Mortality and feeding of mid-stadium larvae of Helicoverpa zea and Heliothis virescens fed a wild strain or a recombinant strain of Baculovirus heliothis expressing an insect-specific toxin of the scorpion Leiurus quinquestriatus hebraeus

Ignoffo, Carlo M.; Wong, Jeffrey A.; Saathoff, Stephen G.

doi:10.1303/aez.34.279

Cited by 7 publications

(9 citation statements)

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“…The parental Wt strains were the single-nucleocapsid baculovirus of the Helicoverpa/Heliothis complex (HzSNPV) and the multiple-nucleocapsid baculovirus of Autographa californica (AcMNPV). The parental Wt strain of AcMNPV was Ac6 (Ayres et al, 1994) and the parental Wt strain of HzSNPV was HzSNPV-I (Ignoffo et al, 1999b). The three Rc used (all polyhedrin-positive strains expressing an insect-specific neurotoxin) were RcHzLqhIT2, RcAcAaIT, and RcAcLqhIT2 (hereafter the designation IT will not be used).…”

Section: Methodsmentioning

confidence: 99%

“…The three Rc used (all polyhedrin-positive strains expressing an insect-specific neurotoxin) were RcHzLqhIT2, RcAcAaIT, and RcAcLqhIT2 (hereafter the designation IT will not be used). Both Rc strains RcHzLqh and RcAcLqh express a venom toxin of the scorpion Leiurus quinquestriatus hebraeus under control of an early promotor (Zilberberg et al, 1992;Jarvis et al, 1996;Ignoffo et al, 1999b). The other Rc strain (RcAcAa) expresses a venom toxin of a different scorpion, Androctonus australis, under control of a late promotor (Mc-Cutchen et al, 1990;Stewart et al, 1991).…”

Section: Methodsmentioning

confidence: 99%

“…Paralysis was defined as larval movement but no mobility (unable to resume feeding), and mortality as no movement after prodding. Frass collected from the individual wells of each larva (after the larva had either died, prepupated or pupated) was used to determine the extent of larval feeding (Ignoffo and Garcia, 1997;Ignoffo et al, 1999b). After collection, the frass of each larva was oven-dried (70Ϯ5°C) for 24 h and then weighed.…”

Section: Methodsmentioning

confidence: 99%

“…One of the biggest disadvantages encountered during this developmental period was that viruses could not kill insect pests as quickly as did chemical insecticides. In an effort to overcome this disadvantage, baculoviruses, over the last decade, have been geneti-cally modified to express safe, quick-acting, insectspecific toxins (Maeda, 1989;Maeda et al, 1991;Stewart et al, 1991;Tomalski and Miller, 1991;Bonning and Hammock, 1992;Black et al, 1997;Popham et al, 1997;Burden et al, 1999;Ignoffo et al, 1999b). Several strains of these genetically modified, toxin-expressing baculoviruses are used in the research reported herein.…”

Section: Introductionmentioning

confidence: 99%

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Sensitivity of heliothine larvae to wild-type and recombinant strains of a single nucleocapsid(HzSNPV) and a multiple nucleocapsid(AcMNPV) baculovirus.

Ignoffo

Wong

McIntosh

et al. 2001

Appl. Entomol. Zool.

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Mid-stadium larvae of Helicoverpa zea were equally susceptible to either the wild-type (Wt) or recombinant (RcHz-Lqh) strain of HzSNPV. There was, however, a significant difference (1.8-fold) in the rate of mortality between the two strains. The LT 50 for the Wt and Rc strain was 3.4Ϯ0.1 days and 1.9Ϯ0.2 days, respectively. In contrast, there was a significant difference in both the rate and extent of mortality of mid-stadium larvae of H. virescens fed either the Wt or Rc strain of HzSNPV (LC 50 : Wt, 11.4Ϯ0.6 OB/cm 2 ; Rc, 42.2Ϯ8.2 OB/cm 2. LT 50 : Wt, 4.1Ϯ0.1 days; Rc, 2.8Ϯ0.2 days). An 8-fold increase in the viral rate of the WtHzSNPV was needed (800 OB/mm 2) to match the effectiveness of the RcHzLqh strain at 100 OB/cm 2. Increasing the RcHzLqh rate above 100 OB/cm 2 did not significantly reduce the LT 50 or larval feeding as measured by frass weight. All viral rates of the Rc strains significantly reduced (ca. 6-to 12fold) mid-stadium larval feeding over that of the control. Differences between the Rc and Wt strains of HzSNPV, using late-stadium H. zea larvae, showed the same tendency as that using mid-stadium larvae, but the differences were not as great (< 2-fold). Mid-stadium larvae of H. virescens were ca. 3-fold more susceptible to RcAcLqh than to either the WtAc or RcAcAa. Both RcAcLqh and RcAcAa strains killed larvae quicker (1.5-to 1.7-fold) and reduced feeding more (1.6-to 1.9-fold) than the WtAc strain. A combination of RcAcLqh and RcAcAa at 5 OB/cm 2 had no additive effect on mortality of H. virescens larvae and the combination was less effective than either Rc strain at 10 OB/cm 2. Unexpectedly, the known level of susceptibility of semi-permissive larvae of H. zea to WtAcMNPV, as measured by percent mortality, LT 50 , and feeding, was significantly enhanced (ca. 2-fold) when H. zea larvae were fed the RcHz-Lqh strain. In contrast, expression of the Lqh-toxin by RcHzLqh did not significantly increase the susceptibility of H. subflexa, larvae previously reported as being highly resistant to WtHzSNPV.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Sensitivity of heliothine larvae to wild-type and recombinant strains of a single nucleocapsid(HzSNPV) and a multiple nucleocapsid(AcMNPV) baculovirus.

