|Molecular Marker-Assisted Rice
Project Leader and Principal UC Investigators
Thomas H. Tai,USDA-ARS, research geneticist, Dept. of Agronomy and Range Science, UC Davis
The purpose of this project is to combine advanced techniques in molecular biology with conventional rice breeding methods. Work advanced on the application of molecular markers to identify genes with desirable disease resistance, cold tolerance and grain quality traits.
Genetic crosses between top California varieties, such as S-102, M-202 and M-206 and a wild species, Oryza rufipogon were made as a first step in developing populations for genetic analysis of stem rot and aggregate sheath spot and for generating new California germplasm with enhanced disease resistance. Marker analysis of the parental lines has resulted in the identification of a substantial set of DNA markers that will be useful in genetic analysis.
Although markers for several blast resistance genes have been reported, the Pi-z gene is of primary interest to California rice breeders. Markers tightly linked to the Pi-z blast resistance gene were used to assess breeding materials from the medium grain program and in a small-scale, marker-assisted selection experiment with the premium quality program.
Efforts to identify genes conferring cold tolerance at the seedling stage are continuing as additional molecular markers become available. Genetic populations for field assessment of booting stage cold tolerance are also being developed.
The "waxy" gene marker was used in a small-scale experiment to assess grain quality as measured by amylose (starch) content classification with materials from the long-grain breeding program. Development of a high-throughput, rapid DNA extraction procedure was a major accomplishment in this project. Use of the waxy DNA marker should assist breeders in making selections well before harvest and may also be used to confirm or clarify results of quality lab testing.