Phytophthora inhibitors

Polyoxins are inhibitors of chitin biosynthesis. Chitin is a component of fungal cell walls except in Phycomycete fungi these contain cellulose as their major cell wall constituent, hence polyoxins are inactive against Plasmopara, Pythium and Phytophthora. 

Peng, J.H. Black, L.L. (1976) Increased Proteinase Inhibitor Activity in Response to Infection of Resistant Tomato Plants by Phytophthora infestans. Phytopathology 66, 958-963. 

Chemical Name 5-ethoxy-3-(trichloromethyl)-l,2,4-thiadiazole ethyl 3-trichloromethyl-l,2,4-thiadiazolyl ether Uses as fungicide for control of Phytophthora and Pythium spp. in cotton, ornamentals, vegetables, groundnuts, cucurbits, tomatoes, and other crops also used as a nitrification inhibitor in maize, cotton and wheat. 

Aliette (aluminum tris-0 ethylphosphonate) has been reported to enhance defense reactions and phytoalexin accumulation in grapes and tomatoes in response to infection by Plasmopara viticola and Phytophthora spp., respectively, and to trigger phenolic accumulation and hypersensitive cell death in tomatoes, peppers, and beans in response to infection while possessing little direct fungitoxicity (116,117). However, recent data cast doubt on the earlier reports of the low activity of Aliette as an inhibitor of Phytophthora sporulation mi vitro (118), and have attributed the protective properties of the compound to phosphorous acid which is formed in plant tissues or in certain buffer solutions of Aliette (119,120). Toxicity of phosphorous acid to Oomycetes is reversible by phosphate ion, and this may explain Aliette s lack of fungitoxicity in certain growth media. 

The fungicidal activity of sceptrin at 10 ppm was found to be >65 % inhibition of Phytophthora infestans (potato late blight) [103]. In addition to its antimicrobial, antiviral [104], antimuscarinic [22], and antihistaminic [30] properties, sceptrin was shown to be the first and most potent nonpeptide somatostatin inhibitor in the submicromolar range [105]. 

M. Rickauer, J. Fournier and M.T. Esquerre-Tugaye, Induction of proteinase inhibitors in tobacco cell suspension culture by elicitors of Phytophthora parasitica var. nicotianae. Plant Physiol., 90 (1989) 1065-1070. 

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