Conduct Field Evaluation of Transgenic Cotton for Pest Resistance and Aflatoxin Contamination

Preharvest aflatoxin contamination of cottonseed is a major food safety problem because cottonseed cakes are fed to cattle. Aflatoxin contamination occurs in arid and semi-arid tropics that include the cotton belt and corn growing areas in the USA and the problem is exacerbated during drought conditions. Improving the host resistance of cotton plant to resist infection by Aspergillus flavus, the causal organism is one of the primary objectives. Transgenic expression of naturally-occurring or synthetic peptides has been shown to impart resistance to Aspergillus under laboratory and greenhouse conditions. Synthetic peptides are often resistant to proteolytic degradation and offer a good broad-spectrum control of several microbial pathogens. We have several transgenic cotton lines expressing synthetic or natural antifungal peptides or proteins in progress. One promising synthetic, lytic peptide is D4E1 and transgenic lines are ready for field test. The objectives of this study are manifold and include: 1) Evaluate transgenic cotton lines (e.g. D4E1) for resistance to Aspergillus flavus and other seedling pathogens (Fusarium, Verticillium) and insect pests as compared to an isogenic control line under normal field conditions in Arizona; 2) Determine the level of preharvest aflatoxin contamination in cottonseed and identify resistant lines; 3) Evaluate agronomic performance of transgenic lines (yield, fiber/seed quality) as compared to control; and 4) Assess possible effects of transgenic lines on diversity of soil microbes and other non-target species.