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Title: Toxicity of chelated iron (Fe-DTPA) in American cranberry

Author
item SIEBACH, SARA - University Of Wisconsin
item COVARRUBIAS PAZARAN, GIOVANNY - University Of Wisconsin
item HARBUT, REBECCA - Kwantlen Polytechnic University
item WORKMASTER, BETH - University Of Wisconsin
item WASK0 DEVETTER, LISA - Washington State University
item Steffan, Shawn
item Guedot, Christelle
item ATUCHA, AMAYA - University Of Wisconsin
item Zalapa, Juan

Submitted to: Journal of Horticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/23/2015
Publication Date: 2/27/2015
Publication URL: http://handle.nal.usda.gov/10113/61028
Citation: Siebach, S., Zalapa, J., Covarrubias-Pazaran, G., Harbut, R., Workmaster, B., Wasko DeVetter, L., Steffan, S., Guedot, C., Atucha, A. 2015. Toxicity of chelated iron (Fe-DTPA) in American cranberry. Journal of Horticulture. 2:129. DOI:10.4172/2376-0354.1000128.

Interpretive Summary: The American cranberry is an acidic soil loving plant species indigenous to peaty, sandy soils characteristic of bog environments, which are regularly wetted or waterlogged and possess high organic matter content. These bog environments typically have abundant concentrations of soluble iron and other metals that may be toxic to non-adapted plant species. Although the physiological mechanisms are not fully understood, cranberry has a reported tolerance to iron. However, there may be a threshold beyond which iron concentrations may become toxic to the species. Cranberry thrives in an optimal pH range of 4.2 to 5.5, with water being a dominant agent in both natural ecosystems and commercial cranberry production systems, potentially altering pH and iron concentrations. A number of Wisconsin cranberry marshes may be subject to abnormally high iron concentrations, resulting in conditions which might be conducive to iron toxicity risks in the commercial beds. This study evaluated the effect of iron commonly used iron fertilizer on total shoot biomass, length (primary shoot and axillary growth), and number of axillary shoots in cranberry plants grown under controlled greenhouse conditions. We observed clear toxicity with increased concentrations the iron fertilizer. Iron tissue levels increased with greater iron fertilizer concentrations, but the greatest iron concentration observed in greenhouse experimental conditions was lower than the naturally occurring high levels of iron observed in field-grown plants. However, high sodium was also detected in tissues treated, but the observed ranges likely could not produce toxicity in cranberry. In conclusion, the toxicity observed is likely due to specific toxicity of cranberry to the chelators in the iron fertilizer used. At this moment, is not clear if iron toxicity in cranberry is a common or even real. More systematic nutrient studies in cranberry need to be conducted. Elucidating the benefits or risks to particular accumulations of iron and other micronutrients are needed in order to establish sufficiency ranges, thresholds, and help growers better understand toxicity risks.

Technical Abstract: 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 total shoot biomass, 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. Shoot fresh weight was recorded and tissues were subjected to nutrient analysis. Shoot growth 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 is likely due to a specific toxicity of cranberry to the chelators used in Fe-DTPA.