Tolerance of MIR604 in reciprocal cross offspring of MIR604-selected and control western corn rootworm colonies

Newly emerged virgin male and female beetles from both the MIR604-selected colony and its control colony (reared on isoline corn) were collected and isolated.  Reciprocal cross colonies were created by combining at least 100 males from the selected colony with 100 females of the control colony and vice versa.  Eggs from these colonies were evaluated along with eggs from both the selected and control colonies.  All four colonies were evaluated in the greenhouse for larval survival, adult emergence, and root damage.  Head capsule width and dry weight were recorded for recovered larvae and adults.   The colonies were also evaluated in diet toxicity assays and the data were used to calculate the LD₅₀ and EC₅₀ of MIR604 for each colony.  Larval recovery results showed the selected colony and the selected female x control male colonies had significantly greater survivability than the control and control female x selected male colonies.  Adult recovery results showed the control female x selected male had significantly greater adult emergence than the selected female x control male colony.   Damage ratings taken from the plants of the adult emergence study showed that control female x selected male colony to have significantly more damage than the other colonies.  LD₅₀ calculations were not possible for the selected colony due to the low mortality at even the highest dose evaluated (24.3 µg/cm²).