Evaluation of the mutagenic potential of corn (Zea mays L.) grown in untreated and atrazine (AAtrex) treated soil in the field.

Bacterial assays using extracts from field corn plants (harvested at one month, silage and mature stages) do not indicate that soil treatment with atrazine, at its maximum use rate, alters the endogenous mutagens present in these extracts, nor that atrazine itself is degraded to mutagenic products. Extracts of corn grown in soil treated with AAtrex were equally mutagenic with those of corn grown in untreated soil when tested in Salmonella typhimurium TA-100 by a reversion assay or in Salmonella typhimurium TM-677 in a forward mutation assay. Higher concentrations of histidine in corn grown in AAtrex treated soil may interfere with the reversion assay, but do not affect the forward mutation assay. The nature of the agent(s) responsible for the positive response was not determined. The mutagenicity may be due to natural plant constituents, an artifact of the sample preparation, or mycotoxins from some unrecognized plant infection. The experimental results in these field studies do not show that atrazine is degraded or metabolized by corn plants to mutagens in this sensitive bacterial assay.

Elucidation of metabolic pathways for pesticides in rotation crops.

Recently the Environmental Protection Agency has granted permission to obtain tolerances for pesticide residues in rotation crops. Pesticides applied either pre or postemergence to crops are generally rapidly metabolized in soil to polar and bound residues. These soil residues are usually less available than the applied pesticide for plant uptake. It is a time consuming and difficult task to obtain metabolism data on rotation crops characterized by low uptake. Methidathion, an insecticide for plants, will be used as an example of low uptake by subsequently grown rotation crops. Techniques will be presented to generate large quantities of metabolites utilizing short-term laboratory studies. These metabolites can then be easily identified by the appropriate spectral techniques. Synthesis of standard compounds must be done for comparison to metabolites found in rotation crops. A variety of chromatographic systems will be discussed and evaluated for their suitability for this purpose.