Abstract

Oat harvested from plants infested with plant pathogenic fungi within the Fusarium head blight (FHB) complex may sometimes contain high levels of mycotoxins, which makes the grain unsuitable for food and feed. Fusarium graminearum, a deoxynivalenol (DON) producer, and Fusarium langsethiae, a T-2 toxin (T2) and HT-2 toxin (HT2) producer, are commonly occurring in Norwegian oats. We have analysed grains of Nordic oat varieties and breeding lines for the content of mycotoxins and DNA of Fusarium species belonging to the FHB disease complex (Hofgaard et al. 2022). The grains were harvested from field trials located in South-East Norway in the years 2011-2020. The ranking of oat varieties according to HT2+T2 levels corresponded with the ranking according to the DNA levels of F. langsethiae. However, this ranking did not resemble the ranking for DON and F. graminearum DNA. Our results implies that a moderate resistance to DON producers does not guarantee a moderate resistance to HT2+T2 producers. Separate tests are therefore necessary to determine the resistance towards DON and HT2+T2 producers in oats. This creates practical challenges for the screening of FHB resistance in oats as todays’ screening focuses on resistance to F. graminearum and DON. We identified oat varieties with generally low levels of both mycotoxins and FHB pathogens which should be promoted to mitigate mycotoxin risk in Norwegian oats.

Abstract

In Norway, high levels of mycotoxins are occasionally observed in oat grain lots, and this cause problems for growers, livestock producers and the food and feed industries. Mycotoxins of primary concern are deoxynivalenol (DON) produced by Fusarium graminearum and HT2- and T2-toxins (HT2+T2) produced by Fusarium langsethiae. Although effort has been made to understand the epidemiology of F. langsethiae in oats, this is still not fully understood. In the present study, we aimed to increase our understanding of the F. langsethiae – oat interaction. Resistance to F. langsethiae was studied in three oat varieties after inoculation at early (booting, heading, flowering) or late (flowering, milk, dough) growth stages in greenhouse experiments. The oat varieties had previously shown different levels of resistance to F. graminearum: Odal, Vinger (both moderately resistant), and Belinda (susceptible). The levels of F. langsethiae DNA and HT2+T2 in harvested grain were measured, and differences in aggressiveness (measured as the level of F. langsethiae DNA in grain) between F. langsethiae isolates were observed. Substantial levels of F. langsethiae DNA and HT2+T2 were detected in grain harvested from oats that had been spray-inoculated at heading or later growth stages, suggesting that oats are susceptible to F. langsethiae from heading and onwards. Vinger had a moderate resistance to F. langsethiae/HT2+T2, whereas Odal and Belinda were relatively susceptible. We observed that late inoculations resulted in relatively higher levels of trichothecene A metabolites other than HT2+T2 (mostly glycosylated HT-2, and smaller amounts of some other metabolites) in harvested grain, which indicate that infections close to harvest may pose a further risk to food and feed safety.

Abstract

In Norway, Fusarium diseases and associated mycotoxin contamination in spring oats occasionally cause problems for growers, livestock producers and the food and feed industries. Besides weather factors, such as rainfall and temperature in the critical periods around flowering and before harvest, inoculum production and disease development are influenced by agricultural practices. The occurrence of Fusarium graminearum and DON in oat grain lots do not generally correlate with that of Fusarium langsethiae and HT-2/T-2-toxins. Therefore, to develop a robust disease management strategy, there is a need to reveal the influence of weather and agricultural practice on disease development in oats for both these fungal species. Through various research projects NIBIO researchers have performed field trials to study the effects of straw management, tillage practice, cultivar, and chemical and biological control treatments on the development of Fusarium spp. and mycotoxins in oats. In particular we have investigated whether the amount of straw residues and tillage practice influences the survival of Fusarium spp. in residues, and the subsequent Fusarium spp. infection of the harvested grains. In addition, Fusarium spp. DNA and mycotoxin content (DON and HT-2/T-2) have been analysed in oats from current official cultivar trials. This work has been a collaboration between NIBIO and the Norwegian Agricultural Extension Service. Results will be presented on the Fusarium spp. and mycotoxin contamination of grains harvested from oats grown under various agricultural practices. High incidence of Fusarium avenaceum are often observed in harvested grains as well as straw residues. Fusarium graminearum is also commonly detected. Despite the high concentrations of F. langsethiae DNA and HT-2/T-2 toxins sometimes recorded in oat grain, only low levels of F. langsethiae have been detected in crop residues and air samples. We speculate that the life cycle of F. langsethiae differs from those of F. graminearum and F. avenaceum with regards to survival, inoculum production and dispersal.

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Abstract

Seed is a critically important basic input of agriculture, because sowing healthy seeds is essential to food production. Using high quality seed enables less use of synthetic pesticides in the field. Seedborne pathogens can reduce yield quantity and quality of the crops produced. Seed treatments protect plant seedlings from pathogen attacks at emergence and at the early growth stages, contributing to healthy crop plants and good yield. However, there is increased concern about the application of synthetic pesticides to seeds, while alternatives are becoming increasingly addressed in seedborne pathogen research. A series of strategies based on synthetic fungicides, natural compounds, biocontrol agents (BCAs), and physical means has been developed to reduce seed contamination by pathogens. The volume of research on seed treatment has increased considerably in the past decade, along with the search for green technologies to control seedborne diseases. This review focuses on recent research results dealing with protocols that are effective in the management of seedborne pathogens. Moreover, the review illustrated an innovative system for routine seed health testing and need-based cereal seed treatment implemented in Norway.

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Abstract

Purpose of Review Because tree seeds have been considered a low-risk pathway for the spread of plant pathogenic fungi, their international movement is not subject to strict phytosanitary regulation. However, recent studies have provided scientific evidence that the biosecurity risk of seed trade may not be as negligible as assumed. This review summarises current knowledge about seed trade activity across the world and seed-borne plant pathogenic fungi and highlights knowledge gaps that need to be filled to mitigate the risk of spreading tree pathogens via seeds. Recent Findings Several outbreaks of severe tree diseases in natural forests and plantations worldwide have been linked to fungal pathogens spread by seed trade. Indeed, recent studies based on modern sequencing technologies have shown that tree seeds harbour highly diverse fungal communities, including well-known pathogens and fungal taxa belonging to unknown species. While it has become clear that even apparently healthy seeds can carry potentially pathogenic fungi, the likelihood of seed-borne pathogens being introduced and becoming established, spreading and causing impact in the new environment is still unclear which challenges the assessment of the phytosanitary risk posed by seed trade. Summary Our analyses show that large amounts of tree seeds have been traded among countries and continents. Based on published literature, the risk of spreading pathogenic fungi via tree seed movement is high. However, the role of the taxonomically and functionally diverse fungal communities associated with seeds is still poorly understood. In particular, more research is needed to assess the likelihood of seed-borne fungi being transmitted to the seedlings and spreading and causing impact in the new environment.

Abstract

Over recent decades, the Norwegian cereal industry has had major practical and financial challenges associated with the occurrence of Fusarium head blight (FHB) pathogens and their associated mycotoxins in cereal grains. Deoxynivalenol (DON) is one of the most common Fusarium-mycotoxins in Norwegian oats, however T-2 toxin (T2) and HT-2 toxin (HT2) are also commonly detected. The aim of our study was to rank Nordic spring oat varieties and breeding lines by content of the most commonly occurring Fusarium mycotoxins (DON and HT2 + T2) as well as by the DNA content of their respective producers. We analyzed the content of mycotoxins and DNA of seven fungal species belonging to the FHB disease complex in grains of Nordic oat varieties and breeding lines harvested from oat field trials located in the main cereal cultivating district in South-East Norway in the years 2011–2020. Oat grains harvested from varieties with a high FHB resistance contained on average half the levels of mycotoxins compared with the most susceptible varieties, which implies that choice of variety may indeed impact on mycotoxin risk. The ranking of oat varieties according to HT2 + T2 levels corresponded with the ranking according to the DNA levels of Fusarium langsethiae, but differed from the ranking according to DON and Fusarium graminearum DNA. Separate tests are therefore necessary to determine the resistance towards HT2 + T2 and DON producers in oats. This creates practical challenges for the screening of FHB resistance in oats as today’s screening focuses on resistance to F. graminearum and DON. We identified oat varieties with generally low levels of both mycotoxins and FHB pathogens which should be preferred to mitigate mycotoxin risk in Norwegian oats.

Abstract

We used metabarcoding of ITS 1 and 2 to compare the mycobiome of Norwegian spring wheat seed lots of two commonly grown spring wheat varieties (Mirakel and Zebra) harvested in 2016 and 2017. The seed lots varied in germination and were grouped according to high and low germination (≥90% and <90% germinated seeds, respectively) determined by the ISTA germination method. In addition, the percentage of each seed lot infested by the most important wheat pathogens (Microdochium spp., Fusarium spp., and Parastagonospora nodorum) was determined using a plate-out test on PDA, and species-specific qPCR was used to quantify the amount of DNA of F. avenaceum, F. culmorum, F. graminearum, F. poae, M. majus, M. nivale, and P. nodorum. Our study indicated that the presence of Microdochium was most associated with poor germination (which is as expected), while P. nodorum; although present at relatively high levels, apparently had limited impact on germination. Among the species quantified by qPCR, M. majus was the most abundant, F. avenaceum was detected at low levels, whereas the other fusaria were barely detected. Metabarcoding data indicated a negative association between the presence of the fungal genus Neoascochyta and germination, while Pyrenophora and Alternaria species appeared positively associated with germination. Our results indicated some co-existence patterns between fungal species, including both pathogenic and non-pathogenic species, with some species combinations associated with the germination potential of wheat seed.

