One major problem facing maize producers in the southern US is
contamination with the mycotoxin aflatoxin, produced by Aspergillus
flavus (Link:fr). Aflatoxin is a serious threat to human and animal
health, with no resistant commercial hybrid available.
Development of resistance to aflatoxin production has several major
limitations. Aflatoxin is highly variable both across and within
environments, even under inoculation, requiring several locations and
replications for breeding. Additionally, there is no screening method that
is reliable, rapid, inexpensive, and allows for high throughput.
Several secondary traits, such as kernel texture, kernel integrity, husk
cover, and visible ear rot, have previously shown to be related to
aflatoxin accumulation. These traits are easily characterized in the field and are candidates for indirect selection if they are correlated to
aflatoxin concentration.
Root lodging, a plantÂs inability to maintain upright stature, is another
complex characteristic of root related traits that traditionally is selected
for indirectly. It can greatly reduce harvestable yield. It is affected by
morphological traits and environmental conditions, but its genetic
components are little understood.
This dissertation comprises three studies presented in chapters II, III,
and IV. Chapter II involved white and yellow hybrid maize trials as well
as quality protein maize trials from several years across Texas
environments. Data was analyzed both per and across location to
determine repeatability of response to aflatoxin. Additionally, aflatoxin
levels were correlated to several secondary characteristics (female
flowering, endosperm texture, husk cover, and ear rot ratings) to
determine usefulness in indirect selection.
Chapter III was a phenotypic evaluation of a recombinant inbred line
(RIL) mapping population, which was derived from divergent parental
inbreds Tx811 and CML176. The trials were conducted in two Texas
locations, and phenotypic data for aflatoxin concentration, kernel integrity, endosperm texture, female flowering date, and root lodging was
collected. Variance components for these traits and genetic and
phenotypic correlations were determined.
Chapter IV was a genotypic evaluation of the Tx811/CML176 mapping
population using simple sequence repeat markers. Genotypic and
phenotypic data were combined to identify quantitative trait loci (QTL)
and epistatic interactions for response to aflatoxin and for root lodging.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/3828 |
| Date | 16 August 2006 |
| Creators | Edwards, Melanie Love |
| Contributors | Betran, F. Javier |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | 464097 bytes, electronic, application/pdf, born digital |
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