Exploratory study on allelopathic effect of selected Malaysian rice varieties and rice field weed species

M. Azmi, M. Z. Abdullah and Y. Fujii

Abstract

Development of allelopathic rice would be an alternative to chemicals and other cultural practices in reducing the occurrence of weed infestation in direct-seeded rice. A study to screen Malaysian indigenous and improved rice varieties for allelopathic activity was conducted in MARDI Research Station, Seberang Perai using plant box method. This method detects the allelopathic effect of root exudates by growing test plant in mixed culture in agar media. Lettuce was used as acceptor-indicator (test plant) and rice plant as a donor. The allelopathic effect of rice varieties was assessed by observing radicle growth of lettuce seedlings. Several traditional varieties like Siam Er 54, Jambok, Wangi and modern varieties viz. MR 77 and MR 84 were found to have strong allelopathic activity on lettuce seedlings. The tests were repeated by replacing lettuce with a selected rice field weed species namely Echinochloa crus-galli (L.) Beauv. Similarly, some rice varieties were detected to have strong allelopathic effect on E. crus-galli seedlings. Traditional varieties such as Padang Gelap, Acheh Puteh, Pasir, Singgora, Merah Isi, Chatek Kuning, Anak Naga and Anak Didek 3 were found to have strongest allelopathic activity on E. crus-galli seedlings. A second study was conducted using bioassay method known as sandwich method to assess the effect of leaf and debris taken from rice field weed species. Again, several rice field weed species showed strong inhibitory action on the growth of lettuce seedlings. The weed species were Pennisetum purpureum Schumach, Isachne globosa (Thunb.) O. K., Cyperus rotundus L., Sagittaria guyanensis H. B. K. and Fimbristylis miliacea (L.) Vahl.

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