Screening for Iranian rice allelopathic varieties by HPLC and bioassays

The study on rice allelopathy is very recent in Iran, hence, till now the Iranian varieties with allelopathic potential have not been identified and categorized. The effects of hull water extracts was evaluated on the seedling growth of arrowhead (Sagittaria trifolia) weed. The extracts of varieties ‘Dinorado’ and ‘Neda’ were most suppressive to arrowhead seedling growth than other varieties. High performance liquid chromatography (HPLC) was used to analyze six phenolic acids in rice hull water extracts. Among the tested varieties, Dinorado variety hull extract had maximum phenolic acids content. None of the six phenolic acids were detected in extracts of Line-229, while, Dashti-sard had highest (p)-hydroxy benzoic acid content. Of the 46 tested varieties, 10 were chosen and grown in hydroponics system to study effects of their root exudates on seedling growth of arrowhead weed. Root exudates of Dinorado, Neda and IR-60 showed higher inhibitory activities against arrowhead seedling growth than other tested varieties. Both hull water extracts and root exudates of Dinorado proved most inhibitory to arrowhead weed growth. From Iranian rice germplasm, Neda cultivar had high allelopathic potential against arrowhead weed.