polyphenol

The effects of some flavonids on t he growth of Piricularia oryzae and Chochliobolus miyabeanus, the pathogens of rice plant, were studied. Rutin and its agulcon , quercetin, were used throughout the experiments though there were no informations about their existence in rice plants. Results obtained from the experiments carried out at 27C were as follows : 1. Rutin (10^-3M) added to the synthetic medium (Tomizawa's medium) promoted the growth of C. miyabeanus, however, no remarkable effect was obtained in the case of P. oryzae (Fig. 1). 2. Quercetin (10^-3M) showed no appreciable effect to the growth of C. miyabeanus but it inhibited the growth of P. oryzae (Fig. 1). 3. Both fungi turned the rutin media remarkably brown, due probably to the enzymatic oxidation of rutin or to the formation of some new pigments derived from rutin. When quercetin was used, the same result was obtained only in case of C. miyabeanus (Fig. 3). The medium which once became brown in the early stage of culture of C. miyabeanus gradually discolored with the growth of the fungus, owing to the decomposition of quinone type of flavonoids formed by the oxidation or to the decomposition of coloring matters produced (Fig. 3). 4. P. oryzae decomposed both rutin (10^-3M) and quercetin (10^-4M) to protocatechuic acid and phloroglucinol (Fig. 2). These products were not detected in the culture solution of C. miyabeanus, probably in consequence of quick decomposition and absorption of these products by the fungus.