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.

Wheat and barley yields in Japan are considerably lower than those in the UK, even where similar Climate Zones (CZs) of relatively cold and humid nature are shared. In order to understand this difference, it is first necessary to find out if any common climate–yield relationship exists between the two countries. The Climate Zonation Scheme (CZS) developed in the Global Yield Gap Atlas (GYGA) was used to analyse actual yield (Ya) with three climatic factors of the GYGA-CZS, i.e., growing degree days (GDD), aridity index (AI) and temperature seasonality (TS). A significant relationship was found between AI scores and Ya values across the two countries. Ya values decreased with an increase in AI scores; in other words, lower yields are associated with higher AI scores. In addition, the degree of yield reduction with the rise in AI scores was greater in Japan than in the UK. The present study also proposed a novel method to link CZs of the GYGA-CZS to regional classification units, especially for countries where statistical crop yield data are available only at a coarse scale.

Rapeseed (Brassica napus L.), as one of the most important oil crops around the world, has been affected by drought considerably, particularly at flowering when crops are most sensitive to water stress. It has been shown that film antitranspirant (AT) can effectively reduce the yield loss of droughted crops if applied at the critical stage. However, the mechanism remains unclear by which AT mitigates drought damage to plants under different rates of water depletion. Two experiments in randomised complete block designs were conducted on spring rapeseed with two levels of irrigation, well-watered (WW) and water-stressed (WS), where slow and fast soil water depletion were imposed during the flowering stage in mesocosms (Expt 1_SD) and pots (Expt 2_FD), respectively, and different concentrations of AT, 0, 0.25%, 0.5%, and 1% and 0, 0.5%, and 1%, were applied. Leaf physiological traits, seed yield, and yield components were determined. The results showed that compared to WW, water stress reduced leaf relative water content (RWC) by 2% and 6% in Expt 1_SD and Expt 2_FD, respectively, and had detrimental effects on stomatal conductance, CO₂ assimilation rate, and intrinsic water use efficiency. Following AT application, a positive linear relationship was observed in leaf RWC against AT concentrations, albeit with large variations. In Expt 1_SD, seed dry weight and aboveground biomass increased significantly with increasing AT concentrations, while no yield responses were observed in Expt 2_FD, indicating that soil water status may play an important role in rapeseed responses to AT application regardless of concentrations. Therefore, the timing of AT application needs to consider soil water conditions in addition to the growth development of rapeseed plants.

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).

From a perspective of food security, the agricultural sector worldwide has a responsibility to improve crop yields. Wheat yield in Japan is about half that of high‐yielding countries in Northwest Europe. Explanations offered so far—such as high temperatures and a rainy summer season shortening wheat's growth period, or comparatively underdeveloped breeding and cultivation techniques—remain speculative. This lack of clarity risks misdirecting research efforts on wheat cultivation in Japan and possibly other parts of the world. To address the issue, the present study focused on the efficiency of yield formation, rather than yield itself, across Japan and Northwest Europe. The efficiency of yield formation, derived from the division of actual yield by sunshine hours during the specific growth period from ear emergence to maturity, was compared between two geographical regions while factoring in climate variables. Despite the large yield difference, there was no significant difference in the efficiency of yield formation of wheat between the two regions. This indicates that Japan's low yield is largely due to climatic adversity for wheat, that is, high temperature, high precipitation and short sunshine hours during the critical growth phase for yield formation of the crop. The implication is that improvements in breeding and cultivation techniques alone are not likely to significantly increase wheat yield in Japan. A fruitful direction for future research endeavors in wheat production in monsoon Asia was discussed.