Antifungal effects of n-hexane extract and essential oil of Drimys winteri bark against Take-All disease

Antifungal effect in vivo of n-hexane extract and in vitro of fractions of the same extract and isolated essential oil of the bark of Drimys winteri J.R. Forster and G. Forster (Winteraceae) was investigated against the soil fungus Gaeumannomyces graminis (Sacc.) von Arx & Olivier var. tritici Walker (Ggt), which affects wheat (Triticum aestivum L.). The bio-test was done in Chillán, Chile, beginning in March of 2007. Wheat seedlings were inoculated with Ggt and treated with different doses of n-hexane extract of the bark of D. winteri while at the same time chemical fractions of the extract and bark essential oil were evaluated in vitro. n-Hexane extract in doses of 250 mg kg−1 exhibited a control of Ggt, causing plant height, accumulated plant biomass, chlorophyll content, and stomatal conductance to be significantly higher than the inoculated control, as well as significantly lowering the severity of the damage regarding the control. The extract alone also had a phytotoxic effect in higher doses. The chemical fractionation and later analysis of the n-hexane extract indicated that the compounds with greater antifungal effect correspond to polygodial, drimenin, drimenol, and isodrimenol. The essential oil had antifungal effect applied by contact or as a volatile. The growth of Ggt was inhibited by 50% with doses of 932 and 30.37 mg L−1, respectively. The components of the oil found in greater concentration were α-pinene (60.78%), β-pinene (12.09%), limonene (2.70%), and β-myrcene (2.50%).