Bollworm (Lepidoptera: Noctuidae) Survival on ‘Bollgard’ and ‘Bollgard II’ Cotton Flower Bud and Flower Components

Abstract

Genetically modified cotton, Gossypium hirsutum L., cultivars ('Bollgard') that produce crystalline proteins from Bacillus thuringiensis (Berliner) are valuable tools for managing lepidopteran insect pests in the United States. However, high numbers of bollworm, Helicoverpa zea (Boddie), larvae have been observed feeding in white flowers of these cultivars. Fresh tissue bioassays were conducted to investigate bollworm survival on Bollgard and 'Bollgard II' cottons. Bollworm survival was higher on square and flower anthers than on other floral structures on 'Deltapine 5415' (conventional cotton) and 'NuCOTN 33B' (Bollgard). Bollworm survival at 72 h was higher on all floral structures from Deltapine 5415 than on corresponding structures from NuCOTN 33B. ELISA tests indicated that CryIA(c) expression varied among plant parts; however, bollworm survival did not correlate with protein expression levels. Trends in bollworm survival on Bollgard II were similar to those on Bollgard and conventional cotton; however, survival was lower on all structures of Bollgard II than on corresponding structures of Bollgard and conventional cotton. These data support field observations of bollworm injury to white flowers and small bolls and provide a better understanding of larval behavior on Bollgard cotton.

Quantification of Cry1Ac and Cry1F <I>Bacillus thuringiensis</I> Insecticidal Proteins in Selected Transgenic Cotton Plant Tissue Types

“…Holt (1998) correlated this decline in Bollgard cultivars to increased survival of H. armigera. Furthermore, season-long differences in expression among cultivars can vary as much as 2-fold throughout the season , and plant structures, such as terminal leaves, express more Cry1Ac compared with certain flower structures (Greenplate, 1999;Greenplate et al, 2000;Gore et al, 2001). Therefore, control strategies may be further compromised by the differential expression of Cry1Ac among plant structures and cultivars that create a spatial source for survivors to develop.…”

Effect of Pyramiding Bt and CpTI Genes on Resistance of Cotton to Helicoverpa armigera (Lepidoptera: Noctuidae) Under Laboratory and Field Conditions

“…In the United States, the level of resistance of cotton with Cry1Ac genes has been raised by expressing additional genes from B. thuringiensis, in particular the Cry2Ab and Cry1F genes (Tabashnik et al 2009). Generally, these double gene varieties have signiÞcantly higher levels of resistance than single-gene varieties expressing Cry1Ac only , Gore et al 2001, Stewart et al 2001. The comparatively strong effect of the additional gene on the resistance level in these double gene varieties would suggest that these genes might complement the effect of the Cry1Ac gene more effectively than the CpTI gene does.…”

Transgenic Bt Cotton: Effects on Target and Non-Target Insect Diversity

“…Some other field studies have shown that there were no significant differences in larval density among Bt and non-Bt cotton [112,113]. As Bt cotton varieties expressing single toxin gene (Cry1Ac) have no resistance against armyworm, Spodoptera species, to overcome this problem a Bollgard ® II cotton was developed that contain Cry1Ac and Cry2Ab, which provide the adequate control of armyworm and cotton bollworms [114][115][116][117][118][119][120][121][122][123].…”