Stubby root nematodes (SRN)-(Trichodorus and Paratrichodorus spp.) are economically important plant parasitic nematodes (PPNs) in east England and have been reported to cause up to 50% root yield reduction in sugar beet (Beta vulgaris). The banning of nematicides such as Vydate (oxamyl) due to environmental concerns limits the management options available to farmers for the management of this nematode. Cover crops (CCs) present a practical option for farmers to manage nematodes whilst enhancing other soil properties such as structure, organic matter content and soil biodiversity, which contributes to the overall soil health. This study evaluated the population dynamics of SRN in field rotations with cover crops. The effect of cover cropping on the yield and quality of follow-up crop, sugar beet, was also evaluated. Field experiments were initiated at two sites in England: Bury St Edmunds, Suffolk (site 1) and Docking, Norfolk (site 2). The cover crops evaluated were-Indian mustard (Brassica juncea), oilseed radish (Raphanus sativus), daikon radish (Raphanus sativus var. longipinnatus), Festuca-lolium hybrid grass (Festulolium loliaceum) with endophyte (E+) and without (E-), Italian rye grass (Lolium multiflorum), phacelia (Phacelia tanacetifolia) and opium poppy (Papaver somniferum). At site 1, plots drilled with brassica cover crops, Indian mustard and oilseed radish, had significantly lower SRN reproduction factor (Rf) (p < .05) compared to the fallow control and daikon radish. In site 2, plots drilled with the cover crops-Italian rye grass, Indian mustard, grass without endophyte (E-) or left fallow and undisturbed had a significantly higher Rf (p < .05) compared to plots with phacelia, opium poppy, and disturbed or sterile fallows. Sugar beet root fanging (%) and root soil tare (%) were lower in plots that had lower SRN reproduction, that is, phacelia, opium poppy, sterile fallow, and disturbed fallow. Environmental variables such as rainfall and soil temperature also influenced SRN densities at different sampling points where SRN increased with increasing rain and decreasing soil temperatures. Results from this study indicate that under field conditions the population dynamics of SRN are influenced by multiple factors such as the host status of the CCs grown, weed occurence which serve as alternative hosts as SRN are polyphagous in nature, soil temperature, rainfall, and soil disturbance. It was also clear that multiplication rate of SRN in CCs such as phacelia and opium poppy was lower despite SRN being able to multiply in all cover crops tested in this study.

Phytophthora rubi has been reported as the primary causal agent of raspberry root rot (RRR) in the UK, resulting in severe economic losses. Recent observations suggest the RRR complex may be more diverse than previously thought. This study investigated the Peronosporales species present in UK raspberry plants and factors affecting their diversity and abundance. Eighty-six symptomatic root and 86 cane samples were collected from seven farms in the UK in 2020 and 2021. Five additional samples were collected from blackberry roots. Symptomatic tissue was plated onto selective media, and resultant isolates were identified by ribosomal internal transcribed spacer (ITS) barcoding. Twelve isolates of five species of Phytophthora (P. citrophthora, P. pini, P. erythroseptica, P. cryptogea and P. pseudocryptogea) and seven isolates of two Phytopythium species (Pp. vexans and Pp. litorale) were collected. Isolate pathogenicity was assessed on detached leaves, with Pp. litorale and Pp. vexans exhibiting significantly higher pathogenicity on raspberry leaves than an isolate of P. rubi. High-throughput sequencing of the ITS region of symptomatic root samples revealed farm location had a significant effect on Peronosporales community composition (p = 0.001), and both farm location and plant variety significantly affected the abundance of taxa (p < 0.002 and p < 2 x 10(-16), respectively). This study presents Pp. vexans and Pp. litorale as new potential pathogens for further study. Furthermore, we recommend the inclusion of other Peronosporales species into resistance screens in raspberry breeding programmes to produce genotypes more resilient to community composition shifts in raspberry root pathospheres in the UK.

