2012 Annual Report
1a.Objectives (from AD-416):
A team of plant molecular biologists, physiologists, geneticists and plant breeders from Embrapa in Brazil, USDA-ARS in Ithaca, and Moi University in Kenya, will take advantage of our discovery of the major sorghum Al tolerance gene, SbMATE, and findings from our recent research in maize, where two major Al tolerance QTLs were co-localized with SbMATE homologues (ZmMATE genes), to characterize and validate functional ZmMATE genes or QTLs conferring superior Al tolerance in maize. The objectives for this research project include:
1. Validation of functional ZmMATE genes or Al tolerance QTLs in the maize Brazilian crosses.
2. Development and screening of molecular markers for ZmMATE genes or Al tolerance QTLs studies.
3. Validation of ZmMATE genes or Al tolerance QTLs in a panel of Kenyan and Brazilian maize lines.
1b.Approach (from AD-416):
This project will utilize our genetic resources already available including near isogenic maize lines for both QTLs, as well as segregating populations and crosses between Brazilian sources of Al tolerance and Kenyan adapted germplasm. This structured germplasm, as well as newly developed crosses, will be subjected to molecular, physiological and field evaluations in order to accomplish the functional validation of candidate genes or QTLs, henceforth referred to as ZmMATE, for improving Al tolerance in different tropical maize germplasm. This project within the Comparative Genomics Challenge Initiative will involve Embrapa, USDA / Cornell University, Moi University and KARI, a research group with a long term history of successful partnership. The research findings from this project will both greatly increase our understanding of the molecular and genetic basis for cereal Al tolerance, and more importantly, will provide the basic materials for molecular breeding programs focusing on improving maize production and stability on acid soils in Africa and other developing country regions.
In 2012, we studied the regulation of expression of a major maize aluminum (Al) tolerance gene, ZmMATE1, we recently identified, which is closely related to sorghum SbMATE, and also is a transporter that pumps citric acid out of the root. We have found that in very Al tolerant maize lines, the expression of the ZmMATE1 gene in root tips is much higher than in root tips of Al sensitive maize lines. This is partially due to the number of copies of the ZmMATE1 gene in the maize genome. Tolerant maize lines have three copies of this gene, while the Al sensitive lines only have one copy. These findings may open up new avenues for improving the acid soil tolerance of maize via molecular breeding.