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Wheat 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]

Stem 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 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 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]

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]

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]

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]

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]

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) 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]

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]

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]

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]

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]

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]

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]

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]

Goss’s bacterial wilt and leaf blight, caused by Clavibacter nebraskensis (syn. C. michiganensis subsp. nebraskensis), is a serious disease of corn. It is not new to North America, but in 2006, the number of outbreaks increased and the pathogen was reported in areas of the USA and Canada where it had not previously been found. The disease is increasing in distribution and severity and new areas such as the northern Prairies may be at higher risk as corn production acreage rises. Therefore, Goss’s wilt monitoring and subsequent management should be priorities in areas where the disease has appeared relatively recently, such as the Canadian Prairie provinces. This update summarizes the current status of Goss’s bacterial wilt and leaf blight in Canada including its geographic distribution as determined through recent monitoring activities and new detection methods. It also discusses current knowledge regarding pathogen biology, disease development, epidemiology and management. [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]

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most devastating diseases of wheat globally. Since 2000, the geographic footprint of Pst has increased in North America due to a combination of changing weather patterns and introductions of new and more virulent strains. Pst is endemic throughout North America, but the emergence of new virulent strains poses an increased risk to wheat cultivation. As climate changes, so will the overwintering and over-summering range of this pathogen, resulting in earlier and more severe disease epidemics in the central and eastern USA and Canada. This perspective aims to highlight the changes taking place in Pst ecology and epidemiology over the last decade in North America, and then presents recommendations for future research to prepare for the changing dynamics of stripe rust. Specifically, to manage stripe rust in the future, molecular surveillance mechanisms need be established to identify and track new virulent races, and to obtain a deeper understanding of the adaptive ability of Pst. This will allow for a better explanation of how new races of Pst emerge, and encourage the development of improved epidemiological models and durable resistance strategies. [ABSTRACT FROM AUTHOR]

Ergot of cereals, caused byClaviceps purpurea, results in yield loss and downgrading of infested grain because of toxic alkaloids in the sclerotia. Resistant wheat genotypes are known, but their effectiveness against differentC. purpureaisolates over geographic regions has not been studied. The objective of this study was to examine the pathogenic variability among isolates ofC. purpureaon wheat lines differing in resistance. Under controlled environmental conditions, 41 single spore isolates ofC. purpureawere obtained from Canadian and UK collections and inoculated onto a set of wheat genotypes composed of durum wheat lines ‘Melita’, ‘Kyle’ and 9260B-173A, and hexaploid spring wheat lines ‘Cadillac’, ‘Vista’, ‘Kenya Farmer’, ‘Lee’ and HY630. Honeydew production and weight of sclerotia produced per spike were assessed. There were significant differences among the wheat genotypes for overall reactions to the pathogen isolates, and among pathogen isolates for geographic origin and host origin. Twenty virulence phenotypes were identified using the honeydew production data, and 23 virulence phenotypes identified using the sclerotial weight data from the 41 isolates. The existence of different virulence phenotypes indicates that variability in virulence exists in populations ofC. purpurea, and knowledge of virulence phenotypes is necessary to effectively breed for resistant commercial lines. [ABSTRACT FROM PUBLISHER]

Stripe rust of wheat (Triticumspp. L.) is an emerging problem in western Canada. The causal pathogen (Puccinia striiformisf. sp.triticiEriks.) has the potential to overwinter, which is a concern because of green bridging leading to earlier establishment of rust epidemics. Resistance conferred by seedling/all-stage and adult plant genes is the most effective approach to manage this disease. However, many Canadian wheat varieties lack seedling or all-stage resistance. The effectiveness ofYrgenes under field conditions was assessed by exposing differentials/varieties carryingYrgenes to natural inoculum in multiple environments. The differentials were planted at multiple Saskatchewan locations in 2013, 2014 and 2016 and significant stripe rust was detected at 12 site-years. Additionally, 33 winter wheat varieties and advanced breeding lines were assessed for stripe rust reaction in 2016 at Swift Current, Saskatchewan. Disease severity was assessed on flag and penultimate leaves between early milk to soft dough growth stages. The genesYr5,Yr15, YrSPand those in ‘Yamhill’ are effective in Saskatchewan under field conditions. Genes/differentials were classified into two major groups based on cluster analysis, one with defeated genes and the other with partial resistant genes. GenesYrA,Yr6, Yr7,Yr8, Yr9,Yr27, Yr29,Yr31, Yr32andYrSuwere not effective in the field to SK races. At Swift Current, winter wheat varieties/lines carryingYr17were resistant in the field, whereas those carryingYr10were not. [ABSTRACT FROM PUBLISHER]

