Journal of Pesticide Science最新文献

We investigated whether various modified cyclodextrins (CDs) and emulsifiers could be applied as dispersing agents in ready biodegradability tests of poorly water-soluble substances. Trimethylated α-, β-, and γ-CDs and partially methylated β-CD were not biodegraded in the test period but accelerated the biodegradation of octabenzone and anthraquinone. The process by which trimethylated α-, β-, and γ-CDs enhance the biodegradation of test substances has been partially uncovered. These CDs create inclusion complexes with the substances, which then coalesce into larger aggregates. These aggregates disperse throughout the testing medium and attach to clusters of activated sludge, known as flocs. This close contact with the sludge speeds up the breakdown of the hydrophobic substances being tested.

A search for antifungal compounds from the mushroom Coprinus comatus using a bioassay-guided chromatographic fractionation approach led to the discovery of a novel polyketide harboring a rare 3,3a,9,9a-tetrahydro-1H-furo[3,4-b]chromen-1-one skeleton. The novel compound was named coprinolide. The inhibitory activity and fungicidal potential of coprinolide were evaluated against five economically important plant-pathogenic fungi. Coprinolide showed inhibitory effects on conidial germination and germ tube elongation of all tested fungi. The strongest effect was observed for Colletotrichum orbiculare with half-maximal inhibitory concentrations of 7.1 ppm and 8.2 ppm for conidial germination and germ tube elongation, respectively. Furthermore, coprinolide exhibited fungicidal activity against the tested fungi by inhibiting conidial germination to conidial death as confirmed by fluorescence microscopy using fluorescein diacetate and propidium iodide. These findings showed the potential of the mushroom as a source of a novel bioactive compound with promising agricultural application as an antifungal agent against different plant-pathogenic fungi.

When a test substance is poorly water-soluble, it can be adsorbed onto silica gel to facilitate dispersibility in a ready biodegradability test. To uniformly adsorb the test substance onto silica gel, the substance is dissolved in a solvent and then mixed with the silica gel. It is desirable for the solvent to completely evaporate afterward. In this study, we identified n-hexane as a suitable solvent for this purpose. Furthermore, through fluorescence observation, we revealed that the test substance adsorbed onto the silica gel adhered to activated sludge flocs. This is thought to improve contact between the test substance and microorganisms, thereby accelerating biodegradation.

Agonists of insect hormones, namely molting hormone (MH) and juvenile hormone (JH), disrupt the normal growth of insects and can be employed as insecticides that are harmless to vertebrates. In this study, a series of experiments and computational analyses were conducted to rationally design novel insect hormone agonists. Syntheses and quantitative structure-activity relationship (QSAR) analyses of two MH agonist chemotypes, imidazothiadiazoles and tetrahydroquinolines, revealed that the structural factors important for the ligand-receptor interactions are significantly different between these chemotypes. On the other hand, a virtual screening cascade combining ligand- and structure-based methods identified a piperazine derivative as a novel JH agonist. The results obtained in this study will be useful for the future development of novel insect growth regulators.

Pyriofenone demonstrates outstanding efficacy in controlling powdery mildew. We investigated the impact of pyriofenone on the infection processes and cytological features of Blumeria graminis f. sp. tritici on wheat leaves. The preventive application of pyriofenone before inoculation did not inhibit conidial germination but effectively suppressed both appressorial and haustorial formation. Notably, haustorial formation was effectively inhibited, resulting in the complete suppression of successive lesion development and sporulation. Curative application of pyriofenone after inoculation also inhibited lesion expansion and sporulation. Furthermore, it had considerable impact on the morphogenesis of powdery mildew fungus. We observed multi-formed secondary appressoria, shrunken or bifurcated hyphae, abnormal conidiophores, and clubbed conidia-like structures. Subsequently, we employed a histochemical approach to analyze the localization of essential components for the polar growth of fungal hyphae. Pyriofenone induced mislocalization of the actin cytoskeleton, β-glucan and cytoplasmic vesicles, although it did not affect tubulin orientation.

