Submitted to: HortScience
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/5/2002
Publication Date: 10/2/2003
Citation: Peterson, J.K., Harrison Jr, H.F., Jackson, D.M., Snook, M.E. 2003. Biological activities and contents of scopolin and scopoletin in sweetpotato clones. Hortscience. 38:1129-1133. Interpretive Summary: Sweetpotatoes are susceptible to a number of fungal diseases which cause stem and root rot in the field and root rot during storage. These diseases, usually introduced after mechanical damage or insect feeding, significantly reduce yield and market value of this corp. The peel of sweetpotatoes contains a number of anti-fungal compounds; two (scopolin and scopoletin) were tested for their ability to suppress growth of four disease causing molds, growth of insect larvae and germination of weed seeds. We also determined the concentration of these chemicals in 14 genetically different sweetpotato varieties. We found that scopoletin, but not scopolin was active in all cases. The four fungal diseases were most sensitive to and were inhibited at low concentrations of scopoletin. Chemical analyses of the 14 varieties showed large differences in concentration, indicating good potentials for breeding to obtain higher concentrations of these anti- fungal compounds.
Technical Abstract: Periderm and cortex tissues of 14 genetically diverse sweetpotato [Ipomoea batatas (L.) Lam.] clones, grown under low stress conditions, were analyzed for their content of scopoletin ((7-hydroxy-6-methoxycoumarin) and scopolin (7-glucosylscopoletin). Large differences in concentrations of both compounds and in both tissues, were found. The two compounds were tested in nvitro for their biological activity (concentration - activity relationships) using the following parameters: germination of proso-millet (Panicum milliaceum L.) seed, mycelial growth of the sweetpotato fungal pathogens Fusarium oxysporum Schlecht. f. sp. batatas (Wollenw.) Snyd. & Hans; F. solani (Sacc.) Mart.; Lasiodiplodia theobromae (Pat.) Griffon & Maubl., and Rhizopus stolonifer (Ehr. ex Fr.) Lind. In addition, the compounds were assayed for their effects on growth and mortality of diamondback moth [Plutella xylostella (L.)] larvae. The glycoside showed little, if any effects, except F. oxysporum was inhibited. The aglycone scopoletin inhibited seed germination and larval growth; however, at much higher concentrations than were measured in the two tissues. However, mycelial growth of the four pathogenic fungi was inhibited at concentrations occurring in some sweetpotato clones.