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Uptake, Translocation, and Decomposition of Systemic Oxathiin Fungicides in Bean. Marten Snel, Graduate student, Department of Botany, University of Guelph, Guelph, Ontario, Canada, Present address of senior author: Eli Lilly (Elanco International), p/a Moersbergselaan 3, Doorn, The Netherlands; L. V. Edgington, Professor, Department of Botany, University of Guelph, Guelph, Ontario, Canada. Phytopathology 60:1708-1716. Accepted for publication 5 June 1970. DOI: 10.1094/Phyto-60-1708.

The systemic oxathiin fungicide, carboxin (5,6-dihydro-2-methyl-1,4-oxathiin-3-carboxanilide) was taken up better by roots of bean than its sulfone analog, oxycarboxin. Radioautography of plants treated either via the roots or foliage with 14C-labeled carboxin and oxycarboxin indicated apoplastic movement which resulted in marginal accumulation of label in transpiring leaves. Label was not redistributed between organs up to 14 days after cessation of treatment. Carboxin was readily oxidized in roots to the non-fungitoxic sulfoxide, while oxycarboxin could be detected in acetone extracts of roots and unifoliate leaves up to 21 days after the beginning of the experiment. More than 60% of the label present in roots was acetone-insoluble, irrespective of the oxathiin fungicide used, while less than 5% of the label in unifoliate leaves was acetone-insoluble. Analysis of the root tissue showed that the carboxamide linkage was hydrolyzed producing aniline which was bound to plant polymers and also formed highly water soluble conjugation products. Chemotherapy studies with bean rust (Uromyces phaseoli typica) confirmed the data of the translocation, distribution and decomposition studies.

Additional keywords: chemotherapy, bean rust.