Pyrenophora tritici-repentis(Ptr), the cause of tan spot of wheat, is a foliar pathogen of economic importance worldwide. Tan spot development is associated with the production of necrotrophic effectors (Ptr ToxA, Ptr ToxB and Ptr ToxC) that serve as fungal pathogenicity and/or virulence factors. The objective of this study was to investigate the sensitivity to each of these effectors in a collection of 100 Canadian wheat cultivars representing all wheat classes and developed over a century by various Canadian breeding programmes. Heterologously expressed, His-tagged Ptr ToxA and Ptr ToxB, and spore germination fluids possessing putative Ptr ToxC activity, were produced and used to screen the cultivars for sensitivity. Of the 100 wheat cultivars tested, 92 were sensitive to at least one effector, 68 were sensitive to Ptr ToxA, 63 were sensitive to Ptr ToxC and 24 were sensitive to Ptr ToxB. Only eight cultivars were insensitive to all three effectors. These results reflect the widespread sensitivity in Canadian wheat cultivars to these necrotrophic effectors, with sensitivity to Ptr ToxA and the putative Ptr ToxC found consistently to be more common than Ptr ToxB sensitivity. The predominance of Ptr ToxA and Ptr ToxC sensitivity in Canadian wheat is consistent with the prevalence of races 1 (Ptr ToxA + Ptr ToxC producer) and 2 (Ptr ToxA producer) of Ptr in North America, and could reflect a competitive advantage for Ptr ToxA-producing isolates in the pathogen population. [ABSTRACT FROM PUBLISHER]

Puccinia triticina Eriks., the causal agent of wheat leaf rust, was collected across Canada in 2010 to determine the virulence spectrum present in the pathogen population. From 314 infected leaf collections, 399 single pustule isolates were recovered, including 341 from Manitoba and Saskatchewan, 38 from Ontario, nine from Quebec and 11 from Prince Edward Island (PEI). When analysed for virulence on 16 standard differential lines, 41 different virulence phenotypes were identified. The most common were MLDS (26.1%), TDBJ (22.8%) and TDBG (11.8%). In Manitoba and Saskatchewan, the most common phenotypes were MLDS (29.6%), TDBJ (25.5%) and TDBG (13.8%), which were also abundant in 2009. In Ontario, the most common were MBTN (23.7%), TDBJ (10.5%), MCGJ, MCTN and MLDS (each at 7.9%), whereas in Quebec, each of the nine isolates analysed had a different phenotype. In PEI, the more commonly isolated phenotypes were MBNQ (six isolates), MBTN and MHNQ (two isolates each). Each population had unique virulence phenotypes, and the eastern populations were more diverse than the Manitoba and Saskatchewan population. Virulence trends from previous years continued in 2010, with increasing levels of virulence found for Lr9 and Lr17 while decreasing virulence was found for Lr2a, Lr14a and Lr24. There was no virulence found in 2010 for Lr19, Lr21, Lr22a, Lr29, Lr32 or Lr52. [ABSTRACT FROM AUTHOR]

