Maleic hydrazide induces genotoxic effects but no DNA damage detectable bythe Comet assay in tobacco and field beans

The plant growth regulator and herbicide maleic hydrazide (MH) induced a hi gh frequency of somatic mutations in leaves of tobacco (Nicotiana tabacum v ar. xanthi) and a high yield of chromosome aberrations in roots of field be ans (Vicia faba, karyotype ACB). In contrast, no significant increase in MH -induced DNA damage, as measured by the Comet assay, could be demonstrated in either plant species. The absence of DNA migration induced by MH was not effected in tobacco by either pH of the MH solution, the sampling time aft er MH treatment or continuous MH treatment for 14 days. To our knowledge, M H represents the first agent which has proved to be highly mutagenic and cl astogenic but does not cause DNA damage as measured by the Comet assay in t he same experimental system.