Book of Abstracts (PDF) - International Mycological Association

IMC7 Friday August 16th Lectures
use to note that only a subset of possible arrangements
occur. These 'haplotypes' have proven highly useful for
making a variety of inferences about population structure,
migration, ages of polymorphisms, and departures from
neutral evolution. An overview of the methods for
inference of haplotypes from genotype data will be
presented, along with illustrations of the applications of
haplotype analysis in populations of Drosophila and other
organisms.
419 - Inferring ancestry from DNA sequences; modeling
and inference with the coalescent process
R.C. Griffiths
University of Oxford, Department of Statistics, 1 South
Parks Road, Oxford, OX1 3TG, U.K. - E-mail:
griff@stats.ox.ac.uk
A unique gene tree describing the mutation history of a
sample of DNA sequences can be constructed as a perfect
phylogeny under an assumption of non-recurrent point
mutations. There is much interest in thinking of the data as
a tree, rather than just sequences. This talk will describe,
with examples, how coalescent trees and gene trees are
used to model and infer ancestry of a sample of DNA
sequences.
420 - Demographic inferences from molecular data
using Bayesian and maximum likelihood methods
R. Nielsen
Department of Biometrics, Cornell University, 439 Warren
Hall, Ithaca, NY 14853-7801, U.S.A. - E-mail:
rn28@cornell.edu
A popular approach for inferring demographic parameters,
such as levels of gene flow between populations, or rates of
population growth, is to collect molecular data and to use
this data to estimate demographic parameters based on
specific population models. In the past there have been few
attempts to test these models and to develop methods for
choosing between alternative models. In this talk I will
present some recent methods for hypothesis testing and
model choice using molecular population genetic data. In
particular I will investigate models for estimating levels of
gene flow and population divergence times.
421 - Progress and pitfalls in aflatoxin studies
D.M. Wilson
University of Georgia, Coastal Plain Station, P. O. Box
748, 109 Plant Science Drive, Tifton, GA 31793, U.S.A. -
E-mail: dwilson@tifton.cpes.peachnet.edu
130
Book of Abstracts
Aflatoxin contamination of foods and feeds is a global
problem which is most severe in the warmer portions of the
globe. Aflatoxin research is difficult because the fungi that
produce the aflatoxins are not aggressive pathogens and
often occur as saprophytes in feedstuffs. Aflatoxin
contamination can occur before harvest, during harvesting
and drying and in storage. The environmental conditions
favoring contamination before harvest generally includes
late season drought and high temperatures. The
relationships between damage and contamination begin in
the field and progress throughout the marketing channels
with moisture content being the most critical post harvest
factor. There are different marketing regulations in the
USA and European Union. The market for the product
sometimes dictates the marketing and management
strategies. Countries with few or unenforced regulations
sometimes have highly contaminated products in the
marketplace. Therefore, management strategies must be
tailored to the climate and the country. There are at present
no completely effective management tools to eliminate
aflatoxin contamination from the human food chain.
422 - Fumonisin exposure in different populations and
reduction of fumonisin by the process of
nixtamalization
M. Dombrink-Kurtzman
Mycotoxin Research, NCAUR, USDA, ARS, 1815 N.
University Street, Peoria, IL 61604, U.S.A. - E-mail:
dombrink@ncaur.usda.gov
In countries where a major part of the daily diet is maize,
the presence of fumonisins in maize products represents an
emerging health concern. The U.S. Food and Drug
Administration has issued recommended guidance levels
for maize. Although unequivocal harm to humans has not
been demonstrated, fumonisins have been shown to cause
diseases in horses and pigs and to produce tumors in
laboratory rats. Exposure to fumonisins is highest in South
Africa and China due to high intake of maize and the
potential for environmental conditions favoring mycotoxin
production. Fumonisins, mycotoxins produced by
Fusarium verticillioides (synonym F. moniliforme) and F.
proliferatum, can be present in normal-appearing maize.
The alkaline-cooking process, nixtamalization, is used to
produce many maize products in Mexico, Central America
and the United States. Research had shown that masa and
tortillas from Mexico and the United States contained
fumonisin B1. To determine the fate of fumonisins during
processing, maize naturally contaminated with fumonisins
underwent nixtamalization for production of tortillas.
Material was analyzed at each step for fumonisins, weights
and moisture contents so that mass balance determinations
could be calculated. Less than twenty percent of the
fumonisins remained in the tortillas. Nixtamalization
appears to be a way to reduce significantly fumonisins
occurring in maize products.