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Abstract

Frequent occurrences of high levels of Fusarium mycotoxins have been recorded in Norwegian oat grain. To elucidate the influence of tillage operations on the development of Fusarium and mycotoxins in oat grain, we conducted tillage trials with continuous oats at two locations in southeast Norway. We have previously presented the content of Fusarium DNA detected in straw residues and air samples from these fields. Grain harvested from ploughed plots had lower levels of Fusarium langsethiae DNA and HT-2 and T-2 toxins (HT2 + T2) compared to grain from harrowed plots. Our results indicate that the risk of F. langsethiae and HT2 + T2 contamination of oats is reduced with increasing tillage intensity. No distinct influence of tillage on the DNA concentration of Fusarium graminearum and Fusarium avenaceum in the harvested grain was observed. In contrast to F. graminearum and F. avenaceum, only limited contents of F. langsethiae DNA were observed in straw residues and air samples. Still, considerable concentrations of F. langsethiae DNA and HT2 + T2 were recorded in oat grain harvested from these fields. We speculate that the life cycle of F. langsethiae differs from those of F. graminearum and F. avenaceum with regard to survival, inoculum production and dispersal.

Abstract

Fusarium graminearum is regarded as the main deoxynivalenol (DON) producer in Norwegian oats, and high levels of DON are occasionally recorded in oat grains. Weather conditions in the period around flowering are reported to have a high impact on the development of Fusarium head blight (FHB) and DON in cereal grains. Thus, it would be advantageous if the risk of DON contamination of oat grains could be predicted based on weather data. We conducted a functional data analysis of weather-based time series data linked to DON content in order to identify weather patterns associated with increased DON levels. Since flowering date was not recorded in our dataset, a mathematical model was developed to predict phenological growth stages in Norwegian spring oats. Through functional data analysis, weather patterns associated with DON content in the harvested grain were revealed mainly from about three weeks pre-flowering onwards. Oat fields with elevated DON levels generally had warmer weather around sowing, and lower temperatures and higher relative humidity or rain prior to flowering onwards, compared to fields with low DON levels. Our results are in line with results from similar studies presented for FHB epidemics in wheat. Functional data analysis was found to be a useful tool to reveal weather patterns of importance for DON development in oats.

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Abstract

Plant diseases may survive and be spread by infected seeds. In this study we monitored the longevity of 14 seed-borne pathogens in 9 crop species commonly grown in the Nordic countries, in addition to a sample of sclerotia of Sclerotinia sclerotiorum. The data from the first 30 years of a 100-year seed storage experiment located in a natural −3.5 °C environment (permafrost) in Svalbard, Norway, are presented. To date, the pathogens, tested by traditional seed health testing methods (freezing blotter, agar plates, growing on tests), have survived. Linear regression analyses showed that the seed infection percentages of Drechslera dictyoides in meadow fescue, Drechslera phlei in timothy, and Septoria nodorum in wheat were significantly reduced compared to the percentages at the start of the experiment (from 63% to 34%, from 70% to 65%, and from 15% to 1%, respectively), and that Phoma betae in beet had increased significantly (from 43% to 56%). No trends in the infection percentage were observed over the years in Drechslera spp. in barley (fluctuating between 30% and 64%) or in Alternaria brassicicola in cabbage (fluctuating between 82% and 99%), nor in pathogens with low seed infection percentages at the start of the experiment. A major part of the stored sclerotia was viable after 30 years. To avoid the spread of seed-borne diseases, it is recommended that gene banks implement routines that avoid the use of infected seeds.

Abstract

Leaf blotch diseases (LBD), such as Septoria nodorum bloch (Parastagnospora nodorum), Septoria tritici blotch (Zymoseptoria tritici) and Tan spot (Pyrenophora tritici-repentis) can cause severe yield losses (up to 50%) in Norwegian spring wheat (Triticum aestivum) and are mainly controlled by fungicide applications. A forecasting model to predict disease risk can be an important tool to optimize disease control. The association between specific weather variables and the development of LBD differs between wheat growth stages. In this study, a mathematical model to estimate phenological development of spring wheat was derived based on sowing date, air temperature and photoperiod. Weather factors associated with LBD severity were then identified for selected phenological growth stages by a correlation study of LBD severity data (17 years). Although information regarding host resistance and previous crop were added to the identified weather factors, two purely weather-based risk prediction models (CART, classification and regression tree algorithm) and one black box model (KNN, based on K nearest neighbor algorithm) were most accurate to predict moderate to high LBD severity (>5% infection). The predictive accuracy of these models (76–83%) was compared to that of two existing models used in Norway and Denmark (60 and 61% accuracy, respectively). The newly developed models performed better than the existing models, but still had the tendency to overestimate disease risk. Specificity of the new models varied between 49 and 74% compared to 40 and 37% for the existing models. These new models are promising decision tools to improve integrated LBD management of spring wheat in Norway.

Abstract

Occasionally, high mycotoxin levels are observed in Norwegian oat grain lots. The development of oat varieties with improved resistance to Fusarium and mycotoxins is therefore highly valued in order to increase the share of high quality grain into the food and feed industry. The Norwegian project “SafeOats” (2016-2020) aimed to develop resistance-screening methods to facilitate the phase-out of Fusarium-susceptible oat germplasm, as well as to give new insight into the biology of Fusarium langsethiae and HT2+T2 accumulation in oats. In naturally infested as well as in inoculated field trials, the relative ranking of oat varieties according to Fusarium graminearum/DON content did not resemble the ranking according to F. langsethiae/HT2+T2 content. One variety regarded as moderate resistant to Fusarium according to studies of DON content, was susceptible to F. langsethiae and thus at high risk for HT2+T2 contamination. Screening of resistance to F. langsethiae/HT2-T2 should therefore be routinely applied in breeding programs in addition to the already established screening of resistance to F. graminearum/DON. The incidence of F. langsethiae in a selection of oat seed lots used for commercial sowing showed a similar ranking of varieties as in the field trials. On average, the fungus was observed on 5% of the kernels in 168 seed lots tested during 2016-2018. No indication of transmission of F. langsethiae from germinating seed to seedling was found in a study with germination of naturally infected seeds. We investigated whether removing of small kernels by size sorting could be a method to reduce the content of mycotoxins in oat grain. For several of the mycotoxins including HT2+T2, the concentrations were considerably higher in the small kernel fraction compared to unsorted grain. Our results demonstrate that the level of mycotoxins in unprocessed oat grain can be reduced by removing small kernels. The results from SafeOats will benefit consumers nationally and internationally by providing tools to increase the share of high quality grain into the food and feed industry. The project was financed by The Agriculture and Food Industry Research Funds /Research Council of Norway with support from the industry partners Graminor, Lantmännen, Felleskjøpet Agri, Felleskjøpet Rogaland & Agder, Fiskå Mølle Moss, Norgesmøllene, Strand Unikorn/Norgesfôr and Kimen Seed Laboratory.

Abstract

To mitigate the risk of erosion and nutrient runoff, reduced tillage has become more prevalent in Norway. Within within recent decades, there have been some years with relatively high occurrence of Fusarium head blight and mycotoxins in Norwegian cereal grain. This is thought to have been caused by an increased inoculum potential (IP) of Fusarium spp. due to larger amount of crop residues remaining on the soil surface, in combination with weather conditions promoting fungal growth and infection of cereal plants. The objective of this work was to elucidate the influence of different tillage practices on the IP of Fusarium spp. and the subsequent Fusarium-infection and mycotoxin contamination of spring wheat grain at harvest. Tillage trials were conducted at two locations in southeast Norway (Solør and Toten) over three years, 2010-2012. Residues of wheat from the previous year were collected in spring. Fusarium avenaceum and Fusarium graminearum were the most common Fusarium species recorded on wheat straw residues. IP was calculated as the percentage of the residues infested with Fusarium spp. multiplied by the proportion of the soil surface covered with residues. The IP of Fusarium spp. was lower in ploughed plots compared to those tilled with harrowing only. Ploughing in spring resulted in a similarly low IP as autumn ploughing. In contrast, harrowing in autumn generally reduced IP more than did spring harrowing. The mycotoxin levels in the harvested wheat were generally low, except for deoxynivalenol at high levels in Solør 2011. Despite a lower IP of ploughed versus harrowed plots, this was not reflected in the content of Fusarium and mycotoxins in harvested grain. The Fusarium species that dominated in the residues examined in this study were the same as those detected in the harvested grain, supporting the finding that residues are an important source of inoculum.

