Allelopathic activity of different Byrsonima spp. leaf extracts on Lactuca sativa L. bioassay

Byrsonima verbascifolia Rich. Ex. A. Juss and Byrsonima intermedia (A) Juss are are important species due to the nutritional and pharmacological properties of their secondary metabolites. However, little is known about the action and attributes of these metabolites in the ecological interactions of these plants, as well as their possible cytogenotoxic effects. In this context, the objective of this study was to investigate the phytotoxicity of B. verbascifolia and B. intermedia leaf extracts in a bioassay with Lactuca sativa L. Aqueous extracts (cold and hot) and ethanolic leaf extract were obtained at a concentration of 5% (w/v) and, subsequently, solutions at concentrations 20, 40, 60, 80 and 100% were prepared. The following were evaluated: germination percentage, germination speed index, number of normal seedlings, root elongation, shoot length, fresh and dry biomass, mitotic index and chromosomal abnormalities. Data were submitted to analysis of variance and the means were compared using the Scott-Knott test at 5% significance. The results show that B. verbascifolia and B. intermedia leaf extracts have phytotoxic and cytotoxic potential. These effects differ as a function of the form of extraction in which the ethanolic extract showed greater toxicity regardless of the species. For most of the analyzed parameters, there was no statistical difference between species but, for number of normal seedlings, B. verbascifolia was more toxic and, for root elongation, B. intermedia presented greater toxicity. Among chromosomal abnormalities, C-metaphase and stickiness were the most frequent, indicating an aneugenic effect of Byrsonima spp. leaf extracts.