This study reports further characterization of the defence mechanism of an EMS-induced mutant (MNR220) that displays enhanced resistance to leaf rust, stem rust, stripe rust and powdery mildew diseases. The broad-spectrum resistance of the mutant was characterized by a microscopy study and additional race screenings of two rust pathogens. The mutant displayed less disease severity in response to all the races tested, when compared with the wild-type. The microscopy study of the pathogenesis of a leaf rust race PBJJG on the mutant revealed that the resistance was first evident at the pre-haustorial stage; formation of haustoria was significantly delayed or inhibited in the mutant compared with the wild-type. The mutant displayed microscopic level of cell death even in the absence of any pathogens. These findings suggest that MNR220 mediates a spontaneous cell death that delays the infection process by delaying haustoria formation of the pathogen. [ABSTRACT FROM PUBLISHER]

Stem rust, caused by Puccinia graminis, is an important disease on wheat, oat, and barley crops worldwide. Because the disease is primarily controlled in Canada using resistant cultivars, determining the virulence structure in pathogen populations is necessary for the early detection of novel virulent races. Surveys of wheat (Triticum aestivum), oat (Avena sativa), and barley (Hordeum vulgare) fields and trap nurseries were conducted in 2009 and 2010 across Canada to provide information on incidence and severity of stem rust infection, and to identify the virulence structure in the pathogen populations. Stem rust was not found on cultivated wheat, and was at trace levels in oat and barley fields in both years. Race QFCSC of P. graminis f. sp. tritici was dominant in 2009 (88.0% of all samples), and was the only race detected in Canada in 2010. Races MCCFC, RFCSC, and TPMKC were found at low levels (<5%) in 2009. Thirteen races of P. graminis f. sp. avenae were found in 2009, with TGD (30.4%), TJN (16.2%), TGN (14.9%), TJJ (11.2%), TJS (9.9%), and TGB (8.6%) the most frequent. Twelve races of P. graminis f. sp. avenae were found in 2010, and TGN (27.3%), TGB (19.8%), TGD and TJN (14.0% each), and TJS (9.9%) were the most frequent. Race TJJ, which is virulent on all Canadian oat cultivars and was first detected in 1998, fell to only 5.2% frequency (total samples) in 2010. One new race (TJL) was detected in three samples from Manitoba in 2009, but is avirulent to gene Pg13 and does not pose a threat to oat production in Canada. [ABSTRACT FROM AUTHOR]

Stem rust, caused byPuccinia graminis, has historically been the most important disease of cereal crops worldwide. It is primarily controlled using resistant cultivars in Canada, although prophylactic use of fungicides is increasing. Determining the virulence structure in pathogen populations is essential to detect new virulent races that may arise. Surveys of barley (Hordeum vulgare), oat (Avena sativa), and wheat (Triticum aestivum) fields and trap nurseries were conducted to provide incidence and severity information and to identify the virulence structure in the pathogen populations. Stem rust samples were collected across Canada in 2007 and 2008. Stem rust was absent on cultivated wheat, and at trace levels in barley and oat fields. Race QFCSC ofP. graminisf. sp.triticiwas dominant in 2007 (95.9%) and 2008 (98.2%) and was the only race present in Quebec, Ontario, Saskatchewan, and Alberta, while races RKQQC, RKQSC, TMRTF, and TPMKC were found at trace levels in Manitoba. Eleven races ofP. graminisf. sp.avenaewere found in 2007, and races TGD (31.7%), TJJ (17.4%), TJS (16.7%), and TGB (13.7%) were dominant. Race TJN, which was first detected in 2006, rose to 8.5% of the population in 2007. Ten races ofP. graminisf. sp.avenaewere found in 2008 and races TGD (49.7%) and TJJ (21.1%) were dominant. Race TGN, which was first detected in 2006, rose to 10.9% of the population in 2008. No new races ofP. graminisf. sp.triticiorP. graminisf. sp.avenaewere detected in Canada in 2007 or 2008. [ABSTRACT FROM AUTHOR]

