Leaf tissue assay for lepidopteran pests of Bt cotton

Authors: Little, Nathan; Mullen, Regina; Allen, Clint; Tyler, Heather

Submitted to: Southwestern Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/26/2017
Publication Date: 11/30/2017
Publication URL: http://handle.nal.usda.gov/10113/5863784
Citation: Little, N., Mullen, R.M., Allen, K.C., Tyler, H.L. 2017. Leaf tissue assay for lepidopteran pests of Bt cotton. Southwestern Entomologist. 42(4):953-958. https://doi.org/10.3958/059.042.0414.
DOI: https://doi.org/10.3958/059.042.0414

Interpretive Summary: In this manuscript, we developed a new leaf tissue assay method for lepidopteran pests Bt cotton. Current laboratory measurements of tolerance to transgenic insecticides have little relevance to the ability of an insect to survive on Bt crops. We found an apparent difference in survival of bollworm on two different dual-gene Bt cottons. Given the high susceptibility of tobacco budworm to Bt toxins, none survived on either of the two transgenic cotton cultivars tested during this study. The leaf tissue-based method described in this manuscript may compliment other laboratory methods by providing a linkage to survival on Bt cotton.

Technical Abstract: Laboratory measurements of susceptibility to Bt toxins can be a poor indicator of the ability of an insect to survive on transgenic crops. We investigated the potential of using cotton leaf tissue for evaluating heliothine susceptibilities to two dual-gene Bt cottons. A preliminary study was conducted with different cotton leaf disk combinations to determine the best procedure for utilizing cotton tissue to assay bollworm and tobacco budworm. Neonate larvae from a laboratory colony were assayed simultaneously on cotton leaf disks of non-Bt and two different dual-gene transgenic cottons in addition to meridic diet overlaid with discriminating doses of a commercially-formulated Bt product. The bollworm laboratory colony exhibited a higher level of tolerance than tobacco budworm to the commercially-formulated Bt product. No tobacco budworm survived on dual-gene Bt cotton leaf disks in this study. However, there was an apparent difference in bollworm larval survival on leaf disks from the two different transgenic Bt cottons. Assays using transgenic cotton leaf disks may compliment current meridic diet-based methods by providing a linkage to insect survival on Bt cotton plants.