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Abstract

There is a need both in organic farming and on farms using integrated pest management for non-chemical measures that control the perennial weed flora. The effect of mechanical weeding and fertilisation on perennial weeds, fungal diseases and soil structure were evaluated in two different experiments in spring cereals. Experiment I included six strategies. The first strategy was (1) without specific measures against perennial weeds. The other strategies encompassed one or two seasonal control measures; (2) rhizome/root cutting with minimal soil disturbance in autumn, (3) hoeing with 24 cm row spacing, (4) combined hoeing and disc harrowing in autumn, (5) ‘KvikUp’ harrowing in spring, and (6) ‘KvikUp’ harrowing in spring and autumn. Experiment II included factor (i) inter-row hoeing and (ii) fertilisation level. This experiment included the comparison between normal row spacing (12 cm) with weed harrowing versus double row spacing (=24 cm) in combination with inter-row hoeing and 4 fertilisation levels (50–200 kg N ha−1). In experiment I the strategies consisting of no or one direct weed control measure (1, 2, 3 and 5) clearly did not control the perennial weeds. The two seasonal control measures (4 and 6) gave a satisfactory weed control and highest crop yield. The combination of best weed control and no measured harmful effects on soil structure or increase of fungal diseases may explain the highest yields for these strategies. In Experiment II, hoeing and 24 cm spacing gave less perennial biomass compared to 12 cm spacing. Grain yields increased linearly with increasing nitrogen input. The study shows that both inter-row hoeing and weed harrows, are important elements in integrated pest management practice and organic farming. In addition, our results indicate that efficient mechanical weeding is possible without harmful effects in crop rotation consisting of various spring cereals as regards soil structure and plant health.

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Abstract

Seedling blight caused by Sirococcus conigenus was recently reported on Norway spruce (Picea abies) from Norwegian forest nurseries. The inoculum source was found to be infected seeds. In a Petri dish assay, the fungicide fludioxonil + difenoconazole was, among other fungicides, found to inhibit mycelial growth of S. conigenus. This fungicide is formulated as a seed treatment and registered for cereals in Norway, and was chosen for an experiment to control S. conigenus on Norway spruce seeds. Samples from two naturally infected seed lots were treated with half, normal and double dose of the recommended rate for cereals. Together with untreated control samples, treated seeds were tested in the laboratory for efficacy against S. conigenus on potato dextrose agar (PDA) in Petri dishes and for germination potential on filter paper. We also recorded seed emergence in soil of one of the seed lots in a growth chamber and in a forest nursery. On agar, the fungus was not detected after seed treatment with fludioxonil + difenoconazole at any of the three dosages, but it was present in the control. Germination on filter paper and emergence in soil was high in both treated and untreated control seeds with no signs of detrimental effects from any of the three fungicide doses.

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Abstract

The bread-making quality of wheat depends on the viscoelastic properties of the dough in which gluten proteins play an important role. The quality of gluten proteins is influenced by the genetics of the different wheat varieties and environmental factors. Occasionally, a near complete loss of gluten strength, measured as the maximum resistance towards stretching (Rmax), is observed in grain lots of Norwegian wheat. It is hypothesized that the loss of gluten quality is caused by degradation of gluten proteins by fungal proteases. To identify fungi associated with loss of gluten strength, samples from a selection of wheat grain lots with weak gluten (n = 10, Rmax < 0.3 N) and strong gluten (n = 10, Rmax ≥ 0.6 N) was analyzed for the abundance of fungal operational taxonomic units (OTUs) using DNA metabarcoding of the nuclear ribosomal Internal Transcribed Spacer (ITS) region ITS1. The DNA quantities for a selection of fungal pathogens of wheat, and the total amount of fungal DNA, were analyzed by quantitative PCR (qPCR). The mean level of total fungal DNA was higher in grain samples with weak gluten compared to grain samples with strong gluten. Heightened quantities of DNA from fungi within the Fusarium Head Blight (FHB) complex, i.e. Fusarium avenaceum, Fusarium graminearum, Microdochium majus, and Microdochium nivale, were observed in grain samples with weak gluten compared to those with strong gluten. Microdochium majus was the dominant fungus in the samples with weak gluten. Stepwise regression modeling based on different wheat quality parameters, qPCR data, and the 35 most common OTUs revealed a significant negative association between gluten strength and three OTUs, of which the OTU identified as M. majus was the most abundant. The same analysis also revealed a significant negative relationship between gluten strength and F. avenaceum detected by qPCR, although the DNA levels of this fungus were low compared to those of M. majus. In vitro growth rate studies of a selection of FHB species showed that all the tested isolates were able to grow with gluten as a sole nitrogen source. In addition, proteins secreted by these fungi in liquid cultures were able to hydrolyze gluten substrate proteins in zymograms, confirming their capacity to secrete gluten-degrading proteases. The identification of fungi with potential to influence gluten quality can enable the development of strategies to minimize future problems with gluten strength in food-grade wheat.

Abstract

Cereal grain contaminated by Fusarium mycotoxins is undesirable in food and feed because of the harmful health effects of the mycotoxins in humans and animals. Reduction of mycotoxin content in grain by cleaning and size sorting has mainly been studied in wheat. We investigated whether the removal of small kernels by size sorting could be a method to reduce the content of mycotoxins in oat grain. Samples from 24 Norwegian mycotoxin-contaminated grain lots (14 from 2015 and 10 from 2018) were sorted by a laboratory sieve (sieve size 2.2 mm) into large and small kernel fractions and, in addition to unsorted grain samples, analyzed with LC-MS-MS for quantification of 10 mycotoxins. By removing the small kernel fraction (on average 15% and 21% of the weight of the samples from the two years, respectively), the mean concentrations of HT-2+T-2 toxins were reduced by 56% (from 745 to 328 µg/kg) in the 2015 samples and by 32% (from 178 to 121 µg/kg) in the 2018 samples. Deoxynivalenol (DON) was reduced by 24% (from 191 to 145 µg/kg) in the 2018 samples, and enniatin B (EnnB) by 44% (from 1059 to 594 µg/kg) in the 2015 samples. Despite low levels, our analyses showed a trend towards reduced content of DON, ADON, NIV, EnnA, EnnA1, EnnB1 and BEA after removing the small kernel fraction in samples from 2015. For several of the mycotoxins, the concentrations were considerably higher in the small kernel fraction compared to unsorted grain. Our results demonstrate that the level of mycotoxins in unprocessed oat grain can be reduced by removing small kernels. We assume that our study is the first report on the effect of size sorting on the content of enniatins (Enns), NIV and BEA in oat grains.

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Abstract

More than 30 years ago, the Nordic Gene Bank established a long-term experiment on seeds stored under permafrost conditions in an abandoned mine corridor in Svalbard, as a tool to monitor storage life under these conditions. The study included seeds from 16 Nordic agricultural and horticultural crops, each represented by two or three cultivars (altogether 38 accessions). All seeds were ultra-dried to 3–5% moisture before being sealed in glass tubes. Germination tests were performed in accordance with the International Seed Testing Association (ISTA) protocols. At the initiation of the experiment, the samples showed good germination with the median value at 92%. The overall picture remained stable over the first twenty to twenty-five years. However, the variation became larger over time and at 30 years, the median value had dropped to 80%. At the lower end, with a high drop in germination, we found rye, wheat, and English ryegrass. At the upper end, we found Kentucky bluegrass and cucumber. The lowest germination was found in samples with the highest initial seed moisture levels. Pre-storage conditions are likely to be of major importance for longevity.

Abstract

Complex communities of microorganisms influence plant and agroecosystem health and productivity. Bacteria and fungi constitute a major part of the wheat head microbiome. A microorganism’s ability to colonize or infect a wheat seed is influenced by interacting microbiome. In Norway, wheat seed lots are routinely analysed for the infestation by Fusarium head blight and seedling blight diseases, such as Fusarium and Microdochium spp., and glume blotch caused by Parastagonospora nodorum using traditional methods (plating grain on PDA, recording presence or absence of fungal colonies) The purpose is to decide if the seed quality is suitable for sowing and whether seed treatment is needed. This method is time consuming, require knowledge within fungal morphology, and do not facilitate identification to species level in all cases. Molecular methods such as sequencing could allow detection and quantification of “all” microbial DNA, only limited by the specificity of the primers. Microbial profiling (metabarcoding) can be very time and cost-effective, since a mixture of many samples can be analysed simultaneously for both fungi and bacteria, and other microbes if required. In our project “Phytobiome” we used metabarcoding to analyse microbial communities in wheat heads and verify this information with results from qPCR and plate studies for a more complete study. Around 150 spring wheat seed lots from the years 2016-2017 (including two cultivars) were selected for analysis. One of the main objectives was to find microorganisms associated with seed germination. We will present findings from this work, but also some challenges when using PCR-based sequencing methods, especially regarding Fusarium head blight fungi.

