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AbstractFusarium graminearum is the most important pathogen of maize and winter wheat in Canada, resulting in yield loss and mycotoxin contamination. Fungicides are essential to manage F. graminearum in cereal crops. Until pydiflumetofen became commercial, the only available fungicides were triazoles, limiting the potential to manage fungicide resistance. Fusarium graminearum isolates were surveyed from wheat, grain maize and overwintering maize stalks in southern Ontario. Chemotype and the baseline sensitivity to pydiflumetofen were determined in addition to sensitivity to common fungicides used to control F. graminearum. Fusarium graminearum has several strains producing different trichothecenes called chemotypes. In Ontario, 73.3% of the F. graminearum isolates were 3ANX chemotypes producing 7α-hydroxy, 15-deacetylcalonectrin, in addition to 15-acetyldeoxynivalenol and deoxynivalenol; the remaining isolates were 15ADON chemotypes producing only 15-acetyldeoxynivalenol and deoxynivalenol. Chemotype was not affected by isolate source (wheat grain, maize grain, maize stalks) nor by location. All isolates were sensitive to pydiflumetofen and fungicide products containing pydiflumetofen. The mean EC50 for isolates exposed to pydiflumetofen was 0.05 µg mL−1 (range 0.01–0.10 µg mL−1). The mean EC50 for isolates exposed to Miravis®Ace (containing pydiflumetofen and propiconazole), Miravis®Neo 300SE (containing pydiflumetofen, azoxystrobin and propiconazole), Caramba® (containing metconazole), Proline® (containing prothioconazole) and Prosaro (containing prothioconazole and tebuconazole) was 0.06, 0.13, 0.18, 0.05, 3.75 and 0.30 µg mL−1, respectively. These data will be useful in monitoring the development of fungicide resistance. [ABSTRACT FROM AUTHOR]

AbstractWheat stripe rust disease caused by Puccinia striiformis f. sp. tritici (Pst) seriously affects wheat yield. We studied the fungal infection process and host response between wheat ‘AvS’ and its near-isogenic line ‘AvS+Yr10’, which formed compatible and incompatible interactions, respectively, when challenged with Pst race CYR32. The difference in reactive oxygen species (ROS) accumulation between the compatible and incompatible interactions was analyzed by measuring the hydrogen peroxide (H2O2) concentration and observing H2O2 production. Hydrogen peroxide concentrations, H2O2 accumulation areas, necrotic areas and expression of several resistance-related genes in the AvS+Yr10/CYR32 interaction were higher than those in the AvS/CYR32 interaction during the entire infection process. Pst growth was effectively inhibited in the AvS+Yr10 all-stage resistant wheat line. Thus, ROS accumulation is crucial in wheat defence against pathogens. [ABSTRACT FROM AUTHOR]

AbstractStem rust of barley and wheat is caused by the obligate pathogen Puccinia graminis f. sp. tritici (Pgt) and stem rust of oat is caused by P. graminis f. sp. avenae (Pga). Stem rust can be a very destructive disease of cereal crops and, until the development of resistant host varieties, was responsible for millions of dollars of losses to producers. Genetic host resistance is the most common and effective method to control stem rust on cereals. Knowledge of the virulence genes and races present in the pathogen population is important to identify effective host resistance genes for use by cereal plant breeders. The objectives of this study were to determine the incidence and severity of P. graminis in wheat, barley and oat in Manitoba, Canada, and assess the virulence frequencies and races of isolates collected from Manitoba, Saskatchewan and Ontario, Canada during 2020 to 2022. Stem rust incidence and severity was very light in Manitoba in 2020, 2021 and 2022. Virulence was not observed on resistance genes Sr30, Sr24 and Sr31 from Canadian collections of Pgt isolates made during 2020 to 2022. Race QFCSC was the most common race of Pgt in Canada, and races MCCFC and TPMKC were also common in Manitoba in 2022. Virulence to resistance genes Pg6, Pg10 and Pg16 was not observed among Pga isolates. The most common race of Pga from Manitoba and Saskatchewan was TGN, followed by SGB and TJS. The most frequent Pga races were TDJ, TDD and TGN in Ontario. [ABSTRACT FROM AUTHOR]

Fusarium head blight (FHB) is primarily caused by Fusarium graminearum and is the most destructive wheat disease in western Canada. The trichothecene toxin deoxynivalenol (DON) and its derivatives 3-ADON and 15-ADON, which are produced by Fusarium, are toxic to humans and livestock. This study aimed to evaluate the Fusarium species and trichothecene-producing genotypes present in producer wheat fields of western Canada in 2019 and 2020. The grain analysis for DON showed that samples collected from both years experienced mild levels of FHB toxin contamination. In spring wheat, the highest mean DON content was recorded from Saskatchewan samples (0.9 ppm) in 2019 and Manitoba samples (0.3 ppm) in 2020. Winter wheat samples had lesser mean DON levels (<0.2 ppm) for all three provinces in both years. The chaff collected from the same spring wheat heads showed a significantly higher DON content than the grain in both years (P < 0.1 for 2019 and P < 0.001 for 2020), suggesting that chaff should be tested for DON before use as livestock feed. Most samples collected were infected by F. graminearum, with the highest F. graminearum percentage observed in the spring wheat from Manitoba. Further, F. avenaceum, F. sporotrichoides, F. culmorum, F. poae and F. acuminatum were found in infected samples. Most of the F. graminearum isolates were of the 3ADON genotype, which is the dominant genotype in FHB disease in western Canada. The study indicated that 3ADON-producing F. graminearum is becoming more frequent in western Canadian fields than the 15ADON genotype. [ABSTRACT FROM AUTHOR]

Puccinia striiformis Westend. f. sp. tritici Eriksson (Pst), the causal agent of stripe rust, is known as an important and destructive pathogen that causes critical wheat losses in many parts of the world. Employing effective resistant genotypes is a safe and operative strategy to combat the disease. Iran is located in the Fertile Crescent, the co-epicentre of wheat and its biotic stresses. Iranian wheat landraces may carry important sources of resistance against rust diseases. Adult plant reactions of 467 Iranian wheat landraces to stripe rust were studied in two cropping seasons in Fars province. One hundred and six landraces showed acceptable levels of resistance and were selected for further seedling and molecular studies based on their lower infection type, coefficient of infection (CI) and average coefficient of infection (ACI). The presence of Yr4, Yr10, Yr24 and Yr32 resistance genes were postulated using 10 different Pst isolates including PstS10, PstS7, PstS3, PstS2+V27, PstS11, PstS8, PstS13, PstS6, PstS0 and Me2018 under greenhouse conditions. Field and greenhouse reactions of near-isogenic lines reconfirmed the presence of the studied Yr resistance genes in 20 genotypes. Moreover, Xcfb3530150, Xpsp3000, Xgwm11, and Xwmc198 SSR markers were employed to identify and validate the presence of the above corresponding genes. The presence of Yr4, Yr10, Yr24 and Yr32 resistance genes in five (1.07%), 10 (2.14%), five (1.07%) and seven (1.5%) experimental landraces were confirmed, respectively. Six genotypes are harbouring more than one resistance gene. These effective resistance sources can be employed in national and international breeding programs. [ABSTRACT FROM AUTHOR]

Stripe rust (Puccinia striiformis f. sp. tritici (Pst)) and powdery mildew (Blumeria graminis f. sp. tritici (Bgt)) are important diseases of wheat in Canada and worldwide. Molecular detection methods permit spore detection of few spores; therefore, there is a need to determine initial inoculum thresholds for pathogens to cause disease under both controlled environments and in the field. Susceptible wheat cultivars 'Avocet' and 'AC Barrie' were inoculated with different quantities of spores (0, 103, 104, 105, 106, and 107) of Pst and Bgt. Disease incidence, severity and infection type were evaluated. Results of controlled environment studies showed that the minimum number of spores necessary to cause appreciable incidence and severity for Pst was at higher spore concentrations of 105–106 spores. Conversely, low incidence and severity levels were observed at 103–104 spores for Bgt. Despite occurrence of natural Pst infection, results of field studies in 2016 and 2017 in Southern Alberta demonstrated that significant increases in severity levels were observed following application of 1.2 × 107 spores. Collectively, these results demonstrated that stripe rust severities increased with increasing spore concentration only at high spore levels. In contrast, Bgt severity increased with spore concentration from 103 to 107 spores mL−1. In vitro and in vivo spore germination tests demonstrated germination rates of Pst spores were reduced at lower spore concentrations compared to germination rates at the higher concentrations. Understanding of minimum spore numbers required for disease development will be a prerequisite for predicting epidemics and devising fungicide control measures for future sustainable agricultural systems. [ABSTRACT FROM AUTHOR]

