Herbivory tolerance of cotton expressing insecticidal proteins from Bacillus thuringiensis: responses to damage caused by Helicoverpa spp, and to manual bud removal. Sadras, V., O. Field Crops Research, 56(3):287-299, 1998.
abstract   bibtex   
Transgenic cotton varieties expressing Cry IA(c) insecticidal proteins from Bacillus thuringiensis ('Bt cotton') remain vulnerable to non-lepidopteran insects. In addition, they are susceptible to lepidopteran pests when the efficacy of Bt toxins falls because of ontogenetic and/or environmental factors. Hence the importance of knowing to what extent Bt cotton is able to tolerate damage. The degree of tolerance of Bt cotton to actual and simulated insect damage was assessed in three field experiments. Exp. 1 compared the effects of Helicoverpa spp. (Lepidoptera: Noctuidae) on the growth, development and yield of Bt cotton with those of its near isogenic non-Bt counterpart in two genetic backgrounds (Siokra V15, Sicala V2) under two regimes of chemical control of insects (S1: nine insecticide applications during the growing cycle, S2: six insecticide applications). Exp. 2 compared insecticide-protected Bt crops with crops manually damaged to simulate (a) early-season loss of vegetative buds, (b) loss of flowerbuds, and (c) loss of both vegetative and reproductive buds. Also using manual damage, Exp. 3 evaluated the effect of timing of flowerbud loss on the yield and maturity time of insecticide-protected Bt crops. In Exp. 1, well-protected Bt crops (S1) yielded 24% more than their less-protected counterparts (S2). The less protected crops had, however, substantially more immature fruit at the end of the season highlighting a considerable potential for recovery. Poor soil conditions, interacting with season length accounted for the difference between potential and actual compensation in crops that were exposed to almost continuous damage by Helicoverpa spp. Under more favourable growing conditions, maturity was delayed but yield of damaged Bt crops was unaffected by discrete episodes of simulated herbivory (Exps. 2 and 3). The introduction of B. thuringiensis genes into cotton does not seem to have reduced the considerable capacity of the crop to tolerate insect damage, and this attribute should be considered in the development of pest management strategies for Bt crops. (C) 1998 Elsevier Science B.V.
@article{
 title = {Herbivory tolerance of cotton expressing insecticidal proteins from Bacillus thuringiensis: responses to damage caused by Helicoverpa spp, and to manual bud removal},
 type = {article},
 year = {1998},
 pages = {287-299},
 volume = {56},
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 abstract = {Transgenic cotton varieties expressing Cry IA(c) insecticidal proteins from Bacillus thuringiensis ('Bt cotton') remain vulnerable to non-lepidopteran insects. In addition, they are susceptible to lepidopteran pests when the efficacy of Bt toxins falls because of ontogenetic and/or environmental factors. Hence the importance of knowing to what extent Bt cotton is able to tolerate damage. The degree of tolerance of Bt cotton to actual and simulated insect damage was assessed in three field experiments. Exp. 1 compared the effects of Helicoverpa spp. (Lepidoptera: Noctuidae) on the growth, development and yield of Bt cotton with those of its near isogenic non-Bt counterpart in two genetic backgrounds (Siokra V15, Sicala V2) under two regimes of chemical control of insects (S1: nine insecticide applications during the growing cycle, S2: six insecticide applications). Exp. 2 compared insecticide-protected Bt crops with crops manually damaged to simulate (a) early-season loss of vegetative buds, (b) loss of flowerbuds, and (c) loss of both vegetative and reproductive buds. Also using manual damage, Exp. 3 evaluated the effect of timing of flowerbud loss on the yield and maturity time of insecticide-protected Bt crops. In Exp. 1, well-protected Bt crops (S1) yielded 24% more than their less-protected counterparts (S2). The less protected crops had, however, substantially more immature fruit at the end of the season highlighting a considerable potential for recovery. Poor soil conditions, interacting with season length accounted for the difference between potential and actual compensation in crops that were exposed to almost continuous damage by Helicoverpa spp. Under more favourable growing conditions, maturity was delayed but yield of damaged Bt crops was unaffected by discrete episodes of simulated herbivory (Exps. 2 and 3). The introduction of B. thuringiensis genes into cotton does not seem to have reduced the considerable capacity of the crop to tolerate insect damage, and this attribute should be considered in the development of pest management strategies for Bt crops. (C) 1998 Elsevier Science B.V.},
 bibtype = {article},
 author = {Sadras, V O},
 journal = {Field Crops Research},
 number = {3}
}

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