2010 Annual Report
1a.Objectives (from AD-416)
Goals are to develop and evaluate corn inbreds demonstrating resistance to aflatoxin contamination in the U.S. and Africa, and to identify biochemical markers in these inbreds useful in marker-assisted breeding.
1b.Approach (from AD-416)
Inbreds will be developed through breeding at International Institute of Tropical Agriculture (IITA) Ibadan, Nigeria, West Africa. They will then be selected based on agronomic traits and foliar and ear rot resistance(s) and sent to the U.S. for evaluation for resistance to aflatoxin contamination using the rapid kernel screening assay (KSA). Information obtained through these screenings will be used to select lines to advance, through breeding, to the next generation. The KSA will also be used to idetify near-isogenic lines differing in aflatoxin accumulation among the breeding materials. Proteomics and microarry analysis will performed on these lines to identify proteins and corresponding genes associated with resistance. Information obtained will be used to develop markers for use in marker-assisted breeding. Resistance will be confirmed in all lines under natural conditions of high disease pressure in Nigeria. Promising germplasm will be released for use in U.S. breeding programs and national programs in Central and West Africa.
International Institute Tropical Agriculture (IITA) in collaboration with Agricultural Research Service-Southern Regional Research Center (ARS-SRRC), New Orleans, developed a large number of inbred lines from populations containing aflatoxin resistant temperate maize germplasm from the United States. Aflatoxin is a cancer causing compound produced by the fungus Aspergillus flavus on crops such as corn. A total of 51 advanced inbred lines were developed. Some of these containing temperate germplasm were also crossed to lines with resistance to fumonisin (another fungal toxin produced on corn) production to generate crosses for developing inbred lines with combined resistance to the two mycotoxins (aflatoxin and fumonisin). A total of 78 S4 lines derived form these crosses were planted at two locations in 2009 for further inbreeding and selection, out of which 43 S5 lines with desirable agronomic traits and resistance to foliar diseases were selected for further inbreeding and use as parents of hybrids. These inbred lines have been multiplied for shipment to ARS-SRRC laboratory in New Orleans for aflatoxin analysis using Kernel-based screening assays (KSA).
In 2009, a total of 19 mid-altitude adapted maize inbred lines selected for resistance to Stenocarpella, an ear-rotting fungus, were evaluated for aflatoxin production in the ARS-SRRC and IITA laboratories using KSA. All ear rot resistant lines, except one, had lower levels of aflatoxin compared to the susceptible check when they were tested in ARS-SRRC laboratory. Interestingly, all ear rot resistant inbred lines had lower levels of aflatoxin production when they were tested in IITA laboratory using a different strain of Aspergillus flavus. These lines were found to be resistant to aflatoxin contamination. The same sets of lines were also evaluated for resistance to aflatoxin contamination in IITA laboratory and showed lower levels of aflatoxin production in comparison to the susceptible check.
Two trials composed of 36 yellow and 20 white hybrids formed from lines selected for resistance to aflatoxin production using KSA were evaluated at three locations in Nigeria. Most of the yellow hybrids produced grain yields which were similar to or higher than the commercial yellow hybrid check (Oba Super II). Eight hybrids had significantly higher yields compared to Oba Super II. These hybrids were also found to be similar to or better than Oba Super II in other desirable agronomic traits and resistance to foliar diseases. Most of the white hybrids included in a trial had similar or higher yields in comparison to the best commercial hybrid check (Oba 98). Among these hybrids, seven produced significantly higher yields than Oba 98. The white hybrids had desirable agronomic traits including resistance to foliar diseases. Such good performance of the hybrids developed from these lines provides an indication of the potential usefulness of the lines in forming high yielding hybrids with low aflatoxin production. Research progress was monitored through teleconferencing, frequent email communications, and reports.