http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Effect of mixed stands of nontransgenic and transgenic cotton expressing CryIA(c) Delta-endotoxin from Bacillus thuringiensis on tobacco budworm and bollworm
Upland cotton, Gossypium hirsutum (L.), genetically engineered to express CryIA(c) (Delta) endotoxin from Bacillus thuringiensis Berliner subsp. kurstaki (BTK cotton) could become ineffective against tobacco budworm, Heliothis virescens (F.) and bollworm, Helicoverpa zea (Boddie), if resistance management strategies are not implemented. One strategy proposes using mixed stands of BTK and non-BTK cotton plants in the same field which would allow non-BTK plants to act as a refuge for susceptible insects. Three experiments were conducted to evaluate the efficacy of a range of stand mixtures of BTK and non-BTY. cotton. First, movement of tobacco budworrn and bollworm larvae among plants in different plant stand ratios was examined in free-choice greenhouse experiments and for tobacco budworm in a free- choice field experiment. Second, a no-choice laboratory experiment was used to measure tobacco budworm survival, growth and fecundity over 2 generations when 5th instars were fed BTK or non-BTK flower buds. Third, suppression of tobacco budworrn and bollworm larval densities and injury to cotton into mixed stands were examined in field experiments. Results of larval movement experiments showed that in the greenhouse 34.4% of 3rd instar tobacco budworrn and, 23.4% of 3rd instar bollworm, and in the field 3 1. 0% of 3rd instar and 57.6% of 5th instar tobacco budworm, moved within 24 h from the plant on which they were placed to a new plant. Tobacco budworms fed BTK flower buds had lower pupal weights, decreased time in the pupal stage, reduced survival of larvae to pupal and adult stages, and reduced survival of pupae to adults in the I st generation. A decreased larval period and increased ratio of males to females were detected in the 2nd generation. However, fecundity, adult longevity and egg viability were not significantly different between the BTK and non-BTK treatments. In field experiments, as the proportion of BTK plants increased in stand mixtures, the yield, injury to terminals, and injury to flower buds and capsules increased; while the number of tobacco budworm and bollworm larvae decreased. Fourth and 5th instar tobacco budworm and bollworm were present in all pure stands and mixtures. Thus, mixed stands may not provide a refuge that produces non-selected tobacco budworm and bollworm adults, because larvae moved and fed on BTK plants and were exposed to the Delta-endotoxin.
In title, Greek letter Delta is a symbol.
Issued also on microfiche from University Microfilms Inc.
Includes bibliographical references: pages 62-75.