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 Lei 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
Xia Xu Postgraduate Researcher, Department of Agronomy and Range Science, UC Davis
|Scientists in the USDA-funded
laboratory at UC Davis studying the genetic mechanisms of important agronomic traits
report progress in the use of chromosomal "microsatellite markers" and DNA
fingerprinting of California varieties. In 1999 they examined 34 rice varieties,
including japonica, indica and Oryza rufipogon types. This will be
supplemented in 2000 with additional markers from Cornell University and Dupont. This
research will help identify genes linked to blast and stem rot resistance, mapping of cold
tolerance genes, and other genes to help California-adapted varieties. This work is
Disese Resistance Tracked
With sophisticated DNA sequencing tools, geneticists continue to identify "microsatellite" markers pinpointing the precise location of stem rot resistance and other disease-resistance traits on rice chromosomes. Previously identified stem rot resistance in the experimental line 87-Y-550 (derived from O. rufipogon) unfortunately could not be applied in medium grain populations. However, two other markers closely linked to stem rot resistance have been identified in long grain populations and will be examined further.
Molecular marker surveys were also conducted for sources of blast resistance in California varieties. Data from this experiment are still being analyzed. Five crosses were made at the Rice Experiment Station between California cultivars and Egyptian japonica cultivars with blast resistance. Seeds were harvested and one population was screened for resistance.
Low temperatures can affect rice plants in many ways, such as poor germination, necrosis, wilting, leaf yellowing or pollen and seed sterility. Scientists zeroed in on the seedling stage to identify tolerance in an M-202 cross with the indica variety IR50R. After subjecting the progeny to cold-induced stress tests, scientists developed a map comprised of 62 microsatellite and three RFLP markers The map suggests a new source of seedling cold tolerance.
Hybrid Rice Production
Researchers have been studying the behavior of male sterility genes in an effort to identify those that are sensitive to photoperiod and could be used in hybrid rice seed production. Mutants identified exhibit marked differences in sterility when grown at Davis, where they showed more sterility, and in Hawaii, where they showed more fertility. Initial indications are that the pollen of these mutants is fertile. Work on male sterile mutants will be phased out if this years findings confirm fertility.
Another experiment involved the analysis of genes from the wild species Oryza nivara as a source of useful traits for M-202. Development of the initial population was very laborious. Plants were analyzed for yield and yield components in 1998 and 1999 in the field at Davis. Additional data collected included seedling vigor traits, grain dimensions and weight, and heading date. Molecular analysis of this population is nearly complete. Fifty-six microsatellite markers have been analyzed on 198 families. Breeding lines with useful characteristics are being increased in the Hawaii winter nursery.