2013 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.
2013 was a no-cost extension year which ended in March of 2013. In this final half year of the project, we completed work on the maize aluminum (Al) tolerance gene, ZmMATE1. This gene, which we identified in 2011, is closely related to the sorghum Al tolerance gene/protein, SbMATE. Like SbMATE, it also encodes a transporter that pumps citric acid out of the root, where the citric acid binds and neutralizes toxic Al3+ ions. 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. We discovered this is the result of the very Al tolerant maize lines having 3 functional copies of the ZmMATE1 gene while there is only 1 copy of ZmMATE in Al sensitive and moderately tolerant maize lines. This is one of the first examples where variation in gene copy number controls an agronomically important trait and this information will assist breeders in generating more Al tolerant maize lines.