The endophytic fungi Simplicillium lamellicola and Clonostachys rosea were assayed for their ability to induce resistance in wheat against disease caused by Fusarium graminearum Schwabe in growth room and outdoor tests. Agar inoculum of the endophytes was applied 4 days before agar inoculum of F. graminearum was applied to adjacent leaves. Simplicillium lamellicola or C. rosea treatments applied on one leaf significantly reduced the disease on another leaf by between 68 and 70% in growth room tests at 11 days post pathogen inoculation and by between 43 and 49% in outdoor tests at 9 days after inoculation compared to pathogen-inoculated controls with no biocontrols. Simplicillium lamellicola is a promising biocontrol agent since it systemically induced disease resistance in wheat against Fusarium graminearum. Future work is needed to investigate the mode of action of the defence responses and the proper formulation and application of this biocontrol agent. [ABSTRACT FROM AUTHOR]

Fusarium head blight (FHB) is a devastating disease of wheat in Canada and disease surveillance is a critical component of integrated disease management, disease forecasting, prioritizing research and breeding efforts, grain handling, and cleaning post harvest. We report on the recent trends of FHB in Canadian wheat including incidence and severity from 1995 to 2021 based on data from 208,247 samples. Our results show a steady increase in FHB incidence from 1995, with an epidemic year in 2016, followed by several years of low incidence. Results also indicated that FHB severity has been stable over time, but not always correlated with incidence. Data from the analysis of 26,538 samples from 2018 to 2021 demonstrate a strong positive correlation between the number of Fusarium damaged kernels (severity) and concentrations of the mycotoxin deoxynivalenol. Together, our results provide the most robust survey of FHB in Canada to date, which complement national and international disease monitoring and management efforts. [ABSTRACT FROM AUTHOR]

Stripe (yellow) rust caused by Puccinia striiformis f. sp. tritici (Pst) is the most devastating disease of wheat in Turkey. Virulence characterization of the Pst population is critical to prevent large-scale epidemics, by developing wheat cultivars with durable resistance against the disease. In this study, 38 Pst races, including 25 races that were not previously reported, were identified from 140 isolates obtained from most regions of Turkey from 2018 to 2020 using a differential set containing 18 single Yr gene wheat lines (NILs) of 'Avocet'. Virulence to Yr15 was not observed among any of the isolates. Virulence to the remaining 17-Yr genes was detected at various frequencies. The frequencies of virulence to Yr6, Yr9, Yr7, Yr8, Yr43, YrExp2, Yr44, YrTr1, and Yr27 were high (57.1 to 100.0%), to Yr1, Yr17, Yr32, and YrTye were moderate (24.3 to 42.9%), and to YrSP, Yr24, and Yr10 were low (9.3 to 17.1%). Only one race was virulent to Yr5 (0.7%). Many of the races identified were common among regions, indicating that Pst races migrate throughout Turkey. However, the Black Sea (BS) and the Mediterranean (ME) regions were differentiated from other regions by unique races absent in other regions, and the Yr5-virulent race, respectively. To sum up, the virulences of the races identified and their distributions among regions provided an understanding of pathogen migration and may contribute to the development of resistant wheat cultivars against stripe rust. [ABSTRACT FROM AUTHOR]

The fungal pathogen Claviceps purpurea can infect numerous grass species including important crops like barley, rye, and wheat, but the ecology of ergot disease is rarely studied in non-crop grass species. Recent outbreaks of ergot in barley production systems in the western U.S. have implicated nearby grass hosts as reservoirs for inoculum and spread of C. purpurea into the barley crop. We surveyed the prevalence of ergot infections among native, invasive, and weedy grass species near barley fields in the San Luis Valley of Colorado over three years. We found that barley fields with a history of ergot disease were surrounded by a grass community composed largely of smooth brome, that smooth brome was very susceptible to ergot infection and had the highest infection rates among grass species, and that disease severity among the grass community increased during the growing season. Over the study period there was a low incidence of barley infections and this precluded analysing the effects unmanaged grass composition and disease incidence had on within field disease incidence. Our findings indicate that smooth brome represents a significant source of C. purpurea inoculum and inoculum levels increase as the composition of brome grass in the grass community increases. There is sufficient inoculum present in the brome grass population in the San Luis Valley to cause sporadic disease in barley fields when environmental conditions are optimal for infection. Future disease management strategies should take into account the large pool of inoculum in the grass population near barley production fields. [ABSTRACT FROM AUTHOR]

Fusarium graminearum is a mycotoxin-producing pathogen involved in Fusarium head blight (FHB) disease of cereals, and is responsible for compromising grain yield and quality.Over the course of infection, the fungus secretes various metabolites and proteins, of which only a handful have been fully characterized in the context of FHB. We report herein the role of a secreted cerato-platanin protein (FGSG_10212, FgCPP1) in the growth and aggressiveness of F. graminearum. Pathogen strains in which FgCPP1 was disrupted (Δfgcpp1) or overexpressed (FgCPP1-OX1) did not differ from the wild-type with respect to macroconidial germination or mycelial growth, nor in sensitivity to chemicals targeting fungal cell walls. Host—plant interaction studies were conducted including disease assays in wheat and host-cell localization of FgCPP1 in tobacco cells. Consistent with previous reports for FgCPP1 disruption mutants of F. graminearum, no difference was observed among FgCPP1-OX1, Δfgcpp1 and the wild-type in their ability to cause disease spread in point-inoculated wheat spikes. Spray inoculation of the wheat spikes with FgCPP1-OX1 resulted in an increase in diseased spikelets as early as 3 days post-inoculation in each of the three wheat genotypes assessed; however, this increase was not observed when the disease assay was repeated in the cultivar 'Penhold' with an additional FgCPP1-OX transformant, FgCPP1-OX2. FgCPP1-OX1 also resulted in increased levels of deoxynivalenol accumulation in axenic culture, as well as in spray-inoculated wheat spikes. We propose that FgCPP1 is a minor contributor to pathogen aggressiveness in wheat. [ABSTRACT FROM AUTHOR]

The cereal cyst nematode (CCN) Heterodera and crown rot caused by Fusarium species limit cereal production and yield potential. Losses increase when CCN and crown rot occur together, especially under water stress conditions. The objective of this study was to investigate the interactions among Heterodera filipjevi, Fusarium culmorum, and drought on a set of wheat germplasm with differing levels of resistance/tolerance to CCN, crown rot and drought. Plant emergence was significantly reduced (56% seedling death) when seeds were planted in a water stress environment where F. culmorum and H. filipjevi were present. Crown rot was more severe under water stress compared with Fusarium inoculation alone. The number of cysts fell significantly when H. filipjevi was co-inoculated with F. culmorum, revealing an antagonistic interaction between the nematode and fungus. The highest number of cysts was found on the susceptible accession 'Seri' under water stress conditions. Water stress caused a significant reduction in plant height, while F. culmorum inoculation did not, unless combined with water stress. Yield components were significantly reduced by each of the single stresses and losses were greater when plants were exposed to double or triple stresses. Water stress and F. culmorum inoculation caused a significant reduction in spike weight and seeds per spike. The chlorophyll content of wheat leaves was negatively affected by water stress and inoculation by both nematode and fungus. In conclusion, water stress exacerbates the damage caused by CCN and crown rot, and planting drought-resistant varieties would be an ideal solution to reduce losses. [ABSTRACT FROM AUTHOR]

The objectives of this study were to investigate the occurrence of eyespot in commercial spring cereal crops in four climatic areas in Tunisia and characterize the dominant species of Oculimacula responsible for the disease. A total of 294 wheat, barley and oat fields were surveyed for eyespot incidence and severity during four cropping seasons from 2010 to 2014. Eyespot was identified in 63.5% of the fields with an average incidence of 23.1% infected stems. The number of infected fields as well as the incidence and severity of disease increased significantly during the 5 years of the study. A significant difference in the occurrence of eyespot among the climatic regions was noted with the wetter areas having greater disease incidence. The highest incidence of eyespot was recorded in durum wheat and bread wheat fields, whereas barley was significantly less infected. The effect of previous crop on eyespot incidence was not significant. All 70 isolates collected in this study were identified as O. yallundae and among them, 39 were identified as MAT1-2 and 31 as MAT1-1. This study highlights the influence of climatic conditions on the distribution of eyespot in the cereal growing areas of Tunisia as well as the increasing occurrence of the disease. The predominance of O. yallundae is an important consideration in the choice of integrated management strategies for eyespot. The presence of both mating types of O. yallundae in similar proportions suggests that sexual reproduction may be occurring. [ABSTRACT FROM AUTHOR]