Root-lesion nematodes (Pratylenchusspp.) are important pests of potato (Solanum tuberosumL.), particularly in sandy soils and in the presence ofVerticillium dahliae. We assessed the effects of crop rotation and soil management practices (reduced tillage, cover crops and composted manure applications) on population densities ofP. neglectuson potato in a sandy loam soil in southern Alberta. Crops in rotation included potato (P), dry bean (DB,Phaseolus vulgarisL.), wheat (W,Triticum aestivumL.), sugar beet (SB,Beta vulgarisL.), oats (O,Avena sativaL.) and timothy (T,Phleum pratenseL.). The rotations included ‘conventional’ and ‘conservation’ versions of 3-year (DB-W-P) and 4-year (W-SB-DB-P) rotations, as well as 5-year (W-SB-W-DB-P) and 6-year (O/T-T-T-SB-DB-P) rotations. Conservation practices included autumn cover crops and incorporation of compost as a substitute for inorganic fertilizer. Population densities ofP. neglectusin the potato phase of each rotation were assessed in autumn of 2006 and 2007, and at the beginning, middle and end of 2008, 2009 and 2010 growing seasons.Pratylenchusneglectuspopulations were affected by rotation length but not soil management practices; population densities in the 3-year rotations were larger than in most other rotations at most sample dates. Potato yields in the 3-year conventional rotation were consistently lower than in longer rotations. In the 3-year rotation, potato was preceded by wheat, which is known to be a good host forP. neglectus. We speculate that greater population build-up on wheat in the year before potato, rather than rotation length or crop diversityper se, was the cause of the larger population densities in the 3-year rotations than in longer rotations. [ABSTRACT FROM AUTHOR]

Ergot, caused by the ascomycete fungusClaviceps purpurea(Fr.) Tul., has been described to occur since the Middle Ages, but more recently has become a significant issue on the Canadian prairies. In 1999, there was an outbreak of ergot where 12% of all Canadian Western Red Spring (CWRS) and 4% of Canadian Western Amber Durum (CWAD) wheat samples delivered to elevators were infested with ergot sclerotia. A similar outbreak occurred in Manitoba in 2005, followed by outbreaks in 2008 and 2011 in all three Prairie provinces. In 2008, 12–15% of all CWRS samples were infested with ergot, while in 2011, these levels rose to 15–29% of all CWRS samples. In CWAD wheat, 15% of samples were infested in Saskatchewan in 2008 and 14% in 2011. Management practices that may influence ergot severity include crop rotation, management and nutrition, seeding practices, pesticide applications, nature of the crop (i.e. autumn vs. spring crop and self-pollinated vs. cross-pollinated host species), and harvest and postharvest management. Recently, research has been conducted on host resistance and avoidance of infection, although problems in assessing host resistance and variability among pathogen strains have been encountered. Unfortunately, none of these control measures has been found to be entirely successful in controlling ergot on their own. As a consequence, producers should always approach ergot management as an integrated process with strategies that target all components of the disease triangle. Although ergot outbreaks can be sporadic in nature, sustained research funding is necessary to support research that leads to the development of more effective strategies for ergot management. [ABSTRACT FROM PUBLISHER]

Fusarium head blight (FHB) of wheat, caused principally byFusarium graminearumin Canada, results in accumulation of mycotoxins in the grain. The fungus produces deoxynivalenol (DON) and its acetylated forms 3-ADON or 15-ADON. Increasing numbers ofF. graminearumisolates collected in Manitoba between 1998 and 2004 were of the 3-ADON chemotype, whereas prior to 1998, the 15-ADON chemotype was considered the only significant cause of FHB in North America. Between 2008 and 2012, a series of studies were conducted at Carman (2008, 2009) and Glenlea, Manitoba (2008–2012) to monitor the ratio of 3-ADON to 15-ADON chemotypes recovered after wheat plots were artificially inoculated, usually in a 1:1 ratio of 3-ADON:15-ADON isolates ofF. graminearum. Additional studies were conducted under controlled conditions. In 2008, the majority of isolates recovered from both Carman and Glenlea were of the 3-ADON chemotype. In subsequent years, however, the ratio was closer to 1:1 or sometimes with a slight predominance of 15-ADON isolates. Under controlled conditions, recovery of 15-ADON isolates predominated at lower incubation temperatures (18–22°C) whereas at 28°C, 3-ADON isolates were more prevalent. At moderate temperature (24°C), results were mixed – seven samples had a 1:1 ratio, three had higher recovery of 3-ADON isolates, and two had higher recovery of 15-ADON. However, an examination of weather variables over the 5-year period of the field studies showed no correlation between recovery of chemotype and temperature or precipitation. [ABSTRACT FROM AUTHOR]

