Plant & Animal Genomes XIV Conference

January 14-18, 2006
Town & Country Convention Center
San Diego, CA

Salinity Tolerance In Rice: Integration Of QTLs, Expression Analysis, And Breeding

Abdelbagi M. Ismail¹ , Glenn Gregorio¹ , Michael Thomson¹ , Ellen Tumimbang² , Harkamal Walia³ , Eduardo Blumwald² , Timothy J. Close³

¹  International Rice Research Institute, DAPO 7777, Metro Manila, Philippines

²  Department of Pomology, University of California, Davis, CA 95616, USA

³  Department of Botany and Plant Sciences, University of California, Riverside, CA 92521, USA

Salt stress is a major constraint to agriculture productivity worldwide and improving salt tolerance of major crops is one approach to utilize soils and water resources that are otherwise underutilized or completely unexploited. In rice, substantial progress has been made in understanding the biology and genetics of tolerance as well as in incorporating tolerance into modern cultivars. However, this progress has been slow because of the complexity of tolerance, which comprise a number of contributing traits. However, the fact that none of the known salt-tolerant genotypes are superior in more than few of these traits suggests that salinity tolerance of rice could substantially be enhanced if superior alleles for all useful mechanisms were combined into popular varieties using molecular tools. We have identified multiple QTLs for salinity tolerance, forming the basis for a molecular breeding strategy that integrates DNA microarray expression data with candidate genes underlying key QTLs, followed by the development and validation of DNA markers targeting specific gene loci. We will present our progress with a major QTL (Saltol) mapped on chromosome 1, associated with selective ion uptake. This locus was further fine-mapped using NILs derived from Pokkali, the original donor, and IR29 as the recurrent parent. Using large-scale gene expression analysis, several candidate genes were identified in the QTL region and are further being validated. Similar strategies are being followed for the other QTLs to facilitate their tagging. With tightly linked markers the transfer of these loci into locally preferred, yet sensitive varieties, is made feasible.