Chemotypes ofCyperus rotundus in Pacific Rim and Basin: Distribution and inhibitory activities of their essential oils.

Four major chemotypes ofCyperus rotundus L. (purple nutsedge) have been reported based on the composition of essential oils in mature tubers. Distribution of the H, M, K, and O type in countries of the Pacific Rim and Basin was investigated. In general, the H type dominates on the islands of Japan, and the O type has the widest range of distribution. The O type also dominates the Pacific Basin islands except for Hawaii, where the K-type is dominant. Inhibitory activity of the essential oils fromC. rotundus tubers against the seedling growth of lettuce and oats was in the order of H > M > K > O. Seven major sesquiterpenes were isolated from the oils and their inhibitory activities determined. Results suggest thatC. rotundus of different chemotypes may have different allelopathic activity in the crop-weed interaction.