Abstract

The SafeOats project was initiated in 2016. An important objective of this project is to develop resistance screening methods to facilitate the phase-out of Fusarium-susceptible oat germplasm. Furthermore, SafeOats will give new insight into the biology of F. langsethiae and HT2+T2 accumulation in oats, and thus facilitate the choice of relevant control measures. The relative ranking of oat varieties according to F. graminearum/DON versus F. langsethiae/HT2+T2 content has been explored in field and greenhouse trials. In the greenhouse studies, we have analysed the content of Fusarium DNA and mycotoxins in grains of selected oat varieties inoculated at different development stages. Furthermore, we are currently studying the transcriptome during F. langsethiae and F. graminearum infestation of oats. The project also focus on the occurrence of F. langsethiae in oat seeds and possible influence of the fungus on seedling development in a selection of oat varieties. SafeOats is coordinated by NIBIO and is a collaboration between NIBIO, NMBU, Kimen Seed Laboratory, and the main Norwegian and Swedish breeding companies, Graminor and Lantmännen. Harper Adam University (UK) and Julius Kühn-Institute (Germany) are international collaborators. The project is financed by The Foundation for Research Levy on Agricultural Products/Agricultural Agreement Research Fund/Research Council of Norway with support from the industry partners Graminor, Lantmännen, Felleskjøpet Agri, Felleskjøpet Rogaland & Agder, Fiskå Mølle Moss, Norgesmøllene, Strand Unikorn/Norgesfôr and Kimen Seed Laboratory. The results from SafeOats will benefit consumers nationally and internationally by providing tools to increase the share of high quality grain into the food and feed industry.

Abstract

Occasionally, high mycotoxin levels are observed in Norwegian oat grain lots. The development of moderate resistant oat cultivars is therefore highly valued in order to increase the share of high quality grain into the food and feed industry. The Norwegian SafeOats project (2016-2020) aims to develop resistance screening methods to facilitate the phase-out of Fusarium-susceptible oat germplasm. Furthermore, SafeOats will give new insight into the biology of F. langsethiae and HT2+T2 accumulation in oats. The relative ranking of oat varieties according to F. graminearum/DON versus F. langsethiae/HT2+T2 content has been explored in naturally infested as well as in inoculated field trials. Routine testing of the resistance to F. graminearum in oat cultivars and breeding lines has been conducted in Norway since 2007. We are currently working on ways to scale up the inoculum production and fine tune the methodology of F. langsethiae inoculation of field trials to be routinely applied in breeding programs. Through greenhouse studies, we have analysed the content of Fusarium DNA and mycotoxins in grains of selected oat varieties inoculated at different development stages. Furthermore, we are studying the transcriptome during F. langsethiae and F. graminearum infestation of oats. The project also focus on the occurrence of F. langsethiae in oat seeds and possible influence of the fungus on seedling development in a selection of oat varieties. On average, the fungus was observed on 5% of the kernels in 168 seed lots tested during 2016-2018. No indication of transmission of F. langsethiae from germinating seed to seedlings was found in a study with germination of naturally infected seeds. So far, the studies have shown that the ranking of oat varieties according to HT2+T2 content in non-inoculated field trials resembles the ranking observed in inoculated field trials. The ranking of oat varieties according to DON content is similar in non-inoculated and F. graminearum inoculated field trials. However, the ranking of oat varieties according to DON content does not resemble the ranking for HT2+T2. The results from SafeOats will benefit consumers nationally and internationally by providing tools to increase the share of high quality grain into the food and feed industry. The project is financed by The Foundation for Research Levy on Agricultural Products/Agricultural Agreement Research Fund/Research Council of Norway with support from the industry partners Graminor, Lantmännen, Felleskjøpet Agri, Felleskjøpet Rogaland & Agder, Fiskå Mølle Moss, Norgesmøllene, Strand Unikorn/Norgesfôr and Kimen Seed Laboratory.

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Abstract

The Nordic Gene bank established the 100 year seed storage experiment in Coal mine no. 3 outside Longyearbyen in 1986. Security duplicate samples of the Nordic seed collection had been deposited in permafrost in the coal mine since 1984. The experiment was established with the aim to monitor the longevity of seeds in this Nordic back-up seed collection and to gain general knowledge about the longevity of seed stored under permafrost conditions, as well as studying the survival of seed borne plant pathogens. The experimental set up included in total 41 seed lots of 17 agricultural and horticultural crop species commonly grown in the Nordic countries. The seed germination experiment included two or three varieties of each crop. The experimental part dedicated to studies of pathogen survival included seeds from 11 crops naturally contaminated by pathogens. The test program comprises germination and pathogen survival tests every 2.5 years during the first 20 years and then every 5 years for the last 80 years. In total 25 identical sets of test seeds placed in sealed glass tubes were packed in wooden boxes, one box for each planned test year. The tests have been carried out according to schedule and this report sums up the results from the first 30 years of the experiment. All tests have been carried out in accordance with the same ISTA-protocols. The results show that 9 of the 17 species after 30 years had retained more than 90 percent of their initial germination percentage. Beet (Beta vulgaris),Onions (Allium cepa), Cucumber (Cucumis sativus) and Kentucky bluegrass (Poa pratensis) had retained between 97 and 99 percent. At the lower end of the scale, rye (Secale cereale) had lost 51 percent of the initial germination percentage. Among the other cereals, barley (Hordeum vulgare)showed the highest viability as it had kept 89 percent viability, whilst wheat (Triticum aestivum) had kept 79 percent of the initial germination percentage. Mean germination of all test samples showed a drop from 87.2% at year0 to 76.9% at year 30. The pathogen tests showed that all pathogens had survived over the 30 years, more or less at the same contamination levels as were detected at the start of the project. To expand the knowledge about seed longevity under long-term seed storage it is recommended to establish a new more comprehensive experiment with seed materials from a wider selection of crops, and to include more replicates and seeds produced over more years, allowing more indepth statistical studies of the longevity development. A new experiment should be placed in the Svalbard Global Seed Vault, in order to provide results relevant for optimal gene bank conservation methods at -18°C and giving direct data on the longevity of seeds stored in the Seed Vault.

Abstract

The proportion of Norwegian wheat used for food has varied significantly during the recent decade, mainly because of the instability of factors that are essential to baking quality (i.e. protein content and gluten functionality). During the same period, serious contamination of Fusarium spp. and mycotoxins was observed in some grain lots [1, 2]. A project was established to generate greater knowledge of the interface between gluten functionality and effects of Fusarium species and other microorganisms on Norwegian wheat quality. Instances of severe degradation of gluten proteins that resulted in an almost complete loss of gluten functionality were observed in some lots of Norwegian wheat. The degradation of the gluten appeared to be caused by exogenous proteases. Metabarcoding of fungi and bacteria in these grain lots identified fungi within the Fusarium Head Blight complex, as well as one bacterial species, as candidate species for influencing gluten functionality. Some of these candidates were inoculated on wheat during flowering [3]. Analysis of baking quality of the flour from this experiment revealed a reduced proportion of un-extractable polymeric proteins (%UPP) and severe reductions in the gluten’s resistance to stretching (RMAX) in wheat flour from plants inoculated with Fusarium graminearum. Flour from wheat inoculated with Fusarium avenaceum was generally less infested, and showed minimal or no reduction in gluten functionality and %UPP compared to flour from the F. graminearum infested samples. Flour from wheat inoculated with Michrodochium majus is yet to be analysed. References 1. Koga, S., et al., Investigating environmental factors that cause extreme gluten quality deficiency in winter wheat (Triticum aestivum L.). Acta Agriculturae Scandinavica, Section B—Soil & Plant Science, 2016. 66(3): p. 237-246. 2. Hofgaard, I., et al., Associations between Fusarium species and mycotoxins in oats and spring wheat from farmers’ fields in Norway over a six-year period. World Mycotoxin Journal, 2016. 9(3): p. 365-378. 3. Nielsen, K.A.G., Effect of microorganisms on gluten quality in wheat., in Faculty of Biosciences. 2017, Norwegian University of Life Sciences: Ås.

Abstract

High concentrations of the mycotoxins HT-2 and T-2 (HT2 + T2), primarily produced by Fusarium langsethiae, have occasionally been detected in Norwegian oat grains. In this study, we identified weather variables influencing accumulation of HT2 + T2 in Norwegian oat grains. Oat grain samples from farmers’ fields were collected together with weather data (2004–2013). Spearman rank correlation coefficients were calculated between the HT2 + T2 contamination in oats at harvest and a range of weather summarisations within estimated phenological windows of growth stages in oats (tillering, flowering etc.). Furthermore, we developed a mathematical model to predict the risk of HT2 + T2 in oat grains. Our data show that adequate predictions of the risk of HT2 + T2 in oat grains at harvest can be achieved, based upon weather data observed during the growing season. Humid and cool conditions, in addition to moderate temperatures during booting, were associated with increased HT2 + T2 accumulation in harvested oat grains, whereas warm and humid weather during stem elongation and inflorescence emergence, or cool weather and absence of rain during booting reduced the risk of HT2 + T2 accumulation. Warm and humid weather immediately after flowering increased the risk, while moderate to warm temperatures and absence of rain during dough development, reduced the risk of HT2 + T2 accumulation in oat grains. Our data indicated that HT2 + T2 contamination in oats is influenced by weather conditions both pre- and post-flowering. These findings are in contrast with a previous study examining the risk of deoxynivalenol contamination in oat reporting that toxin accumulation was mostly influenced by weather conditions from flowering onwards.

