Corn crops expressing insecticidal crystalline (Cry) proteins derived from Bacillus thuringiensis (Bt) are nearly omnipresent throughout Illinois. While the Cry proteins are highly-specific to target pests, a narrow suite of non-target organisms can be adversely affected by exposure to certain Bt traits.  Residual post-harvest crop debris can collect in surface waters adjacent to agricultural fields, raising concerns regarding potential toxicity to non-target aquatic organisms.  The objective of this study was to address the fate of the Cry1Ab protein in senescent leaf tissue after introduction into an aquatic microcosm.  River water and sediment were exposed to senescent corn leaves from plants expressing the Cry1Ab protein or a non-Bt near-isoline.  Triplicate samples from each treatment were housed at 23oC and removed at 2, 6, 12, and 24 hours, and 2, 7 and 14 days for extraction and quantification of the Cry1Ab protein using enzyme-linked immunosorbent assay.  Prior to the experiment, the river water, sediments, and non-Bt leaves were confirmed to be devoid of the Cry1Ab protein.  The results show a rapid dissipation of the Cry1Ab protein from the leaf tissue with a half-life (t1/2) of less than 2 hours.  The leaching of the Cry1Ab protein from the leaf tissue corresponded to a rapid increase of the Cry1Ab protein in the water column, followed by a gradual decrease over time. The rapid dissipation and degradation of the Cry1Ab protein from the leaf tissue and water samples is consistent with previous studies.  Interestingly, the Cry1Ab protein slowly accumulated in the sediment over time, presenting a possible route of chronic exposure to benthic invertebrates.  In addition, the rapid decline of the Cry1Ab proteins in corn tissue following water submersion warrants consideration for aquatic bioassay designs and risk assessments.

Evaluating the fate of Cry1Ab from <i>?Bacillus thuringiensis </i>?corn in an aquatic microcosm

248th National Meeting (2014)

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Evaluating the fate of Cry1Ab from ?Bacillus thuringiensis ?corn in an aquatic microcosm