Abstract
Cry1Ac protoxin (the active insecticidal toxin in both Bollgard and Bollgard II cotton [Gossypium hirsutum L.]), and Cry2Ab2 toxin (the second insecticidal toxin in Bollgard II cotton) were bioassayed against five of the primary lepidopteran pests of cotton by using diet incorporation. Cry1Ac was the most toxic to Heliothis virescens (F.) and Pectinophora gossypiella (Saunders), demonstrated good activity against Helicoverpa zea (Boddie), and had negligible toxicity against Spodoptera exigua (Hübner) and Spodoptera frugiperda (J. E. Smith). Cry2Ab2 was the most toxic to P. gossypiella and least toxic to S. frugiperda. Cry2Ab2 was more toxic to S. exigua and S. frugiperda than Cry1Ac. Of the three insect species most sensitive to both Bacillus thuringiensis (Bt) proteins (including H. zea), P. gossypiella was only three-fold less sensitive to Cry2Ab2 than Cry1Ac, whereas H. virescens was 40-fold less sensitive to Cry2Ab2 compared with CrylAc. Cotton plants expressing Cry1Ac only and both Cry1Ac and Cry2Ab2 proteins were characterized for toxicity against H. zea and S.frugiperda larvae in the laboratory and H. zea larvae in an environmental chamber. In no-choice assays on excised squares from plants of different ages, second instar H. zea larvae were controlled by Cry1Ac/Cry2Ab2 cotton with mortality levels of 90% and greater at 5 d compared with 30-80% mortality for Cry1Ac-only cotton, depending on plant age. Similarly, feeding on leaf discs from Cry1Ac/Cry2Ab2 cotton resulted in mortality of second instars of S.frugiperda ranging from 69 to 93%, whereas exposure to Cry1Ac-only cotton yielded 20-69% mortality, depending on plant age. When cotton blooms were infested in situ in an environmental chamber with neonate H. zea larvae previously fed on synthetic diet for 0, 24, or 48 h, 7-d flower abortion levels for Cry1Ac-only cotton were 15, 41, and 63%, respectively, whereas for Cry1Ac/Cry2Ab2 cotton, flower abortion levels were 0, 0, and 5%, respectively. Cry1Ac and Cry2Ab2 concentrations were measured within various cotton tissues of Cry1Ac-only and Cry1Ac/Cry2Ab2 plants, respectively, by using enzyme-linked immunosorbent assay. Terminal leaves significantly expressed the highest, and large leaves, calyx, and bracts expressed significantly the lowest concentrations of Cry1Ac, respectively. Ovules expressed significantly the highest, and terminal leaves, large leaves, bracts, and calyx expressed significantly (P < 0.05) the lowest concentrations of Cry2Ab2. These results help explain the observed differences between Bollgard and Bollgard II mortality against the primary lepidopteran cotton pests, and they may lead to improved scouting and resistance management practices, and to more effective control of these pests with Bt transgenic crops in the future.
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Claims 13
Claim · model-written summary
Cry1Ac was most toxic to Heliothis virescens and Pectinophora gossypiella in diet bioassays.
- Interactor
- Heliothis virescens
Heliothis virescense0pest - Gene
- Cry1Ace0
- Outcome
- most toxice0
- Direction
- most toxice0
Not reportedTaxon
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cry1Ac was the most toxic to Heliothis virescens (F.) and Pectinophora gossypiella (Saunders)”
Claim · model-written summary
Cry1Ac had good activity against Helicoverpa zea.
- Interactor
- Helicoverpa zea
.jpg?width=60)
Helicoverpa zeae0pest - Gene
- Cry1Ace1
- Outcome
- good activitye0
Not reportedTaxon
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“demonstrated good activity against Helicoverpa zea (Boddie)”
e1“Cry1Ac was the most toxic”
Claim · model-written summary
Cry1Ac had negligible toxicity against Spodoptera exigua and Spodoptera frugiperda.
- Interactor
- Spodoptera exigua
Spodoptera exiguae0pest - Gene
- Cry1Ace1
- Outcome
- negligible toxicitye0
Not reportedTaxon
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“had negligible toxicity against Spodoptera exigua (Hübner) and Spodoptera frugiperda (J. E. Smith)”
e1“Cry1Ac was the most toxic”
Claim · model-written summary
Cry2Ab2 was most toxic to P. gossypiella and least toxic to S. frugiperda.
- Interactor
- P. gossypiella
Pectinophora gossypiellae0pest - Gene
- Cry2Ab2e0
- Outcome
- most toxice0
Not reportedTaxon
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cry2Ab2 was the most toxic to P. gossypiella and least toxic to S. frugiperda”
Claim · model-written summary
Cry2Ab2 was more toxic than Cry1Ac to S. exigua and S. frugiperda.
