Control of Aspergillus Flavus Infection and Growth

Aspergillus flavus infection of agriculturally important crops such as tree nuts, maize, peanuts, and cotton has decreased crop value. Researchers have identified three major approaches to combat A. flavus growth and aflatoxin accumulation: identifying natural resistance in crops, genetically engineering crops for enhanced resistance, and introducing an atoxigenic fungal strain as a competitor. In this dissertation, I investigated two of the three means to control A. flavus growth and infection: genetically engineered crops and identification of natural resistance. My studies of natural resistance in cotton crop show that Sa 1595, a Gossypium hirsutum cultivar, is significantly more susceptible to A. flavus infection; however, no significantly resistant cultivars were observed, but I did observe a trend of diminished susceptibility in A2 186 and Tamcot Sp 23. I then examined synthetic antimicrobial peptide, D4E1, as a means to increase resistance in crops. My research shows that D4E1 effectively increases reactive oxygen species (ROS), an apoptosis precursor at concentrations as low as 1 µM. Breaches in the membrane that allow infiltration and subsequent fluorescence from Sytox® green occur at higher concentrations. Finally, genetically engineered tobacco plants were examined for D4E1 localization. My research shows that the HA-D4E1 construct was present in the most abundance in the chloroplast of plastid transformed plants, while nuclear transformed plants had nuclear localization. All of my findings suggest that cotton crops do not exhibit any significant enhanced natural resistance to A. flavus infection and growth; however, engineering crops with D4E1 will exhibit enhanced crop resistance