Journal
ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA
Volume 124, Issue 1, Pages 117-123Publisher
WILEY
DOI: 10.1111/j.1570-7458.2007.00560.x
Keywords
Diatraea saccharalis; Bt-resistance management; Lepidoptera; Crambidae; corn
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The sugarcane borer, Diatraea saccharalis (F.) (Lepidoptera: Crambidae), strain (F52-3-R) was developed from F-3 survivors of a single-pair mating on commercial Cry1Ab Bacillus thuringiensis (Bt) corn plants in the greenhouse. The susceptibility of a Bt-susceptible and the F52-3-R strain of D. saccharalis to trypsin-activated Cry1Ab toxin was determined in a laboratory bioassay. Neonate-stage larvae were fed a meridic diet incorporating Cry1Ab toxin at a concentration range of 0.0625 to 32 mu g g(-1). Larval mortality, larval weight, and number of surviving larvae that did not gain significant weight (< 0.1 mg per larva) were recorded on the 7th day after inoculation. The F52-3-R strain demonstrated a significant level of resistance to the activated Cry1Ab toxin. Larval mortality of the Bt-susceptible strain increased in response to higher concentrations of Cry1Ab toxin, exceeding 75% at 32 mu g g(-1), whereas mortality of the F52-3-R strain was below 8% across all Cry1Ab concentrations. Using a measure of practical mortality (larvae either died or gained no weight), the median lethal concentration (LC50) of the F52-3-R strain was 102-fold greater than that of the Bt-susceptible insects. Larval growth of both Bt-susceptible and F52-3-R strains was inhibited on Cry1Ab-treated diet, but the inhibition of the F52-3-R strain was significantly less than that of the Bt-susceptible insects. These results confirm that the survival of the F52-3-R strain on commercial Bt corn plants was related to Cry1Ab protein resistance and suggest that this strain may have considerable value in studying resistance management strategies for Bt corn.
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