Analytical Study of Umbelliferone and Scopoletin Synthesis in Sweet Potato Roots Infected by Ceratocystis fimbriata

Abstract

A chromatographic method was developed for the quantitative estimation of umbelliferone and scopoletin in sweet potato (Ipomea batatas) root tissues infected by the black rot fungus, C. fimbriata. In the variety Norin No. 1, a marked synthesis of umbelliferone occurred 12 hours after inoculation, whereas scopoletin synthesis started alter a lag phase of 1 day. The amount of umbelliferone at its maximum stage was about twice that of scopoletin. The formation of these coumarin compounds was very low in the uninoculated cut tissues, and thus coumarin synthesis is believed to occur after infection. The synthesis of the 2 coumarins was compared in 2 varieties, Norin No. 10, resistant, and Norin No. 4, susceptible. Coumarin synthesis was more conspicuous in the resistant root variety as compared to the less marked synthesis in the susceptible one. The black rot fungus was found to degrade umbelliferone and scopoletin during a 4-day incubation period in liquid culture. Scopoletin was degraded more easily (about 90%) than umbelliferone (about 20%). Neither transformations between these coumarins nor endogenous formation by the fungus alone was detected.