Specific accumulation of antifungal 5-alk(en)ylresorchinol homologs in etiolated rice seedlings

The accumulation of a mixture of 5-alk(en)ylresorcinol homologs (ARs) composed of C-13:0, C-15:1, C-15:0, C-17:1, and C-17:0 carbon chains in rice seedlings (Oryza sativa, cv. RD-25) that exhibited high antifungal activity against the rice blast fungus was specific to etiolated plants. ARs accumulated specifically in the etiolated plants, this accumulation being much more in the underground sections, and decreased rapidly when the etiolated seedlings were exposed to light. Indica- and Africa-type cultivars and weedy- and wild-type rice accumulated the ARs, but Japonica-type cultivars did not. Interestingly, the ratio of ARs in the wild rice varieties distantly related to the cultivars was significantly different from that of the wild rice closely related to the cultivars and weedy types.