Abstract

Fusarium head blight and seedling blight, both caused by Fusarium spp. and Microdochium spp., and glume blotch caused by Parastagonospora nodorum, are important diseases in wheat. In Norway, wheat seed lots are routinely analysed for infestation by these pathogens using traditional methods (plating grain on PDA, recording presence or absence of fungal colonies). This method is time consuming, require knowledge within fungal morphology, and do not facilitate identification to species in all cases. Molecular methods such as quantitative PCR (qPCR) could allow detection and quantification of fungal DNA at the species level in a relatively time effective way, particularly since the method allows for automation in different steps such as DNA extraction and pipetting. Whether the latter method is suitable within seed health evaluations will depend on the relationship between the amount of DNA of the different fungal species and field performance, and the purpose of the test (evaluation of planting value, need for seed treatment, survey of fungal species, quality of grain for consumption etc). To compare the two different methods, about 150 spring wheat seed lots from the years 2016-2017 (including two cultivars) were selected for the analysis of different fungi using species-specific qPCR and compared with the results from routine testing on PDA. In the 2016 material (81 samples), a mean seed infestation rate of 26% was observed for Microdochium spp. in the PDA test. The level of Fusarium was lower (mean infestation rate of 5%). A strong relationship was observed between the percentage of seeds infested by Microdochium and the level of Microdochium DNA (sum of DNA from Microdochium majus and Microdochium nivale) quantified by qPCR (R2 of 0.76, p<0.01). The relationship between Fusarium infested seeds and the level of Fusarium DNA (sum of DNA from three species) was moderate (R2 of 0.33, p<0.01). The samples were also analysed for the presence of P. nodorum. Compared to Fusarium and Microdochium, P. nodorum was present at an intermediate level (mean infestation rate of 12%). The relationship between the two different methods was weaker for this fungus (R2 of 0.21, p<0.01) than for Fusarium and Microdochium. The relationship between germination capacity and rating of the three groups of fungi by either method was studied. Preliminary results suggest that of the three fungi, Microdochium was associated with germination capacity in the 2016 material, and that the Microdochium infestation rate on PDA was slightly better correlated to germination capacity than the level of Microdochium DNA. Further results will be presented at the conference, including the association between the relative DNA content of the different Microdochium and Fusarium species and seed germination.

Abstract

Different seed lots of Pinus spp. cultivated within South Africa were screened for the presence or absence of seed-borne fungi according to modified ISTA (International Seed Testing Association) prescribed protocols. Numerous (454 isolates) fungi were successfully isolated, purified and stored using agar slants and cryopreservation. Sydowia polyspora was isolated from six different seed lots from three Pinus species (P. greggii (South), P. elliottii and P. taeda) and was morphologically and molecularly identified. Koch’s postulates was fulfilled by inoculating one year old seedlings (wounded and unwounded) with a spore suspension (107 ml-1) obtained from 30 day old pure cultures grown on PDA. Inoculated and uninoculated control seedlings were incubated in a greenhouse at 220C until symptom development. Sydowia polyspora was re-isolated from symptomatic needles with both wounded and unwounded needles showing characteristic symptoms. No symptoms were apparent on the control seedlings. To the best of our knowledge, this is the first report of the fungus being isolated and recorded within the country. Further investigations will look at the prevalence, pathogenicity and characterization of the fungus within South Africa.

Abstract

Sclerotinia stem rot (SSR) is the most important disease of oilseed Brassica crops in Norway. Fungicide applications should be aligned with the actual need for control, but the SSR prediction models used lack accuracy. We have studied the importance of precipitation, and the role of petal and leaf infection for SSR incidence by using data from Norwegian field and trap plant trials over several years. In the trials, SSR incidence ranged from 0 to 65%. Given an infection threshold of 25% SSR, regression and Receiver Operating Characteristics (ROC) analysis were used to evaluate different precipitation thresholds. The sum of precipitation two weeks before and during flowering appeared to be a poor predictor for SSR infection in our field and trap plant trials (P = 0.24, P = 0.11, respectively). Leaves from three levels (leaf one, three, five), and petals were collected at three to four different times during flowering from nine field sites over two years and tested for SSR infection with real-time PCR. Percentage total leaf and petal infection explained 57 and 45% of variation in SSR incidence, respectively. Examining the different leaves and petals separately, infection of leaf three sampled at full flowering showed the highest explanation of variation in later SSR incidence (R2 = 65%, P < 0.001). ROC analysis showed that given an infection threshold of 45%, both petal and leaf infection recommended spraying when spraying was actually needed. Combining information on petal and leaf infection during flowering with relevant microclimate factors in the canopy, instead of the sum of precipitation might improve prediction accuracy for SSR.

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Abstract

The Svalbard Global Seed Vault was opened in 2008. The aim was to secure genetic diversity of crop plants important to future food production. The Seed Vault has the capacity to store 4.5 million seed samples, each containing on average 500 seeds sealed in airtight aluminum bags. By the end of 2016, the Vault had approximately 880,000 accessions representing more than 5000 plant species. The samples, originating from 71 gene banks and research institutes from all across the world, include major food crops such as wheat, rice, barley, sorghum, maize, legumes and forage crops, and vegetables. The seed samples are duplicates (backups) of seed stored in national, regional and international gene banks. Deposits can only be made by following a depositor agreement and the seed samples in the Vault remain the property of the depositing gene bank. The Vault is situated in permafrost at -3 to -4°C, but artificial cooling maintains a temperature of -18°C inside the Vault. Management of the Vault is secured through an agreement between the Norwegian Ministry of Agriculture and Food, the Crop Trust and the Nordic Genetic Resource Centre (NordGen). Secure storage of gene bank seeds in Svalbard was initiated during the 1980s, when the Nordic Gene Bank placed a collection of seed duplicates in an abandoned coal mine outside Longyearbyen in Svalbard. In addition to the secure storage of the base collection, a study of the longevity (germination and seed health) in long-term storage (100 years) in permafrost was started in 1986. A total of 42 seed samples of 16 common agricultural and horticultural Nordic species were included in the study. A set of sub-samples has been taken out for analyses every two and a half years during the first 20 years, and are taken out every five years for the next 80 years.

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Abstract

The estimated potential yield losses caused by plant pathogens is up to 16% globally (Oerke 2006) and most research in plant pathology aims to reduce yield loss in our crops directly or indirectly. Yield losses caused by a certain disease depend not only on disease severity, but also on the weather factors, the pathogen’s aggressiveness, and the ability of the crop to compensate for reduced photosynthetic area. The yield loss-disease relationship in a certain host-pathogen system might therefore change from year to year, making predictions for yield loss very difficult at the regional or even at the farmer’s level. However, estimating yield losses is essential to determine disease management thresholds at which acute control measures such as fungicide applications, or strategic measures such as crop rotation or use of resistant cultivars are economically and environmentally sensible. Legislation in many countries enforces implementation of integrated pest management (IPM), based on economic thresholds at which the costs due to a disease justify the costs for its management. Without a better understanding of the relationship between disease epidemiology and yield loss, we remain insufficiently equipped to design adequate IPM strategies that will be widely adapted in agriculture. Crop loss studies are resource demanding and difficult to interpret for one particular disease, as crops are usually not invaded by only one pest or pathogen at a time. Combining our knowledge on disease epidemiology, crop physiology, yield development, damage mechanisms involved, and the effect of management practices can help us to increase our understanding of the disease-crop loss relationship. The main aim of this paper is to review and analyze the literature on a representative host-pathogen relationship in an important staple food crop to identify knowledge gaps and research areas to better assess yield loss and design management strategies based on economic thresholds. Wheat is one of the most important staple foods worldwide and is susceptible to several important plant diseases. In our article, we focus on Septoria nodorum blotch (SNB) or Glume blotch of wheat as an example for a stubble-borne, seed-transmitted disease with a worldwide distribution causing considerable and regular yield losses. In their review on yield losses due to wheat pathogens in Australia, Murray and Brennan (2009) estimated the current annual economic loss due to SNB as high as $108 × 106, with potential costs as high as $230 × 106. The causal fungus, Parastagonospora nodorum, is currently serving as a model organism for molecular studies of the intimate relationship between necrotic effector-producing fungal strains and their corresponding susceptibility genes present in wheat cultivars (Oliver et al. 2012). In this paper, we analyze the literature on the biology of this common wheat pathogen, the yield loss it reportedly has caused, and the effect of control strategies to reduce this loss. Based on this analysis, we will evaluate the use of common management practices to reduce disease-related yield loss and identify related research needs.

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Abstract

Deoxynivalenol (DON) is the most common mycotoxin in Norwegian cereals, and DON is detected in most samples of crude cereal grain and cereal food commodities such as flour, bran, and oat flakes. The Norwegian Scientific Committee for Food Safety assessed the risk for adverse effects of deoxynivalenol (DON) in different age groups of the domestic population. This review presents the main results from the risk assessment, supplemented with some recently published data. Impairment of the immune system together with reduced feed intake and weight gain are the critical effects of DON in experimental animals on which the current tolerable daily intake was established. Based on food consumption and occurrence data, the mean exposure to DON in years with low and high levels of DON in the flour, respectively, were in the range of or up to two times the Tolerable Daily Intake (TDI) in 1-year-old infants and 2-year-old children. In years with high mean DON concentration, the high (95th-percentile) exposure exceeded the TDI by up to 3.5 times in 1-, 2- , 4-, and 9-year-old children. The assessment concluded that exceeding the TDI in infants and children is of concern. The estimated dietary DON intakes in adolescent and adult populations are in the range of the TDI or below, and are not a health concern. Acute human exposure to DON is not of concern in any age group.

