Susceptibility of Cry1Ab-susceptible and -resistant sugarcane borer to transgenic corn plants containing single or pyramided Bacillus thuringiensis genes

Larval survival and plant injury of Cry1Ab-susceptible, -resistant, and -heterozygous genotypes of the sugarcane borer on transgenic corn containing single or pyramided Bt genes

“…The larval survivorship (72-84% on leaf tissue after 6 d and 42.6-62.5% on intact plants after 21 d) observed in the current study was similar to that reported in other earlier studies (Walker et al, 2000;Wu et al, 2007;Ghimire et al, 2011). Larvae of all three genotypes of D. saccharalis on non-Bt corn plants also made a substantial number of entry/exit holes on the stalks and caused significant tunneling inside stalks.…”

“…Leaf tissue bioassays were carried out in the laboratory following methods similar to those described in Huang et al (2006) and Ghimire et al (2011). In the bioassay, six pieces of leaf tissue (~20 cm 2 ) of a corn hybrid were placed in each well of 8-well trays (Bio-Smart-8, C-D International, Pitman, NJ).…”

“…Cry1Ab corn) that was commonly planted in the mid-southern region did not express a high dose against D. saccharalis as desired for the "high dose/structured refuge" IRM strategy (Wu et al, 2007). Recently, Ghimire et al (2011) evaluated six other Bt corn hybrids including four Cry1Ab (YieldGard® Corn Borer) and two Cry1F (Herculex I®) corn hybrids against Cry1Ab-susceptible, -resistant, and -heterozygous genotypes of D. saccharalis. The results showed that all six Cry1Ab corn hybrids did not express a high dose for D. saccharalis.…”

Susceptibility of Cry1Ab maize-resistant and -susceptible strains of sugarcane borer (Lepidoptera: Crambidae) to four individual Cry proteins

“…In addition, a known Cry1Ab-resistant strain (Cry1Ab-RR-2004) of D. saccharalis was also included in the bioassays in this study to serve as a positive control. Cry1Ab-RR-2004 was established from a field collection in 2004, which has been well documented to be highly resistant to both Cry1Ab-maize plants and purified Cry1Ab protein (Huang et al, 2007a(Huang et al, , 2007bWu et al, 2007;Ghimire et al, 2011;Wangila et al, 2012). Individuals of the seven resistant strains were backcrossed 2-3 times with individuals from the Cry1Ab-SS strain and re-selected for Bt resistance using leaf tissue from Cry1Ab expressing maize plants during the F 2 generations of the backcross.…”

“…Studies have shown that D. saccharalis is inherently less susceptible to Bt proteins than other major maize borer species such as European corn borer, Ostrinia nubilalis (Hübner), and southwestern corn borer, Diatraea grandiosella Dyar . Both Wu et al (2007) and Ghimire et al (2011) also reported that most commercial Cry1Ab maize hybrids did not express a ''high dose'' of Bt proteins for D. saccharalis. To ensure the long-term success of Bt maize for managing stalk borers in the mid-southern region, since 2004, a cost-effective Bt resistance monitoring program has been implemented in the region (Huang et al, 2012a).…”