Host-Induced Gene Silencing of the Aspergillus flavus O-Methyl Transferase Gene Enhanced Maize Aflatoxin Resistance

Maize is one of the major crops that are susceptible to <i>Aspergillus flavus</i> infection and subsequent aflatoxin contamination, which poses a serious health threat to humans and domestic animals. Here, an RNA interference (RNAi) approach called Host-Induced Gene Silencing (HIGS) was employed to suppress the <i>O</i>-methyl transferase gene (<i>omtA</i>, also called <i>aflP</i>), a key gene involved in aflatoxin biosynthesis. An RNAi vector carrying part of the <i>omtA</i> gene was introduced into the B104 maize line. Among the six transformation events that were positive for containing the <i>omtA</i> transgene, OmtA-6 and OmtA-10 were self-pollinated from T1 to T4, and OmtA-7 and OmtA-12 to the T6 generation. These four lines showed at least an 81.3% reduction in aflatoxin accumulation at the T3 generation under laboratory conditions. When screened under field conditions with artificial inoculation, OmtA-7 at T5 and T6 generations and OmtA-10 at T4 generation showed a reduction in aflatoxin contamination between 60% and 91% (<i>p</i> < 0.02 to <i>p</i> < 0.002). In order to develop commercial maize lines with enhanced aflatoxin resistance, the <i>omtA</i> transgene in OmtA-7 was introduced into three elite inbred lines through crossing, and the resulting crosses also exhibited significantly lower aflatoxin accumulation compared to crosses with non-transgenic controls (<i>p</i> < 0.04). In addition, high levels of <i>omtA</i>-specific small RNAs were only detected in the transgenic kernel and leaf tissues. These results demonstrate that suppression of <i>omtA</i> through HIGS can enhance maize resistance to aflatoxin contamination, and this resistance can be transferred to elite backgrounds, providing a viable and practical approach to reduce aflatoxin contamination in maize.