The development of resistant cultivars is a preferred way to manage the wheat rust pathogens. Successful breeding relies on the continuous discovery, characterization and deployment of genetically diverse resistance sources. This investigation covers the identification and characterization of the stripe rust (caused by Puccinia striiformis f. sp. tritici) resistance carried by a pre-Green Revolution wheat genotype, Aus27492, from France and its transfer to modern backgrounds. Genetic analysis of stripe rust resistance using an F3 population derived from the cross of Aus27492 with the susceptible parent 'Avocet S' indicated digenic inheritance of all stage resistance. The underlying genes were tentatively named YrAW6 and YrAW7 and these loci were located in the long arms of chromosomes 2B and 5A, respectively, through the Illumina iSelect 90 K Infinium SNP genotyping array-based bulked segregant analysis (BSA). While YrAW7 was shown to be the same as the previously described stripe rust resistance gene Yr34 based on pathotypic specificity, YrAW6 appears to represent a new locus. To take these results from the laboratory to farmers' fields, derivatives of Aus27492 in the Australian wheat cultivars 'Emu Rock', 'Mace' and 'Suntop' were delivered to Australian wheat-breeding companies for use as donor sources. [ABSTRACT FROM AUTHOR]

This study was conducted to identify and map stem rust resistance genes in Canada Western Red Spring (CWRS) wheat variety 'AAC Prevail' and elite line 'BW961ʹ. A population of 227 doubled haploid lines from 'AAC Prevail'/'BW961ʹ and parents were evaluated for their response to stem rust (Puccinia graminis) at Njoro, Kenya, from 2016–2019 and genotyped using a targeted genotyping by sequencing SeqSNP assay. 'AAC Prevail' and 'BW961ʹ were susceptible to race TTKSK in seedling tests in Canada. We identified stable QTL (significant in most environments tested) associated with field stem rust resistance on chromosome arms 2BS and 7AL, and minor QTL on 5AL, 6AS and 7BL. The QTL on 5AL, 7AL and 7BL were contributed by 'AAC Prevail', while those on 2BS and 6AS were contributed by 'BW961ʹ. The QTL on 7AL was detected across all environments and explained 9.5% to 39% of the variation in disease severity (DS) and infection response (IR). The QTL on 2BS was associated with DS in all environments and in three of four environments for IR, and explained 4.8% to 12% of the variation in DS and IR. In two environments, the combination of 2BS and 7AL significantly enhanced field stem rust resistance compared with either QTL singly. Using SNP markers closely linked to the novel QTL on 2BS and 7AL, Kompetitive Allele Specific PCR markers were developed and validated in the population. These results provide breeders with new information and markers to utilize these sources of stem rust resistance. [ABSTRACT FROM AUTHOR]

Stripe rust, caused by Puccinia striiformis Westend. f.sp. tritici Erikss. (Pst), is one of the most devastating diseases of wheat (Triticum aestivum L.) globally. Exploring and utilizing new sources of resistance is essential for breeding resistant wheat cultivars. Thus, a doubled haploid population (n = 291) derived from the cross 'AAC Innova'/'AAC Proclaim' was evaluated to dissect the genetics of resistance in the cultivar 'AAC Innova'. This population was evaluated for stripe rust severity in disease nurseries at Creston, British Columbia (in 2016 and 2020), and Lethbridge, Alberta (in 2016, 2017 and 2020), and genotyped using the wheat 90 K SNP assay. A high-density genetic map was constructed which consisted of 7112 SNP markers with an average marker interval of 2.3 cM. Quantitative trait loci (QTL) mapping identified one major (QYr.lrdc-2A) and 10 minor effect (QYr.lrdc-2B.1, QYr.lrdc-2B.2, QYr.lrdc-2B.3, QYr.lrdc-2B.4, QYr.lrdc-2D, QYr.lrdc-3B, QYr.lrdc-5A, QYr.lrdc-5B, QYr.lrdc-5D and QYr.lrdc-7D) loci. The QTL QYr.lrdc-2A was consistently effective against Pst races across all environments and explained up to 33.0% of the phenotypic variation. Other QTLs were either less consistent or environment specific. 'AAC Innova' contributed stripe rust resistance alleles for most of the QTLs except for QYr.lrdc-2D, QYr.lrdc-5A and QYr.lrdc-7D. The QTLs identified in this study should be valuable for diversifying the sources of genetic resistance against current and new virulent races of Pst. In particular, the 'AAC Innova'-derived QTL QYr.lrdc-2A could be a valuable source of resistance to incorporate into commercial cultivars and combine with other genes using the associated SNP markers identified in this study. [ABSTRACT FROM AUTHOR]

Puccinia striiformis f. sp. tritici (Pst) causes wheat stripe rust (also called yellow rust, Yr), one of the most important diseases worldwide. Characterization of virulence in Pst populations is essential for developing wheat cultivars with effective and durable resistance to control the disease. A total of 138 Pst races, including 120 races that were not previously reported, were identified from stripe rust collections made from Canada, China, Ecuador, Egypt, Italy and Mexico in 2013–2020 using a set of 18 Yr single-gene differentials. Virulence of the resistance gene Yr5 or Yr15 was not found in isolates from any of the countries, indicating their effectiveness against the Pst populations. Virulence to 16 Yr genes was detected, but the frequencies varied greatly among countries. On average, the frequencies of virulence to Yr6, Yr7, Yr9, Yr43, Yr44 and YrExp2 were high (81.7–90.6%), those to Yr1, Yr8, Yr17, Yr27, YrSP and Yr76 were moderate (34.0–56.8%), and those to Yr10, Yr24, Yr32 and YrTr1 were low or very low (0.4–18.5%). The same races detected in different countries and different races from different countries clustered into the same virulence groups, indicating Pst migration among different countries, especially between eastern Asia and the Mediterranean region. These results should be useful for breeding wheat cultivars with effective resistance to stripe rust in these countries as well as globally. [ABSTRACT FROM AUTHOR]

Wheat leaf rust, caused by Puccinia triticina Eriks., is a common and destructive disease of wheat worldwide. The durable leaf rust-resistance gene Lr34 is typically described as an adult plant resistance gene, which is not expressed at the seedling stage at normal greenhouse temperatures. However, Lr34 is expressed at the seedling stage when plants with Lr34 are grown at low temperatures, i.e. approximately 8°C. Lines and cultivars with Lr34 demonstrate a range of responses from near immunity to intermediate reactions on the primary leaf. The Thatcher-Lr34 near isogenic lines 'RL6058ʹ (Thatcher*6/PI58548) and 'RL6091ʹ (Tc*6/Chinese Spring) were resistant to a number of P. triticina virulence phenotypes at the seedling stage when grown under these cool conditions, but were susceptible at typical greenhouse temperatures. A double haploid population from a cross between 'Thatcher' and 'RL6058ʹ, previously genotyped for Lr34, was grown at 8°C and screened for leaf rust response at the seedling stage. The population is segregated by a seedling resistance gene that corresponds to the presence of a resistance allele of Lr34. After extended incubation at cold temperatures, the seedling progeny lines with Lr34 also developed distinct leaf tip necrosis; this phenotype was absent in susceptible plants, similar to their reaction as adult plants. When uninfected plants from this population were grown to the adult plant stage at 10°C, those with the Lr34 resistance allele had extensive leaf necrosis and shrunken, sometimes sterile, spikes. [ABSTRACT FROM AUTHOR]

Stripe (yellow) rust, caused by the biotrophic fungal pathogen Puccinia striiformis f. sp. tritici (Pst), is emerging as a serious threat to wheat (Triticum aestivum L.) production in many regions of North America. Genetic resistance to stripe rust is typically conditioned by the products of resistance genes that detect pathogen-associated molecular patterns and initiate a cascade of signalling events, culminating in the generation of reactive oxygen species (ROS) and a hypersensitive response (HR) that eventually suppress the pathogen. Complete resistance with no symptoms (immunity response) has also been observed, but less frequently, in certain Pst-wheat interactions. However, such HR-independent resistance responses to Pst have not been well studied. Here we report that the Pst-resistant near isogenic line Avocet-Yr15 (carrying the Yr15 resistance gene) exhibited an immunity response to an isolate of Pst collected in Elora, Ontario, while the Avocet-S line (lacking Yr15) was highly susceptible to the same isolate. In particular, histochemical assays of defence-associated ROS generation and HR were negative during the early stages of the interaction between Pst and the resistant Avocet-Yr15. Microscopic analysis indicated that the pathogen was not able to penetrate the stomata of Avocet-Yr15. Moreover, RNA-sequencing of the immunity response of Avocet-Yr15 to Pst highlighted the activation of a global anti-oxidative-stress response consisting of genes involved in the maintenance of cell viability, redox homoeostasis and photosynthesis. These results provide insights into the molecular mechanisms controlling the immunity response to stripe rust of wheat. [ABSTRACT FROM AUTHOR]

