Alterations in growth of tissue-cultured tansy (Tanacetum vulgare L.) treated with antibiotics

Effects of three antibiotics (cefotaxime, rifampicin and gentamicin) were t ested on in vitro shoots cultures of tansy (Tanacetum vulgare L.). These an tibiotics were selected because endophytic bacteria isolated from the in vi tro shoot cultures of tansy showed that all bacteria were Gram-negative and their growth was reduced by these three antibiotics. Five isolates were En terobacteriaceae, three were fluorescent Pseudomonas, and two were aerobic bacteria. Increased concentrations of antibiotics caused usually linear or quadratic changes on the initiation of shoot growth, shoot number, growth r ate, and shoot height. These changes and changes in pH of the culture media were tansy genotype-dependent following treatments with gentamicin. Also, the treatment with rifampicin or cefotaxime showed a genotype-dependent eff ect, because they resulted in significantly higher percentage of rooted pla nts in one of the three tansy genotypes tested. The growth rate and length of shoots were reduced in the media containing both gentamicin and rifampic in, but less so than in media containing both gentamicin and cefotaxime.