Title: The effect of Gossypolone on the growth and development of Helicoverpa zea (Boddie) Authors
|O Neil, Thomas|
|Lopez, Juan, Jr -|
|Hake, Kater -|
Submitted to: Southwestern Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 14, 2014
Publication Date: March 2, 2014
Citation: Stipanovic, R.D., Esquivel, J.F., Westbrook, J.K., Puckhaber, L.S., O Neil, M., Bell, A.A., Duke, S.E., Dowd, M.K., Lopez, J.D., Hake, K. 2014. The effect of gossypolone on the growth and development of Helicoverpa zea (Boddie). Southwestern Entomologist. 39(1):1-7. Interpretive Summary: The cotton plant is attacked by insects that consume the plant’s foliage and thus reduce yield. The plant produces chemicals that are toxic to some of these insects; thus, they act as defense compounds. One of these compounds, called gossypolone, was discovered several years ago, but it toxicity to these insects had not been investigated. We have completed an experiment in which gossypolone was fed in an artificial diet to newly hatched corn earworms, which also attack cotton. The effect of gossypolone on development of the corn earworm was compared to that of a closely related compound called gossypol that is also produced by cotton plants. Unlike gossypolone, the effect of gossypol on development of the corn earworm has been widely studied. We found that at the low levels tested, gossypolone increased the time for larvae to mature compared to larvae fed gossypol or to larvae fed a control diet with no added chemical. This may indicate that increasing the levels of gossypolone in cotton plants, by conventional breeding or by genetic engineering techniques, could delay maturation of these larvae and thus reduce their overall survival rate due to the extended time the larvae are exposed to adverse environmental conditions, insect pathogens, and predators.
Technical Abstract: The pigment glands of the cotton plant (Gossypium) produce a group of structurally related terpenoid aldehydes that protect the plant from herbivorous insects. Of these terpenoids, the most extensively studied is gossypol. Gossypolone, a compound closely related to gossypol, has been reported in these pigment glands but its activity against Helicoverpa zea (Boddie) has not been reported. We now report the effect of gossypol and gossypolone fed to first instar of H. zea at concentrations of 0.06%, 0.08% and 0.12% in an artificial diet. In previous studies, gossypol showed a hormetic effect when fed to Heliothis virescens (Fabricius) or Helicoverpa armigera (Hübner); in the present study gossypol also showed a hormetic effect when fed to H. zea. Gossypolone did not exhibit a hormetic effect at the concentrations tested, but pupae from larvae fed 0.12% gossypolone were significantly smaller than those fed the control diet or any of the diets with gossypol. Gossypol at the concentrations tested did not extend days-to-pupation, but in an earlier study gossypol at 0.16% extended days-to-pupation from 13.9 days (± 0.5) to 22.6 days (± 1.0). In this study, gossypolone also extended days to pupation but at a lower concentration [i.e., gossypolone at 0.12% extended days-to-pupation from 13.3 days (± 0.1) for the control to 20.8 days (± 0.7)]. A delay in days-to-pupation will reduce the number of generations that develop during a growing season, and may reduce larval survival. The biosynthesis of gossypolone may be due to a single gene. If so, increased expression of this gene could provide an overall increase in resistance to Heliothines pests of cotton.