Artificial inoculation is required for most studies of cereal rust diseases. The techniques used to inoculatePuccinia triticinaEriks., the causal agent of wheat leaf rust, have been successfully employed for decades without many alterations. Field experiments are often exposed to natural as well as artificial infection. Greenhouse experiments are usually limited by space, particularly if inoculations are conducted on adult plants. Multiple genes present in a cultivar can be differentiated by inoculating the cultivar with different races. This is usually done by inoculating one set of plants with one race and a second set with a second race. A technique was developed to inoculate two or moreP. triticinaraces on a single plant, which saved time, growing space and effort. The difference between rust inoculations with a single race and the double-inoculation technique is that the plants are subjected to two cycles of inoculation. Tillers were divided and covered with vinyl cylinders to protect them from the inoculum spray when they were not being inoculated. The double-inoculation technique allowed perfect differentiation between resistant and susceptible rust reactions on a single plant. This technique is a good method to study adult plant resistance. [ABSTRACT FROM AUTHOR]

The multicomponent NADPH oxidase enzyme complex (Nox) converts molecular oxygen in a stepwise reduction to superoxides leading to the production of H2O2. This study characterized the role of the catalytic subunit (gp91phox) of Nox, NoxA and NoxB inF. graminearum. Targeted deletion of the genesNoxAandNoxBshow that they differentially regulate the production of superoxides during mycelial development. The nitro blue tetrazolium staining method revealed that both the singlenoxAmutant and the doublenoxA/Bmutant strains are restricted in the production of superoxides. This limitation, however, did not affect their ability to synthesize 15-ADON in culture. Deletion analyses also revealed thatNoxA, but notNoxB, is involved in perithecia development and ascospore production. Anin-vitrobased cellophane breach assay indicated that bothNoxAandNoxBcontribute to virulence. The pathogenicity tests performed on a susceptible variety of wheat, ‘Roblin’, confirmed that these two genes act synergistically to promote virulence. Cumulatively, we provide evidence that the Nox homologues have non-redundant functions inF. graminearum. [ABSTRACT FROM AUTHOR]

Common bunt, caused byTilletia tritici(Bjerk.) G. Wint. in Rabenh. andT. laevisKϋhn in Rabenh., is an economically important disease of wheat (Triticum aestivumL.) worldwide. The hexaploid wheat cultivar ‘McKenzie’ possesses effective resistance against known races of common bunt in western Canada. Understanding the nature of this resistance through DNA marker mapping will be useful for breeding. Disease reaction toT. triticirace T19 andT. laevisrace L16 from field tests was analysed with simple sequence repeat markers for 174 doubled haploid lines using interval mapping. MarkersXgwm573andXwmc17, located on wheat chromosome 7B, were strongly associated with the resistance. The quantitative trait locus was designatedQCbt.spa-7B.1. The markers were validated on two other populations in which ‘McKenzie’ was in the parentage. The markers will be useful in breeding as a tool for selecting for common bunt resistance from ‘McKenzie’ and will assist in identifying the resistance among potential new sources. [ABSTRACT FROM AUTHOR]

