Identification of phytotoxic substances from early growth of barnyard grass (Echinochloa crusgalli) root exudates.
Barnyard grass is a problematic weed worldwide. It competes with crops and causes reduction in crop yields. In this study, barnyard grass suppressed rice emergence, and the degree of rice inhibition was proportional to the density of barnyard grass. Root exudates of barnyard grass reduced germination and growth of lettuce, rice, and monochoria. Fifteen compounds potentially involved in the phytotoxic activities of barnyard grass were isolated and identified, including phenolics, long-chain fatty acids, lactones, diethyl phthalate, acenaphthene, and derivatives of phthalic acids, benzoic acid, and decane. Quantities of diethyl phthalate, decanoic acid, myristic acid, stearic acid, 7,8-dihydro-5,6-dehydrokavain, and 7,8-dihydrokavain were 2.7, 11.1, 19.6, 35.5, 10.3, and 15.5 microg/ml of barnyard grass root exudates, respectively. The two lactones exhibited the greatest inhibition, followed by the phenolics and the derivatives of phthalic acids. Fatty acids had stronger suppression than diethyl phthalate and ethyl ester-4-ethoxy-benzoic acid. The acenaphthene and decane derivatives were the least phytotoxic. The phytotoxins released by barnyard grass roots showed strong inhibition on growth of broadleaf indicator plants and paddy weeds, but were less effective on barnyard grass itself and rice. Our study revealed that in addition to competition, barnyard grass also interferes with rice and other plants in its surroundings by chemical means.
Xuan
Tran Dang
TD
Department of Bioscience and Biotechnology, Faculty of Agriculture, University of the Ryukyus, Okinawa, 903-0213, Japan.
Chung
Iii Min
IM
Khanh
Tran Dang
TD
Tawata
Shinkichi
S
D031747:Echinochloa / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D018545:Lactuca / Q000187:drug effects / Q000254:growth & development; D000455:Medicago sativa / Q000187:drug effects / Q000254:growth & development; D012275:Oryza / Q000187:drug effects* / Q000254:growth & development; D010675:Pheromones / Q000302:isolation & purification / Q000494:pharmacology*; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D018520:Plant Shoots / Q000187:drug effects / Q000254:growth & development; D031685:Sesamum / Q000187:drug effects / Q000254:growth & development
D010675:Pheromones