This study investigated the potential of utilising cool season grasses naturally associated with Epichloë endophytic fungi for the management of plant-parasitic stubby root nematodes (Trichodorus spp. and Paratrichodorus spp.). Stubby root nematodes are economically important in East England where they cause docking disorder in sugar beet which causes up to 50% root yield reduction. The lack of chemical nematicides for the management of stubby root nematodes due to environmental concerns warrants the development of more eco-friendly measures. Epichloë fungal endophytes are known to confer protection from herbivory to their cool-season grass hosts, via the production of alkaloidal compounds. Several Epichloë species are known to produce loline alkaloids, a group of compounds known for their insecticidal and insect-deterrent properties. Lolines have also been reported to inhibit nematode mobility, egg hatching and mortality. In this study, Festulolium loliaceum and its associated endophyte Epichloë uncinata, known for its production of loline alkaloids, were investigated for their efficacy in suppressing stubby root nematodes. In a field experiment in Docking, Norfolk, England, endophyte-infected grasses significantly reduced the reproduction of stubby root nematodes by seven times compared to endophyte-free grass associations. Laboratory experiments using extracts from shoots and roots of F. loliaceum plants showed that both endophyte-infected and endophyte-free plants could immobilize nematodes. Age, source of extract and extract concentration had a significant effect on the nematocidal activity. Extracts from younger grasses were more potent compared to older grasses, where shoot extracts from 8-week-old endophyte-infected grass plants had six times lower LD50 values compared to 20-week-old grass plants. A contrasting effect was found for grass root extracts where roots from older plants were more potent than extracts from roots from younger plants, and had lower potency compared to shoot extracts. Further laboratory experiments showed that artificial wounding of endophyte-infected F. loliaceum plants elevated the loline alkaloids in the regrowth tissue within the first 11 days. Nematicidal activity of extracts from this regrowth tissue was significantly greater as compared to extracts from unwounded grass tissue. Overall, the results from this study suggest that endophyte-infected grasses could serve as a potential cultural management strategy for stubby root nematodes in a sugar beet crop rotation system. It is also evident that stubby root nematodes are sensitive to loline alkaloids produced from the grass-endophyte symbiosis used in this study, and this system could be optimised in the future to support nematode suppression under field conditions.

Phospholipase D (PLD)-mediated lipid signalling is a crucial component of plant defence responses. However, the PLD gene family remains poorly characterised in hexaploid wheat ( Triticum aestivum L.), particularly regarding its role in resistance to Fusarium head blight (FHB), a devastating fungal disease. This study identified 178 non-redundant PLD genes in the wheat genome and comprehensively analysed their phylogenetic relationships, conserved domains, chromosomal distribution, promoter cis-elements, and expression profiles under Fusarium graminearum infection. These PLDs were classified into C2-dependent, PX–PH, and uncharacterised types. Promoter analysis revealed stress- and hormone-responsive cis-elements, while expression profiling demonstrated genotype-dependent induction patterns, with several PLDs strongly upregulated in the resistant genotype. We experimentally validated that tae-miR160 targets specific TaPLD transcripts, revealing a post-transcriptional regulatory layer. Furthermore, polymorphic SSR markers were developed from PLD loci for potential use in marker-assisted breeding. This study provides the first evidence of a miRNA–PLD regulatory network in wheat defence and highlights PLDs as critical mediators of FHB resistance.

Plant parasitic nematodes (PPNs) have a negative impact on a broad range of UK-grown ornamental crops, including Narcissus. As a consequence of direct damage through infection and feeding, the nematodes Ditylenchus dipsaci, Pratylenchus penetrans, and Aphelenchoides subtenuis can cause a reduction in the viability, quality, and marketability of bulbs and flowers. Management practices such as lifting after two, three, and four years, limited rotations, and bulk handling predispose Narcissus to nematode attack. To mitigate the impact of PPNs, growers rely on pre-planting methods such as hot water treatment, quarantine/field sanitation, and nematode-free bulbs, as there are no available nematicides with label permission for use on Narcissus. However, these management options, coupled with the legislative removal of synthetic nematicides, are insufficient to manage PPNs of Narcissus. Furthermore, hot water treatment can damage bulbs, and the lack of available land for Narcissus production leads to constrained rotations. Plant parasitic nematodes and associated diseases infecting UK ornamental crop production are generally an understudied area. Here, we review the current status of nematodes associated with Narcissus in the UK, their pathogenicity and management, and highlight areas of potential research towards sustainable management of nematodes in Narcissus.

