Isolation of strigol, a germination stimulant for Striga asiatica, from host plants

The germination of Striga asiatica, a root parasite of many cereal and leguminous crops, is stimulated by several host and nonhost plant derived stimulants. HPLC revealed the presence of three active compounds in root exudates from Striga host plants, maize and sorghum, and also from proso millet. A fourth active compound was present in sorghum exudates. Acetate and heptafluorobutyrate derivatives were prepared and analyzed by HPLC and mass spectrometry. Each step involved in the isolation, chromatographic purification, and derivatization was followed by a sensitive Striga seed germination bioassay. We report the isolation of strigol as the major Striga seed germination stimulant in maize and proso millet root exudates and as a minor component of the total activity in sorghum root exudates. Strigol was previously isolated only from cotton, a nonhost plant