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Maize inbred Tex6 is resistant to several pests. The objectives of this study were to characterize gene expression profiles in Tex6 kernels and identify unique genes that expressed up- or down-ward in developing kernels in the later stages. Because of the resistance of Tex6 kernels, we reasoned that it would be an interesting candidate for microarray study. By using maize microarray, we analysed gene expression profiles in developing kernels from 25 DAP (days after pollination) to 45 DAP. A total of 8497 positive array spots were detected with unique IDs, in which 4247 genes were detected in all samples. The trends of total expressed genes were decreasing when kernels were maturing. Expression patterns of some genes in several metabolic pathways, including starch, lipid and storage proteins, were analysed. In comparison with 25 DAP, expressions of 211 gene features were significantly different at 45 DAP (P < 0.05), which will be used to produce a macroarray for germplasm assessment and evaluation. The real-time qRT-PCR was used to validate microarray study. [ABSTRACT FROM AUTHOR]

Scientists with the U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS) and scientists with the University of Georgia located at the Coastal Plain Experiment Station in Tifton, Georgia, have been conducting research on aflatoxin contamination of peanut since the early 1960s. Early efforts were focused on identifying the risk factors for increased aflatoxin contamination and helped to document the importance of drought, high soil temperatures, and pod damage. Later efforts were focused on the development of screening techniques and the identification of sources of resistance to Aspergillus colonization and/or aflatoxin contamination. This laid the foundation for a conventional resistance breeding program and has resulted in the development of peanut breeding lines that have high yield and low aflatoxin contamination relative to standard control cultivars. Recent research efforts include studies on the use of molecular genetic approaches to reduce aflatoxin contamination. This includes the evaluation of genetically engineered peanut and the development of molecular markers. [ABSTRACT FROM AUTHOR]

Aspergillus flavus (Link:Fr.) infection and aflatoxin contamination of maize (Zea mays L.) grain are an extremely serious problem. Maize genotypes resistant to A. flavus attack are needed. Maize breeders and plant pathologists must identify resistance sources and incorporate resistance into adapted breeding material. Maize population GT-MAS:gk has been released for use as a resistance source. In this study, we surveyed the genetic variation in this population and made the breeders/plant pathologists aware of the heterogeneous nature in this maize population by using RAPD analysis and correlated the RAPD marker association with the resistance to A. flavus and aflatoxin production. Of 40 RAPD primers, only 15 gave sufficient numbers of reproducible and readily scored polymorphic bands suggesting that this population was highly homogeneous. However, genetic distances, ranging from 0.08 to 0.28 and averaging 0.17, suggest that there is variation within the population. Cluster analysis distinguished three major polymorphic groups. Laboratory bioassay revealed that group I contained the most resistant individuals, i.e., those with less aflatoxin production. Group II had the least resistance, and group III was intermediate. This study showed that the maize population GT-MAS:gk is heterogeneous and individuals are different in resistance to A. flavus and aflatoxin production. Resistance should be confirmed through progeny testing before further development. The RAPD marker OPX-04, which may be associated with the resistance trait, has been cloned and further characterization will be pursued. [ABSTRACT FROM AUTHOR]