Wheat leaves infected with Puccinia triticina, the causal agent of wheat leaf rust, were collected annually throughout Canada from 2015 to 2019. There were 47, 75, 44, 38 and 54 different virulence phenotypes, respectively, found annually, representing 154 unique virulence phenotypes. From Alberta, there were three virulence phenotypes, MBDS, TDBJ, and TDBS, found in 2015 and eight in 2019, the most common being MBDS and TNBJ (both 20%). The most common virulence phenotypes found in Manitoba and Saskatchewan were MBDS (17.8%) and TNBG (16.3%) in 2015, MNPS (17.2%) and MBDS (15.9%) in 2016, MNPS (41.9%) and TBBG (17.2%) in 2017, MNPS (35.3%) and TBBG (34.8%) in 2018, and MNPS (54.7%) and MBDS (10.7%) in 2019. In Ontario, the most common virulence phenotypes found were MBTN (25%) and MBDS (16.7%) in 2015, MCQQ (13.6%) in 2016, MBTN (33.3%) and PBDG (19.0%) in 2017, TFPJ (13.6%) in 2018, and MCTN (14.5%) and MBTN (10.9%) in 2019. In Quebec the most common virulence phenotypes found were TBBG (66.7%) and MLDS (33.3%) in 2015, TCGJ (23.1%) and MBTN (15.4%) in 2017, MCQH (26.3%) and FCPT (21.1%) in 2018, and MBTN and MCRS (both 18.2%) in 2019. The frequencies of virulence varied on all resistance genes over these years. Within Canada, virulence on Lr21 peaked in 2018 at 39.9% and then declined in 2019, with a similar trend noticed for virulence on Lr2a and Lr2c. There was no virulence detected on Lr19, Lr29, Lr32, Lr52, and Lr22a, while virulence on Lr25 was rare. [ABSTRACT FROM AUTHOR]

Stem rust, caused by Puccinia graminis f. sp. tritici (Pgt), is a major disease of wheat. In Kenya, Pgt has caused sporadic but serious losses to farmers since large-scale wheat production began in the early twentieth Century. Breeding for stem rust resistance in Kenya has been conducted since 1910. Mutants of Pgt are common in Kenya as large pathogen populations survive on wheat crops planted throughout the year, with virulence to effective major genes developing shortly after release of resistant cultivars. Gene Sr31 was first deployed in Kenya in 'Kenya Pa'a' in 1982 and subsequently in 'Duma' in 1993, the latter grown on large acreage. Virulence to Sr31 was first detected in Uganda in 1998, in what became known as Pgt-Ug99 (race TTKSK). Virulence to Sr31 may have occurred earlier in Kenya, but Ug99 was first reported in 2001. Race TTKSK has migrated across East Africa and to Yemen and Iran, spreading to 13 countries with 13 race variants. Other Pgt races (TKTTF, TTRTF, TTTTF) with broad virulence were recently detected in Kenya, likely originating from central Asia. A 'Sounding the Alarm' message from Norman Borlaug in 2005 triggered extensive research on worldwide virulence in Pgt, and on finding, characterizing, and developing molecular markers for Sr genes effective to Ug99-lineage pathotypes of Pgt. While fungicides can control Pgt, the best strategy uses host resistance. The best gene stewardship practice to provide enduring resistance combines effective major and minor adult plant resistance (APR) genes prior to release of new wheat cultivars. [ABSTRACT FROM AUTHOR]

Powdery mildew caused by Blumeria graminis f. sp. tritici (Bgt) is a major disease of wheat (Triticum aestivum) in Ontario, which can cause 20% yield loss. The development of resistant commercial wheat cultivars is the most economical means of controlling this disease, but only if the resistance genes used are incompatible with the virulence phenotypes present in the pathogen population. The virulence structure of Bgt in Ontario was examined in 2018 and 2019. Of the 42 single colony isolates collected in Ontario greenhouses and commercial fields, 40 virulence phenotypes, assigned VP1 to VP40, were identified on a set of 24 single-gene differential genotypes. Of the 24 resistance genes possessed by the differential genotypes, eight genes including Pm1a, Pm1b, Pm1c, Pm12, Pm16, Pm21, Pm37, and MlAG12 were effective against all of the Bgt isolates. Four genes including Pm3d, Pm29, Pm34, and NCAG13 were mostly effective with resistance reactions to more than 80% of the isolates. There were no significant differences in numbers of virulence genes per isolate between the two years, or between the greenhouse and field origins. The virulence frequencies of Bgt isolates for these effective and mostly effective genes were also not significantly affected by the year of collection and their origins, suggesting that the Bgt population is relatively stable. The effective genes identified in this study may be deployed singly or used for gene pyramiding in wheat breeding programs for developing powdery mildew-resistant cultivars in Ontario. [ABSTRACT FROM AUTHOR]

Fusarium head blight (FHB) has a negative impact on cereal food safety, quality and yield. The majority of FHB resistance genes in wheat (Triticum spp.) have been identified based on reaction to Fusarium graminearum, which, in Canada, has two prevalent trichothecene chemotypes, 3-acetyl-deoxyinvalenol (ADON) and 15-ADON. Three hexaploid (Triticum aestivum L.) and four tetraploid (Triticum turgidum L. ssp. durum and Triticum turgidum L. spp. dicoccoides (Korn. ex Asch. & Graebn.) Thell.) wheat genotypes with different genes for resistance and with different reactions to F. graminearum were evaluated in replicated greenhouse trials to determine if the resistance genes currently deployed in Canadian wheat are effective against both the 3-ADON and 15-ADON chemotypes. The development of FHB was rated as disease severity. The genotypes showed differential responses, with a higher level of disease development in the hexaploid wheat genotypes inoculated with the 3-ADON than with the 15-ADON chemotype. The opposite was observed in the tetraploid wheat genotypes. Tetraploid genotype BGRC3487 and a hexaploid genotype ND2710 showed similar resistance to both 3-ADON and 15-ADON chemotypes. These would be effective sources to breed lines resistant to both 3-ADON and 15-ADON chemotypes and reduce FHB risk. [ABSTRACT FROM AUTHOR]

Tan spot is a destructive disease of wheat caused by the fungus Pyrenophora tritici-repentis (Ptr), with most fungal isolates in Canada known to produce the necrotrophic effector (NE) ToxA. In this study, 144 Ptr isolates collected from durum, winter bread wheat, and grasses in western Canada were evaluated for race classification on a host differential set. The susceptibility of 114 durum and winter bread wheat genotypes to Ptr races 2 (R2), 3 (R3), and 5 (R5), producing the NEs ToxA, ToxB, and ToxC, respectively, was evaluated in bioassays. The host genotypes were tested for the presence of Tsn1, the ToxA-sensitivity gene, by PCR analysis. Race composition varied based on the host type and ploidy level from which the isolates were recovered. R1 (ToxA and ToxC-producer) and R2 were predominant on wheat and occurred in equal frequency on durum, while R1 occurred twice as frequently as R2 on winter bread wheat. R3 was recovered only from durum wheat, and the non-pathogenic R4 was the only race recovered from grasses. Susceptibility to R2 and R3 was more common in Canadian than in European wheat, while susceptibility to R5 was more common in durum and European wheat. Tsn1 amplified at a higher percentage in Canadian (51.2% in winter bread, 59.0% in durum) vs. European (20.5%) wheat genotypes. The presence of Tsn1, however, did not result in susceptibility to ToxA-producing isolates in 35.9% of durum genotypes, indicating that other factors are involved in the Ptr-durum interaction and that ToxA-Tsn1 may not play a significant role in tetraploid wheat. [ABSTRACT FROM AUTHOR]

Fusarium head blight (FHB) is a major fungal disease that contributes to severe economic losses for wheat and barley production in Canada and other parts of the world. Rapid developments in molecular biology over the past three decades have improved the ability to devise predictive management tools to combat the effects of the disease. Important aspects of Fusarium species in terms of the epidemiology associated with FHB in wheat and barley have been reported. The role of mycotoxin production in the epidemiology of the disease is beginning to receive much needed research attention. Evolutionary factors and the use of fungicides have resulted in more virulent forms of the FHB pathogens. Advances in next-generation sequencing technologies, including whole genome sequencing (WGS), genome-wide association studies (GWAS), genotyping by sequencing (GBS) and RNA sequencing (RNA-Seq) have facilitated the selection of resistant-breeding lines through marker-assisted selection. Many quantitative trait loci (QTL) associated with moderate disease resistance have been identified in wheat and barley. Changes in weather conditions play an important role in FHB epidemics and dissemination, thus a systematic and long-term research approach is needed to provide effective forecasting and risk assessment models. This review discusses the history and epidemiology of FHB pathogens in wheat and barley at the global level, as well as potential plant defence mechanisms, the recent progress made in resistance breeding, and modern tools utilized in disease prediction. It also provides future directions for improving the management of the disease with these two important cereals. [ABSTRACT FROM AUTHOR]

