Discovering New Sources for Tolerance to Various Abiotic Stresses.

Several abiotic stresses such as drought, flooding, low temperature and salinity are common problems in rice growing areas of the world. With the current climatic changes, these stresses can further aggravate the problem of increasing world rice production and meet the ever increasing demands for rice. Although some rice varieties for specific abiotic stress such as drought, cold, submergence and salinity were developed, these were derived from limited sources. Gene discovery is currently on-going in several countries and this has to be continued to identify new and better sources, enhance diversity, and avoid homogeneity of gene sources.

Screening for tolerance to Liberty (glufosinate) and Roundup (glyphosate) herbicides was conducted at Texas AgriLife Research in Beaumont, Texas since 2003. This aimed to identify new sources of herbicide tolerance that can alleviate the red rice problem in major rice production areas in U.S. Breeding lines derived from EMS (ethyl methane sulfonate) treated seeds of some U.S. released varieties, germplasm from the gene bank through the Germplasm Resources Information Network (GRIN) of U.S. Department of Agriculture's Agricultural Research Service, advanced lines from the state breeding program and survivors in plot alleyways sprayed with herbicides were screened using the recommended rate of both Liberty and Roundup herbicide. Several plants survived and these were advanced for further spraying and selection. While these herbicide tolerant lines were being studied in detail, screening for cold tolerance at germination and seedling was conducted using the seeds from surviving genotypes after herbicide application. Three years of cold tolerance evaluation using early planting (late February to early March) of dry seeds and two years of dry seeds and pre-germinated seeds screening in early planting and controlled temperature (10^oC) identified donors that can  germinate when dry seeded in February or at 10^oC, and can continue growing in early  planting. Some genotypes had very consistent high percent germination in both early planting and 10^oC growing condition. Preliminary evaluation for seedling drought and submergence tolerance of selected germplasm from previous herbicide and cold tolerance screenings showed that the current group of materials could be a good genetic resource for tolerance to multiple abiotic stresses.