Ignoffo

Wong

McIntosh

et al. 2001

Appl. Entomol. Zool.

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“…Genetic modification has been pursued as a means to improve their lethal time (3). For example, survival times of the tobacco budworm, Heliothis virescens, and the bollworm, Helicoverpa zea, were reduced when infected with Heliothis NPV expressing highly specific toxin from the scorpion Leiurus quinquestriatus hebraeus (DuPont construct HzSNPV.LqhIT2) (16).…”

mentioning

confidence: 99%

Quantification of Soil-to-Plant Transport of Recombinant Nucleopolyhedrovirus: Effects of Soil Type and Moisture, Air Currents, and Precipitation

Fuxa

Richter

2001

Appl Environ Microbiol

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Persistence and Distribution of Wild-Type and Recombinant Nucleopolyhedroviruses in Soil

et al. 2001

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Persistence of recombinant and wild-type nucleopolyhedroviruses (NPV) was compared in field and laboratory microcosm experiments. Horizontal and vertical distribution of the viruses also was monitored in the field agricultural soil. Mixed populations of the bollworm, Helicoverpa zea, and tobacco budworm, Heliothis virescens, in cotton were sprayed five times during a growing season with wild-type H. zea NPV (HzSNPV.WT) or with a genetically modified H. zea NPV expressing an insect-specific neurotoxin (HzSNPV.LqhIT2). HzNPV.WT accumulated 2.3 times as many occlusion bodies (OB) as HzSNPV.LqhIT2 in soil by the end of the growing season in October 1997. Both NPVs were detected at all soil depths down to 26-35 cm. Both NPVs were randomly distributed among 0-2 cm soil samples throughout the plots according to analysis with Taylor's power law. By 4 August 1998, soil concentration of HzSNPV.WT was only 11-13 OB/g at depths from 0 to 14 cm, and the wild-type virus was not detected below 14 cm. HzSNPV.LqhIT2 was detected only in trace amounts at 0-2 cm at this time. Neither NPV was detected in bioassays of cotton leaves nor in insects sampled from the plots in 1998. Viral persistence also was monitored in laboratory soil microcosms. Three viruses-wild-type Autographa californica NPV (AcNPV.WT), A. californica NPV expressing a scorpion toxin (AcNPV.AaIT), and A. californica NPV expressing juvenile hormone esterase (AcNPV.JHE-S201G)-were introduced into soil microcosms by each of two methods, in water suspension or in host cadavers, for a total of six treatments plus controls. After 17 months, the number of viable OB remaining did not differ among the treatments. The results indicate that the only differences in soil populations of wild-type versus recombinant NPVs are due to the greater amounts of the wild-type viruses that accumulate, probably because they have a greater capacity to replicate in the host insect population.

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Mortality and feeding of mid-stadium larvae of Helicoverpa zea and Heliothis virescens fed a wild strain or a recombinant strain of Baculovirus heliothis expressing an insect-specific toxin of the scorpion Leiurus quinquestriatus hebraeus

Cited by 7 publications

References 4 publications

Sensitivity of heliothine larvae to wild-type and recombinant strains of a single nucleocapsid(HzSNPV) and a multiple nucleocapsid(AcMNPV) baculovirus.

Sensitivity of heliothine larvae to wild-type and recombinant strains of a single nucleocapsid(HzSNPV) and a multiple nucleocapsid(AcMNPV) baculovirus.

Quantification of Soil-to-Plant Transport of Recombinant Nucleopolyhedrovirus: Effects of Soil Type and Moisture, Air Currents, and Precipitation

Persistence and Distribution of Wild-Type and Recombinant Nucleopolyhedroviruses in Soil

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