Genetics - 98


 
 

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Project Leader and Principal UC Investigators

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

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

Xiaomao Lei, Staff Research Associate, Department of Agronomy and Range Science, University of California, Davis

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

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

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

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

Dao Viet Bac, Post-doctoral Fellow, Department of Agronomy and Range Science, University of California, Davis

Li Li, Visiting Scientist from China

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

Genetics.jpg (189027 bytes)The keys to the successful future of California rice production are locked in the genetic makeup of current rice varieties and related germplasm sources. Scientists at work in a USDA-funded laboratory at UC Davis are discovering the genetic mechanisms of disease resistance, improved plant vigor, cold tolerance and other important agronomic traits. Last year's research activities focused on analyzing chromosomal ˘markers÷ that can be used to identify genes linked to blast and stem rot resistance; mapping of cold tolerance genes; and evaluation of mutant crosses for potential use in hybrid rice production. Progress in these areas is reported below.

Disease resistance tracked

Geneticists are building on previous work in which they identified a source of stem rot resistance in the wild species Oryza rufipogon. Last year the search continued with 34 rice varieties, including japonica, indica and O. rufipogon types. Research continued with the aid of a new DNA sequencer to help identify "microsatellite" markers that are helping pinpoint the precise location of stem rot resistance and other desirable traits on rice chromosomes. (These DNA markers are relatively easy to detect and show high variation among different strains of rice, making them superior to other types of DNA markers.) Detailed analyses are still in progress but progress is reported in DNA fingerprinting of California and Japanese rice cultivars. The research emphasis has also shifted to discover sources of blast resistance, which has become a very high priority. Researchers anticipate progress on identifying markers for these genes, as well as for mapping genes for cold tolerance.

Hybrid rice production

The Hawaii nursery is proving particularly useful in identifying mutants with useful types of male sterility. Knowledge of factors such as whether these lines self-pollinate under long-day conditions is needed to determine their potential for hybrid rice production. The mutants are being increased in Hawaii and will be tested in several locations in 1999. The most promising mutants will be considered for use in research as a germplasm source.

Two experiments were carried out during the summer of 1998 with a new advanced backcrossing procedure to help access useful traits of the wild species Oryza nivara. The "ABQTL" method of introducing genes from wild species is a promising approach for producing new genetic variation for agronomic traits in high-yielding rice varieties. (This technique uses multiple backcrosses of progeny to the adapted variety, in this case M-202, to remove undesirable genes introduced from wild species.) Lines produced thus far with this technique have promising plant type characteristics and look very productive. Traits measured last year included days to heading, plant height and number of tillers per panicle. Seedling vigor was also evaluated with a slantboard test.

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