Ecological Relevance of the Major Allelochemicals in Lycopersicon esculentum Roots and Exudates

Stigmasterol, bergapten, and alpha-tomatine were isolated from tomato roots. The preliminary phytotoxic activities of stigmasterol and a-tomatine were evaluated in a wheat-coleoptile bioassay, and alpha-tomatine was more active than stigmasterol. To confirm its phytotoxic activity, alpha-tomatine was tested on Lactuca sativa and two weeds (Lolium perenne and Echinochloa crusgalli), and it was active in all cases. The stimulatory activities of a-tomatine and stigmasterol on parasitic-plant germination were also evaluated, and alpha-tomatine was found to be active on Phelipanche ramosa, a parasitic plant of tomato. alpha-Tomatine was identified in root exudates by LC-MS/MS. This confirms that alpha-tomatine is exuded by roots into the environment, where it could act as both an allelochemical and a stimulator of P. ramosa, a parasitic plant of tomato.