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.

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.

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.

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.

Festulolium hybrids are cool-season forage grasses that form symbiotic relationships with the fungus Epichloë uncinata, which produces loline alkaloids that protect the host from herbivores. This study evaluated the nematotoxicity of shoot and root extracts of Festulolium loliaceum against the stubby root nematode Trichodorus primitivus. Methanolic root and shoot extracts from plants aged 8, 12, 16, and 20 weeks were tested in vitro at five concentrations (312.5–5000 µg mL⁻¹) over 24, 48, and 72 h. Nematode immobility, mortality, and phytochemical profiles, including flavonoids, loline alkaloids, and phenols, were quantified. Extracts from shoots caused significant concentration and time-dependent immobility of T. primitivus (p = 0.001), reaching ≥90% at 5000 µg mL⁻¹ after 72 h in 8–12-week-old plants. Endophyte presence enhanced nematotoxicity, where LD₅₀ values for E+ roots were two-fold lower at 12 weeks and fifty-fold lower at 20 weeks compared with E− root extracts. Shoot extracts of E+ grass had the highest nematicidal activity at 8 weeks, with a significantly lower LD₅₀ value than E− (p < 0.05). Loline alkaloid concentrations increased with plant age, while flavonoids and phenols declined. Nematotoxicity of F. loliaceum extracts was strongly influenced by plant age and endophyte presence. Younger E+ shoots produced the most potent shoot extracts, whereas older plants produced the most potent root extracts. Flavonoid content was negatively correlated with shoot biomass (R = −0.94, p < 0.001). Similarly, phenol content was negatively correlated to both root biomass (R = −0.79, p < 0.001) and shoot biomass (R = −0.67, p < 0.005).