This article reviews the recent progress of research on fusarium head blight (FHB) of wheat. It addresses the broad areas of strategies for disease management, biological control, the pathogen (Fusarium graminearum(teleomorphGibberella zeae)), mycotoxins, the effects of dwarfing genes on FHB severity, quantitative trait loci (QTLs) and new perspectives. Where there are recent reviews on this subject, we have deliberately examined the subsequent literature to provide an update on research. With few resistant cultivars available even now, the main tools to manage the disease remain rotation, varietal selection, disease forecasting and fungicides. A few biocontrol organisms are being considered for commercial application. The pathogen's sexual life cycle has been investigated in depth, and with its complete genome sequence known, the pathways and genes controlling the sexual development and ascospore release ofF. graminearumare being explored. The 3-acetyldeoxynivalenol chemotype ofF. graminearumhas increased in prevalence in Canada with attendant risks of higher DON levels in cereal grain. Stringent limits on allowable levels ofFusariummycotoxins in the food/feed chain have been enacted in Europe and the USA, but regulations for Canada are only at the discussion stage with the Canadian Food Inspection Agency. Efforts to develop FHB-resistant lines proceed apace, as these can be selected in most wheat populations despite the adverse effects of dwarfing genes on FHB severity. While more quantitative trait loci (QTLs) for disease resistance continue to be identified and mapped, new resistant cultivars remain disappointingly few. We present some encouraging early results from an alternative approach based on epigenetics. [ABSTRACT FROM AUTHOR]

One hundred and four isolates ofPuccinia striiformiswere obtained primarily from central Alberta during 2009–2011 from wheat, barley, foxtail barley and triticale. Isolates were identified asP. striiformisf. sp.tritici(Pst) orP. striiformisf. sp. hordei(Psh) based on virulence on differential seedlings. Twenty-five wheat differentials separated 67Pstisolates into 12 pathotypes, with a single pathotype representing 48% ofPstisolates. Wheat differentials with resistance genesYr5andYr15were resistant to all 12 pathotypes, while wheat lines with genesYr1,Yr10,Yr24,Yr28,YrTyeeandYrSPwere resistant to 80–98% of the isolates. The remainder of the wheat differentials were susceptible to allPstisolates. Within the 37Pshisolates, 12 pathotypes were detected based on 12 barley differentials, half of which were previously unreported in Alberta. The two most commonPshpathotypes combined accounted for 46% of the isolates. One half of thePshisolates may be the result of hybridization between the two formae speciales since they exhibited virulence on a large number of wheat and triticale lines in addition to barley lines.Pshisolates with these virulence factors were more frequently recovered from six-row than two-row barley. For both formae speciales, there was no apparent association between pathotype and location, with pathotypes being widespread and recovered from multiple locations. [ABSTRACT FROM AUTHOR]

Fusarium head blight (FHB) continues to threaten the economic sustainability of many small grain producers in Manitoba by causing losses in grain yield and quality. In this 2-year study, four fungicides were tested on two spring wheat cultivars with different levels of resistance to FHB inoculated with 3ADON and 15ADON chemotypes ofFusarium graminearum. All fungicides (prothioconazole, tebuconazole, metconazole and prothioconazole+ tebuconazole) reduced FHB index, per centFusarium-damaged kernels (% FDK) and deoxynivalenol (DON) levels and increased yield compared with the non-sprayed control in the moderately resistant cultivar ‘Glenn’. In the highly susceptible cultivar ‘Roblin’, all fungicides reduced FHB index and increased yield compared with the non-sprayed control; however, inconsistent results were observed for FDK and DON. Differences were observed between the two chemotypes for all variables in both years except for FDK and yield in 2010. This study confirmed that host resistance plays an important role in host–pathogen–fungicide interaction. Therefore, the combined effect of growing moderately resistant cultivars with fungicide application can reduce damage caused by FHB even under high FHB severity. [ABSTRACT FROM AUTHOR]

