Breeding and Mapping of Aflatoxin Genetic Resistance in Maize
Location: Corn Host Plant Resistance Research
Project Number: 6406-21000-011-16
Specific Cooperative Agreement
Start Date: Nov 01, 2012
End Date: Oct 31, 2015
The objective of this project is to identify and characterize new inbred lines displaying high and stable resistance to A. flavus and aflatoxin accumulation and to identify and validate new genes and gene-based markers linked to these traits. Germplasm and genes will be ready for use in practical breeding programs to develop resistant varieties for developing world farmers within three years. Inbred lines will be characterized for aflatoxin and A. flavus resistance in growing conditions typical of African and Latin American farmers. Specific and general combining ability will be tested, and information on performance of the lines in hybrid combinations in different environments will be made publically available to maize breeders and small seed companies. Genes for resistance will be identified via association analysis or QTL mapping, and all identified sequences will be run in an independent mapping (QTL or association) population for validation.
Considerable work has already been done in the mapping of aflatoxin and A. flavus resistance in maize, and five fully phenotyped and genotyped QTL mapping populations and two association mapping panels are currently available for this project. These resources will allow many gene sequences identified as associated with aflatoxin or A. flavus resistance in one panel to be validated in the other panel as well. Any candidate gene of large phenotypic effect identified via association mapping will be used to develop user-friendly SNP, SSR, or InDel markers from the sequence of the gene. These will allow for the mapping of these genes in any of the QTL mapping populations that segregate for these sequences. We hope that this will identify new QTLs, or allow the immediate fine mapping of previously identified QTLs, and will be further independent validation of the gene(s) as associated with fungus or toxin resistance. QTL mapping will also verify the utility of these markers, which should allow more rapid progress in the ultimate development of resistant hybrids and varieties. In the process of phenotyping the two association mapping panels (one at CHPRRU, one at CIMMYT), most known sources of resistance, and many new potential resistant lines, will be well characterized in a comprehensive manner. New inbred lines with high levels of stable resistance should be identified in the course of this work. These new resistant lines (the best 20 – 30 from each panel), will be field tested in various hybrid combinations and tested for enhanced resistance to aflatoxin accumulation in new hybrids. These hybrids can be used as cultivars for farmers in parts of the world where aflatoxin poisoning has been an ongoing and serious problem. In the first year, aflatoxin resistant inbred lines from CHPRRU will be test crossed onto CIMMYT elite breeding lines and seed will be increased of the inbred lines. The association mapping panel from CIMMYT will be phenotyped (for a second year, as it has been phenotyped in one year already). Association mapping will begin. In the second year, the test crosses made in year one will be phenotyped for yield and disease resistance under local growing conditions, and association mapping will continue, particularly to verify genes identified in the CHPRRU panel. In the third year, the testcrosses will be phentypted again.