Identification of active substances in garlic responsible for breaking buddormancy in grapevines

The active substances in garlic responsible for breaking bud dormancy in gr apevines were investigated by employing single bud cuttings of 'Kyoho' (Vit is vinifera x V. labruscana Bailey). Four major gas-chromatographic peaks w ere detected in the essential oil extracted from freshly grated garlic clov es and commercial garlic oil, but only the first two peaks were found in vo latiles from freshly grated garlic and commercial garlic oil. Based on a co mparison of the retention time with authentic chemicals and GC-MS analysis, the compounds were identified as diallyl mono-, di-, tri-, and tetra-sulfi des. The highest peak was diallyl disulfide, followed by diallyl tri-, mono -, and tetra-sulfides, but only trace amounts of dimethyl mono- and di-sulf ides were present. When painted to the upper cross-sectional cut surface of cuttings, dimethyl disulfide and diallyl disulfide greatly promoted budbre ak. Diallyl trisulfide treatment resulted in a rate of budbreak that was no t uniform, although the first budbreak was accelerated. Exposure to volatil es of diallyl di- and tri-sulfides was the most effective treatment in prom oting budbreak, irrespective of the concentration and the duration of expos ure. However, exposure of cuttings to volatiles of 30% dimethyl disulfide s uspension markedly inhibited budbreak, although both authentic dimethyl dis ulfide (a.i. 99%) and its 10% suspension promoted budbreak. The effects of dimethyl sulfide and diallyl sulfide on budbreak varied among the concentra tions and the duration of exposure. These results indicate that the active substances in garlic, responsible for breaking bud dormancy in grapevines, are sulfur-containing compounds with an allyl group (CH2CHCH2), particularl y diallyl disulfide.