Activity of the botanical aphicides 1,5‐diphenyl‐1‐pentanone and 1,5‐diphenyl‐2‐penten‐1‐one on two species of Aphididnae

1,5‐Diphenyl‐1‐pentanone (A) and 1,5‐diphenyl‐2‐penten‐1‐one (B) are natural products extracted for the first time from Stellera chamaejasme. Laboratory bioassay showed that the two products have strong contact activity and very good anti‐feedant activity against Aphis gossypii and Schizaphis graminum. Both products showed dose‐dependent relationships for both forms of activity against the two aphids, the contact activity of B being about twice that of A. Both products were inferior to methomyl in contact activity but superior in anti‐feedant activity against the two aphids. This is the first report of aphicidal activity in these two compounds, which may represent a new class of aphicide. © 2001 Society of Chemical Industry     

Synthesis and antifungal activity of 2‐azetidinonyl‐5‐(2‐benzoylphenoxy)methyl‐1,3,4‐oxadiazoles against seed‐borne pathogens of Eleusine coracana (L.) Gaertn

BACKGROUND: Finger millet is a major food crop as well as feed and fodder for livestock, especially in regions of southern India. A sturdy crop to fluctuating environmental conditions, it can be cultivated in all seasons of the year. Leaf, neck and finger blast caused by Pyricularia grisea Sacc. and Bipolaris setariae (Saw.) Shoem, as well as leaf spot disease, Bipolaris nodulosa (Berk & M.A.Curtis) Shoem, are major production constraints in southern India. Apart from environmental conditions, the use of harvested seeds by farmers is a major reason for disease prevalence. Benzophenone analogues have been investigated for controlling phytopathogenic fungi. In addition, the most important applications of azetidin‐2‐ones are as antibiotics. Based on this information, the present study was conducted to explore the antifungal activity of integrated 2‐azetidinonyl and 1,3,4‐oxadiazoles moieties into a benzophenone framework. RESULTS: A simple high‐yielding method for the integration of heterocyclic rings, namely 2‐azetidinonyl, at the benzophenone nucleus has been achieved, starting from substituted 2‐hydroxybenzophenones under mild conditions on a wet solid surface using microwave irradiation. In the present study, an array of newly synthesised compounds, 2‐azetidinonyl‐5‐(2‐benzoylphenoxy)methyl‐1,3,4‐oxadiazoles, were screened for their antifungal property against blast and leaf spot causing fungi associated with the seeds of finger millet, cv. Indof‐9. CONCLUSION: Two of the newly synthesised compounds showed promising effects in depleting the incidence of seed‐borne pathogenic fungi of finger millet. The suppression of Pyricularia grisea and Bipolaris setariae resulted in enhanced seed germination and seedling growth. Copyright © 2009 Society of Chemical Industry     

Residues of the herbicide fenoxaprop‐P‐ethyl,its agronomic safener isoxadifen‐ethyl and their metabolites in rice after field application

BACKGROUND: Fenoxaprop‐P‐ethyl is a herbicide used on cereals and in particular on rice, the degradation of which leads to several relevant metabolites. The herbicide is used together with an agronomic safener such as isoxadifen‐ethyl, which also generates some metabolites. The present work was aimed at developing and validating an analytical method for the determination of the above parent compounds and their main metabolites in the edible fractions of rice. Parent compounds were extracted in acetonitrile and determined by gas chromatography with a mass spectrometer detector, while metabolites were extracted in acetonitrile and analysed by liquid chromatography tandem mass spectrometry. RESULTS: The method was validated through recovery tests in rice straw, grain and plant: accuracy was in the range 76–86% and 90–103% for parent compounds and metabolites respectively. Precision, as relative standard deviation, was in the range 3–11% and 6–17% for parent compounds and metabolites respectively. The limit of detection was 0.01 mg kg^?1 for each analyte, while the limit of quantification was set at 0.05 mg kg^?1. CONCLUSION: The analytical method is suitable for quantitative determination of each analyte considered in rice commodities. Copyright © 2010 Society of Chemical Industry     

Cycloate,an inhibitor of fatty acid elongase,modulates the metabolism of very‐long‐side‐chain alkylresorcinols in rye seedlings

BACKGROUND: Cycloate inhibits the biosynthesis of very‐long‐chain fatty acids, the essential constituents of plant waxes and suberin. Fatty acids also serve as precursors of aliphatic carbon chains in resorcinolic lipids, which play a fundamental role in the plant defence system against fungal pathogens. In this study, the effect of cycloate on the biosynthesis of 5‐n‐alkylresorcinols in rye seedlings (Secale cereale L.) grown under various light and thermal conditions was examined. RESULTS: The content of alkylresorcinols biosynthesised in rye was generally increased by the herbicide in both green and etiolated plants. The presence of cycloate also affected patterns of alkylresorcinol homologues in plants grown at 15 and 22 °C; very‐long‐side‐chain compounds were less abundant, whereas both short‐chain saturated and unsaturated homologues were generally accumulated. No cycloate‐related effects caused by homologue pattern modifications were observed at elevated temperature. CONCLUSION: This study extends present understanding of the mode of action of thiocarbamate herbicides. Cycloate markedly affected the biosynthesis of very‐long‐side‐chain resorcinolic lipids in rye seedlings, confirming the existence of parallels in both fatty acid and alkylresorcinol biosynthetic pathways. The observed cycloate‐driven accumulation of 5‐n‐alkylresorcinols may improve the resistance of cereals to infections caused by microbial pathogens. Copyright © 2009 Society of Chemical Industry     

