Two experiments were carried out in order to verify the toxicity of nalidixic acid, chloramphenicol and streptomycin to avocado 'Ouro Verde' in vitro culture. In the first experiment, it was tested the effect of the antibiotics to callus initiation on leave explants, using a concentration range of 0, 12.5, 25, 50, 100 and 200 mg/L. In the second experiment, sprouting from nodal segments were tested. The callus formation was reduced by 50% with 50 mg/L of chloramphenicol and the highest reduction in callus weight was observed with 12.5 mg/L. The length of sprouts was reduced by incorporating antibiotics into plant growth medium. Results showed that the three antibiotics were toxic to avocado, and they must be used only in real necessity cases, depending on the bacterial susceptibility and the adequate concentration to control the contaminants.
antibiotics; avocado; Persea americana; phytotoxicity; micropropagation