Tolerance of eCry3.1Ab in reciprocal cross offspring of eCry3.1Ab-selected and control western corn rootworm colonies

Virgin females and males of a colony selected for tolerance to eCry3.1Ab (5307) corn and its paired control colony were collected and isolated from each other.  Reciprocal cross colonies were created by combining a minimum of 100 males with 100 females from both colonies to create control♀×selected♂ (Con♀) and selected♀×control♂ (Sel♀) colonies.  Eggs from these colonies were collected and evaluated along with those of the parental selected and control colonies.  Diet toxicity assays were conducted to determine the LC₅₀ and EC₅₀ of eCry3.1Ab on neonate larvae of each colony.  Calculated LC₅₀ values were 1.59 (0.12-6.04), 11.47 (7.0-23.30), 50.96 (17.17-771.54), and 24.19 (10.00-210.49) µg/cm² for the control, Con♀, Sel♀, and selected colonies, respectively.  The Sel♀ and Con♀ reciprocal crosses required significantly more toxin to produce 50% mortality compared to the control colony. The LC₅₀ values of the Con♀ and Sel♀ were not significantly different compared to the selected colony.  EC₅₀ values were 0.47(0.34–0.6), 4.14 (3.21–5.07), 8.38 (-3.91–20.66), and 7.09 (4.53–9.64) µg/cm² for the control, Con♀, Sel♀, and selected colonies, respectively.  The EC₅₀ value of the control colony was significantly less than the EC₅₀ value of all other colonies.  The EC₅₀ value of the Con♀ was also significantly less than the EC₅₀ value of the selected and Sel♀ colonies.  EC₅₀ data indicates that the Sel♀ and Con♀ reciprocal crosses required significantly more eCry3.1Ab to reduce larval weight by 50% compared to the control colony.  These results indicate that the inheritance of eCry3.1Ab tolerance is not recessive.