Transgenic Cotton for Insect Control Peter C. Ellsworth, Ph.D. IPM Specialist, University of Arizona Maricopa Agricultural Center Maricopa, AZ, USA

Disclosure Those engaged in the dialog on biotechnology should fully disclose their relationships and opinions “up front” so that audiences can consider the context. Partial support for my research comes from companies with interests in biotechnology. The balance of support comes from state and federal sources of competitively available public funds.

Disclosure (continued) Biotechnology and its products are neither inherently good nor bad. The specific process and each of its products should be scientifically and independently evaluated.

Transgenic Cotton for Insect Control What is available now & in the future? Origin, identity & development Insect target(s) in the U.S. Efficacy & utility in the Arizona system (benefits) Safety (risks) Resistance Impact of gene on plant Biodiversity non-target effects

Products Available for Cotton Insect Control Only 1 ‘trans’-gene has been commercialized Based on the crystalline protein produced by Bacillus thuringiensis (Bt) Developed by Monsanto as Bollgard® and incorporated into commercial varieties by several cotton seed companies (e.g., Delta Pineland Co. & Stoneville Pedigreed Seed Co.) Sold in the U.S., Australia, Mexico, South Africa, India, China, Argentina, Indonesia

Bacillus thuringiensis (Bt) Common soil bacterium Present in nature in a variety of forms (species & strains) Produces proteins that are toxic to insects Commonly used in garden sprays & for commercial agriculture, including organic farming Extremely well-known toxin in terms of human health & environmental safety

Bacillus thuringiensis (Bt) Crystalline proteins are classified according to structure & have a specific nomenclature (e.g., Cry1Ac) Cotton has been transformed with Cry1Ac (narrow spectrum; Lepidoptera only) Protein binds with receptors in the insect gut causing pores which perforate the midgut & lead to cell leakage & insect death

The Transformation Coker 312 The gene of interest is spliced out of the bacterium using a vector, like Agrobacterium tumefasciens, & transferred to cotton cells grown in tissue culture The cells are grown into a plant & then, after testing, plants are back-crossed into commercial lines to make new varieties Recurrent back-crossing

BG Cotton Efficacy Young larvae present regardless of cotton type Little difference between Bt & non-Bt (-) varieties

BG Cotton Kills Small Larvae PBW larvae must feed in order to be killed. Large larvae survive mainly in non-Bt varieties.

Impact on Arizona Cotton In 1990, > 6.8 sprays were made against PBW; still, > 5% yield loss Since 1996 when Bt cotton was introduced, it has never required oversprays for PBW control, AND Since 1997, only 0.5 sprays have been made against PBW over all cotton acreage (Bt and non-Bt); i.e., an areawide reduction of PBW has occurred The net reduction in insecticide use has resulted in huge savings to farmers, and large improvements to the agroecosystem in terms of beneficial insect communities & IPM

Safety - Resistance Given time & exposure, insects have the capacity to overcome most insecticides. Bt cotton may be no different, however, there are safeguards: Refugia High-Dose Strategy Development of additional proteins