Stem rust is a major disease on barley, oat, and wheat crops worldwide. The primary means of control is by host resistance genes that are incorporated into commercial varieties and have been effective against most races of Puccinia graminis Pers., the causal pathogen. Since this pathogen continually mutates, analyzing the population virulence structure is crucial to detect new races with increased virulence. Stem rust samples were collected from 2015 to 2019 from the Canadian provinces of Manitoba, Ontario, Quebec, and Saskatchewan to find the prevalence of stem rust in barley (Hordeum vulgare L.), oat (Avena sativa L.), and wheat (Triticum aestivum L.) fields and the virulence dynamics in the two pathogen populations. Stem rust was absent in cultivated wheat and at trace (<1%) levels of incidence in barley and oat fields in all years. While the dominant races of P. graminis f. sp. tritici were MCCDC (54.5%) and TPMKC (27.3%) in 2015, and TMRTF (29.2%) in 2016, race QFCSC was dominant in 2017 (52.0%), 2018 (88.4%), and 2019 (81.3%). The dominant race of P. graminis f. sp. avenae was TJS from 2015 to 2018. Race TJS declined in frequency across the years, from 89.5% (2015) to 73.7% (2016), 42.6% (2017), 49.1% (2018), and only 14.3% in 2019. The dominant races in 2019 were SGB (51.7%) and TGN (19.6%). One new race (TJQ) of P. graminis f. sp. avenae was detected in 2016 at one location near Emerson, Manitoba, which may have arisen from a single-step mutation to avirulence to Pg15 from race TJS. [ABSTRACT FROM AUTHOR]

Root rot is an important disease of field pea (Pisum sativum L.) on the Canadian Prairies. The composition and alternative crop hosts of fungal and oomycete communities colonizing pea residues from Alberta and Manitoba were studied in field trials over two years. Standing pea residues were sampled from diseased and asymptomatic patches of 17 commercial fields in 2013 and 2014 after harvest and again in early spring the following year prior to seeding. The pea residue was ground to a powder and mixed with sterile Cornell potting mix. Plants of pea, wheat, and canola were grown in this mixture under controlled conditions. The root rot severity on each plant was evaluated and sections from diseased roots were plated on agar medium. Fungal and oomycete communities isolated from symptomatic roots were identified based on culture morphology and PCR analysis. About 3000 fungal isolates, belonging to some 50 species, were identified. Canola was less susceptible to infection than pea or wheat. Fusarium avenaceum (Fr.) Sacc. was the most abundant species infecting the three hosts; F. culmorum (Wm.G.Sm.) Sacc. and Bipolaris sorokiana (Sacc.) Shoemaker were more frequently isolated from wheat, and F. solani (Mart.) Sacc., F. oxysporum Schlecht. and Aphanomyces euteiches Drechsler were more frequently isolated from pea. Pathogen communities from asymptomatic and diseased patches of fields were similar. Overall, composition of the fungal community changed over winter, but the most abundant species did not change. The results show that multiple pathogens, and particularly Fusarium spp., can survive overwinter on pea residue. [ABSTRACT FROM AUTHOR]

Wheat is affected by many fungal diseases that can cause severe yield and quality losses. Disease prediction models generally employ weather data to estimate potential for infection to determine timing for fungicide applications, but these models fail to account for the presence and quantity of pathogen inoculum. This study adapted highly specific qPCR primers to identify and quantify, in real-time, inoculum present in air for the six most important wheat pathogens in Canada. Fungal spores were collected using either Burkard spore collectors and quantified using qPCR or microscope slides covered with adhesive tape and identified and quantified using microscopy. Samples were collected from seven different sites in southern Alberta throughout the 2015–2017 growing seasons. The results demonstrated that qPCR can reliably identify and quantify spores from Puccinia striiformis f. sp. tritici, P. triticina, P. graminis f. sp. tritici, Blumeria graminis f. sp. tritici, Pyrenophora tritici-repentis, and Fusarium graminearum. The limits of detection of DNA for primer pairs in singleplex tests ranged from 0.0001 ng for P. graminis to 0.001 ng for P. tritici-repentis, which corresponded to approximately 3 spores for P. tritici-repentis and F. graminearum and 1 spore for the other pathogens. Conversely, microscopy permitted identification of rusts to the genus but not to the species level and was ineffective in quantification of the remainder of the wheat pathogens. This study will contribute to the development of a fast and reliable forecasting system that will enable identification and quantification of airborne pathogens in real-time before initial disease symptoms appear. [ABSTRACT FROM AUTHOR]

Symptoms of partially bleached and completely white heads were observed in a triticale (× Triticosecale) cultivar 'BARI Triticale 1ʹ in the research plots at the Regional Agricultural Research Station, Jashore, Bangladesh, during April 2019. Foliar symptoms with elliptical or eye-shaped lesions were also found on plant leaves. The main intention of this study was to isolate and identify the causal organism of the disease. Morphological characteristics of the pathogen showed the presence of pyriform 2-septate hyaline conidia and coloured conidiophores, indicating the presence of the fungus Magnaporthe oryzae. Molecular analyses by ITS sequence analysis and amplification of the product with MoT3 primers confirmed the identity of the fungus as M. oryzae pathotype Triticum. The pathogenicity of the representative isolates was confirmed by inoculation of triticale heads and leaves under laboratory conditions, resulting in similar symptoms as observed in the field. To our knowledge, this is the first report of triticale blast caused by M. oryzae pathotype Triticum in Bangladesh. [ABSTRACT FROM AUTHOR]

Stem rust, caused by Puccinia graminis, is a catastrophic disease that has and continues to cause yield losses in barley, oat, and wheat crops worldwide. Use of host resistance genes is the most economic, efficient, and environmentally best method to control the disease. Resistance genes have been incorporated into most commercial cultivars and have been effective, for races in the North American populations of P. graminis. However, new races of stem rust are constantly emerging and therefore it is imperative to monitor the virulence structure in the populations to detect new races with increased virulence. Stem rust samples were collected in 2013 and 2014 in Manitoba, Ontario, Quebec, and Saskatchewan to determine the incidence and severity of stem rust in barley (Hordeum vulgare), oat (Avena sativa), and wheat (Triticum aestivum) fields and to characterize the virulence dynamics in the pathogen populations. No stem rust was found in cultivated wheat, and incidence was at trace (<1%) levels in barley fields and very low (0–5%) levels in oat fields in 2013 and 2014. In wheat trap plots and collections from barley, race QFCSC of P. graminis f. sp. tritici was dominant in 2013 (85.9%) and was the only race found in 2014. Races MCCFC, QTHJF, RFCSC, RKQSC, and TMRTF were at low (<5%) levels in 2013. From collections in oat fields and stands of wild barley, nine races of P. graminis f. sp. avenae were found in 2013, with TJS (56.9%) and TJJ (23.5%) the most frequent. In 2014, we found only six races and TJS (74.5%) and TJJ (19.1%) were the most frequent. No new races of stem rust were detected in Canada in 2013 or 2014. [ABSTRACT FROM AUTHOR]

Hybrid wheat shows promise to increase yield potential, but many questions remain about the hybrid system. One of the most important is how hybrids will perform in terms of diseases such as Fusarium head blight (FHB). It is unknown if a hybrid produced from a resistant by susceptible cross will express acceptable resistance levels. This experiment tested hybrids produced from four resistant parents crossed with a common susceptible parent (2398). The results indicated that the hybrids were resistant compared with the susceptible parent and mid-parent, while they were less resistant compared with their respective resistant parent. The hybrids were between the mid-parent and resistant parent in resistance to FHB traits. This may indicate that the resistance in the hybrids may be controlled by partial dominance gene action. The findings also indicated that accumulation of more resistance genes provided improved resistance to FHB. In conclusion, successful hybrids with a good level of FHB resistance could be produced through crossing parents with contrasting resistance to this disease. [ABSTRACT FROM AUTHOR]

