2011 Annual Report
1a.Objectives (from AD-416)
To identify corn germplasm with resistance to Aspergillus flavus infection and aflatoxin accumulation and to identify genes associated with resistance.
1b.Approach (from AD-416)
A panel of 300 corn inbred lines have been crossed with a common tester line. The resulting testcrosses will be evaluated for aflatoxin accumulation at locations in Texas and Mississippi. An association mapping analysis of genotypic and phenotypic data will be conducted to identify alleles associated with resistance to Aspergillus flavus infection and aflatoxin accumulation.
Our primary objective was to breed and test several different germplasm sources for aflatoxin accumulation in multiple environments. This includes both developing new lines and testing corresponding hybrids. This year 1,096 yield trial plots were planted in Weslaco, TX; 1,223, in College Station, TX; and 364, in Corpus Christi, TX. Data on plant height, ear height, flowering time, lodging, yield, moisture, and test weight were taken. In all locations and for the majority of hybrids the plants were inoculated with Aspergillus flavus around female flowering. During harvest, subsamples of each plot were taken and samples of both whole and ground kernels were scanned using Fourier transformed near infrared spectroscopy to develop aflatoxin calibrations. Quantification of aflatoxin was conducted for a subset of samples with monoclonal antibody affinity columns and fluorescence determination. Seven new experimental Texas A&M University (TAMU) entries were included in the Southeast Regional Aflatoxin Test (SERAT) of 31 hybrids and checks planted at eight locations and evaluated for yield and/or aflatoxin. Cooperators contributed several entries in order to obtain better analyses of the environmental interactions among their best germplasm. Entries included in the trial included two generations of the Texas Argentine Composite population, as well as WE09-ISO-Pro-111, WE09-ISO-Pro-64, CS09-QPMX-005, CS09-QPMX-050, and CS09-QPMX-059. Five of these hybrids accumulated less aflatoxin than the mean of the test at College Station (312 ng/g), with three accumulating less than 200 ng/g. One of these three hybrids, WE-ISO-Pro-111, had yield performance superior to two commercial checks, and accumulated only 102 ng/g of aflatoxins, the lowest in the trial. For a second year we planted a 300 entry, 3-replicate hybrid association mapping trial. All whole kernel samples and ground kernel samples were scanned into a Fourier Transformed Near Infrared Spectroscopy machine to develop calibrations for aflatoxin/A. flavus. The ground samples were then analyzed for aflatoxin. For breeding material, the summer College Station nursery had approximately 800 lines in various inbreeding stages planted and less than 3% of plants had ears selected based on criteria of plant desirability, lack of foliar diseases, husk coverage, lack of ear rots, high number of kernel rows, ear length, kernel size, high ear heft, and grain color. From this, 384 ear-to-row aflatoxin resistance breeding plots were planted in the fall nursery located in Weslaco. These were further inbred, and 2-5 ears were selected from each plot and seed from the best ear was planted at College Station, TX, in 2011. Additionally, these new lines along with many older lines were crossed with 1-4 commercial inbreds to evaluate in hybrid combination. The project was monitored through a meeting with cooperating scientists held in Raleigh, NC; conference calls with cooperating scientists; written reports; e-mails; and phone calls.