1Department of Horticulture, Faculty of Agricultural Technology, King Mongkut's Institute of Technology Ladkrabang, Chalongkrung Road, Ladkrabang District, Bangkok-10520, Thailand.
2Department of Chemistry, Faculty of Agricultural Technology, King Mongkut's Institute of Technology Ladkrabang, Chalongkrung Road, Ladkrabang District, Bangkok-10520, Thailand.
*Correspondence Author. E. Mail: klchamro@kmitl.ac.th
We selected and examined 10 ecotypes of vetivergrass for their allelopathic effects. The allelopatbhic effects of aqueous extracts of each ecotype leaf, rhizome and root plant parts were determined on germination of radish (Raphanus sativas L.). All studied ecotypes inhibited the radish germination and magnitude of their inhibitory effects were ecotypes dependent and varied among plant parts. Nakhon Sawan ecotype was most inhibitory to radish seed germination. Leaves caused strongest inhibition, followed by rhizomes and roots. In another bioassay, the aqueous extracts (concentration of 100 mg/ml) from leaves of Nakhon Sawan ecotype were applied at germination of 15 bioassay plants. Radish, Pearl millet (Pennisetum americanum L.) and Chinese kale (Brasica oleracea var. alboglabra) were the most sensitive to the extract. Besides, a pot experiment showed that Nakhon Sawan leaf residues used as mulch on the soil surface or incorporated into soil reduced the germination and biomass of radish. To isolate inhibitory allelochemicals, methanol extract of Nakhon Sawan ecotype leaf was partitioned into ethyl acetate soluble acidic, neutral and aqueous fractions. The inhibition activities of three fractions were compared with the original extract. The results showed that inhibitory effects increased after solvent partitioning. The original extracts caused 22% inhibition in germination of radish seed at 4,000 ppm, while, ethyl acetate soluble acidic fraction at 4,000 ppm completely inhibited the seed germination.
Allelochemical, allelopathy, bioassay, inhibition, radish, vetivergrass