Summary Brassica plants naturally produce glucosinolates as secondary metabolites hydrolysed to biocidal isothiocyanates (ITCs). As such, they have the potential for nematode management through a strategy known as biofumigation. Pratylenchus penetrans causes significant yield losses in many important crops. Understanding the relative impact of different ITCs on the motility and mortality of this nematode species could provide some insights into the selection of relevant brassica biofumigants. The effects of 3.125, 6.25, 12.5, 25, and 50 μ g ml −1 of pure Allyl, 2-Phenylethyl and Benzyl ITCs on the motility and mortality of P. penetrans were evaluated in laboratory in vitro assays. Motility was assessed after incubating the nematodes in ITCs for 24, 48 and 72 h with distilled water as a negative control. Motile and non-motile nematodes were counted. After motility assessment at 72 h, nematodes were rinsed and incubated in water for 48 h, after which live and dead nematodes were counted. Nematodes were considered dead if they remained non-motile after probing with a picking needle. Nematode motility and mortality were significantly affected by the type of ITC, concentration and time of exposure. The number of non-motile nematodes increased with increasing concentration and time of exposure across all tested ITCs. The ED 50 values (concentration required to cause 50% non-motility) of Allyl, 2-Phenylethyl and Benzyl were 37.4, 12.8 and 8.6 μ g ml −1 after 24 h exposure. The ITC with potentially the greatest nematicidal effect was Benzyl (LD 50 = 3.2 μ g ml −1 ), followed by 2-Phenylethyl (LD 50 = 5.2 μ g ml −1 ), and Allyl (LD 50 = 9.9 μ g ml −1 ). The LD 50 of all ITCs were not different from the ED 50 after 72 h, meaning the effects of ITCs could be considered irreversible. This study suggests that brassica biofumigants that produce Benzyl, Allyl and 2-Phenylethyl ITCs are promising candidates for biofumigation of P. penetrans .

Wheat (Triticum aestivum L.), a vital cereal crop, provides over 20

Summary Pratylenchus crenatus, P. neglectus, P. penetrans and P. thornei are globally the most commonly occurring species of root-lesion nematodes (RLN). Correct identification and quantification of these nematodes is important for strategic management interventions such as rotation choice and nematicide use. A real-time quantitative PCR can provide a fast and reliable alternative to morphological identification, which requires significant taxonomic experience. A TaqMan hydrolysis probe method based on the 28S rDNA D2-D3 expansion region was developed and validated for the identification and quantification of these four root-lesion nematode species. Standard curves for each target RLN species were generated by plotting known gene copy number, obtained by a ten-fold serial dilution of purified plasmids, with corresponding Ct values. Each standard curve had a strong linear correlation () between Ct value and gene copy number. There was consistent amplification of samples with target species from different geographic locations within the UK, whereas a lack of amplification was noted for selected non-target species: P. coffeae, P. pseudocoffeae, P. vulnus, P. fallax, Globodera rostochiensis, Meloidogyne hapla, Trichodorus primitivus and Bitylenchus hispaniensis. Specificity and sensitivity of the methods were confirmed by three experiments that explored different life stages, increasing the number of target species, and had mixed Pratylenchus samples. Finally, estimates obtained by qPCR methods were compared with counting carried out by microscopy showing a good correlation (). The TaqMan real-time PCR developed in this study provides a specific, fast and accurate quantification of P. crenatus, P. neglectus, P. penetrans and P. thornei.

The aim of this study was to compare the susceptibility of oats to Fusarium langsethiae infection, as measured by combined HT-2 and T-2 mycotoxin concentration (HT2 + T2) in harvested oat grain samples. Over 10 years (2004-2013), samples from single replicates of each UK Recommended List oat trial were analyzed for HT-2 and T-2. For spring oats, there were small but statistically significant differences between varieties, whereas for winter oats, they had a broader range and higher mean of HT2 + T2 concentration compared with spring oats. For winter oats, the short-strawed varieties had consistently high HT2 + T2 levels compared with other varieties, whereas naked varieties were at the lower end of the range, and short, naked varieties had intermediate levels. A separate set of harvested oat grain samples of eight common varieties from 17 field experiments were analyzed by modified joint regression analysis. Results showed that environment had the strongest impact on HT-2 and T-2 concentrations but that the varietal susceptibility to HT-2 and T-2 contamination was highly stable across environments. This methodology can be used to calculate a Fusarium (HT2 + T2) resistance score for oats to aid grower selection of suitable varieties, as is available for Fusarium (DON) resistance for wheat varieties in many countries.

