Yasuhiko Uesugi

Movement and metabolism of S‐benzyl O,O‐diisopropyl phosphorothiolate (Kitazin P®) and O‐ethyl S,S‐diphenyl phosphorodithiolate (edifenphos) in various types of soils

Movement and Metabolism of 32P and 35S-double labeled Kitazin P (S-benzyl O,O-diisopropyl phosphorothiolate) and 35S-labeled edifenphos (O-ethyl S,S-diphenyl phosphorodithiolate) were examined with three types of soils, sandy loam, alluvial clay loam, and volcanic ash loam. Vertical movement of both the compounds in soil column was different with soil types, and the order of mobility in soil column was as follows: sandy loam greater than alluvial clay loam greater than volcanic ash loam. Persistence of edifenphos in soil was shorter than that of Kitazin P. Main degradation products at the initial stage of metabolism were S,S,S-triphenyl phosphorotrithiolate, O,O-diethyl S-phenyl phosphorothiolate, S-phenyl dihydrogen phosphorothiolate and diphenyl disulfide in edifenphos and O,O-diisopropyl hydorgen phosphorothioate in Kitazin P. Sulfur atom of Kitazin P was found in sulfuric acid at a minor level through dibenzyl disulfide and toluene-alpha-sulfonic acid, and that of edifenphos was converted to sulfuric acid through diphenyl disulfide and benzenesulfonic acid. Kitazin P under flooded condition of alluvial clay loam was slightly more persistent as compared with upland condition. Sterilized condition of Kitazin P did not cause any appreciable degradation throughout the experimental period, but such condition did not necessarily prevent the degradation of edifenphos.

METABOLISM OF A PHOSPHOROTHIOLATE FUNGICIDE IBP BY STRAINS OF PYRICULARIA ORYZAE WITH VARIED SENSITIVITY

Abstract A survey was made for metabolism of an organophosphorus fungicide, S -benzyl O, O -diisopropyl phosphorothiolate (IBP, Kitazin P), by strains of Pyricularia oryzae , the rice blast fungus, primarily consisting of those recently isolated from the field in Japan. All the field-isolates sensitive to IBP degraded it by cleavage of both S-C and P-S bonds, while all the moderately resistant field-isolates degraded it by cleavage of S-C bond and no appreciable cleavage of P-S bond was found. Most of the moderately resistant field-isolates degraded IBP faster than sensitive ones. The field-isolates resistant to IBP, the type rarely found in the field, hardly degraded IBP. This type of resistant field-isolate was quite similar to laboratory-derived resistant mutants in that the group is specifically sensitive to some phosphoramidates and unable to metabolize phosphoramidate and IBP. The metabolism of IBP in sensitive and moderately resistant isolates seems inducible by phenobarbital and by IBP itself and was inhibited by piperonyl butoxide, but that in resistant field-isolates and laboratory-derived mutants was hardly inducible. The characteristic mode of IBP metabolism in strains having varied sensitivity suggests an involement of the metabolism in resistance mechanism, and the cleavage of P-S bond may have direct or indirect connection with the fungicidal action of IBP while the cleavage of S-C bond seems a detoxification.

A Survey of Cross-resistance between Kasugamycin and Other Protein Biosynthesis Inhibitors in Pyricularia oryzae

タンパク合成阻害剤であるカスガマイシンに感受性を異にする各種イネいもち病菌菌株を供試し, 選択性を異にする各種タンパク合成阻害剤の抗菌力を測定して, カスガマイシンとの交差耐性を検討した. 5種の抗細菌性抗生物質および除草剤アシュラム, EPTCは100μg/mlですべての菌株に対して殺菌活性を示さなかった. 除草剤 barban, propanil, chlorpropham は32μg/ml, 抗かび性抗生物質 cycloheximide は0.32μg/mlですべてめ菌株に対して殺菌活性を示したが, カスガマイシンとの交差耐性は見られなゆった. カスガマイシンとブラストサイジンSとの間に交差耐性を示す菌株が多かったが, 前者のみに耐性を示す室内変異菌株および圃場分離菌株もあり, カスガマイシン耐性を支配する遺伝因子が複数個存在することが示唆された.

Uptake of Homologous Series of P-n-Alkylphenols by Phytopathogenic Fungi

Uptake of homologous series of p-n-alkylphenols by fungi from aqueous phase was studied using spores of Piricularia oryzae and Gibberella fujikuroi, and mycelia of P. oryzae as test organisms.Process of uptake seemed to be physical, because dead cells took up as much phenol as did living cells. Amount of phenol taken up by fungal cells equilibrated with concentration of remaining phenol in external aqueous phase. Uptake was found to increase with increasing alkyl side chain length, and solubility of the homologous series decreases at higher rate than uptake increases. Uptake of higher homologue is not supposed to reach the level enough to inhibit growth of fungi, on account of its slight solubility.These results explain the reason why antifungal activity of p-n-alkylphenol increases with increasing alkyl chain length up to a certain homologue, and decreases for the higher members.