Genetically engineered corn expressing crystalline proteins for insect control and encoded by genes
derived from soil bacterium Bacillus thuringiensis (Bt) are widely adopted in the United States. Among the
seven different events of Bt corn available commercially, YieldGard® Rootworm (event MON863) expresses
a variant of the cry3Bb1 protein in the root tissue to control corn rootworm larvae. Nematodes
reside in the rhizosphere and are potentially exposed to Cry3Bb1 toxins exudated from roots of Bt corn.
We test the hypothesis that coleopteran-active Bt corn does not affect non-target soil nematodes.
Experimental treatments were: 1) a Bt hybrid, 2) a non-Bt isoline treated with a conventional soil
insecticide, and 3) a non-Bt isoline without insecticide. Nematodes were extracted from soil samples
collected prior to planting (May), at peak anthesis (August), and after harvest (October) in 2003 and
2004, enumerated and identified to genus. A total of 73 nematode genera were encountered in soil and
litter combined. During the growing season, maturity index values and relative abundance of fungivorous
nematodes were greater in the Bt hybrid than the non-Bt isoline with or without insecticide. Nematode
trophic diversity values were greater in the Bt hybrid than non-Bt isoline with insecticide and this effect
continued through the following spring. Abundance of nematode predators increased two weeks after
insecticide was applied to non-Bt isoline, but decreased without insecticides on either Bt or the non-Bt
isoline. In decaying roots of corn treatments, maturity index values and the relative abundance of
nematode predators was greater in the Bt hybrid than non-Bt isoline with insecticide. Effects at the
overall community structure and nematode genera varied more by seasonal phenology than corn
treatment. The isoline with insecticide had more non-target effects on nematode communities than the
Bt hybrid. This treatment increased the relative abundance of predaceous nematodes temporarily but
eventually reduced successional maturity by harvest time, which continued to decline during the winter
in both soil and decaying corn root
active
Genetically engineered corn expressing crystalline proteins for insect control and encoded by genesderived from soil bacterium Bacillus thuringiensis (Bt) are widely adopted in the United States. Among theseven different events of Bt corn available commercially, YieldGard® Rootworm (event MON863) expressesa variant of the cry3Bb1 protein in the root tissue to control corn rootworm larvae. Nematodesreside in the rhizosphere and are potentially exposed to Cry3Bb1 toxins exudated from roots of Bt corn.We test the hypothesis that coleopteran-active Bt corn does not affect non-target soil nematodes.Experimental treatments were: 1) a Bt hybrid, 2) a non-Bt isoline treated with a conventional soilinsecticide, and 3) a non-Bt isoline without insecticide. Nematodes were extracted from soil samplescollected prior to planting (May), at peak anthesis (August), and after harvest (October) in 2003 and2004, enumerated and identified to genus. A total of 73 nematode genera were encountered in soil andlitter combined. During the growing season, maturity index values and relative abundance of fungivorousnematodes were greater in the Bt hybrid than the non-Bt isoline with or without insecticide. Nematodetrophic diversity values were greater in the Bt hybrid than non-Bt isoline with insecticide and this effectcontinued through the following spring. Abundance of nematode predators increased two weeks afterinsecticide was applied to non-Bt isoline, but decreased without insecticides on either Bt or the non-Btisoline. In decaying roots of corn treatments, maturity index values and the relative abundance ofnematode predators was greater in the Bt hybrid than non-Bt isoline with insecticide. Effects at theoverall community structure and nematode genera varied more by seasonal phenology than corntreatment. The isoline with insecticide had more non-target effects on nematode communities than theBt hybrid. This treatment increased the relative abundance of predaceous nematodes temporarily buteventually reduced successional maturity by harvest time, which continued to decline during the winterin both soil and decaying corn rootactive
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