Leaves of yam (Dioscorea alata) cv. White Lisbon are highly susceptible to infection by the anthracnose fungus Colletotrichum gloeosporioides. Ethanolic extraction of young leaves followed by vacuum concentration of the filtrate and partitioning into ethyl acetate revealed the presence of an antifungal compound in the ethyl acetate fraction as detected by TLC and bioassay using C. gloeosporiodes. The compound had an Rf value of 0.32 on silica plates run in hexane: ethyl acetate: methanol (60:40:1) and showed no phenolic reaction to ferric chloride reagent. An extract from the highly resistant cv. Plimbite also contained this compound and, in addition, three other antifungal compounds with Rf values of 0.39, 0.21 and 0.15. These compounds produced blue/green spots with ferric chloride reagent indicating that they were phenolics. The results indicate that resistance to anthracnose in D. alata cv. Plimbite may be controlled by phenolic antifungal compounds.
Plumbley, R.A.; Sweetmore, A. Phenolic compounds and resistance of yam (Dioscorea alata) to anthracnose caused by Colletotrichum gloeosporoides. Acta Horticulturae (1995) 381 (2) 667-670.