Journal of Horticulture
Open Access

Abstract

Toxicity of Chelated Iron (Fe-DTPA) in American Cranberry

Sarah Siebach, Giovanny Covarrubias-Pazaran, Rebecca Harbut, Beth Workmaster, Lisa Wasko DeVetter, Shawn Steffan, Christelle Guédot, Amaya Atucha and Juan Zalapa

American cranberry (Vaccinium macrocarpon) is naturally adapted to environments with high concentrations of soluble iron. Yet, there is a need to further explore iron nutrition in cranberry given concerns of toxicity problems from irrigation with iron-rich water. This study investigated the threat of iron toxicity by evaluating its effects on shoot growth total shoot weight, length (primary shoot and axillary growth), and number of axillary shoots in cranberry plants exposed to varying levels of a commonly used chelated iron, specifically Sequestrene 330 (ferric diethylenetriamine penta-acetate; Fe-DTPA). Cranberry plants were grown under controlled greenhouse conditions and received varying concentrations of Fe-DTPA in their irrigation water solutions. Four treatments of Fe-DTPA were applied (0, 14 ppm, 28 ppm, 56 ppm Fe), and shoot growth measurements were taken weekly over the course of 20 weeks. At the end of the course, total fresh shoot weight was recorded for each plant and tissues were sampled for nutrient analysis. Overall, shoot length (primary shoot and axillary) was significantly (P<0.05) reduced with increasing Fe-DTPA concentrations and plant symptoms included leaf drop, necrosis, and mortality in the higher concentration treatments. The number of axillary shoots per upright significantly (P<0.05) increased with treatment intensification. Nutrient analysis revealed increasing amounts of iron with increasing Fe-DTPA dosages. However, iron tissue levels were within the normal range found in healthy field plants (142.8-880.7 ppm) in all treatments. We hypothesized that the toxicity symptoms observed in cranberry plants treated with Fe-DTPA are likely not due to iron, but to a specific toxicity of cranberry to the chelators or other unknown components used in Fe-DTPA.