Fusarium head blight (FHB) and the associated mycotoxin deoxynivalenol (DON) negatively impact the wheat industry worldwide. In North America, FHB is mainly caused by Fusarium graminearum sensu stricto. The purpose of this study was to evaluate, under storage conditions, the expression of the DON biosynthetic gene trichodiene synthase (Tri5) of F. graminearum in grain of hard red winter wheat cultivars 'Overley' (FHB-susceptible) and 'Overland' (moderately resistant to FHB) from field plots treated or untreated with the triazole fungicide Prosaro and the strobilurin fungicide Headline. Infected grain was stored and periodically sampled to determine gene expression by qRT-PCR analysis. The F. graminearum housekeeping gene GAPDH was consistently detected, indicative of metabolically active fungi, and Tri5 detection was significantly higher in 'Overley' compared with 'Overland'. Tri5 gene expression and DON concentrations showed little to no correlation; consequently, Tri5 expression levels did not accurately predict DON concentrations. The strobilurin did not significantly reduce Tri5 gene expression compared with untreated wheat. In the triazole treatment, a significant reduction in the relative expression of Tri5 was detected after 120 days, as well as a downregulation of Tri5 from 60 to 120 days of storage in 'Overley'. In grain from strobilurin-treated plots of both cultivars, the expression of Tri5 increased from 0 to 30 days after tempering. Genetic expression of Tri5 that is necessary for the production of DON can increase during storage of high-moisture grain. Fusarium fungi can persist in wheat kernels for several months postharvest and may actively produce toxin during this period. [ABSTRACT FROM AUTHOR]

Yield losses in wheat and barley cultivars varying in stripe rust reactions were determined under natural infection conditions in fungicide treated and untreated plots at Lacombe and Olds, central Alberta, from 2012 to 2014. Stripe rust caused by Puccinia striiformis was the major disease observed during the 3-year test. Moderate stripe rust severity caused significant yield losses of over 20% in a highly susceptible wheat, 'AC Crystal', while no severe yield losses occurred for resistant and moderately resistant cultivars/lines. However, a moderate level of stripe rust and the leaf spot complex caused reductions in thousand kernel weight (TKW) ranging from 5.4% to 13.5% for all wheat and barley cultivars/lines tested except for 'Lillian' wheat and 'Seebe' barley. When stripe rust developed early in the growing season resulting in severe disease, there were significant yield losses ranging from 17.6% to 91% for five wheat and two barley genotypes. Severe TKW and test weight losses also occurred for susceptible wheat and barley. The magnitude of yield losses in resistant and intermediate cultivars was smaller than in susceptible cultivars in the same tests. The present study demonstrated that one foliar-applied fungicide application was generally capable of protecting susceptible wheat and barley cultivars from stripe rust, while the use of resistant and intermediate cultivars was necessary for yield protection when moderate levels of disease occurred. Fungicide application was needed to reduce yield losses for resistant and moderately resistant cultivars when leaf spot diseases were prevalent and an early onset of stripe rust was observed, which can lead to severe stripe rust development even in resistant varieties. [ABSTRACT FROM AUTHOR]

Several Fusarium species cause Fusarium head blight (FHB), a devastating disease that affects wheat and other small grain cereals. Besides causing significant yield losses, FHB pathogens reduce the quality of the grain and may produce mycotoxins that are harmful to both humans and animals. The development of effective management strategies for this disease requires an understanding of the composition of the FHB pathogen populations, which is important because different populations could be affected selectively. Recent reports of shifts in populations of FHB pathogens have shown that these populations are dynamic and change continuously, often associated with increased yield losses or changes in the mycotoxins produced in the grain. These population shifts include: replacement of F. graminearum by F. poae in Italy, hypothesized to be due to variation in environmental conditions; replacement of F. culmorum by F. graminearum in Europe, associated with climate change and increased maize production; a more aggressive and toxigenic F. asiaticum 3-ADON population replacing the existing NIV population in China; and a highly toxigenic population composed mainly of F. graminearum 3-ADON isolates replacing the existing 15-ADON population in North America. Additionally, reports of recent introductions of foreign species or populations into new areas include: F. asiaticum outside of Asia, F. graminearum NIV isolates in the USA and Luxembourg, F. graminearum 15-ADON isolates in Norway, F. graminearum in South Korea, F. boothii in Europe and USA, F. vorosii in Hungary and F. cortaderiae in New Zealand and Europe. [ABSTRACT FROM AUTHOR]

Wheat stem rust, caused by the fungal pathogen Puccinia graminis f. sp. tritici (Pgt), has re-emerged as an important disease of wheat. This pathogen continues to spread and evolve new virulent races. The international letter-code system of nomenclature has been used to pathotype these new emerging races, and gene SrMcN from 'McNair 701' winter wheat, which is one of the differential lines, was examined in this study. The chromosome and map position of gene SrMcN have not been determined, and thus the objective of this research was to genetically map SrMcN. A doubled haploid population (n = 186) was made from the cross 'LMPG'/'McNair 701' and inoculated with Pgt race QCCJB. The DH population segregated 95 resistant : 91 susceptible lines, which fitted the expected 1 : 1 ratio (χ2 = 0.09, P = 0.77, NS) for a single gene. SrMcN mapped to chromosome 2DL using the 90K iSelect wheat SNP array, and Kompetitive allele specific (KASP) polymerase chain reaction markers located SrMcN to the same position as Sr54 previously found in 'Norin 40'. Comparison of stem rust seedling reactions using 12 diverse Pgt races indicated that SrMcN and Sr54 had an identical pattern of responses and similar low infection types (from ; to 2−) to races LBBLB, LCBNB and QCCJB. Based on the same chromosomal location on 2DL and identical seedling responses as Sr54 to several races of Pgt with diverse virulence, we assert that the resistance gene in 'McNair 701' winter wheat previously designated as SrMcN is most likely Sr54. [ABSTRACT FROM AUTHOR]

Fusarium head blight is a globally devastating disease of wheat, for which sources and mechanisms of resistance are urgently needed. The goal of this research was to elucidate the chemical nature of changes incurred in the rachis of a susceptible wheat ('Chinese Spring', CS), and a related addition line (CS-7EL) with resistance conferred by a fragment of the 7E chromosome from a wild wheat relative (Thinopyrum elongatum) in response to infection by Fusarium graminearum. Gravimetric analysis, followed by more targeted extractions and hydrolyses was used to study responses in the rachis of both genotypes at 7 days after fungal and mock inoculations. The most significant changes in the gravimetric analyses were an increase in the proportion of lignin in CS-7EL, and an increase in the proportion of hot water soluble compounds in CS. HPLC analysis of sugar profiles indicated higher degradation of arabinoxylan and cellulose in CS compared with CS-7EL. Differences were also observed in the profiles of the free, conjugated, and bound phenolic fractions for both varieties, with the conjugated fraction showing the greatest variation. The dominant phenolic acid in all samples was p-coumaric. A biplot analysis incorporating phenolic and sugar data was employed to provide an overview of responses to mock- and Fusarium-inoculation in CS and CS-7EL. Overall, our results suggest cell wall degradation in CS, and fortification in CS-7EL via increased lignification, in response to Fusarium infection. [ABSTRACT FROM AUTHOR]

Wheat leaves infected with leaf rust collected across Canada in 2013 were used to isolate 265 Puccinia triticina Eriks. single uredinial isolates. When these were analysed for virulence on 16 standard differential wheat lines 38 virulence phenotypes were found, with MBDS (11.7%), TBBG (11.3%), TNBG (10.2%) and MBTN (8.3%) the most common. In Manitoba and Saskatchewan, 29 virulence phenotypes were found among 236 isolates, with MBDS (13.1%), TBBG (12.7%) and TNBG (11.4%) being the most common. From Ontario, four virulence phenotypes MBTN (73.7%), LCDN (10.5%), MGPS (10.5%) and TCRJ (5.3%) were determined among 19 isolates. There were 10 isolates from Prince Edward Island which grouped into seven different virulence phenotypes, the most common being MBNQ (three isolates) and MCNQ (two isolates). The frequencies of virulence to Lr9, Lr26, Lr3ka, Lr17, Lr30, Lr14a and Lr21 increased, and virulence to Lr2a, Lr2c, Lr16, Lr24, Lr11, Lr10 and Lr18 decreased, when compared with 2012. The increase in virulence frequency to Lr21 is important since many Canadian wheat cultivars have this gene, and could become more susceptible. There were no virulence phenotypes in common between Ontario and Prince Edward Island, and only one virulence phenotype from each of these regions was found in the larger sample from Manitoba and Saskatchewan, demonstrating the differences in the populations across Canada. [ABSTRACT FROM AUTHOR]

