This study investigated the accumulation of cultivar-specific phytoalexins in rice—abietoryzins and oryzalactone—as well as known phytoalexins—momilactone A, phytocassane A, and oryzalexins A and S—in response to sap sucking by the brown planthopper (BPH) and the green rice leafhopper (GRL). The analysis revealed that BPH feeding induced abietoryzin accumulation in a cultivar known to accumulate these phytoalexins following fungal infection. Additionally, oryzalactone and oryzalexin S accumulated after insect attack in specific cultivars, unlike oryzalexin A. Plant hormone profiling revealed distinct associations: momilactone A accumulation was strongly correlated with salicylic acid (SA); phytocassane A with jasmonic acid, jasmonic acid-isoleucine, isopentenyladenine, and abscisic acid (ABA); and oryzalactone/oryzalexin S with both SA and ABA. These findings suggest that distinct signaling pathways regulate the induction of specific phytoalexins. The analysis of phenolic metabolites showed only minor changes in response to insect feeding. The findings highlight the broad inducibility of phytoalexins in rice and reveal the complex hormonal regulation underlying their biosynthesis during herbivore attack.

Tests of sensitivity to isofetamid conducted with Botrytis cinerea isolated from Hokkaido (2011–2016) and other districts in Japan (2017–2018) revealed the absence of isolates with reduced sensitivity. Isolates of B. cinerea with mutation H272Y/R in sdhB, collected in Germany and Japan, resulted in high and moderate resistance to boscalid and many other succinate dehydrogenase inhibitors (SDHIs), respectively. However, these isolates were as sensitive as wild-type isolate to isofetamid. In contrast, isolate BC-50 [P225F] and BC-49 [H272L] caused moderate to high resistance to isofetamid. Considerable differences in mycelial growth, conidiation, conidial germination, and pathogenicity were not observed between these resistant isolates and sensitive isolates. A competitive assay between resistant isolate BC-50 [P225F] and BC-49 [H272L] and B05.10 [wild type], however, revealed the disappearance of resistant isolates after several generations of mixed incubation in in vitro and in vivo conditions.

New asteltoxins U (1) and V (2) were obtained from the solid-state fermentation of Pochonia suchlasporia TAMA 87. The spectroscopic characterization of 1 and 2 revealed that their chemical structures are similar to that of asteltoxin H, except for the modification of the α-pyrone moiety. Specifically, the methyl group on the γ-position of the α-pyrone moiety in asteltoxin H is replaced with a hydroxymethyl group in 1 and 2. In addition, 1 and 2 are a pair of isomers that differ in the geometry of the double bond between C-11 and C-12 in the conjugated triene moiety and that contain an all-trans (9E, 11E, 13E) moiety and a 9E, 11Z, 13E conjugated triene moiety, respectively. Compound 1 showed inhibitory activity toward the first cleavage of sea urchin embryos with a minimum inhibition concentration value of 3.1 µg/mL, whereas compound 2 did not show inhibitory activity up to a concentration of 25 µg/mL.

This study evaluated the matrix effect (ME) in a multiresidue analysis with the modified official Japanese method for agricultural products using liquid chromatography-tandem mass spectrometry (LC-MS/MS). In ME comparisons between the vegetable and fruit samples, it was found that more numerous analytes exhibited ion suppression in the vegetable samples than in the fruit samples, and substantial ion enhancement was not observed in most of the analyte–sample combinations. The ME could significantly vary, even within the same commodity, and it was suggested that sampling has greater influence than measurement when there is a wide ME variability. Dilution, the internal standard calibration method and the matrix-matched calibration method are practical countermeasures against MEs, but certain limitations in their applications should be considered. Moreover, a novel cleanup procedure suitable for hydrophilic neonicotinoid pesticides that minimized the usage of expensive internal standard solutions was suggested.