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Abstract Background Aspergillus flavus Link:Fr, an opportunistic fungus that produces aflatoxin, is pathogenic to maize and other oilseed crops. Aflatoxin is a potent carcinogen, and its presence markedly reduces the value of grain. Understanding and enhancing host resistance to A. flavus infection and/or subsequent aflatoxin accumulation is generally considered an efficient means of reducing grain losses to aflatoxin. Different proteomic, genomic and genetic studies of maize (Zea mays L.) have generated large data sets with the goal of identifying genes responsible for conferring resistance to A. flavus, or aflatoxin. Results In order to maximize the usage of different data sets in new studies, including association mapping, we have constructed a relational database with web interface integrating the results of gene expression, proteomic (both gel-based and shotgun), Quantitative Trait Loci (QTL) genetic mapping studies, and sequence data from the literature to facilitate selection of candidate genes for continued investigation. The Corn Fungal Resistance Associated Sequences Database (CFRAS-DB) (http://agbase.msstate.edu/) was created with the main goal of identifying genes important to aflatoxin resistance. CFRAS-DB is implemented using MySQL as the relational database management system running on a Linux server, using an Apache web server, and Perl CGI scripts as the web interface. The database and the associated web-based interface allow researchers to examine many lines of evidence (e.g. microarray, proteomics, QTL studies, SNP data) to assess the potential role of a gene or group of genes in the response of different maize lines to A. flavus infection and subsequent production of aflatoxin by the fungus. Conclusions CFRAS-DB provides the first opportunity to integrate data pertaining to the problem of A. flavus and aflatoxin resistance in maize in one resource and to support queries across different datasets. The web-based interface gives researchers different query options for mining the database across different types of experiments. The database is publically available at http://agbase.msstate.edu.

Many projects have identified candidate genes for resistance to aflatoxin accumulation or Aspergillus flavus infection and growth in maize using genetic mapping, genomics, transcriptomics and/or proteomics studies. However, only a small percentage of these candidates have been validated in field conditions, and their relative contribution to resistance, if any, is unknown. This study presents a consolidated list of candidate genes identified in past studies or in-house studies, with descriptive data including genetic location, gene annotation, known protein identifiers, and associated pathway information, if known. a candidate gene pipeline to test The phenotypic effect of any maize DNa sequence on aflatoxin accumulation resistance was used in this study to determine any measurable effect on polymorphisms within or linked to The candidate gene sequences, and The results are published here. [ABSTRACT FROM AUTHOR]

Maize (Zea mays L.) susceptibility to ear rot by Aspergillus flavus (Link:Fr) and aflatoxin accumulation causes global economic and human health damage. Host plant resistance is an ideal solution, but commercial varieties lack sufficient resistance to solve the problem. Due to general lack of resistant maize germplasm, no currently available association mapping panels are expected to contain significant variation for the trait. A new association mapping panel containing the majority of aflatoxin accumulation resistant maize lines at the time of compilation is presented here along with genetic and phenotypic characterization data. Phenotypic data from testcrossed lines include aflatoxin levels, days to silking, and corn earworm [Helicoverpa zea (Boddie)] damage measured in seven environments and fungal biomass of kernels measured in three. In addition to identifying previously reported aflatoxin resistant lines, new resistant lines were discovered, which may be used for breeding improved germplasm. The Mexican landrace Tuxpeño is the progenitor or one main contributor for most of the resistant lines and likely the source of resistance, but a few other sources may allow additional novel resistance to be pyramided into future breeding lines. Genetic characterization of kinship, genetic diversity, and substructure analysis presented here will allow this resource to be used for association mapping of aflatoxin and identification of factors responsible for this challenging quantitative trait. [ABSTRACT FROM AUTHOR]

Evaluation of corn genotypes for resistance to aflatoxin accumulation has evolved over the past 30 years. Inoculation techniques have been developed to ensure that plants are exposed to Aspergillus flavus and resistant genotypes can be identified. We compared two inoculation techniques (side needle and knife) and different inoculation rates in Georgia and Mississippi. The relative performance of side-needle and knife inoculation techniques did not change or interact significantly across site years, suggesting that both the needle and knife are consistent inoculation techniques for discriminating between resistant and susceptible corn hybrids at the Mississippi State and Tifton locations. [ABSTRACT FROM AUTHOR]

The opportunistic pathogen Aspergillus flavus infects important seed crops, including corn, peanuts, and cotton. A. flavus is capable of producing mycotoxins called aflatoxins. Aflatoxin B1, the major mycotoxin contaminant of maize, is a potent carcinogen and has been directly linked to hepatocellular carcinoma. Natural sources of maize fungal resistance exist, but efforts to increase resistance through traditional plant breeding have yielded little success. Using the maize Unigene 1-1.05 arrays, a comparison of resistant (Mp313E) and susceptible (Va35) inbred maize lines 48 hours post- A. flavus infection identified 236 genes as significant. During infection, 135 genes were up-regulated in the susceptible maize line Va35, 112 genes were up-regulated in the resistant maize line Mp313E, 12 genes were up-regulated in both lines, and 1 gene was down-regulated in both lines compared to uninfected lines. Comparisons of the biological profile responses of these maize lines revealed a striking difference in reaction to infection. These identified genes will serve as the initial step for developing molecular markers to understand this complex interaction and help with introgression of A. flavus resistance into maize hybrids. [ABSTRACT FROM AUTHOR]

Corn genotypes evaluated for aflatoxin resistance in field studies must be artificially inoculated with Aspergillus flavus due to the sporadic nature of aflatoxin contamination from year to year. We compared a spray inoculation technique with the side-needle technique and natural infection for inducing aflatoxin contamination in commercial corn hybrids in two soil types from 2000 to 2006. Hybrids inoculated using the side-needle technique consistently had high levels of aflatoxin contamination. Hybrids inoculated with the spray technique and grown in a loam soil were more prone to drought stress and had higher levels of aflatoxin contamination than those grown in a silty clay loam soil with a high water-holding capacity. The association of maximum daily temperatures and cumulative rainfall during nine periods before or after A. flavus inoculation with aflatoxin contamination was determined. In the silty clay loam, maximum daily temperatures during the 14-day period following inoculation were positively correlated with aflatoxin contamination. Cumulative rainfall during periods of 14 to 28 days and 21 to 42 days following inoculation was negatively correlated with aflatoxin contamination. In the loam, maximum daily temperatures before and after inoculation were positively correlated with aflatoxin contamination. Also, cumulative rainfall during a period 21 to 42 days before inoculation was negatively correlated with aflatoxin contamination. Our results also demonstrated that temperature and moisture stress prior to inoculations may have a significant effect on aflatoxin contamination. [ABSTRACT FROM AUTHOR]