Potential of Ypt1 and ITS gene regions for the detection of Phytophthora species in a lab‐on‐a‐chip DNA hybridization array

A novel DNA‐chip hybridization assay that uses the ras‐related GTP‐binding protein 1 gene (Ypt1) was developed for the identification of several devastating Phytophthora species. The hybridization was conducted in a portable microfluidic lab‐on‐a‐chip device for fast and accurate detection of 40 Phytophthora, two Pythium and one Phytopythium species. Moreover, the functionality of the Ypt1 region was examined in comparison to an array for the internal transcribed spacer (ITS) region by in silico modelling. The difference in species‐specific capture probe sequences was lower for the ITS than for the Ypt1 region. While ITS‐probes of Phytophthora ramorum, Phytophthora fragariae and Phytophthora lateralis cross‐reacted with up to 11 non‐target species, Ypt1‐probes were specific except for P. fragariae/Phytophthora rubi. First analyses of artificially inoculated Rhododendron leaves successfully demonstrated the usability of the respective capture probes for the Ypt1 and the ras‐related plant protein Rab1a gene region. The on‐chip hybridization enabled the detection of up to 1 pg μL^?1 target DNA depending on the species examined. Due to the complementarity of ITS and Ypt1 genetic features, the use of multiple loci is recommended to identify targets of different taxonomic rank.     

Involvement of cytochrome P‐450 enzyme activity in the selectivity and safening action of pyrazosulfuron‐ethyl

To investigate the selectivity and safening action of the sulfonylurea herbicide pyrazosulfuron‐ethyl (PSE), pyrazosulfuron‐ethyl O‐demethylase (PSEOD) activity involving oxidative metabolism by cytochrome P‐450 was studied in rice (Oryza sativa L cv Nipponbare) and Cyperus serotinus Rottb. Cytochrome P‐450‐dependent activity was demonstrated by the use of the inducers 1,8‐naphthalic anhydride and ethanol, the herbicides PSE, bensulfuron‐methyl, dimepiperate and dymron, or the inhibitor piperonyl butoxide (PBO). Growth inhibition in C serotinus seedlings was more severe than that in rice seedlings. O‐Dealkylation activities of PSE were induced differently in rice and in C serotinus, with distinctly higher activity in rice seedlings. The induced PSEOD activities were slightly inhibited by PBO in rice seedlings, whereas they were strongly inhibited in C serotinus seedlings. Dimepiperate and dymron were effective safeners of rice against PSE treatment. Treatments with herbicide alone resulted in less induction of PSEOD activity compared with combined treatments of the herbicide and safener. PSEOD activity in rice seedlings induced with herbicide alone was strongly inhibited by PBO, whereas it was weakly inhibited in rice seedlings induced with combinations of PSE and two safeners. These results suggest that O‐demethylation by cytochrome P‐450 enzymes may be involved in the metabolism of PSE and may contribute to its selectivity and safening action. Furthermore, these results suggest the existence of a multiple form of cytochrome P‐450 in plants. © 2001 Society of Chemical Industry     

Silencing of Erwinia amylovora sy69 AHL‐quorum sensing by a Bacillus simplex AHL‐inducible aiiA gene encoding a zinc‐dependent N‐acyl‐homoserine lactonase

Quorum sensing in Gram‐negative bacteria is regulated by diffusible signal molecules called N‐acyl‐l ‐homoserine lactones (AHLs). These molecules are degraded by lactonases. In this study, six Bacillus simplex isolates were characterized and identified as a new quorum‐quenching species of Bacillus. An aiiA gene encoding an AHL‐lactonase was identified based on evidence that: (i) it showed high homology with other aiiA genes of Bacillus sp.; (ii) the deduced amino acid sequence contained two conserved regions, ¹⁰⁴SHLHFDH¹¹¹ and ¹⁶⁵TPGHTPGH¹⁷³, characteristic of the metallo‐β‐lactamase superfamily; and (iii) the protein had zinc‐dependent AHL‐degrading activity. Additionally, the expression of the aiiA gene was significantly up‐regulated by 3‐oxo‐AHL. The AHL‐lactonase inhibited multiplication of the 3‐oxo‐C6‐AHL‐producing plant pathogen Erwinia amylovora sy69 both in vitro and in planta. The results provide support for the use of the quorum‐quenching functionality of B. simplex in the integrated control of the devastating fire blight pathogen.