Assessment of allelopathic properties of Baccharis dracunculifolia DC in laboratory and field conditions

In plantations of B. dracunculifolia, a noticeable decrease in diversity and development of monocots species was observed. Hence, phytotoxic studies were done to determine the in vitro toxicity of essential oils of B. dracunculifolia on monocot (Lolium multiflorum) and dicot (Lactuca sativa). The essential oil at concentration of 1000 mg/L drastically decreased the hypocotyl growth of L. multiflorum (90%) and L. sativa (60%). The analysis of essential oil by gas chromatography showed a high percentage of compounds with phytotoxic effects, such as limonene, alpha and beta-pinene. The field experiments showed that the inhibition under B. dracunculifolia was not due to the effect of shading nor to nutrient competition. The reduction in germination of L. multiflorum under B. dracunculifolia was > 90%. In the soil under the plantation, a high concentration of phenolics was measured (15mg/100g of soil). These results indicate that allelopathic activity of B. dracunculifolia may be explained through a combination of phytotoxic effects (emission of volatile compounds and the accumulation of phenolics in the soil profile).