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Abstract

During August 2013, white-grayish lesions, typical of Sclerotinia stem rot, had developed around leaf axils on the stems of turnip rape ‘Pepita’ in a field at the NIBIO research station Apelsvoll in Oppland County, Norway. Sclerotia were collected from inside infected turnip rape stubble and from harvested seeds, surface sterilized, bisected, and placed onto potato dextrose agar (PDA). Following 1 to 2 days incubation at 20°C, fast-growing white mycelium characteristic of Sclerotinia was observed, and within 5 to 7 days, new sclerotia had started to develop. Sclerotia size and growing pattern although variable was characteristic of S. sclerotiorum. DNA extraction, PCR amplification, and sequencing of the ITS regions of the rDNA was then carried out for 20 isolates. BLASTn analysis of 475 bp amplicons showed that 15 isolates were S. sclerotiorum, while five were identified as S. subarctica (previously called Sclerotinia sp 1; Holst-Jensen et al. 1998; Winton et al. 2006, 2007), with 100% identity to a U.K. S. subarctica isolate (Clarkson et al. 2010). A representative ITS region sequence was deposited in GenBank (accession no. KX929095). The identity of the S. subarctica isolates was further confirmed by the lack of a 304-bp intron in the LSU rDNA compared with S. sclerotiorum (Holst-Jensen et al. 1998), which was visualized by PCR amplification and gel electrophoresis. Sclerotia of two S. subarctica isolates were placed on PDA and incubated for 7 days. Agar plugs of actively growing mycelium were used for the pathogenicity testing of spring oilseed rape plants (‘Mosaik’) in the greenhouse. Plants were inoculated at growth stage BBCH 57/59 (preflowering) and BBCH 64 (40% of flowers open) by attaching two PDA plugs of actively growing mycelium per main stems with small needles, using four plants per treatment. Noninoculated PDA agar plugs were attached to the control plants. The experiment was repeated three times. Symptoms typical of stem rot appeared after 1 to 2 weeks of incubation at 16 to 20°C, 100% relative humidity. Stems started to develop white lesions with fluffy mycelium around the inoculation sites. Control plants did not show the characteristic symptoms for Sclerotinia infection. After senescence of the plants, sclerotia were collected from inside the stems and cultured on PDA. White mycelium started to grow after 1 to 2 days and new sclerotia were formed within 7 days, similar to the ones used for producing the initial isolate. Brassica oil seed crops are cultivated as important break crops in the cereal-based production system in Norway and can be severely affected by Sclerotinia stem rot. The disease is observed in all regions where Brassica oil seed crops are grown, and in severe cases, a reduction in oilseed yield of 25% has been recorded in untreated control treatments of fungicide trials. Although S. subarctica has been previously reported on wild hosts (Holst-Jensen et al. 1998), this is the first report of the pathogen on a crop plant in Norway. In the United Kingdom, Clarkson et al. (2010) demonstrated pathogenicity of S. subarctica isolated from Ranunculus acris on oilseed rape. As symptoms for S. subarctica and S. sclerotiorum are indistinguishable, S. subarctica might be present undetected in many farmer fields.

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Abstract

Sclerotinia species are important fungal pathogens of a wide range of crops and wild host plants. While the biology and population structure of Sclerotinia sclerotiorum has been well-studied, little information is available for the related species S. subarctica. In this study, Sclerotinia isolates were collected from different crop plants and the wild host Ranuculus ficaria (meadow buttercup) in England, Scotland, and Norway to determine the incidence of Sclerotinia subarctica and examine the population structure of this pathogen for the first time. Incidence was very low in England, comprising only 4.3% of isolates while moderate and high incidence of S. subarctica was identified in Scotland and Norway, comprising 18.3 and 48.0% of isolates respectively. Characterization with eight microsatellite markers identified 75 haplotypes within a total of 157 isolates over the three countries with a few haplotypes in Scotland and Norway sampled at a higher frequency than the rest across multiple locations and host plants. In total, eight microsatellite haplotypes were shared between Scotland and Norway while none were shared with England. Bayesian and principal component analyses revealed common ancestry and clustering of Scottish and Norwegian S. subarctica isolates while English isolates were assigned to a separate population cluster and exhibited low diversity indicative of isolation. Population structure was also examined for S. sclerotiorum isolates from England, Scotland, Norway, and Australia using microsatellite data, including some from a previous study in England. In total, 484 haplotypes were identified within 800 S. sclerotiorum isolates with just 15 shared between England and Scotland and none shared between any other countries. Bayesian and principal component analyses revealed a common ancestry and clustering of the English and Scottish isolates while Norwegian and Australian isolates were assigned to separate clusters. Furthermore, sequencing part of the intergenic spacer (IGS) region of the rRNA gene resulted in 26 IGS haplotypes within 870 S. sclerotiorum isolates, nine of which had not been previously identified and two of which were also widely distributed across different countries. S. subarctica therefore has a multiclonal population structure similar to S. sclerotiorum, but has a different ancestry and distribution across England, Scotland, and Norway.

Abstract

Over the recent decades, the Norwegian cereal industry has had major practical and financial challenges associated with the occurrence of Fusarium and mycotoxins in cereal grains. From 2011, payment reductions to farmers were implemented for oat grain lots with high levels of deoxynivalenol (DON). However, according to preliminary results by NIBIO, NMBU and Graminor, certain oat varieties with generally medium or low DON contamination, may contain high levels of HT-2 and T-2-toxins (HT2+T2). These mycotoxins, formed by Fusarium langsethiae, are considerably more toxic than DON. Resistance to F. langsethiae is not included in the variety screening in Norway. In 2016 a new project, SafeOats, was initiated. This project is led by NIBIO and is a collaboration between NIBIO, NMBU, Kimen, and the main Norwegian and Swedish breeding companies, Graminor and Lantmännen. Harper Adam University (UK) and Julius Kühn-Institut (Germany) are international collaborators. SafeOats will develop resistance screening methods in order to facilitate the phase-out of susceptible oat germplasm. Furthermore, SafeOats will give new insight into the biology of F. langsethiae and HT2+T2 accumulation in oats, and thus facilitate the choice of relevant control measures. The results from SafeOats will benefit consumers nationally and internationally by providing tools to increase the share of high quality grain into the food and feed industry. SafeOats is financed by The Foundation for Research Levy on Agricultural Products/Agricultural Agreement Research Fund/Research Council of Norway with support from the industry partners Graminor, Lantmännen, Kimen, Felleskjøpet Agri, Felleskjøpet Rogaland Agder, Fiskå Mølle Moss, Norgesmøllene and Strand Unikorn/Norgesfor.

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Abstract

During the last ten years, Norwegian cereal grain industry has experienced large challenges due to Fusarium spp. and Fusarium mycotoxin contamination of small-grained cereals. To prevent severely contaminated grain lots from entering the grain supply chain, it is important to establish surveys for the most prevalent Fusarium spp. and mycotoxins. The objective of our study was to quantify and calculate the associations between Fusarium spp. and mycotoxins prevalent in oats and spring wheat. In a 6-year period from 2004-2009, 178 grain samples of spring wheat and 289 samples of oats were collected from farmers’ fields in South East Norway. The grains were analysed for 18 different Fusarium-mycotoxins by liquid chromatography – mass spectrometry. Generally, the median mycotoxin levels were higher than reported in Norwegian studies covering previous years. The DNA content of Fusarium graminearum, Fusarium culmorum, Fusarium langsethiae, Fusarium poae and Fusarium avenaceum were determined by quantitative PCR. We identified F. graminearum as the main deoxynivalenol (DON) producer in oats and spring wheat, and F. langsethiae as the main HT-2 and T-2-toxins producer in oats. No association was observed between quantity of F. graminearum DNA and quantity of F. langsethiae DNA nor for their respective mycotoxins, in oats. F. avenaceum was one of the most prevalent Fusarium species in both oats and spring wheat. The following ranking of Fusarium species was made based on the DNA concentrations of the Fusarium spp. analysed in this survey (from high to low): F. graminearum = F. langsethiae = F. avenaceum > F. poae > F. culmorum (oats); F. graminearum = F. avenaceum > F. culmorum > F. poae = F. langsethiae (spring wheat). Our results are in agreement with recently published data indicating a shift in the relative prevalence of Fusarium species towards more F. graminearum versus F. culmorum in Norwegian oats and spring wheat.

Abstract

High concentrations of the mycotoxin deoxynivalenol (DON), produced by Fusarium graminearum have occurred frequently in Norwegian oats recently. Early prediction of DON levels is important for farmers, authorities and the Cereal Industry. In this study, the main weather factors influencing mycotoxin accumulation were identified and two models to predict the risk of DON in oat grains in Norway were developed: (1) as a warning system for farmers to decide if and when to treat with fungicide, and (2) for authorities and industry to use at harvest to identify potential food safety problems. Oat grain samples from farmers’ fields were collected together with weather data (2004–2013). A mathematical model was developed and used to estimate phenology windows of growth stages in oats (tillering, flowering etc.). Weather summarisations were then calculated within these windows, and the Spearman rank correlation factor calculated between DON-contamination in oats at harvest and the weather summarisations for each phenological window. DON contamination was most clearly associated with the weather conditions around flowering and close to harvest. Warm, rainy and humid weather during and around flowering increased the risk of DON accumulation in oats, as did dry periods during germination/seedling growth and tillering. Prior to harvest, warm and humid weather conditions followed by cool and dry conditions were associated with a decreased risk of DON accumulation. A prediction model, including only pre-flowering weather conditions, adequately forecasted risk of DON contamination in oat, and can aid in decisions about fungicide treatments.

