Differentiation of Ecotypes in Oryza Sativa L. : I. Re-examination for Color Reaction with Phenol

Abstract

The color reaction of rice grains with phenol can be clearly and quantitatively determied by the present method in which both the colorations of grain surface and phenol solution are measured after soaking grains in diluted phenol solution for 3 to 5 days. This method is more effective to clarify the phenol reaction of the cultivars with colored hull and brown rice, as compared to the ordinary method in which only the coloration of grain surface is observed. The phenol oxidation system is localized only in grains, but not in rachis, branches, leaves, nodes and internodes. Hull and brown rice separated from the grain showed different reaction with phenol each other. F₃ hybrid seeds of the cross between wild (positive phenol reaction) and cultivated (negative phenol reaction) rice segregated into four combinations of hull and brown rice regarding their color reaction with phenol, i.e, both positive, positive and negative, negative and positive, and both negative, respectively. Therefore, when testing the phenol reaction, hull and brown rice should be examined separately. Phenolase activity test suggested that the rice cultivars showing negative reaction with phenol are unable to be further hydroxylated into aromatic ring of phenol due to a lack of hydroxylating enzyme and/or a shortage of electron donors.