The somatic white-ivory eye spot test does not detect the same spectrum of genotoxic events as the wing somatic mutation and recombination test in Drosophila melanogaster

A group of six chemical compounds was tested in parallel in two different somatic genotoxicity assays in Drosophila melanogaster, the wing somatic mutation and recombination test (SMART) and the white‐ivory eye spot test. The wing spot test makes use of the wing cell markers multiple wing hairs (mwh) and flare (flr) and detects both mitotic recombination and various types of mutational events. The white‐ivory eye spot test makes use of the white‐ivory (w′) quadruplication and detects the somatic reversion of the recessive eye color mutation w′ to the wild‐type (w+). Three‐ or two‐day‐old larvae were fed chronically with the compounds ethylnitrosourea (ENU), N‐nitrosopyrrolidine (NNP), caffeine (CAF), chromium (VI) oxide (CRO), potassium chromate (POC), and 2,4‐dichlorophenoxyacetic acid (2,4‐D). All six compounds are genotoxic to various degrees in the wing spot test. The percentage of the genotoxic activity that is due to mitotic recombination was between 84% and 91% for the hexavalent chromium compounds CRO and POC and about 68% for 2,4‐D. In contrast, ENU and NNP showed only 46% and 25% recombinagenic activity, respectively. In the white‐ivory eye spot test, the three compounds [CRO, POC, and 2,4‐D] with high recombinagenic activity and CAF were clearly nongenotoxic, whereas only ENU and NNP gave a positive response. From these results, it is concluded that the spectrum of genotoxic events detected by the two assays is different. In particular, the white‐ivory eye spot test appears not to detect mitotic recombination the way the wing spot test does. © 1996 Wiley‐Liss, Inc.