Summary Brassicas contain glucosinolates (GSLs), which are converted into different isothiocyanates (ITCs) that possess biocidal activity. These different ITCs result in a range of toxicities to various target species. Laboratory assays were conducted to evaluate the sensitivity of stubby root nematodes (SRN), Trichodorus and Paratrichodorus spp., to three pure, commercially available ITCs, i.e., 2-phenylethyl (PEITC), allyl (AITC) and sulforaphane (SITC) at different concentrations (1.625, 3.125, 6.25, 12.5, 25 and 50 μg ml−1). The effect on nematode mobility was assessed after 24, 48 and 72 h. Mortality of SRN was assessed after 48 h incubation of the nematodes in distilled water post ITC treatment. Mortality for all ITCs at all tested concentrations was significantly higher than the controls, distilled water and 1% DMSO. Concentration and type of ITC had a significant effect on SRN mobility and mortality, whilst increase in exposure time did not significantly increase the immobility of SRN. The average 24 h ED50 (dose that resulted in 50% immobility) for SRN were 7, 5 and 44 μg ml−1, and the average LD50 (dose that resulted in 50% mortality) after 48 h recovery in distilled water was 7, 11 and 24.3 μg ml−1 for PEITC, AITC and SITC, respectively. SITC was significantly less potent compared to PEITC and AITC, which had LD50 values that were four times and two times lower, respectively. These results indicate the potential use of brassica associated with the tested ITC in the process of biofumigation for SRN suppression.

Claviceptaceous endophytic fungi in the genus Epichloë mostly form a symbiotic relationship with cool-season grasses. Epichloë spp. are capable of producing bioactive alkaloids such as peramines, lolines, ergot alkaloids, and indole-diterpenes, which protect the host plant from herbivory by animals, insects, and nematodes. The host also benefits from enhanced tolerance to abiotic stresses, such as salt, drought, waterlogging, cold, heavy metals, and low nitrogen stress. The bioactive alkaloids produced can have both direct and indirect effects towards plant parasitic nematodes. Direct interaction with nematodes’ motile stages can cause paralysis (nematostatic effect) or death (nematicidal effect). Indirectly, the metabolites may induce host immunity which inhibits feeding and subsequent nematode development. This review highlights the different mechanisms through which this interaction and the metabolites produced have been explored in the suppression of plant parasitic nematodes and also how the specific interactions between different grass genotypes and endophyte strains result in variable suppression of different nematode species. An understanding of the different grass–endophyte interactions and their successes and failures in suppressing various nematode species is essential to enable the proper selection of grass–endophyte combinations to identify the alkaloids produced, concentrations required, and determine which nematodes are sensitive to which specific alkaloids.

Twenty-two root samples from raspberry plants exhibiting symptoms consistent with Phytophthora infection, i.e. cane wilt, chlorotic leaves, and blackened roots, were collected from two farms in Perthshire, Scotland, in November 2021 (Fig. 1). Roots were rinsed with water, cut into 20 mm sections, transferred into 70% (v/v) ethanol for 10 seconds and dried on sterile filter paper. Five root sections per sample were aseptically transferred to Petri dishes containing CMA-PARP medium (Stewart et al., 2014), sealed and incubated in the dark at 18°C. The hyphal tips of growing colonies were transferred onto fresh CMA-PARP. Five isolates were obtained, with two distinct morphotypes: one produced sub-globose, non- to semi-papillate sporangia, while the second produced globose and papillate sporangia (Fig. 2). Root material (c. 1–2 g per sample) was freeze-dried in 2 mL microfuge tubes prior to DNA extraction with a PowerSoil Pro Kit (Qiagen, Germany) as per the manufacturer's instructions. PCR was performed using the Phytophthora genus-specific primer pair YPh1F/YPh2R (Schena et al., 2008). The Phytophthora species P. idaei, P. ilicis and P. plurivora were detected in the samples but no isolates of these species were obtained from root samples. To determine the identity of the isolates, the ITS region was amplified and sequenced with ITS5 and ITS4 primers (White et al., 1990). BLAST analysis revealed one isolate with a 99.49% identity to a Phytopythium vexans isolate found in China (GenBank Accession No. MW800643). A fragment of 860 bp was deposited in GenBank (OQ170787). Four further isolates had a 99.54% sequence identity to a Phytopythium litorale isolate found in Chile (KU961896.1). A fragment of 662 bp from one isolate was deposited in GenBank (OQ449690). Metabarcoding analysis of the samples using the primers in Scibetta et al. (2012) detected Pp. litorale and Pp. vexans in 81% and 63% of samples, respectively. A detached root assay, using healthy one year old raspberry cv. Tulameen, was performed. Roots were rinsed in water and submerged in 70% (v/v) ethanol for one minute, rinsed twice in sterile distilled water. Roots were placed on sterile filter paper with 500 μL of sterile water in Petri dishes, 10 replicates per isolate. The basal section of each root was suspended in 500 μL sterile water in a 1.5 mL microfuge tube sealed with plastic film to prevent drying. The apical portion was wounded with a sterile needle and 5 μL of a 1×104 zoospore/mL suspension was pipetted onto the wound. Petri dishes were sealed and incubated at 20°C in the dark for 14 days (Fig. 3). Black lesions were noted on the apical zone of the roots inoculated with Pp. vexans, the basal root zone remained healthy. Pp. litorale caused blackened lesions throughout the entire root. Both species were re-isolated from the diseased roots using the method above. The co-detection of the Phytopythium with the Phytophthora species P. idaei, P. ilicis and P. plurivora in these samples may suggest both genera are involved in root rot on these sites. Both species have been reported on strawberry in the Czech Republic by Pánek & Střížková (2021). This is the first report of Pp. litorale and Pp. vexans exhibiting pathogenicity on red raspberry. The authors acknowledge Katherine Stewart, Georgina Fagg and Jennifer Kingsnorth for their assistance. The work was carried out as part of the Collaborative Training Partnership for Fruit Crop Research (CTP-FCR) programme; code CTP-FCR-2020-9 and funded by the AHDB and the BSPP.

