1a.Objectives (from AD-416)
Develop a whole genome association platform for sorghum and identify SNP markers associated with aluminum tolerance.
Identify polymorphisms associated with Al tolerance in maize.
Develop innovative methods for analysis of root architecture and the role it plays in acid soil tolerance.
Determine the genetic architecture of high Al tolerance in maize based on previously identified Al tolerance QTL and orthology to sorghum AltSB.
Improve Al tolerance in maize by introgressing AltSB homologs co-localized with Al tolerance QTLs as well as other Al tolerance QTLs into maize tropical breeding lines.
Assess the yield advantage of Al tolerant maize in Kenyan environments and begin to investigate the contribution of Al tolerance to drought tolerance.
1b.Approach (from AD-416)
We will use a combination of association and QTL mapping to identify and verify novel sorghum and maize Al tolerance genes, and use marker assisted breeding to introgress the best alleles of these genes into maize and sorghum for generating cereal crops better suited for cultivation on acidic, Al toxic soils.
Progress involves the identification of two genes in maize that are closely related to our sorghum aluminum (Al) tolerance gene, AltSB (now called SbMATE). These genes, called ZmMATE1 and ZmMATE2, map to regions of the corn genome where we now know major maize Al tolerance genes must be located. Characterization of ZmMATE1 indicates it is the homolog of SbMATE, and is the root citrate transporter that plays the same function in maize as SbMATE in sorghum. ZmMATE2, however, has different expression patterns and transport properties than ZmMATE1 and SbMATE, and is not an organic acid transporter. Thus it must play a novel and currently unknown role in maize Al tolerance.