Abstract

The proportion of Norwegian wheat used for food has recently been dramatically lower due to both reduced production and poor quality. Furthermore, the Norwegian milling and baking industries have experienced major challenges in utilizing Norwegian wheat due to the instability of factors, such as protein content and gluten functionality, that are of major importance for baking quality. The variation in the wheat quality can itself cause economic losses for the milling and baking industry due to uncertainty in the marketplace. In the same period as a large variation in baking quality was reported in Norwegian wheat, serious contamination of Fusarium spp. and mycotoxins were observed in some grain lots. We have revealed the severe degradation of gluten proteins in some Norwegian wheat samples leading to an almost complete loss in the gluten functionality. The degradation of the gluten appears to be caused by exogenous proteases, and was associated with the presence of Fusarium spp., and their metabolites, and other microorganisms in the wheat. Increased knowledge is needed to establish the cause of the poor gluten functionality and to develop control measures to reduce the amount of poor quality wheat entering the food value chain. In 2014, a new project was established to generate deeper knowledge in the interface between gluten functionality and effects of Fusarium spp. and other microorganism on wheat quality, and to better utilize Norwegian wheat grown in this challenging environment. A metagenomic analysis, designed to identify microorganisms associated with reduced baking quality, has been undertaken. To study the influence of the identified microorganisms and their metabolites on gluten functionality, wheat plants were inoculated with microorganisms, selected based upon the results of the metagenomics study. Fusarium species are among those microorganisms being tested.

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Abstract

This paper presents peer-reviewed studies comparing the content of deoxynivalenol (DON), HT-2+T-2 toxins, zearalenone (ZEA), nivalenol (NIV), ochratoxin A (OTA) and fumonisins in cereal grains, and patulin (PAT) in apple and apple-based products, produced in organically and conventionally grown crops in temperate regions. Some of the studies are based on data from controlled field trials, however, most are farm surveys and some are food basket surveys. Almost half of the studies focused on DON in cereals. The majority of these studies found no significant difference in DON content in grain from the two farming systems, but several studies showed lower DON content in organically than in conventionally produced cereals. A number of the investigations reported low DON levels in grain, far below the EU limits for food. Many authors suggested that weather conditions, years, locations, tillage practice and crop rotation are more important for the development of DON than the type of farming. Organically produced oats contained mainly lower levels of HT-2+T-2 toxins than conventionally produced oats. Most studies on ZEA reported no differences between farming systems, or lower concentrations in organically produced grain. For the other mycotoxins in cereals, mainly low levels and no differences between the two farming systems were reported. Some studies showed higher PAT contamination in organically than in conventionally produced apple and apple products. The difference may be due to more efficient disease control in conventional orchards. It cannot be concluded that any of the two farming systems increases the risk of mycotoxin contamination. Despite no use of fungicides, an organic system appears generally able to maintain mycotoxin contamination at low levels. More systematic comparisons from scientifically controlled field trials and surveys are needed to clarify if there are differences in the risk of mycotoxin contamination between organically and conventionally produced crops.

Abstract

Fusarium and Microdochium may cause seedling blight and poor germination of cereal seeds. However, indications of poor survival of Fusarium in seed and improved germination after some months of storage have been observed. A study was carried out to investigate if seed storage can contribute to improved seed quality. Samples from seed lots of barley, oats and spring wheat were tested for germination capacity and Fusarium /Microdochium infection frequencies a few days after harvest, and after 5, 12 and 15 months of storage. In barley, the average germination percentage increased slightly, from 92% at harvest to 95% after five months of storage. In oats, the average germination percentage increased from 82% to 85% during the first five months. In spring wheat, the average germination percentage was reduced from 81% at harvest to 67% after five months. In barley and oats, average Fusarium /Microdochium frequencies were reduced during storage, with the highest reduction observed during the first five months (from 50% to 37%, and from 60% to 46%, barley and oats respectively). In spring wheat, no significant reduction in average infection level was recorded (58% at harvest, 50% after 15 months of storage). There was however, variation between seed lots in all three cereal species in both germination percentage and Fusarium /Microdochium frequencies during the storage period. It is concluded that storage of barley and oats seeds for 5 months after harvest may in some cases increase the seed quality and thereby meet the certification requirements of minimum 85% germination.

Abstract

The plant pathogenic fungus Fusarium langsethiae produces the highly potent mycotoxins HT-2 and T-2. Since these toxins are frequently detected at high levels in oat grain lots, they pose a considerable risk for food and feed safety in Norway, as well as in other north European countries. To reduce the risk of HT-2/T- 2-contaminated grain lots to enter the food and feed chain, it is important to identify factors that influence F. langsethiae infection and mycotoxin development in oats. However, the epidemiology of F. langsethiae is unclear. A three-year survey was performed to reveal more of the life cycle of F. langsethiae and its interactions with oats, other Fusarium species, as well as insects, mites and weeds. We searched for inoculum sources by quantifying the amount of F. langsethiae DNA in weeds, crop residues, and soil, sampled from a predetermined selection of oat-fields. To be able to define the onset of infection, we analysed the amount of F. langsethiae DNA in oat plant material sampled at selected growth stages (between booting and maturation), as well as the amount of F. langsethiae DNA and HT-2 and T-2 toxins in the mature grain. We also studied the presence of possible insect- and mite vectors sampled at the selected growth stages using Berlese funnel traps. All the different types of materials were also analysed for the presence F. graminearum DNA, the most important deoxynivalenol producer observed in Norwegian cereals, and which presence has shown a striking lack of correlation with the presence F. langsethiae in oat. Preliminary results show that F. langsethiae DNA may occur in the oat plant before heading and flowering. Some F. langsethiae DNA was observed in crop residues and weeds, though at relatively low levels. More results from this work will be presented at the meeting.

Abstract

The plant pathogenic fungus Fusarium langsethiae produces the highly potent mycotoxins HT-2 and T-2. Since these toxins are frequently detected at high levels in oat grain lots, they pose a considerable risk for food and feed safety in Norway, as well as in other north European countries. To reduce the risk of HT-2/T- 2-contaminated grain lots to enter the food and feed chain, it is important to identify factors that influence F. langsethiae infection and mycotoxin development in oats. However, the epidemiology of F. langsethiae is unclear. A three-year survey was performed to reveal more of the life cycle of F. langsethiae and its interactions with oats, other Fusarium species, as well as insects, mites and weeds. We searched for inoculum sources by quantifying the amount of F. langsethiae DNA in weeds, crop residues, and soil, sampled from a predetermined selection of oat-fields. To be able to define the onset of infection, we analysed the amount of F. langsethiae DNA in oat plant material sampled at selected growth stages (between booting and maturation), as well as the amount of F. langsethiae DNA and HT-2 and T-2 toxins in the mature grain. We also studied the presence of possible insect- and mite vectors sampled at the selected growth stages using Berlese funnel traps. All the different types of materials were also analysed for the presence F. graminearum DNA, the most important deoxynivalenol producer observed in Norwegian cereals, and which presence has shown a striking lack of correlation with the presence F. langsethiae in oat. Preliminary results show that F. langsethiae DNA may occur in the oat plant before heading and flowering. Some F. langsethiae DNA was observed in crop residues and weeds, though at relatively low levels. More results from this work will be presented at the meeting.

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Abstract

In 2008, an epidemic caused by a new Neonectria sp. was discovered on white fir (Abies concolor) in several counties in southern Norway [1]. Later the pathogen was also found on other fir species in Norway and Denmark [2]. Typical symptoms and signs were dead shoots, flagging (dead branches), canker wounds, heavy resin flow, and occasionally red fruiting bodies (perithecia). Pathogenicity tests on several Abies spp. proved the fungus to be very aggressive, which corresponds well with observations of mortality of white fir and subalpine fir (A. lasiocarpa) from different age classes under field conditions. Sequencing of the internal transcribed regions (ITS) of the ribosomal DNA showed that this Neonectria sp. was most similar to N. ditissima (only 5 bp different from isolates in the GenBank), a common pathogen worldwide on broad leaf trees. The ITS sequences were very different (> 20 bp) from N. fuckeliana, a well-known fungus on Norway spruce in Scandinavia and other parts of the world, especially in the northern hemisphere. In 2011, the new Neonectria species was found on diseased trees in a Danish nordmann fir (Abies nordmanniana) seed orchard. Resin flow was seen from mature cones, and tests revealed that the seeds were infected by the Neonectria sp.

Abstract

Sydowia polyspora was found to be seed borne on true fir (Abies spp.) where it is associated with two serious diseases; current season needle necrosis (CSNN) and Sclerophoma shoot dieback [1]. To our knowledge, S. polyspora was previously only reported to be seed borne on Scots pine (Pinus sylvestris) [3]. In 2009, we discovered S. polyspora on Norway spruce (Picea abies) seedlings from germination tests at the Norwegian Forest Seed Center. This indicated that S. polyspora also was seed borne on spruce. Based on this, we wanted to investigate how widespread S. polyspora was on conifer seeds. In 2010, we tested 44 seed lots from 8 genera. S. polyspora was isolates from seeds from the following genera; Abies, Larix, Picea, Pinus, Pseudotsuga, Thuja, and Tsuga. Interestingly, they are the exact same genera that Funk [2] reported S. polyspora from on diseased foliage and shoots. We found S. polyspora on Norway spruce harvested in 1970, thus, the fungus may survive for decades in seed lots. In Norway, Sclerophoma shoot dieback has been found on Norway spruce in Christmas tree fields. Fungal species from a number of other genera were also detected in the seed test, but here we only report S. polyspora.

