Enhancing Corn with Resistance to Aflatoxin Contamination and Insect Damage

Approach: <BR> Objective 1. Determine the effects of indigenous fungal species and ear-feeding
insects on A. flavus infection and aflatoxin accumulation in corn grain.
Colonization of corn grain is rarely by a single fungal species, but rather a mixture
of fungi. Fusarium verticillioides (syn. F. moniliforme) is the most commonly
reported fungus infecting corn in the USA, and it is frequently found together with
A. flavus. Acremonium zeae is a common contaminant of preharvest corn in the
Southeast. It has been reported to suppress growth of both A. flavus and F.
verticillioides in laboratory experiments. The interactions of these fungi will be
investigated to determine whether F. verticillioides and A. zeae affect A. flavus
infection of corn grain and the subsequent accumulation of aflatoxin, and if so,
whether these fungi are impediments to the identification of aflatoxin-resistant corn
germplasm. The association between insect damage and aflatoxin accumulation in
different corn genotypes will be investigated and the extent to which resistance to
damage by southwestern corn borer, Diatraea grandiosella; fall armyworm, Spodoptera
frugiperda; or corn earworm, Helicoverpa zea, reduces aflatoxin contamination will be
determined. <BR> <BR> Objective 2. Identify new sources of corn germplasm with resistance to A.
flavus infection and aflatoxin accumulation and/or resistance to damage by
southwestern corn borer, fall armyworm, and corn earworm. Corn germplasm from
diverse backgrounds will be screened for resistance to A. flavus/aflatoxin,
southwestern corn borer, fall armyworm, and corn earworm. Information on the effects
of other fungi or insects on A. flavus/aflatoxin accumulation (Objective 1) will be
used to refine and improve techniques for evaluating germplasm for resistance. Newly
identified sources of resistance will be used to pursue Objectives 3 and 4.<BR> <BR>
Objective 3. Identify quantitative trait loci, genes, and proteins associated with
resistance in corn to A. flavus infection, aflatoxin accumulation, and insect damage.
Populations of F2:3 families and recombinant inbred lines derived from crosses
between aflatoxin or insect resistant inbred lines and susceptible lines will be used
to identify quantitative trait loci (QTL) associated with resistance. Resistant and
susceptible corn inbred lines and recombinant inbred lines will be used in
complementary investigations to identify candidate genes and proteins associated resistance. Molecular markers identified in these investigations will be used in
developing improved germplasm lines (Objective 4). <BR> <BR> Objective 4. Enhance corn
germplasm with resistance to A. flavus infection, aflatoxin accumulation, and insect
damage and release germplasm lines as sources of resistance. Both breeding methods
based on phenotypic performance and those based on molecular markers will be used to
enhance germplasm with resistance to aflatoxin contamination and insect damage. The
effectiveness of molecular markers based on QTL, genes, and proteins identified in
Objective 3 in transferring resistance to A. flavus/aflatoxin and insect damage into
germplasm lines with desirable agronomic qualities will be determined.