The culture media recommended for the isolation and enumeration of the Fusarium spp. lack selectivity for Fusarium graminearum. Five fungicides—Amistar® (250 g·L−1 azoxystrobin), Filan® (500 g·kg−1 boscalid), Comet® 200 (200 g·L−1 pyraclostrobin), Imtrex® (62.5 g·L−1 fluxapyroxad), Poraz® (450 g·L−1 prochloraz)—were investigated for their potential as selective inhibitors in culture media for the isolation of F. graminearum from soil and plant material. Based on the screening, fluxapyroxad was further tested for selective inhibition for the isolation of F. graminearum from soil. Additionally, selective media were compared for the isolation of F. graminearum from plant material. The fungicides tested did not prove to be effective inhibitors for the development of selective media. For the detection of F. graminearum in plant material, Czapek Dox propiconazole dichloran agar was found to be a better medium than Komada’s media, as the former resulted in colonies with darker pigmentation over a shorter incubation time and appeared to have a less inhibitory effect on F. graminearum growth.

Fusarium head blight (FHB) is an important disease of small grain cereals worldwide, resulting in reduced yield and quality as well as the contamination of harvested grains with mycotoxins. The key mycotoxin of concern is deoxynivalenol (DON), which has legislative and advisory limits in numerous countries. Cereal growers have a number of control options for FHB including rotation, cultivation, and varietal resistance; however, growers are still reliant on fungicides applied at flowering as part of an IPM program. Fungicides currently available to control FHB are largely restricted to triazole chemistry. This study conducted three field experiments to compare a new co-formulation of pydiflumetofen (a succinate dehydrogenase inhibitor (SDHI) with the tradename ADEPIDYN™) and prothioconazole (a triazole) against current standard fungicides at various timings (flag leaf fully emerged, mid-head emergence, early flowering, and late flowering) for the control of FHB and DON. Overall, the co-formulation showed greater efficacy compared to either pydiflumetofen alone or current fungicide chemistry. This greater activity was demonstrated over a wide range of spray timings (flag leaf fully emerged to late flowering). The availability of an SDHI with good activity against FHB and the resulting DON contamination of harvested grain will give growers an additional tool within an IPM program that will provide a greater flexibility of spray application windows and reduce fungicide resistance selection pressure.

High levels of mycotoxins are occasionally observed in Norwegian oat grain lots. Mycotoxins of primary concern in Norwegian oats are deoxynivalenol (DON) produced by Fusarium graminearum and HT2- and T2-toxins (HT2 + T2) produced by Fusarium langsethiae . Improved understanding of the epidemiology of Fusarium spp. is important for the development of measures to control mycotoxins. We studied the susceptibility to F. langsethiae after inoculation at early (booting, heading, flowering) or late (flowering, milk, dough) growth stages in three oat varieties in greenhouse experiments. The varieties had previously shown different levels of resistance to F. graminearum : Odal, Vinger (both moderately resistant), and Belinda (susceptible). The level of F. langsethiae DNA and HT2 + T2 were measured in harvested grain. In addition, we observed differences in aggressiveness (measured as the level of F. langsethiae DNA in grain) between F. langsethiae isolates after inoculation of oats at flowering. Substantial levels of F. langsethiae DNA (mean ≥ 138 pg per μg plant DNA) and HT2 + T2 (≥348 μg/kg) were detected in grain harvested from oats that were spray-inoculated at heading or later stages, but not at booting (mean ≤ 10 pg/μg and ≤ 25 μg/kg, respectively), suggesting that oats are susceptible to F. langsethiae from heading and onwards. Vinger was the most resistant variety to F. langsethiae /HT2 + T2, whereas Odal and Belinda were relatively susceptible. We observed that late inoculations yielded high levels of other trichothecene A metabolites (mean sum of metabolites of 35–1048 μg/kg) in addition to HT2 + T2, in harvested grain, an indication that infections close to harvest may pose a further risk to food and feed safety.

