1 |
Entwicklung von immunanalytischen, chromatographischen und massenspektrometrischen Methoden zur Bestimmung von Aflatoxinen in LebensmittelnCervino, Christian January 2009 (has links)
Zugl.: München, Techn. Univ., Diss., 2009
|
2 |
Studies on the formation of mycotoxins, microbial interaction and biochemical composition during ripening stages of different cultivars of date fruit from the United Arab EmiratesShenasi, Mariam H. January 2002 (has links)
No description available.
|
3 |
Preharvest aflatoxin in maize genotypes under inoculation with Aspergillus flavusMayfield, Kerry L. 15 May 2009 (has links)
Pre-harvest aflatoxin contamination is a major limitation to maize production in
Texas and the southern United States, causing major economic loss and severe health
problems worldwide. Screening for resistance to aflatoxin accumulation is commonly
conducted through inoculation with a highly concentrated solution of Aspergillus flavus
FR: Link spores, a naturally occurring fungus which infects maize and produces a toxic
metabolite (aflatoxin) to humans and animals consuming the grain. No commercial
hybrids exist with full resistance to aflatoxin accumulation; however, sources exist to
reduce susceptibility. These sources commonly lack good agronomic characteristics for
use in commercial hybrids. Exotic germplasm with favorable traits for reduced aflatoxin
accumulations are introgressed with temperate and locally adapted lines. This program
utilizes only one isolate of A. flavus even though many isolates exist in the environment.
The objectives of this thesis are i) to evaluate the progress of the Maize Breeding and
Genetics Program’s accomplishments of breeding maize for the reduction in
susceptibility of aflatoxin accumulation in yellow inbreds through analysis of hybrid and
inbred per se trials and ii) to determine whether interaction exists between geneticallydifferent
isolates of A. flavus and several genotypes of maize. Response to aflatoxin accumulation for hybrids and inbreds was measured at up to three environments across
Texas. Significant differences were detected for most years and environments. Maize
lines CML285, CML288, CML323, CML325, CML326, CML338, Tx601y and lines
derived from Population 69 and from Tx772 crosses in hybrid combinations tended to
accumulate less aflatoxin than commercial hybrid checks. Significant differences were
detected at each environment aflatoxin accumulation was measured for inbred lines per
se. Inbreds Tx772, Tx601y, CML289, CML294, CML323 and derived lines from
Population 69 show reduced aflatoxin accumulations. Interaction between genetically
different isolates of A. flavus and several genotypes of maize were not detected in hybrid
or inbred trials at two or three environments, across locations and across years.
Introgression of exotic germplasm into locally adapted germplasm has improved
agronomic characteristics for use in the Southern U.S. and brought sources for decreased
aflatoxin accumulation.
|
4 |
Phenotypic and genotypic evaluation of generations and recombinant inbred lines for response to aflatoxinBello, Halima Thelma 15 May 2009 (has links)
Aspergillus flavus is a fungus pathogen of maize that causes contamination of maize
with aflatoxin. Aflatoxin is a carcinogenic toxin that can cause harm to human and
animal health. Several management practices have been developed, such as cultural,
chemical, biological and breeding, for host resistance. Development of host plant
resistance has been the most desirable but this has been hampered by several factors,
such as environmental influence, time consuming phenotyping and costly inoculation
and field evaluations. Because of the problems associated with breeding for aflatoxin
resistance, heritability estimates along with genetic correlations for aflatoxin and its
secondary traits were estimated in this study. This experiment was conducted in two
Texas locations (College Station and Weslaco) and phenotypic data were collected for
aflatoxin concentration, maturity, endosperm texture, percentage of rotten ears and grain
yield per ear.
The heritability was moderate to high for aflatoxin and secondary traits such as
endosperm texture and percentage of rotten ears. Aflatoxin was observed to be
negatively correlated to grain yield and positively correlated to percentage of rotten ears.
A population of recombinant inbred line derived from a cross between CML161 and
B73o2 were evaluated in replicated trials in two environments for resistance to aflatoxin
contamination. The families were genotyped using simple sequence repeat (SSR)
markers. The mapping Recombinant Inbred Line population was used to detect and
characterize Quantitative Trait Loci associated with aflatoxin accumulation. Alleles for reducing aflatoxin contamination came from both parents across the chromosomes.
Thirty-eight epistatic interactions were detected for aflatoxin resistance.
Several other QTLs were identified for other traits such as grain yield, endosperm
texture, and percentage of rotten ears. The QTLs reported in this experiment are
promising and need to be validated in other environment and genetic backgrounds for
further use in marker assisted selection.
