| dc.description.abstract | Infection of seed with two major ear rot pathogens of maize, Fusarium verticillioides and Aspergillus flavus, lead to high yield losses and detrimental health effects to humans and animals through the production of mycotoxins, fumonisin and aflatoxin, respectively. These carcinogenic compounds are some of the most agriculturally important mycotoxins, consumption of which in food and feed can lead to various cancers and stunted growth. While atoxigenic strains of A. flavus are used for biocontrol of the pathogenic strain, no similar biocontrol agent exists for F. verticillioides. I hypothesized that F. verticillioides may antagonize A. flavus and promote plant growth. Here I screened 150 putative Fusarium isolates collected from maize across Texas that produce a broad range of fumonisin levels from highly toxigenic to almost non-detectable levels. I confirmed that selected isolates do not produce fumonisin in vitro and determined that their effects on plant growth promotion are variable. Atoxigenic strains of F. verticillioides, 302-A6 and PAL 401, significantly inhibited aflatoxin contamination in a kernel bioassay compared to kernels only infected with A. flavus but were unable to definitively inhibit aflatoxin or fumonisin by in planta experiments.
A broad range of microbes have been studied for their ability to induce defense pathways in plants towards improved resistance to pathogens and insect herbivores, as well as for promoting plant growth and yield. Here, I show that a selection of beneficial fungal symbionts applied in two locations over two years hold potential for reducing mycotoxin contamination by inducing maize resistance to A. flavus and F. verticillioides. In particular, Epicoccum nigrum TAMU32, Pleospora herbarum TAMU473, and Acremonium alternatum TAMU505 led to reductions of aflatoxin in B73 inbred and specific hybrid maize lines. Emphasizing that each fungal treatment must be rigorously tested before marketing, treatments with E. nigrum 89 and P. herbarum 473 increased aflatoxin in the already resistant Tx779 hybrid. Seed treatment with A. alternatum 505 before planting led to promising reductions of aflatoxin and fumonisin in College Station and Lubbock, and showed reduced occurrence of insect damage, suggesting it may improve resistance to both mycotoxins and herbivores depending on genotype and location. | |
