Selection for Cry3Bb1 Resistance in a Genetically Diverse Population of Nondiapausing Western Corn Rootworm (Coleoptera: Chrysomelidae)

Abstract

Five short-diapause laboratory lines of western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), were selected for resistance to MON863, a variety of corn genetically modified with the Bacillus thuringiensis Berliner (Bt) transgene that expresses the Cry3Bb1 delta-endotoxin. Three of the selected lines were developed by incremental increase in the duration of exposure to MON863 over 11 generations (moderate selected lines). Two selected lines were developed from a control group by constant exposure to MON863 for at least 14 d posthatch over seven generations (intense selected lines). At the end of the experiment, survivorship, as measured by adult emergence, was approximately 4 times higher in each of the selected lines reared on MON863 compared with control lines. Estimates of realized heritabilities (h2) were 0.16 and 0.15 for the moderate and intense selected lines, respectively, and are consistent with h2 estimates reported previously from a variety of pest insects. These lines provide data necessary for evaluating the potential for Bt resistance within diabroticite beetles and will be useful for developing improved insect resistance management strategies.

Adaptation by Western Corn Rootworm (Coleoptera: Chrysomelidae) to Bt Maize: Inheritance, Fitness Costs, and Feeding Preference

“…Future experiments with additional strains will be needed to gain a better understanding of the inheritance of resistance in western corn rootworm. Oswald et al (2011) measured the realized heritability values (h 2 ) for the resistant strain used in the current study at generations 6, 8, and 10 and found low heritability (h 2 ϭ 0.16), indicating that survival on Bt maize is heavily inßuenced by environmentally based variation relative to genetically based variation. Few studies have examined the inheritance (h) of resistance alleles in western corn rootworm, although evidence of nonrecessive inheritance of Cry3Bb1 resistance in western corn rootworm has been found previously (Meihls et al 2008).…”

“…Both strains originated from the same nondiapausing genetically diverse base population and were originally obtained from the U.S. Department of AgricultureÕs North Central Agricultural Research Laboratory (USDAÐARS) in Brookings, SD. To produce the base population, nondiapausing females from a strain maintained at the USDAÐARS laboratory for Ͼ30 yr (Ͼ150 generations) were crossed to Þeld-collected males from four different geographic regions across the Corn Belt, as described in Oswald et al (2011). Selection for resistance to the Bt toxin Cry3Bb1 was achieved by incrementally increasing the duration of larval exposure to Cry3Bb1 maize roots over 11 generations (Oswald et al 2011).…”

“…To produce the base population, nondiapausing females from a strain maintained at the USDAÐARS laboratory for Ͼ30 yr (Ͼ150 generations) were crossed to Þeld-collected males from four different geographic regions across the Corn Belt, as described in Oswald et al (2011). Selection for resistance to the Bt toxin Cry3Bb1 was achieved by incrementally increasing the duration of larval exposure to Cry3Bb1 maize roots over 11 generations (Oswald et al 2011). Initially, the resistant strain was selected for a duration of 24 h. The duration of selection increased in 12-h increments through the fourth generation and then increased in 24-h increments through generation 9, with one Þnal 12-h increment at generation 10 (Oswald et al 2011).…”

“…Selection for resistance to the Bt toxin Cry3Bb1 was achieved by incrementally increasing the duration of larval exposure to Cry3Bb1 maize roots over 11 generations (Oswald et al 2011). Initially, the resistant strain was selected for a duration of 24 h. The duration of selection increased in 12-h increments through the fourth generation and then increased in 24-h increments through generation 9, with one Þnal 12-h increment at generation 10 (Oswald et al 2011). This resulted in a strain that displayed signiÞcantly increased survivorship on Bt maize (average survival to adulthood on Bt maize increased six-fold over the Þnal six generations) (Oswald et al 2011), thus demonstrating that the strain was Bt resistant (Tabashnik 1994).…”

Effect of Bt Maize and Soil Insecticides on Yield, Injury, and Rootworm Survival: Implications for Resistance Management

“…For the western corn rootworm, widespread Þeld-evolved resistance to Bt maize is a potential threat, given this insectÕs history of rapid adaptation to numerous management practices, including crop rotation and some conventional insecticides (Meinke et al 1998, Wright et al 2000, Levine et al 2002. In addition, evidence from recent studies suggests a lack of substantial Þt-ness costs of resistance (Oswald et al 2011, Meihls et al 2012, PetzoldÐMaxwell et al 2012a, and nonrecessive inheritance of resistance (Meihls et al 2008, PetzoldÐMaxwell et al 2012a, both of which increase the risk of resistance evolution. Thus, sustainable insect resistance management (IRM) strategies are essential for prolonging the effectiveness of Bt maize for management of western corn rootworm.…”