Doctor of Philosophy (PhD)


Plant Pathology and Crop Physiology

Document Type



Aspergillus flavus is a soil-borne fungal pathogen that infects maize and produces aflatoxins. In the current study, portions of the alkaline protease (alk) and the O-methyl transferase (omtA) genes, which are key in A. flavus virulence and aflatoxin biosynthesis, respectively, were targeted for suppression through an RNAi (RNA interference) approach known as Host-Induced Gene Silencing (HIGS). Separate RNAi vectors were designed to carry regions of the alk and omtA gene fragments (Alk-RNAi and OmtA-RNAi) and introduced into B104 maize zygotic embryos. Eight and six transformation events were positive for the alk and omtA transgene, respectively. Alk positive events, Alk-3 and Alk-7, were self-pollinated through T1 to T4 and Alk-4, and Alk-9 through T1 to T6 generations. Up to 87% reduced aflatoxin accumulation was observed in four T3 Alk-transgenic lines under laboratory conditions. The homozygous T4 Alk-3 and Alk-7 lines and homozygous T5 and T6 Alk-4 and Alk-9 showed up to 83% reduced aflatoxin accumulation compared to their non-transgenic controls under field inoculations (PA. flavus growth and ß-tubulin levels was confirmed in transgenic compared to the non-transgenic control kernels during in-vitro infection, indicating reduction in A. flavus infection. In addition, OmtA-6, OmtA-7, OmtA-10 and OmtA-12 lines showed up to 93% reduction in aflatoxin accumulation at T3 generation under laboratory conditions. However, only OmtA-10 at T4 generation, and OmtA-7 at T5 and T6 generations showed significant reduction (up to 63%) in aflatoxin under field conditions (Palk and omtA-specific small RNAs only in the transgenic leaf and kernel tissues demonstrate the efficacy of suppressing alk and omtA genes through HIGS in managing aflatoxin contamination in maize.



Committee Chair

Chen, Zhi-Yuan