Abstract

Sydowia polyspora is a pathogenic, seed borne fungus on conifers [1]. It is especially troublesome in the Christmas tree industry, where it causes current season needle necrosis (CSNN) on fir (Abies spp.). Needles get chlorotic spots or bands and in severe cases the entire needles turn necrotic and shed. The fungus also commonly kills current year shoots (Sclerophoma shoot dieback) on both fir and spruce (Picea spp.). The latter we proved on subalpine fir (A. lasiocarpa) inoculated by S. polyspora from noble fir (Abies procera) seeds. Two conifer seed lots known from previous tests to contain a high percentage of S. polyspora were selected for a treatment experiment; alpine pine (Pinus mugo var. rotundata) and Noble fir. Both seed lots received the following five treatments; surface sterilized (10 sec. in 70 % ethanol plus 90 sec. in 0,5 % NaOCl), dipped in 15 % acidic acid, mixed with 0,36 gram Signum (boskalid and pyraklostrobin) per 100 gram seeds, mixed with 0,8 gram Mycostop (Streptomyces griseovirides) per 100 gram seeds, dipped in different concentrations of thyme oil (extracted from Thymus vulgaris), and control (no treatment). Based on the results we recommend Signum for conifer seed treatment. This fungicide controlled S. polyspora well and did not influence on the germination ability. Agricultural

Abstract

Three primary causal agents are involved in the leaf blotch disease (LBD) complex of Norwegian winter and spring wheat: Phaesophaeria nodorum, Mycospaerella tritici, and Pyrenophora drechslera-tritici. The dynamics of symptom development, similarity of symptoms caused by each agent, and confounding of disease symptoms by leaf senescence interfere with accurate assessment of disease. Empirical and regression models for disease and yield loss forecasting are only as good as the data upon which they are based. Accurately describing the relationship between symptoms and yield loss is therefore critical to meaningful economic thresholds for management decisions and advisory systems. A general guideline for yield loss and disease severity has been described as 1% yield loss per 1% disease severity on the flag leaf at BBCH stage 70-75 (King et al., 1983). However, several years of field trials in Norway indicate that disease severity can increase exponentially during these developmental stages, making disease severity highly dependent upon time of assessment. LBD severity on flag leaves of the spring wheat variety ‘Bjarne’ at two different locations in 2010 varied during the above BBCH stages from 27% to 44% and from 4.45% to 23.2%. Different varieties may compensate differently for loss of photosynthetic area on the flag leaf due to leaf blotch pathogens, rendering the general guide line for yield loss inaccurate. Preliminary studies in Norway indicated that the relation between yield reduction (TKW) and disease severity of the flag leaf differed substantially for five different spring varieties and ranged from 0.03 to 1.4 at BBCH 70 and from 0.8 to 4.1 at BBCH 75, at one field site at Aas, Norway in 2010. The causes of the observed variation in the relationship between flag leaf severity and yield reduction are poorly understood. Effects of other diseases are not accounted for by leaf blotch assessments, nor are fungicides applied to reference plots necessarily eliminating all disease effects on yield. Timing of assessments may be as critical as the accuracy of the assessments; making it necessary to time the assessments properly, and distinguish clearly between leaf senescence and leaf blotch symptoms.

Abstract

The osmotic method has been used for many years in Norway and Sweden as a routine method for detection of Pyrenophora teres (anamorph Drechslera teres) and P. graminea (anamorph D. graminea) on barley. The method is based on the ability of Pyrenophora spp. to produce red pigments. However, it cannot distinguish between P. teres and P. graminea because they produce the same pigment. A validation study has been carried out with the aim to provide the necessary documentation for including the method in the International Rules for Seed Testing (ISTA Rules). Seven laboratories participated and each tested 3 x 300 seeds of three barley seed lots. Analyses of the results demonstrate that the method gives sufficient repeatability and there is no particular problem with this test at a laboratory level. Furthermore, in previous studies with the osmotic method organized by a Nordic working group, it has been shown that the osmotic method easily gives reproducible results for Pyrenophora teres/P. graminea in barley when used by experienced laboratories. Moreover, the osmotic method is well suited for routine analyses because it is quick and easy to carry out. The study showed, that if used correctly and with proper equipment the osmotic method for detection of Pyrenophora teres/P. graminea is easy to perform and it showed good conformity amongst laboratories.

Abstract

In Norway, Nordmann fir (Abies nordmanniana) and subalpine fir (A. lasiocarpa) are the dominant Christmas tree species, and noble fir (A. procera) the dominant bough plant species. To determine if fungi found to cause diseases on fir in Norway might be seed borne, samples from twelve seed lots, including Nordmann fir from Austria, Georgia and Russia, subalpine fir from Canada and Norway and noble fir from Norway were tested using agar plate methods (PDA and WA). The most important finding was that Sydowia polyspora was present on seed from all firs from all countries (nine samples infected, 0.5 - 85 % infected seeds). Recently, it has been demonstrated in Norway that this fungus is the cause of current season needle necrosis (CSNN), which is considered a major disease in the Christmas tree and bough production both in Europe and USA. Sirococcus coniguenus was found in a Norwegian A. procera seed lot (31% infected seeds), which to our knowledge is the first report of this pathogen on fir seeds. Caloscypha fulgens was detected on subalpine fir seed from Canada. In addition the following fungal genera were detected: Acremoniella, Acremonium, Alternaria, Aspergillus, Botrytis, Chaetomium, Cladosporium, Diaphorte, Dictyopolyschema, Epicoccum, Fusarium, Genicularia, Mucor, Neonectria, Penicillium, Phoma, Rhizopus, Sordaria, Trichoderma, Trichothecium, and an unidentified fungus.

Abstract

Microdochium nivale (syn. Microdochium nivale var. nivale) and Microdochium majus (syn. Microdochium nivale var. majus) are important pathogens which cause snow mould on grasses and winter cereals. These fungi are also able to cause leaf blotch of oat and seedling blight, foot rot and ear blight in cereals. Although no distinct differences in the host range of M. nivale and M. majus are found, indications for differences in host preferences between these fungal species have previously been discussed. The culture collection at Bioforsk contains about 250 Microdochium sp. isolated from grasses and cereals over the last 20 years. Most of the isolates collected from leaves of cereals displaying snow mould symptoms in spring, were identified as M. nivale (71 %), whereas most of the isolates collected from cereal seeds (mostly wheat) belong to the species M. majus (92 %). All, except one out of the sixty nine Microdochium sp. isolated from grass leaves were identified as M. nivale (99 %). The relatively higher incidence of M. majus vs. M. nivale on cereal seeds (mostly wheat) harvested in Norway, is in agreement with studies in UK (Parry et al. 1995). Parry et al. suggested that higher natural occurrence of M. majus (vs. M. nivale) on seeds of cereals could be partly due to the higher proportion of M. majus isolates producing perithecia and thus, a relatively higher amount of M. majus spores spreading to the ear (Parry et al. 1995). The high frequency of M. nivale (99 %) vs. M. majus on grasses collected in Norway could indicate that M. nivale is more aggressive on certain grass species. Studies in our lab indeed point towards a higher aggressiveness of M. nivale vs. M. majus on perennial ryegrass at low temperature (2?C) (Hofgaard et al 2006). However, the high incidence of M. nivale on grass leaves could also be caused by differences in temperature preferences, saprophytic ability or ability to infect certain plant parts. Isolates of M. nivale display a higher in vitro growth rate compared to isolates of M. majus at 2?C (Hofgaard et al. 2006). In conclusion, the higher natural occurrence of M. nivale vs. M. majus on turf grasses and the relatively higher aggressiveness of M. nivale on perennial ryegrass could indicate that M. nivale somehow is better adapted to infect certain grass species.

Abstract

A survey of the loose smut frequencies in certified barley seed lots in Norway during 1997"2002 showed that the disease has become more prevalent and has occurred at higher infection frequencies in recent years. Laboratory analyses (embryo method) of barley seeds harvested in 2001 and 2002, including both certified and farm saved seed, showed a large number of infected seed lots with higher than expected infection frequencies. One lot of farm saved seed (cv. Otira) from 2002 had 32% seed infection. Unexpectedly high loose smut infection frequencies recorded in fields sown with carboxin treated barley seed suggest a reduced effectiveness of the fungicide. A seed treatment experiment was conducted in 2002 using both greenhouse and field trials with two infected seed lots (cv. Otira with 14.4% and cv. Fager with 6.9% infected seeds) to evaluate and compare the effect of Fungazil C (carboxin + imazalil) and Premis Robust (triticonazol + imazalil) against loose smut. Fungazil C at normal rates reduced loose smut frequencies by approximately 50% or less. At twice the normal rate, loose smut symptoms were reduced by 60-80%. Premis Robust showed more effective loose smut control, but did not confer complete control.