Baseline Susceptibility and Changes in Susceptibility to Bacillus thuringiensis subsp. kurstaki Under Selection Pressure in European Corn Borer (Lepidoptera: Pyralidae)

Chronic Exposure of the European Corn Borer (Lepidoptera: Crambidae) to Cry1Ab <I>Bacillus thuringiensis</I> Toxin

“…These results support those of Huang et al (1997) and Bolin et al (1999) who also observed signiÞcantly decreased susceptibility of O. nubilalis populations after exposure to B. thuringiensis toxins for multiple generations. In populations from Iowa and Kansas (Huang et al 1997), signiÞcant resistance was found after three to seven generations of exposure to Dipel ES, a composite of Cry1Aa, Cry1Ab, Cry1Ac, Cry2A, and Cry2B endotoxins and after four generations of selection with Cry1Ac toxin in Minnesota populations (Bolin et al 1999). Two of the initial subpopulations selected at the University of Nebraska did not develop signiÞcant levels of resistance despite continued exposure for at least 10 generations (data not shown), suggesting that there is some variation in the ability of populations to develop resistance.…”

“…Resistant strains have been selected from populations collected in Iowa, Kansas, (Huang et al 1997(Huang et al , 1999a, and southeastern Minnesota (Bolin et al 1999). The high-dose refuge strategy currently recommended for U.S. corn production (Ostlie et al 1997, International Life Sciences Institute 1998 requires that the increased Þtness conferred by Bt resistance alleles is recessive, i.e., heterozygous individuals either do not survive at doses of toxin produced by Bt corn or survive but with a Þtness close to zero (Bourguet et al 2000).…”

“…Survival and Þtness of heterozygotes depends not only on the dominance of B. thuringiensis resistance but also on the resistance level conferred by resistance alleles (Bourguet et al 2000). Therefore, it is important to determine whether the relatively low resistance ratio reported by Huang et al (1997Huang et al ( , 1999a and Bolin et al (1999) is a general feature in O. nubilalis populations or whether higher B. thuringiensis resistance can be obtained in laboratory-selected populations.…”

A single major QTL controls expression of larval Cry1F resistance trait in Ostrinia nubilalis (Lepidoptera: Crambidae) and is independent of midgut receptor genes

“…Although O. nubilalis resistance to Bt toxins is not observed in field environments, varying levels of resistance to Cry1Ab (Huang et al 1997;Bolin et al 1999;Chaufaux et al 2001;Siqueira et al 2006;Coates et al 2007;Crespo et al 2009) and Cry1F toxins was observed following laboratory selection (Pereira et al 2008a, b). Additionally, resistance to Bt toxins has been reported in the lepidopteran species Helicoverpa armigera (Gahan et al 2001) and Pectinophora gossypiella under laboratory conditions (Morin et al 2003).…”

Stability of Cry1Ab protein during long-term storage for standardization of insect bioassays

“…However, the evolution of resistance of target pest populations to transgenically expressed Cry1Ab is considered as a severe drawback of this new control strategy. In laboratory experiments using ECB populations it was demonstrated that the Cry1Ab susceptibility significantly decreased after only seven generations when selected with commercial Bt formulations (Huang et al, 1997). Field monitoring data in transgenic cotton revealed resistance of some field populations of Helicoverpa zea to Cry1Ac protein, though field-evolved resistance in other five major lepidopteran pests (O. nubilalis, Sesamia nonagrioides, H. armigera, Heliothis virescens, Pectinophora gossypiella) * Corresponding author: johannes.jehle@dlr.…”