The Effect of Beta-Caryophyllene Derivatives in a Tri-Species Cotton Hybrid on Cotton Aphid Infestation and Population Growth Potential

Abstract. Currently, insecticide applications and genetically-modified plants expressing Bacillus thuringiensis (Bt) toxins are the primary means for managing insect pests in cotton, but many of the pests have developed resistance to Bt proteins and insecticides. Thus, host plant resistance may be a viable solution to help prevent significant yield losses. Tri-species cotton hybrids consisting of either Gossypium hirsutum L., G. arboreum, and G. armouranium, or G. hirsutum, G. arboreum, and G. turneri have been reported to produce β-caryophyllene derivatives (12-hydroxy-β-caryophyllene and hydroxy-β-caryophyllene acetate) and have demonstrated resistance to nematodes, drought, and heat stress. Yet, there is lack of evidence whether these hybrids affect cotton insect pests. A series of field, greenhouse, and laboratory experiments were conducted to assess the impact a tri-species cotton hybrid expressing β-caryophyllene or its alcohol and acetate derivatives, have on cotton aphid, Aphis gossypii Glover. Although inconclusive in field trials, greenhouse choice test revealed the tri-species hybrid cotton had less colonization and fewer alate cotton aphids than G. hirsutum. Furthermore, in a cotton aphid reproduction study, the intrinsic rate of increase and finite rate of increase were lower for aphids feeding on the tri-species hybrid plants expressing β-caryophyllene or its alcohol derivative compared with G. hirsutum. Results suggest that the tri-species cotton hybrid, especially those capable of expressing the β-caryophyllene alcohol derivative, negatively impacts cotton aphid population development.