An antifungal polyene-decalin polyketide natural product, burnettiene A (1) has been re-discovered from the culture broth of Lecanicillium primulinum (current name: Flavocillium primulinum) FKI-6715 strain utilizing our original multidrug-sensitive yeast system. This polyene-decalin polyketide natural product was originally isolated from Aspergillus burnettii. The antifungal activity of 1 against Candida albicans has been reported. However, only one fungal species for the antifungal activity of 1 has been revealed, and details of the antifungal activity against other pathogenic fungus remain unknown. After extensive screening for antifungal activity, we found that 1 exhibits broad antifungal activity against pathogenic plant fungi, including Colletotrichum gloeosporioides, Botrytis cinerea, Pyricularia oryzae, Leptosphaeria maculans, and Rhizoctonia solani. Furthermore, we synthesized 12 derivatives from 1 and evaluated their antifungal activity to reveal the detailed structure-activity relationship. The methyl ester derivative showed antifungal activity against Saccharomyces cerevisiae 12geneΔ0HSR-iERG6 100-fold more potent than that of 1. Our research indicates that 1 would be a promising natural product as a new fungicidal candidate and the methyl ester derivative especially has great potential.

Strigolactones (SLs) are a class of plant hormones that play several roles in plants, such as suppressing shoot branching and promoting arbuscular mycorrhizal symbiosis. The positive regulation of plant disease resistance by SLs has recently been demonstrated by analyses using SL-related mutants. In Arabidopsis, SL-mediated signaling has been reported to modulate salicylic acid-mediated disease resistance, in which the priming of plant immunity plays an important role. In this study, we analyzed the effect of the synthetic SL analogue rac-GR24 on resistance against necrotrophic pathogen Botrytis cinerea. In rac-GR24-treated plants, disease resistance against B. cinerea was enhanced in an ethylene- and camalexin-dependent manners. Expression of the ethylene-related genes and the camalexin biosynthetic gene and camalexin accumulation after pathogen infection were enhanced by immune priming in rac-GR24-treated plants. These suggest that SL-mediated immune priming is effective for many types of resistance mechanisms in plant self-defense systems.

The objective of the present study is to provide reliable concentration values as assigned values for target pesticides in brown rice samples used in proficiency testing (PT) organized by the Hatano Research Institute (HRI). The test samples for PT were prepared by immersing brown rice in the pesticide solution and using a spray dryer by the HRI. Homogeneity and stability assessments were performed for PT samples, and the relative uncertainties due to inhomogeneity and instability were 0.58 %–0.78 % and 0 %–0.96 %, respectively. Quantification for the assigned values of target pesticides by the National Metrology Institute of Japan (NMIJ) was carried out using the multiple analytical methods including Japanese official analytical method, QuEChERS, and modified QuEChERS, which were combined with isotope dilution mass spectrometry, to ensure the reliability of the analytical results. The NMIJ assigned values were 0.065±0.004 mg/kg for chlorpyrifos, 0.217±0.012 mg/kg for diazinon, 0.138±0.008 mg/kg for fenitrothion, and 0.138±0.008 mg/kg for malathion.

As Sustainable Development Goals (SDGs) and the realities of climate change become widely accepted around the world, the next-generation of integrated pest management will become even more important for establishing a sustainable food production system. To meet the current challenge of food security and climate change, biological control has been developed as one sustainable crop protection technology. However, most registered bacteria are ubiquitous soil-borne bacteria that are closely related to food poisoning and spoilage bacteria. Therefore, this review outlined (1) the mechanism of action of bacterial pesticides, (2) potential concerns about secondary contamination sources associated with past food contamination, and, as a prospective solution, focused on (3) principles and methods of bacterial identification, and (4) the possibility of identifying residual bacteria based on mass spectrometry.

Approximately 3000 Bacillus thuringiensis (Bt) isolates were screened to discover novel three-domain (3D) Cry proteins active against Helicoverpa zea (corn earworm). From 400 active isolates found during the primary screening, Cry1Ac and Cry2A, which are known to be active against H. zea, were removed using multiplex-primer PCR and high-throughput column chromatography. This process reduced the number of active cultures to 48. DNA segments encoding Domain III of these 48 cultures were amplified by PCR and sequenced. Sequencing revealed two novel Cry1B-type Domain IIIs. Further sequencing of the flanking regions of these domains revealed that one was part of Cry1Bj (GenBank: KT952325). However, the other Domain III lacked Domains I and II. Instead, this Domain III was associated with two open reading frames, ORF1 and ORF2. ORF1 was identified as an ATP-binding protein, and ORF2 as an ATPase, suggesting that Bt exchanges Domain III among homologous Cry proteins.