Fusarium graminearum is a globally important cereal pathogen, causing head blight in wheat, resulting in yield losses and mycotoxin contamination. Currently, triazole fungicides are used to suppress Fusarium graminearum, however, the declining effectiveness of triazoles and concerns over the safety of pesticides have led to the pursuit of safe alternative crop protection strategies such as biofumigation. In the present study, species belonging to Brassicaceae (Brassica juncea, Raphanus sativus, Eruca sativa) were assessed for their biofumigation potential against F. graminearum and the glucosinolate profile of the brassicas was determined. In Petri dishes, mycelial plugs of Fusarium graminearum were exposed to frozen/defrosted leaf discs of brassicas collected at early-leaf, stem-extension, and early-bud stages. Additionally, F. graminearum inoculum was incubated in soil amended with chopped tissues of brassicas in a closed jar experiment. Glucosinolate analysis of the leaf tissue of brassicas revealed that the total glucosinolate concentration of B. juncea ‘Brons’ increased with advancing growth stage (24.5–51.9 µmol g−1). Brassica juncea leaf discs were effective against mycelial growth, while the sinigrin content in the leaf tissue corresponded to the level of suppression. At the stem-extension and early-bud stages, B. juncea ‘Brons’ showed 87–90% suppression with four leaf discs, and 100% suppression with eight leaf discs. Brassica juncea ‘Caliente Rojo’ leaf discs collected at the stem-extension stage showed 94% inhibition with eight discs. In the closed jar experiment, each brassica species significantly suppressed F. graminearum inoculum by 41–55%. The findings suggest that the brassica species investigated in the present study could be effective in reducing the inoculum of F. graminearum in soil prior to cereal production.

Fusarium graminearum is the most important causal agent of head blight in wheat, and stalk and ear rot in maize. A field experiment was conducted to investigate the effect of incorporation of Brassicaceae cover crops on Fusarium graminearum in a wheat-maize rotation. Five species belonging to Brassicaceae (Brassica juncea, Eruca sativa, Raphanus sativus, B. carinata, B. oleracea var. caulorapa L.) were used in the field experiment to investigate their potential to suppress F. graminearum inoculum in soil, disease incidence in maize and to reduce subsequent mycotoxin contamination in maize. Brassica juncea was found to contain the highest glucosinolate concentration in shoots (31 µmol g−1). Severity of ear rot and stalk rot in maize was not significantly reduced in the amended plots. Incorporation of R. sativus ‘Terranova’ significantly decreased the amount of F. graminearum DNA by 58% compared with the cultivated fallow treatment, however the DNA concentration was not significantly different to fallow uncultivated. Fusarium graminearum DNA and deoxynivalenol in maize was 50% lower after incorporation of B. oleracea var. caulorapa L. compared to after fallow treatment but the difference was not significant. The brassica crops used in the present field experiment were not effective in suppressing F. graminearum, therefore further studies to optimise the current approach are recommended.

Isothiocyanates are biotoxic degradation products formed as a result of enzymatic hydrolysis of glucosinolates present in Brassica species. The application of biofumigant Brassica crops, as an alternative crop protection method for soilborne pathogens and pests is increasingly gaining interest. However, little is known of the potential of biofumigation to reduce the inoculum of Fusarium species affecting cereals. The aim of this study was to evaluate the antifungal activity of five isothiocyanates, namely allyl, benzyl, ethyl, 2-phenylethyl and methyl isothiocyanates, against germination and growth of Fusarium graminearum under in vitro conditions. Aromatic isothiocyanates were more inhibitory than the aliphatic isothiocyanates against mycelial growth, whereas the reverse was observed for conidial germination. Among the tested isothiocyanates, allyl and methyl isothiocyanates were more efficient overall, showing lower ED50 values (35-150 mg/L) for conidial germination and mycelial radial growth. The findings suggest that Brassica plants containing allyl and methyl glucosinolates could have a suppressive effect, reducing the inoculum of F. graminearum in soil prior to cereal production.

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.

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.