Genetics - 97


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Project Leader and Principal UC Investigators

David J. Mackill Research Geneticist, USDA-ARS, Department of Agronomy and Range Science, UC Davis

Peter Colowit Biological Technician, USDA-ARS, Department of Agronomy and Range Science, UC Davis

Xiaomao Kei Staff Research Associate, Department of Agronomy and Range Science, UC Davis

Seong-ah Han Graduate Student, Department of Agronomy and Range Science, UC Davis

Kenong Xu  Graduate Student, Department of Agronomy and Range Science, UC Davis

Pericles Neves Graduate Student, Department of Agronomy and Range Science, UC Davis

Virgelio Andaya Graduate Student, Department of Agronomy and Range Science, UC Davis

Dao Viet Bac  Postdoctoral Fellow

Li Li visiting scientist from China

Xia Xu  Postgraduate Researcher, Department of Agronomy and Range Science, UC Davis

Waving grain.jpg (55106 bytes)Scientists working on this project are gazing into the future of California rice production. In a USDA-funded laboratory at UC Davis, geneticists use sophisticated techniques in molecular biology to identify the genes conferring disease resistance and other important agronomic traits. Their research is guided by three important objectives.
  • To assemble and maintain a diverse set of rice varieties and wild rice species, including germplasm imported from other countries.
  • To identify chromosomal locations of useful genes with DNA markers.
  • To develop the genetic mechanisms necessary for the commercial production of hybrid rice.

The following narrative summarizes highlights of 1997 research in this area.

Identification Of Useful Genes

"Significant progress" is reported on the genetics of stem rot. The resistance is derived from the wild species Oryza rufipogon. Researchers tracked a single genetic marker with a high degree of association with stem rot resistance. The identification of a molecular marker on a rice chromosome opens up the exciting possibilities for improving the efficiency of selection for stem rot resistance in the rice breeding program at Biggs by eliminating the need for laborious screening with the pathogen in each season.

Researchers also continue to track other useful genes, including seed traits such as panicle size, submergence tolerance, cold tolerance and heat tolerance. They note that among California cultivars, S-102 had the highest heat tolerance, M-202 had superior tolerance, L-204 had low tolerance but that generally California cultivars probably have sufficient heat tolerance for most years.

Rice Genetic Resources

In 1997 gencticists experimented in three basic areas to improve and maintain the genetic resources available to them.

DNA Samples.jpg (55970 bytes)Probably the most significant development in this area of research was the acquisition of a DNA sequencer from the USDA-ARS. This machine will greatly facilitate the ability of the lab to map important genes and,to apply this technology to a practical breeding program. In- creased automation is essential to more widescale application of molecular markers in rice improvement. After many experiments with the sequencer, geneticists report a reliable procedure to detect "microsatellite" markers. This information will facilitate the development of a genetic map useful for breeding japonica rice.

Geneticists are also using DNA markers to characterize California rice for genetic variability among traits such as seedling vigor. In the future the technique could be used to reliably distinguish the variability of other agronomically important traits in commercial cultivars.

Also in 1997 researchers grew out an advanced backcross between Oryza nivara and M-202. Plants were selected based on agronomic characteristics and propa- gated in a greenhouse. Tissue samples will be collected during the winter for DNA extraction and seed harvest. Additionally, a new cross was made between M-202 and Oryza glaberrima, a rice characterized by high competitiveness against weeds.

Hybrid Rice

The promise of hybrid rice continues to encourage scientists to explore the mechanisms of its production. In 1997 geneticists observed the performance of previously identified male sterile mutants. A few showed particular promise and will continue to be evaluated at the Hawaiian winter nursery.

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