About
  PDF
Full Text
(135 K)

Hybrid Bacillus Thuringiensis *-Endotoxins Provide Enhanced Spectrum of Activity against Lepidopteran Pests of Cotton

Saku Sivasupramaniam, Victor Kabuye, Tom Malvar, Lisa Ruschke, Phil Rahn and John Greenplate


 
ABSTRACT

Studies were conducted to fully characterize the relative activities of Cry1Ac, Cry2Ab2, Cry1Fa, variant of Cry1Ca, and selected hybrid proteins against Lepidopteran cotton insects in diet bioassays using purified proteins. Bollworms (cotton bollworm, Helicoverpa zea; pink bollworm, Pectinophora gossypiella; and tobacco budworm, Heliothis virescens) and armyworms (Spodoptera exigua and beet armyworm, Spodoptera frugiperda) were used as test insects. The activity profile of four primary proteins - Cry1Ac, Cry2Ab2, Cry1Fa, and variant of Cry1Ca and those of the hybrid proteins of Cry1Ac and Cry1Fa and Cry1Ac and variant of Cry1Ca were determined in laboratory bioassays.

Based on LC 50 values, Cry1Ac, has good to excellent activity on all bollworm species and little or no activity on armyworms. Cry1Fa on the other hand, is not toxic to H. zea, but has good activity on other more susceptible bollworms as well as on armyworms. In comparison, variant of Cry1Ca has no activity on H. zea, exhibits good activity on S. exigua but is not active on S. frugiperda.

The Cry1Ac/Cry1Fa hybrid proteins tested in these experiments extend the spectrum of activity of the two parent proteins, Cry1Ac and Cry1Fa. In contrast, the Cry1Ac/1Ca hybrid, is not toxic to H. zea at 100 F g/ml (highest dose tested), but was found to be toxic to both Spodoptera species, although the native Cry1Ac and variant of Cry1Ca were not toxic to S. frugiperda

Square and leaf tissue from R 1 cotton plants expressing a Cry1Ac/Cry1Fa hybrid protein were tested for activity against 3 rd instar H. zea and S. frugiperda, respectively. The results obtained were very promising, and the line tested compared very favorably with the Cry1Ac/Cry2Ab2 line which was used as a positive control in this experiment.





Reprinted from Proceedings of the 2001 Beltwide Cotton Conferences pp. 837 - 840
©National Cotton Council, Memphis TN

[Main TOC] | [TOC] | [TOC by Section] | [Search] | [Help]
Previous Page [Previous] [Next] Next Page
 
Document last modified XXXXXX, XXX XX 2001