Sixty-one field collections of Puccinia striiformis, primarily from central Alberta during 2007–2008, were identified to be P. striiformis f. sp. tritici (Pst) or P. striiformis f. sp. hordei (Psh) based on virulence on differential seedlings. Wheat differentials separated 38 Pst isolates into 13 pathotypes, with most pathotypes consisting of single isolates. Two pathotypes consisted of two isolates, and three pathotypes were represented by three, seven and 16 isolates. Wheat lines with resistance genes Yr1, Yr5, Yr15 and YrSP were resistant to all 13 pathotypes, while wheat lines with genes Yr10, Yr24 and Yr28 were resistant to 82–92% of the isolates. Differentials YrA, Yr2, Yr6, Yr7, Yr8, Yr9, Yr17, Yr26, Yr27, Yr31 and YrCV were susceptible to 71–100% of the isolates. Twenty-three Psh isolates were identified to 15 Psh pathotypes, with virulence on two to eight barley differentials, including ‘Topper’, ‘Hiproly’, ‘Varunda’, ‘Abed Binder 12’, ‘Trumpf’, ‘Mazurka’, ‘Bigo’, ‘I 5’ and ‘Bancroft’ and avirulent on ‘Heils Franken’, ‘Emir’ and ‘Astrix’. Ten pathotypes consisted of a single isolate, four pathotypes had two isolates and one pathotype consisted of five isolates. The possible origin and virulence of P. striiformis pathotypes in central Alberta is discussed in relation to using cultivar resistance for disease control. [ABSTRACT FROM PUBLISHER]

Pyrenophora tritici-repentis induces tan spot, one of the most important fungal diseases of wheat. At least eight races of the pathogen are known to occur based on their virulence on a wheat differential set. In 2009 and 2010, 87 commercial wheat fields were sampled for tan spot in the Southern Cone region of South America, namely Argentina, Brazil and Uruguay. An average of three isolates from each field were tested for their virulence on the differential wheat hosts ‘Glenlea’, 6B365, 6B662, ‘Salamouni’, ‘Coulter’ and 4B1149. Of 273 isolates tested, 52.4% were classified as race 1 and 47.6% were classified as race 2, with no other races identified. This low level of pathogenic diversity was somewhat expected, since the bread wheat grown in this region has a narrow genetic diversity with respect to tan spot resistance. To fully assess virulence patterns in the Southern Cone, use of this differential set is recommended. To our knowledge, this is the first report of the race structure of P. tritici-repentis in South America. [ABSTRACT FROM PUBLISHER]

Stagonospora nodorum blotch (SNB) caused by Phaeosphaeria nodorum is an important foliar disease of wheat. Efficient breeding for SNB resistance requires detailed knowledge of the pathosystem so that targeted improvements can be made. The objective of this study was to examine the wheat–P. nodorum pathosystem for evidence of host specificity amongst Canadian isolates. To this end, 49 P. nodorum isolates were inoculated on 16 wheat lines in indoor seedling inoculation experiments. Biologically significant host × pathogen interactions were identified, indicating that host specificity exists in the Canadian isolates tested. This observation is consistent with an inverse gene-for-gene pathosystem based upon host-selective toxins. Unweighted Pair Group Method with Arithmetic Mean (UPGMA) analysis of disease reaction data suggested nine virulence clusters; however, additional sub-groupings could be argued based upon the reaction of specific wheat lines to isolates within virulence clusters. The common wheat lines 86ISMN 2137, RL5407 and W7984 had good resistance to the P. nodorum isolates in seedling tests, which will be useful for improvements in common wheat and possibly durum wheat. The development of a SNB differential set is discussed. P. nodorum isolates characterized in this study will be useful for future studies in the wheat–P. nodorum pathosystem. [ABSTRACT FROM AUTHOR]

