Bioorganic chemistry of rice diseases by considering interactions between organisms, and its development in plant protection and breeding.

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Objectives : 1) As a result of our investigation on a host plant and pathogen, ten novel kauran-related antibacterial compounds, oryzalides, have been isolated from leaves of a rice plant, Norin 27. A role of oryzalides has been determined to be as an inhibitin by quantitative analysis using the GC-SIM method. Further investigations are required to use oryzalides as a marker of resistance of rice plant against bacterial leaf blight. 2) Studies on the biosynthetic pathway of oryzalic acid A.3) Isolation and identification of anti-microbial compounds against plant pathogens.Results : 1) Studies on resistance mechanism of rice plant against a bacterial leaf blight caused by Xanthomonas campestris pv oryzae. a) Quantitative analysis of oryzalides in leaves of various cultivars using GC-SIM to investigate correlation between level of resistance and content of oryzalides. Oryzalides were observed in each cultivar and their role as an inhibitin was confirmed. However, their content in each le … More af did not show a primary correlation with level of resistance. During these investigations oryzadione (compound D) was found to be an important compound as a precursor of oryzalic acid A.A method of quantitative analysis of oryzadione was established using LC-MS-MS.b) Quantitative analysis of oryzalides in leaves of seedling stage was investigated in order to detect resistance rapidly. A similar result as in the tillering stage was obtained. 2) A biosynthetic pathway of oryzalides was preliminarily investigated as follows : a) Establishment of cell culture condition of Norin 27. Production of oryzalic acid A was stimulated ten times using four times the seed amount and a further 2 to 3 times by the addition. of chitin and oxalate. b) Feeding experiments of C14-labeled mevalonic acid and kaurene using intact plant were carried out. At present their results remain unclear due to insufficient incorporation into oryzalic acid fraction. 3) An antifungal compound was investigated from rice cultivars and several wild rice strains. Several novel resorcinol-related compounds were isolated from extract of etiolated RD-25 and their structures were determined. Less