%). Quantitative polymerase chain reaction (qPCR) assays were developed to detect viruses and bacteria known to be associated with bovine respiratory disease (BRD) in necropsy and nasal swab samples: Bovine coronavirus (BCoV, Betacoronavirus 1), Bovine herpesvirus 1 (BoHV-1), Bovine viral diarrhoea virus (BVDV), Bovine respiratory syncytial virus (BRSV), Bovine parainfluenza virus 3 (BPIV-3), Histophilus somni, Mycoplasma bovis, Mannheimia haemolytica and Pasteurella multocida Two-thirds (130/195) of animals from which lung samples were collected had histological changes and/or positive qPCR results suggestive of infectious lung disease: 93/130 (72%) had evidence of primary bacterial infection, 4 (3%) with primary viral infection, 29 (22%) with concurrent bacterial and viral infections, and for 4 (3%) the causative organism could not be indentified. M. bovis, H. somni, P. multocida, M. haemolytica and BCoV were significantly associated with respiratory disease during voyages. Results from nasal swab and serological samples collected at entry to the pre-export assembly depot indicated that there were significant differences in nasal and seroprevalence between animals sourced from different properties. Combined nasal swab and serum results suggest that BCoV and BVDV are likely to be important infectious agents in the development of BRD in live export cattle while BPIV-3 is unlikely to play a major role. The contribution of BoHV-1, BRSV and bacteria of interest is difficult to determine. Analysis of animal and voyage data collected by industry between January 1995 and December 2012 revealed that while there has been an overall reduction in voyage mortality rates since 2000, there remain significant differences in mortality rate between load and discharge regions. Examination of daily mortality data available for research voyages revealed that peak daily mortality risk occurs at 3-4 weeks post-departure. The development of methods for spatial analyses coupled with data available in the National Livestock Identification System database allowed the description of patterns of animal movement prior to export. This study has improved our understanding of causes of death and risk factors for mortality in Australian live export cattle. We now have baseline data on the prevalence of BRD organisms in live export cattle that could be used to develop strategies for BRD prevention and control prior to loading and during voyages

Feeling the Heat: Investigating the dual assault of Zymoseptoria tritici and Heat Stress on Wheat (Triticum aestivum)

As a result of climate change, field conditions are increasingly challenging for crops. Research has shown how elevated temperatures affect crop performance, yet the impact of temperature on host-pathogen relationships remains unknown. Understanding the effects of combined abiotic and biotic stresses on crop plants and the plant-microbial interaction is crucial in developing strategies to improve crop stress tolerance and manage diseases effectively. Lipids sense, signal, and mitigate temperature elevation effects, and lipid remodelling plays a key role in the plant and fungal response to heat stress. Our study uses a systems approach to examine the Z. tritici wheat model system, combining transcriptomics, lipidomics, and phenotyping to decipher the impact of high-temperature stress on the plant-pathogen interaction. Microscopy in vivo and RNA-Seq analyses confirmed that Z. tritici responds to high-temperature treatments with morphological and transcriptomic changes. Temperature-related configuration of the transcriptome was associated with the accessory chromosomes and expression of ‘accessory’ pan-genome-derived genes. Metabolism-related gene expression predominated, indicated by GO enrichment and analysis of KOG classes, and large-scale lipid remodelling was likely given the proportion of lipid transport and metabolism-related expression changes in response to temperature. Changes in lipid content and composition were then validated by LC-MS analysis. Heat-responsive fungal genes and pathways, including scramblase family genes, are being tested by reverse genetics to ascertain their importance for fungal adaption to elevated temperatures. Elevated temperature schemes were applied to wheat to study the impact of combined stress on the plant-pathogen interaction, based on long-term climate data from Rothamsted Research, using transcriptomic, lipidomic and phenotypic analyses. Comparing non-infected and infected wheat plants under typical and elevated temperatures. Our initial analysis of the transcriptomic data indicates a delay in the development of Z. tritici, followed by its adaptation to the warmer environment. Once the infection was established, the fungus exhibited resilience to the impact of higher external temperatures. Our results indicate that temperature elevations associated with climate change directly impact plant-pathogen interactions. Furthermore, the study demonstrates a need for further detailed understanding to sustain crop resilience

Effects of temperature on wheat-pathogen interactions

Climate change is affecting UK agriculture, and research is needed to prepare crops for the future. Wheat is the UK’s most important crop, and needs to be protected from losses caused by disease. While direct effect of the environment on pathogen spread is often reported, effect of the environment on host defence is not. Many wheat resistance genes are temperature sensitive and these were used as a starting point to investigate defence temperature sensitivity in wheat starting with yellow rust resistance gene Yr36, previously shown to be temperature-sensitive. The effect of temperature on resistance was shown to be independent of Yr36 in breeding line UC1041, and was more likely to be due to a previously-uncharacterised background temperature sensitivity. These results suggest that temperature changes, rather than thresholds, might influence some disease resistance mechanisms. Understanding this phenomenon could enable the breeding of more stable defence in crops. In order to gain further insight into how temperature changes influence resistance, plants were grown under different thermoperiods and challenged with different types of pathogens; Results showed that resistance to multiple pathogens in one cultivar Claire was enhanced under variable temperatures, compared to constant temperatures. Taken together, the research presented revealed that defence temperature sensitivity in plants is much more complex than previously thought, considering that both temperature changes and different thermoperiods can influence aspects of wheat defence. To ascertain which research approaches will be most valuable in preparing for climate change, the effect of the environment on take-all was also investigated. Vulnerable periods for wheat from the threat of take-all development were identified by analysing historical datasets, and controlled environment experiments. Results showed a relationship between initial post-sowing temperatures and spring take-all levels in 2nd 3rd or 4th winter wheats, depending on the location. The work on yellow rust resistance and take-all both identify vulnerable periods for wheat caused by the environment, be it weakening of host defence responses, or increased threat from disease pressure. Further characterisation and understanding of vulnerable periods will be essential to control disease outbreaks under an increasingly unstable climate

Wheat Improvement

This open-access textbook provides a comprehensive, up-to-date guide for students and practitioners wishing to access in a single volume the key disciplines and principles of wheat breeding. Wheat is a cornerstone of food security: it is the most widely grown of any crop and provides 20% of all human calories and protein. The authorship of this book includes world class researchers and breeders whose expertise spans cutting-edge academic science all the way to impacts in farmers’ fields. The book’s themes and authors were selected to provide a didactic work that considers the background to wheat improvement, current mainstream breeding approaches, and translational research and avant garde technologies that enable new breakthroughs in science to impact productivity. While the volume provides an overview for professionals interested in wheat, many of the ideas and methods presented are equally relevant to small grain cereals and crop improvement in general. The book is affordable, and because it is open access, can be readily shared and translated -- in whole or in part -- to university classes, members of breeding teams (from directors to technicians), conference participants, extension agents and farmers. Given the challenges currently faced by academia, industry and national wheat programs to produce higher crop yields --- often with less inputs and under increasingly harsher climates -- this volume is a timely addition to their toolkit