Inheritance studies using generation mean analysis in six crosses showed additive and
dominance effects to be mainly responsible for aflatoxin resistance. Two inbreds,
CML176 and CML161, were identified as sources of resistance in breeding programs
and use for selection.
|
5 |
Genotypic and phenotypic characterization of response to aflatoxin and secondary traits in maizeEdwards, Melanie Love 16 August 2006 (has links)
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.
|
6 |
Creating New Germplasm to Improve Aflatoxin Resistance in MaizeOgunola, Oluwaseun Felix 14 December 2018 (has links)
Maize (Zea mays L), the third largest crop produced in the world is susceptible to pre and post contamination of aflatoxin. Aflatoxin is a secondary carcinogenic metabolite produced by Aspergillus flavus, an opportunistic fungus of maize that causes ear-rot and subsequent production of aflatoxin. Host plant resistance is one of the promising long term solution to combat aflatoxin contamination in maize grains. Resistance to aflatoxin is heritable and resistant germplasms that can be used to reduce aflatoxin resistance has been developed. Creating quantitative trait loci (QTL) mapping populations to identify regions within maize chromosomes contributing to aflatoxin resistance help identify markers that can be used for successful introgression of the QTL into desirable backgrounds. To further confirm and validate QTL detected in a mapping population, creating near isogenic lines (NILs) with identified QTL is important. Furthermore, stacking of validated QTL through recurrent selection (RS) will help to improve aflatoxin resistance in maize. In this study, an F2:3 mapping population was derived from crossing CML69, an aflatoxin resistant inbred genotype unrelated to other genotypes used in previous mapping population and Va35, an aflatoxin susceptible inbred germplasm adapted to southeastern U.S. The F2:3 families were phenotyped for aflatoxin at Mississippi State, MS and Lubbock TX in 2016 and 2017 and genotyped using 1331 polymorphic markers. Composite interval mapping (CIM) identified 16 significant QTL in all four environments on chromosomes 1, 2, 3, 4, 5, and 7, and these QTL explains between 4% - 18% of the phenotypic variation observed in the population. Fourteen of the 15 QTL co-locate with previously identified QTL, suggesting that they will be stable in different genetic backgrounds and environments, and one novel QTL will provide additional resistance. Sixteen single nucleotide polymorphism (SNP) markers linked to QTL identified in a previous genome wide association mapping (GWAS) study were also used to create Near Isogenic Lines (NILs) to validate their effect on aflatoxin resistance. Finally, recurrent selection (RS) populations were created to increase the frequency of aflatoxin-resistant alleles from an 8-way cross derived from 8 aflatoxin resistant inbred maize lines.
|
7 |
Biosynthesis and biodegradation of aflotoxin by Asperigillus flavus 102566Hamid, A. B. January 1986 (has links)
No description available.
|
8 |
Evaluation of Argentine maize hybrids and exotic x temperate testcrosses across environmentsOchs, Brett Allen 01 November 2005 (has links)
Maize (Zea mays L.) is grown in a wide range of environments and altitudes
worldwide. Maize has transitioned from open pollinated varieties to single cross hybrids
over the last century. While maize production and genetic gain has increased, genetic
diversity among U.S. maize hybrids has narrowed. Problems, such as insect pressure,
diseases, and mycotoxins, present obstacles for breeders. One approach is to use exotic
germplasm in breeding programs to provide useful, novel alleles for productivity, grain
quality, and disease resistance. Little exotic germplasm has been used, because of lack
of agronomic adaptation and problems with lodging, earliness, and tall plants in more
temperate areas. Using exotic elite materials and evaluating them in targeted regions
might increase success. Objectives of this research were: to characterize and evaluate
agronomic adaptation and performance of Argentine commercial hybrids in the U.S., to
evaluate semi-exotic testcrosses developed from semi adapted 100% tropical lines and
elite U.S. inbred LH195, and to estimate response to aflatoxin contamination of
Argentine hybrids and semi-exotic testcrosses under inoculation with Aspergillus flavus. Agronomic data was collected during 2004 in eleven Texas environments for
Argentine hybrids, and eight Texas environments for semi-exotic testcrosses. Response
to aflatoxin was measured in three southern Texas environments. U.S. commercial
hybrids were used as checks. Significant differences among hybrids were observed for
most environments and traits. In general, Argentine hybrids yielded lower, had lower
1000 kernel weights, and greater test weights than U.S. hybrids. Hybrids AX889,
AX882MG, and AX890MG were competitive with U.S. hybrids for grain yield and were
stable across environments. Semi-exotic testcrosses had similar lodging and grain
moisture percentages, heavier test weights and competitive grain yields compared with
U.S. hybrids. Hybrid TX-LAMA2002-9-2-B/lH195 had the highest overall grain yield
mean for semi-exotic testcrosses and yielded better than two U.S. hybrids. Argentine
hybrids had lower aflatoxin concentration than U.S. hybrids; several hybrids had less
than 50 ng g-1 aflatoxin. Semi-exotic testcrosses had reduced aflatoxin compared to U.S.
hybrids, with several hybrids under 35 ng g-1. These elite, exotic materials show promise
for breeding programs, with competitiveness for grain yield, kernel traits, and reduced
aflatoxin levels.
|
9 |
The development and validation of rapid, robust, low-cost methods for the determination of mycotoxins in cerealsYeo, Stephen Philip January 2000 (has links)
No description available.
|
10 |
Characterization of Maize Genes in Response to Aspergillus Flavus Infection and Aflatoxin AccumulationAsters, Matthew Constantine 13 December 2014 (has links)
Aspergillus flavus is a pathogenic fungus causing maize ear rot disease and producing aflatoxins that are carcinogenic to humans and animals. Characterizing maize host resistance mechanisms and prioritizing candidate resistance genes are important to the development of resistant maize germplasm. This study investigated transcriptomics approaches and statistics methods on the identification of maize host resistance genes. Full-length cDNA libraries were also constructed and evaluated for gene cloning and functional analysis. This study established important sources for functional studies on differentially expressed genes and for identification of allelic gene forms to characterize gene polymorphisms and facilitate the development of DNA markers.
|
Page generated in 0.0437 seconds