Submitted to: International Association for Plant Tissue Culture & Biotechnology Congress
Publication Type: Abstract Only
Publication Acceptance Date: 2/2/2002
Publication Date: N/A
Technical Abstract: Mycotoxin contamination is a major problem in food and feed crops such as corn, cotton, peanut, and tree nut crops. We are interested in developing transgenic cottons that are resistant to the saprophytic fungus Aspergillus flavus, which produces carcinogenic aflatoxin on lipid-rich cottonseed. Several independently transformed lines of cotton expressing antifungal genes coding for either the chloroperoxidase (CPO-P) or the synthetic, linear peptide D4E1 (17aa) have been produced in our laboratory by the Agrobacterium method. In vitro assays using crude leaf extracts from transformed cotton plants (R0 and R1) demonstrated reduced number of colonies from pre-germinated spores of A. flavus, Fusarium moniliforme, and Verticillium dahliae. In situ assays using immature cottonseeds, inoculated with a virulent, Green Fluorescent Protein-expressing A. flavus strain showed that the transgenic plants are capable of delaying and reducing the fungal advance in seed coat and cotyledons. We are currently in the process of evaluating in planta resistance in R1 progeny against one or many cotton pathogens: Pythium, Fusarium, Rhizoctonia solani, V. dahliae, or Thielaviopsis basicola. In addition to establishing the disease-resistant phenotype of the transformed cotton plants and their progeny, we are also conducting experiments to determine 1) mode of action of CPO-P and 2) expression levels of the synthetic peptide in transgenic plants. Quantifying small peptide molecules, which are subject to degradation by plant proteases, is very difficult without the availability of suitable antibodies. The advantages of transgenic approaches in broad-spectrum control of phytopathogens including mycotoxin-producing fungi will be highlighted.