Stem rust, caused by Puccinia graminis, is a disease of cereal crops worldwide. In Canada, it is primarily controlled using resistant cultivars. Tracking the virulence structure in the pathogen populations is essential to detect new virulent races that may occur. Surveys of barley (Hordeum vulgare), oat (Avena sativa) and wheat (Triticum aestivum) fields and trap nurseries were conducted to provide incidence and severity information and to identify the virulence structure in the pathogen populations. Stem rust samples were collected in Manitoba and Saskatchewan in 2006. Stem rust was not found on cultivated wheat and was at trace levels in barley and oat fields. From wheat and barley samples, four races of P. graminis f. sp. tritici were found and QFCSC (89%) was predominant. Thirteen races of P. graminis f. sp. avenae were found in 2006. From cultivated oat samples, the predominant races were TJJ (67%), TJS (17%), and TGD (9%). From wild oat samples, the predominant races were TJJ (40%), TGD (23%), and TGB (12%). Two new races of P. graminis f. sp. avenae (TGN and TJN) with virulence to Pg12 but avirulence to Pg13 were detected on both cultivated and wild oat both in Manitoba and Saskatchewan in 2006. [ABSTRACT FROM AUTHOR]

Stripe rust, caused by Puccinia striiformis f. sp. tritici (PST), has historically been the most frequently destructive disease of wheat (Triticum aestivum) in the western United States and has become a more frequent problem in the central and southeastern states since 2000. The race composition of PST has been determined every year from rust-infected leaf samples of wheat and grasses collected in the United States on a set of 20 differential wheat genotypes. In 2006, a total of 18 races were detected, of which five were detected for the first time. In 2007, a total of 30 races were detected, of which 11 were newly detected. Among the 16 new races detected in 2006 and 2007, PST-127 was the most important as it has the broadest virulence spectrum identified so far (virulent to all 20 differential genotypes except for 'Moro', AVS/6*Yr5 (Yr5), and 'Tres') and combined virulence factors to 'Tyee' (YrTye) and 'Hyak' (Yr17 and YrTye) and those common in the race group detected since 2000. The distribution, frequency changes, and evolutionary relationships for races detected from 2000 to 2007 were analyzed. Three major waves of race changes were identified during the eight-year period. From 2000 to 2002, the predominant races were PST-78 and PST-80, which were virulent on wheat genotypes 'Lemhi', 'Heines VII', 'Lee', 'Fielder', 'Express', AVS/6*Yr8, AVS/6*Yr9, 'Clement' and 'Compair'. Race PST-80 is also virulent on 'Produra'. From 2003 to 2006, the predominant race was PST-100, with the same virulence formula as PST-80 plus virulence on 'Yamhill' and 'Stephens'. Starting in 2006, races with the same virulence formula of PST-100 plus virulence to Yr1 became predominant in California and races with the virulence of PST-100 plus virulence on Yr10 became predominant in the Pacific Northwest. During 2000 to 2007, races with more virulence factors became more predominant in the United States, indicating that races with increased virulence factors are at an advantage in the pathogen population over those with fewer virulence factors because they are able to infect more wheat cultivars. [ABSTRACT FROM AUTHOR]

Understanding the genetic resistance to wheat leaf rust, caused by Puccinia triticina, in Canadian wheat cultivars is critical for maximizing resistance in future-bred cultivars. This knowledge also helps to predict the impact of changes in virulence to specific resistance genes within the P. triticina population. 'Superb' and 'McKenzie' are two of the most popular high-yielding wheat cultivars in Canada. 'HY644' has moderate resistance to Fusarium head blight (caused primarily by Fusarium graminearum). All three of these cultivars have been used extensively as parents in Canadian wheat breeding programmes. To analyze the nature of resistance in these cultivars, they were crossed and then backcrossed to the susceptible cultivar 'Thatcher'. The BC1F3 populations were inoculated at the seedling and adult plant stages with various P. triticina races to determine the number and identity of the resistance genes in each cultivar. Allelism tests, to confirm the postulated genes, were performed by crossing each cultivar to the 'Thatcher' isolines containing the postulated genes and analyzing the F2 progeny for rust resistance. 'Superb' was demonstrated to have genes Lr2a and Lr10, 'McKenzie' had Lr10, Lr13, Lr16 and Lr21, and 'HY644' had Lr1, Lr17, Lr34 and an unknown resistance gene. [ABSTRACT FROM AUTHOR]