Fusarium head blight (FHB) caused by Fusarium graminearum Schwabe is a major disease of wheat (Triticum aestivum L.). FHB preferentially infects immature spikes and mycotoxins accumulate in developing grains, reducing yield and nutritional quality. The mycotoxins are type B trichothecene group of compounds including deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-ADON), 15-acetyldeoxynivalenol (15-ADON), and nivalenol (NIV) that also act as virulence factors during FHB infection and disease progression. An enzyme UDP-glucosyl transferase (EC 2.4.1.x) glycosylates DON to deoxynivalenol-3-glucoside (D3G), thus rendering it ineffective as a virulence factor. The present study analysed the association of DON, 3A-DON, and D3G with FHB severity using in vitro spike culture for FHB screening. The mycotoxins in FHB-resistant and -susceptible spikes were extracted using a single step extraction method, and their concentration was determined using an LC-MS/MS method that differentiated all the five mycotoxins. Pairwise comparisons of FHB-resistant and -susceptible spike culture derived variants (SCDV) using Tukey's method showed significant (P ≤ 0.001) variation for disease severity and accumulation of DON, 3-ADON, and D3G at seven and nine days after fungal inoculation. FHB severity showed a significant positive correlation to the accumulation of DON, 3-ADON, and D3G, but an inverse correlation to the ratio between D3G and DON. [ABSTRACT FROM AUTHOR]

The objectives of this study were to investigate the Fusarium damage-deoxynivalenol (FUS DMG-DON) relationship in various wheat growing locations in western Canada in 2016 and to compare the relationships to the Prairie-wide FUS DMG-DON assessment of that harvest year. Fusarium head blight was prevalent in spring wheat and durum grown in western Canada in 2016. Harvest survey samples for Canada Western Red Spring (CWRS) wheat and Canada Western Amber Durum (CWAD) were inspected for Fusarium damaged kernels, and analyzed using an enzyme-linked immunosorbent assay for the Fusarium-produced mycotoxin DON. For CWAD and most CWRS, there was a significant relationship between FUS DMG (represented as the mass percentage of Fusarium damaged kernels) and DON, whose presence is regulated in food products to minimize consumers' exposure. However, CWRS from south-central Alberta contained much lower DON than expected by the reported visual symptoms of FUS DMG of the samples. High throughput real-time PCR analysis showed that DON-producing Fusarium species were associated with less than 40% of the Fusarium damaged kernels in the CWRS. This was different from what was observed with CWAD grown in the same area in 2016. Multi-mycotoxin analysis by liquid chromatography with tandem mass spectrometry did not show an increased presence of mycotoxins produced by other Fusarium species, and therefore suggested that the observed damage in CWRS from south-central Alberta was not caused by Fusarium species. [ABSTRACT FROM AUTHOR]

In addition to causing disease in wheat and other grain crops, Fusarium graminearum is associated with a wide range of forage, weedy and non-cultivated gramineous species.. The nature of these associations is often unclear, and interactions between F. graminearum and these hosts are not well characterized, despite their prevalence in and around cereal fields. We observed differences in the host suitability (competency) of spring wheat and six common grasses during three stages of the pathogen life cycle. Pathogen survival in artificially infested stem tissue was comparable between grasses and wheat over two years with the exception of one host. Sexual and asexual spore production on host stems under laboratory conditions varied significantly but exceeded 1 × 105 spores per dry gram of tissue for all grass species. A seedling root infection assay revealed the apparent resistance of two grasses to root rot and indicated that host preference could vary between pathogen isolates. These findings are relevant for how the role of wild grass hosts in disease epidemics of proximate crops and in pathogen evolution is viewed. Managing weedy grasses in field margins and avoiding gramineous pasture–wheat rotations may reduce local sources of F. graminearum inoculum. Changes in the relative pathogenicity of isolates depending on host species suggest that wild grasses could exert selective pressure on F. graminearum and requires further investigation. [ABSTRACT FROM AUTHOR]

Wheat stem base disease (WSD) is an important disease complex which can be caused by various pathogens with variable life cycles, ecological requirements and sensitivities to fungicides. Agronomic practices are considered important tools to control this disease complex and influence the spectrum of fungal communities in infected wheat stems. The aim of the present study was to determine the impact of crop rotation schemes and soil tillage methods on the development of WSD and to elucidate the spectrum of causal agents of this disease. The development of WSD was assessed in a two-factorial (soil tillage practice and crop rotation) experiment. The incidence of WSD was evaluated at the BBCH growth stages 83–85. Causal agents of WSD and other fungi were identified using molecular methods. The soil tillage method did not influence the development of WSD, but the impact of crop rotation was significant, and the cropping system where oilseed rape, barley and faba beans were included decreased disease levels. Members of the genera Oculimacula and Fusarium were the most prevalent fungi associated with WSD. Moreover, fungi from other taxonomic groups were detected, with Phaeosphaeria spp. being prevalent. An increasing occurrence of Microdochium spp. was also observed. In conclusion, agronomic practices influenced the level of WSD, but no distinct impact on the fungal spectrum was identified. Further investigation is required to clarify the roles that pathogens and fungi from other taxonomic groups play in the fungal–wheat relationship. [ABSTRACT FROM AUTHOR]

The objectives of this work were to investigate the presence of a variety of mycotoxins in Canadian wheat and durum and to characterize the relationship between concentrations of the Fusarium-produced deoxynivalenol (DON) and the presence of visible Fusarium damage. There is a lack of reported mycotoxin surveillance data for Canadian wheat and durum; this work addresses this information gap. Wheat and durum harvest samples from the 2010, 2011 and 2013–2016 growing seasons were analysed for mycotoxins produced by a variety of fungal species, including Fusarium graminearum and Alternaria alternata. The Alternaria-produced tentoxin was observed the most frequently; it was present in 90% of the samples analysed at concentrations up to 0.063 mg kg−1. Fusarium-produced DON and enniatins B and B1 were present in over 70% of samples analysed. The plant transformation product DON-3-glucoside was quantified in up to 30% of samples. There was variability in the presence of the various mycotoxins amongst years. In particular, for DON, the variability reflected the level of visible Fusarium damage noted in grain samples. The geographic source of samples also influenced DON concentrations, which decreased from eastern to western growing regions on the Prairies. Concentrations of DON varied from 0.066 to 0.895 mg kg−1 in south central Manitoba and <0.03 to 0.053 mg kg−1 in central Alberta. DON concentrations were significantly correlated (P < 0.001) with visible Fusarium damage in Canada Western Red Spring wheat for all four years investigated. For Canada Eastern Soft Red Winter wheat and Canada Western Amber Durum, there were significant correlations (P < 0.001) in three of the four years investigated for each grain class. The years with no significant correlation between DON and Fusarium damage occurred when the presence of Fusarium species other than the DON-producing F. graminearum were predominant. This work provides a picture of the presence, and absence, of a number of mycotoxins in Canadian wheat and durum. [ABSTRACT FROM AUTHOR]

Fusarium spp. associated with fusarium head blight (FHB) on cereals in Ontario was monitored in this study. Nine species were recovered from 24 300 putatively infected kernels collected from 486 affected spring wheat fields from 2001 to 2017, 11 species from 13 250 kernels from 265 barley fields from 2005 to 2017, and nine species from 8800 kernels from 176 oat fields from 2008 to 2017. Fusarium avenaceum, F. equiseti, F. graminearum, F. poae and F. sporotrichioides were the most commonly isolated species, occurring in 23–66% of the infected fields and 1.3–27.0% of the infected kernels. In spring wheat, F. graminearum was predominant, occurring in 88% of fields and in 60.4% of kernels, and represented 90% of the pathogen population. In barley, F. poae and F. graminearum were equally dominant, occurring in 77% and 64% of fields, 17.6% and 17.0% of kernels, and represented 42% and 40% of the pathogen population, respectively. In oat, F. poae was predominant, occurring in 93% of fields and 23.5% of kernels, and represented 68% of the pathogen population. Growth seasons characterized as an FHB epidemic occurred in 11 of 17 years surveyed in spring wheat, 3 of 13 years surveyed in barley, and no epidemic years were observed over the 10-year period in oat. There were no significant differences in frequency of isolation of the Fusarium species, except for F. graminearum which increased by 60% in wheat and by 210% in barley in the FHB epidemic years compared with the non-epidemic years, suggesting that F. graminearum was responsible for the FHB epidemics in Ontario. [ABSTRACT FROM AUTHOR]

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a destructive disease of wheat in the USA and fungicides have been used to manage the disease. However, it is not clear whether Pst has developed resistance to the commonly used fungicides. In this study, historical and recent Pst isolates were tested for sensitivity to Tilt, a propiconazole demethylation inhibitor fungicide, and Headline, a pyraclostrobin quinone outside inhibitor fungicide. Both Tilt and Headline at their labelled full concentration completely prevented urediniospore germination of all tested isolates. However, differences in germination rate among Pst isolates were observed at reduced fungicide concentrations. In the infection tests of both seedlings and adult plants, the full labelled concentration of either fungicide applied at the same day as inoculation with Pst completely prevented sporulation, but differences in rust sporulation or disease severity were observed among isolates at some reduced fungicide concentrations, or at the same full concentration applied either one day before or 3 or 7 days after inoculation. Thus, the fungicides are still effective for managing stripe rust at the full concentrations, but differences in sensitivity exist among Pst isolates. The results provide the technique and baseline for continually monitoring Pst populations for changes in fungicide sensitivity. [ABSTRACT FROM AUTHOR]

