Composition of Welsh onion (Allium fistulosum L.) root exudates and their allelopathy on cucumber sprouts and Fusarium oxysporum f.sp cucumerinum

The root exudates of Welsh onion (Allium fistulosum L.) were collected with the continuous root exudates trapping system and extracted with organic solvents of different polarities. The allelopathy of different extracted components on cucumber (Cucumis sativus L.) and Fusarium oxysporum f.sp. cucumerinum was studied and the composition was analyzed by using gas chromatography-mass spectrum (GCMS). All components extracted by different organic solvents promoted the growth of cucumber sprouts but inhibited the growth of F. oxysporum f.sp. cucumerinum mycelia. The components extracted by ethyl acetate had strongest allelopathic potential and were similar to those extracted by ether. Following further separation of major components, the allelopathy of components extracted by 80% ethyl acetate and 20% ethyl ether was strongest. The potential allelochemicals of Welsh onion root exudates were: diethyl phthalate, dibutyl phthalate, diisooctyl phthalate, 2-(methylthio) benzothiazole, benzothiazole, benzoic acid p-tolyl ester and cycluron. Dibutyl phthalate, benzoic acid, 4-methylphenyl ester and benzothiazole had significant allelopathic effects on the growth of cucumber sprouts and F. oxysporum f.sp. cucumerinum.