Degree

Doctor of Philosophy (PhD)

Department

Plant Pathology and Crop Physiology

Document Type

Dissertation

Abstract

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.

Date

1-12-2021

Committee Chair

Chen, Zhi-Yuan

Available for download on Monday, January 08, 2024

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