R. Glenn Anderson was Norman Borlaug's 'green fingered agricultural scientist' and a humanitarian who captained the wheat revolution in India during the 1960s. Afterwards, he directed the CIMMYT International Wheat Program where he was instrumental in establishing increased wheat disease surveys, broadening of the wheat genetic diversity for adaptation and disease resistance. He institutionalized multi-location yield and disease testing/analysis and regional breeding programmes, as well as strengthening the training of young scientists. Aspects of his work and other issues will be discussed in relation to present day global food security. [ABSTRACT FROM AUTHOR]

The population structure and genetic diversity of Pyrenophora tritici-repentis from hexaploid wheat were examined using 51 simple sequence repeat (SSR) markers designed to represent each chromosome of the pathogen. A total of 83 isolates representing races 1 and 2 of Ptr were analysed, including 35 isolates from Canada and 48 isolates from Iran. Isolates of the same two races but originating from different regions were compared in order to examine the effect of geographic origin on grouping. Most of the variation (91%) was observed within the examined populations and only 9% between populations. In addition, a moderate amount of gene flow (Nm = 2.8134) was found between populations. The average gene diversity and the percentage of polymorphic loci were estimated to be 0.2764 and 68.63%, respectively. Applying the unweighted pair group method with arithmetic mean procedure and Dice similarity coefficient revealed no obvious clustering of isolates based on race designation. In contrast, the grouping of isolates was consistent with geographic origin to some extent, with most isolates from Iran and Canada clustering separately regardless of race. These results indicate a link between geographic origin and the grouping of Ptr isolates, which could be detected by comparison of the same two races from two different regions. Previous research compared variable races, making it difficult to draw conclusions regarding the effect of geographic origin. [ABSTRACT FROM AUTHOR]

Fusarium head blight (FHB) is a devastating disease of wheat because of direct detrimental effects on grain yield, quality, and marketability and production of mycotoxins (e.g. deoxynivalenol or DON). Conditions most favourable for the development of FHB are high humidity, frequent rainfall and relatively warm night temperatures at heading, especially in regions where host crop residues are present. These risk factors have resulted in a significant westward expansion of FHB in the Canadian prairies, while favouring continued development in Ontario, Quebec and the Maritimes. Since cultivar selection is a key integrated pest management (IPM) strategy, a systems approach that couples genetic resistance with management tactics is required. Thus, successful FHB mitigation is an ideal case study in Genotype (G) × Environment (E) × Management (M) interactions where more resistant cultivars (G) are grown in at-risk regions (E), and unique approaches to management (M) for sustainable wheat production are required. Since no cultivar is completely resistant to FHB, greater attention to management strategies is needed. The over-arching principle for FHB management is the manipulation of agronomic factors that facilitate completion of critical crop developmental phases, such as flowering, while doing so rapidly and uniformly, as a consequence of early sowing and increased seeding rates. These strategies and the adoption of practices involving proper fungicide selection, and optimal application timings and methods will lead to improved yield stability and quality in high-risk environments. This paper explores the potential synergies that exist for FHB mitigation when appropriate genetics are combined with an array of key agronomic strategies. [ABSTRACT FROM AUTHOR]

Stem rust, caused byPuccinia graminis, is a devastating disease attacking barley, oat, and wheat crops globally. The most common control method for stem rust is the use of resistant cultivars. Typically, the identity of deployed resistance genes in a region is known and concomitantly the races they are effective against are also known. Thus, it is critical to identify the virulence dynamics in the pathogen populations to detect new races with virulence to deployed genes. Surveys were performed in 2011 and 2012 in Saskatchewan, Manitoba, Ontario, and Quebec to determine the incidence and severity of stem rust in barley (Hordeum vulgare), oat (Avena sativa), and wheat (Triticum aestivum) fields and to collect infected stem samples to identify the virulence structure in the pathogen populations. Stem rust infection was at trace levels in barley and oat fields and absent in cultivated wheat in 2011 and 2012. Race QFCSC ofP. graminisf. sp.triticiwas dominant in 2011 and 2012 (95.6% and 82.8% of all samples, respectively). Races QCCJB, QFCJC, and RKQSC were at low (<3%) levels in 2011. In 2012, race RKQSF was at 6.9%, RKQSC at 3.5%, and all others (QFCJC, RTHJF, TMRTF, and TPMKC) at 1.7%. We identified 11 races ofP. graminisf. sp.avenaein 2011, with TGN (43.7%), TJS (19.3%), TGD (16.0%), TJJ (7.6%), and TGB (7.6%) being the most frequent. In 2012, 15 races were found and TJS (48.3%), TGN (24.3%), and TJJ (13.9%) were the most frequent. Race TJS is a major threat to oat production as it is virulent on all Canadian oat cultivars. Two new races ofP. graminisf. sp.avenae(TNB from Quebec, TQN from Saskatchewan) were detected in 2012, but are avirulent to genePg13and do not threaten oat production in Canada. La rouille noire, causée parPuccinia graminis, est une maladie dévastatrice qui s’attaque à l’orge, à l’avoine et au blé, et ce, à l’échelle mondiale. La façon la plus courante de lutter contre la rouille noire est d’utiliser des cultivars qui lui sont résistants. En règle générale, l’identité des gènes de résistance déployés dans une région est connue et, concomitamment, les races contre lesquelles ils sont efficaces sont également connues. Ainsi, il est essentiel de caractériser la dynamique de virulence dans les populations d’agents pathogènes afin de détecter de nouvelles races virulentes à l’égard des gènes déjà déployés. En 2011 et 2012, des études ont été menées en Saskatchewan, au Manitoba, en Ontario et au Québec pour déterminer l’incidence et la gravité de la rouille noire dans les champs d’orge (Hordeum vulgare), d’avoine (Avena sativa) ainsi que de blé (Triticum aestivum) et pour collecter des échantillons de tiges infectées et ainsi définir la structure de virulence dans les populations d’agents pathogènes. En 2011 et 2012, il n’y avait que des traces d’infection témoignant de la rouille noire dans les champs d’orge et d’avoine et il n’y en avait aucune dans les champs de blé. En 2011 et 2012, la race QFCSC deP. graminisf. sp.triticidominait (95.6 % et 82.8 % de tous les échantillons, respectivement). En 2011, les races QCCJB, QFCJC, et RKQSC affichaient un faible taux (< 3 %). En 2012, la race RKQSF affichait un taux de 6.9 %, la race RKQSC, 3.5 % et toutes les autres (QFCJC, RTHJF, TMRTF, et TPMKC), 1.7 %. En 2011, nous avons identifié 11 races deP. graminisf. sp.avenae, TGN (43.7 %), TJS (19.3 %), TGD (16.0 %), TJJ (7.6 %), et TGB (7.6 %) étant les plus courantes. En 2012, nous avons trouvé 15 races et, parmi celles-ci, TJS (48.3 %), TGN (24.3 %), et TJJ (13. 9 %) étaient les plus courantes. La race TJS représente une sérieuse menace pour la production d’avoine, puisqu’elle est virulente à l’égard de tous les cultivars d’avoine canadienne. En 2012, deux nouvelles races deP. graminisf. sp.avenae(TNB au Québec et TQN en Saskatchewan) ont été détectées, mais elles ne sont pas virulentes à l’égard du gène Pg13et ne menacent donc pas la production d’avoine au Canada [ABSTRACT FROM AUTHOR]

Tan spot, caused by Pyrenophora tritici-repentis (Ptr), is one of the most destructive leaf spot diseases of wheat in Canada. Several races of the fungus are known to occur. Wheat growers have adopted fungicides to manage tan spot; however, intensive spraying may lead to development of reduced sensitivity to fungicides in the pathogen. In this study, 62 Ptr isolates were collected from across Saskatchewan and Alberta and characterized to race on a wheat differential set, with confirmation of race designations by polymerase chain reaction. This same set of isolates, and 27 isolates from an earlier study, were also evaluated for sensitivity to propiconazole and pyraclostrobin fungicides by determining the effective concentration of each needed to inhibit radial growth and conidiospore germination by 50%. Races 1 and 2 were predominant in western Canada, with 57% of isolates classified as race 1 and 40% as race 2. In Alberta, race 1 was most common (76%), while in Saskatchewan, it was race 2 (57%). Two of 26 isolates were classified as race 3, which was detected only in Saskatchewan in 2013. There was no evidence of reduced sensitivity of either fungicide in the Ptr isolates examined. This study provides a baseline for Ptr sensitivity to propiconazole and pyraclostrobin to which future collections of the pathogen may be compared. [ABSTRACT FROM AUTHOR]