- Interactor
- S. exiguaSpodoptera exiguae0pest
- Gene
- Cry2Ab2e0
- Outcome
- more toxice0
- Direction
- more toxice0
- Comparator
- Cry1Ace0
Not reportedTaxon
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cry2Ab2 was more toxic to S. exigua and S. frugiperda than Cry1Ac”
Claim · model-written summary
P. gossypiella was three-fold less sensitive to Cry2Ab2 than Cry1Ac.
- Interactor
- P. gossypiellaPectinophora gossypiellae0pest
- Gene
- Cry2Ab2e0
- Outcome
- sensitivee0
- Direction
- less sensitivee0
- Value
- three-folde0
- Comparator
- Cry1Ace0
Not reportedTaxon
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“P. gossypiella was only three-fold less sensitive to Cry2Ab2 than Cry1Ac”
Claim · model-written summary
H. virescens was 40-fold less sensitive to Cry2Ab2 than Cry1Ac.
- Interactor
- H. virescensHeliothis virescense0pest
- Gene
- Cry2Ab2e0
- Outcome
- sensitivee0
- Direction
- less sensitivee0
- Value
- 40-folde0
- Comparator
- CrylAce0
Not reportedTaxon
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“H. virescens was 40-fold less sensitive to Cry2Ab2 compared with CrylAc”
Claim · model-written summary
Cry1Ac/Cry2Ab2 cotton caused at least 90% H. zea larval mortality after five days on excised squares, versus 30-80% for Cry1Ac-only cotton.
- Taxon
- cotton
Gossypium hirsutume0 - Organ / stage
- excised squarese1
- Treatment
- Cry1Ac/Cry2Ab2 cottone0
- Interactor
- H. zeaHelicoverpa zeae0pest
- Outcome
- H. zea larvae were controllede0
- Direction
- controllede0
- Value
- 90% and greatere0
- Qualifier
- 30-80% mortalitye0
- Comparator
- Cry1Ac-only cottone0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“second instar H. zea larvae were controlled by Cry1Ac/Cry2Ab2 cotton with mortality levels of 90% and greater at 5 d compared with 30-80% mortality for Cry1Ac-only cotton, depending on plant age”
e1“In no-choice assays on excised squares from plants of different ages”
Claim · model-written summary
Cry1Ac/Cry2Ab2 cotton leaf discs caused 69 to 93% S. frugiperda second-instar mortality, versus 20-69% for Cry1Ac-only cotton.
- Taxon
- cottonGossypium hirsutume0
- Organ / stage
- leaf discse0
- Treatment
- Cry1Ac/Cry2Ab2 cottone0
- Interactor
- S.frugiperda
.jpg?width=60)
Spodoptera frugiperdae0pest - Outcome
- mortality of second instars of S.frugiperdae0
- Direction
- resulted in mortalitye0
- Value
- 69 to 93%e0
- Qualifier
- 20-69% mortalitye0
- Comparator
- Cry1Ac-only cottone0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“feeding on leaf discs from Cry1Ac/Cry2Ab2 cotton resulted in mortality of second instars of S.frugiperda ranging from 69 to 93%, whereas exposure to Cry1Ac-only cotton yielded 20-69% mortality”
e1“leaf discs from Cry1Ac/Cry2Ab2 cotton”
Claim · model-written summary
Flower abortion after H. zea infestation was 15%, 41%, and 63% for Cry1Ac-only cotton after prior larval feeding for 0, 24, or 48 h.
- Taxon
- cottonGossypium hirsutume0
- Material
- Cry1Ac-only cottone0
- Organ / stage
- flowere0
- Interactor
- H. zeaHelicoverpa zeae1pest
- Outcome
- flower abortion levelse0
- Value
- 15, 41, and 63%e0
- Qualifier
- 0, 24, or 48 he1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“7-d flower abortion levels for Cry1Ac-only cotton were 15, 41, and 63%, respectively”
e1“with neonate H. zea larvae previously fed on synthetic diet for 0, 24, or 48 h”
Claim · model-written summary
Flower abortion after H. zea infestation was 0%, 0%, and 5% for Cry1Ac/Cry2Ab2 cotton after prior larval feeding for 0, 24, or 48 h.
- Taxon
- cottonGossypium hirsutume0
- Material
- Cry1Ac/Cry2Ab2 cottone0
- Organ / stage
- flowere0
- Interactor
- H. zeaHelicoverpa zeae1pest
- Outcome
- flower abortion levelse0
- Value
- 0, 0, and 5%e0
- Qualifier
- 0, 24, or 48 he1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“for Cry1Ac/Cry2Ab2 cotton, flower abortion levels were 0, 0, and 5%, respectively”
e1“with neonate H. zea larvae previously fed on synthetic diet for 0, 24, or 48 h”
Claim · model-written summary
Terminal leaves had the highest Cry1Ac concentration, while large leaves, calyx, and bracts had the lowest.
Not reportedTaxon
Verbatim
e0“Terminal leaves significantly expressed the highest, and large leaves, calyx, and bracts expressed significantly the lowest concentrations of Cry1Ac”
Claim · model-written summary
Ovules had the highest Cry2Ab2 concentration, while terminal leaves, large leaves, bracts, and calyx had the lowest.
Not reportedTaxon
Verbatim
e0“Ovules expressed significantly the highest, and terminal leaves, large leaves, bracts, and calyx expressed significantly (P < 0.05) the lowest concentrations of Cry2Ab2”