Plant & Animal Genomes XV Conference Plant & Animal Genomes XV ConferenceJanuary 13-17, 2007
Town & Country Convention Center
San Diego, CA
Michael J. Thomson , Marjorie deOcampo , James Egdane , Meggy Katimbang , M. Akhlasur Rahman , Rakesh K. Singh , Glenn B. Gregorio , Abdelbagi M. Ismail
Salt stress is a major constraint across many rice producing areas because of the high sensitivity of modern rice varieties. Tolerance to salinity is complex, involving a number of different physiological mechanisms, such as sodium exclusion from roots, controlled sodium transport between root and shoot, and sequestering of sodium in older tissues and in the vacuoles. Previously, 80 RILs from a cross between IR29 and the landrace Pokkali were used to map several salt tolerance QTLs, including Saltol, a major QTL on the short arm of chromosome 1. Current efforts have expanded the QTL population to 130 RILs and additional SSRs have been added to improve genome coverage. QTLs underlying salt tolerance at the seedling stage are being targeted for NIL development. In addition, fine-mapping of the Saltol QTL is in progress and indel markers based on candidate genes in this region have been developed. This data will help determine if the Nona Bokra-derived salt tolerance QTL SKC1 is allelic to Saltol or if these represent closely-linked QTLs. Furthermore, a precision marker-assisted backcrossing system is being employed to efficiently transfer the Pokkali Saltol QTL into popular varieties such as IR64, BR28, and Swarna. A diverse set of germplasm is also being characterized for physiological traits underlying salinity tolerance to identify different sources of tolerance in preparation for association mapping. The long term goal is to identify and combine genes and QTLs controlling different physiological mechanisms to achieve a higher level of salt tolerance in high yielding rice varieties.