Germplasm Development-79
 

 

 

Home.gif (3162 bytes)

Next.gif (3180 bytes)

Back.gif (3162 bytes)

Project Leader and Principal UC Investigators

M.L. Peterson, UC Davis

J.N. Rutger

D.B. Jones

T.V. Dat

J.E. Board

P.J. Brrokhouzen

K.S. McKenzie

R.A. Figoni

H.P. Moon

L. Azzini

 

The USDA-UCD rice genetics and physiology program is important to the programs of the Rice Experiment Station. New germplasm is developed and made available to the rice breeders for varietal improvement. Examples include induced mutations, cold tolerant lines, and wild species.

Induced Mutations

"UCD-based scientists developed and released six germplasm lines . . . which are resistant to cold-induced sterility."

The UCD program demonstrated the usefulness of induced mutation in rice improvement in California. Calrose 76, the first short-stature variety released in California, is a mutant developed by irradiation of seeds of Calrose. Through hybridization, the short-stature gene from Calrose 76 has been used to develop four more short-stature varieties: M7, M-101, M-301, and S-201. This gene for short stature results in a 15 percent grain yield increase and about a 15 percent decrease in straw production. Before the UCD work, induced mutation worldwide was not considered to be a very useful breeding method. The short-stature success has conclusively demonstrated the value of induced mutants.

Cold Tolerant Germplasm

Ph.D. candidate Dat Van Tran (left) compares a mini-leaf mutant selected out of the irradiated Calrose program at the UCD facility with M-101 held by Dr. M.L. Peterson.

Davis is an ideal site for rice cold tolerance studies. UCD-based scientists developed and released six germplasm lines (CI 11039-11044) which are tolerant to cold-induced sterility. In 1976, a very cool year at Davis, the best of these lines, CI 11041, averaged only 11.8 percent sterility compared with 21.3 percent sterility for Calrose 76 and 40.6 percent for CS-M3. Under warm conditions CI 11041 is not as high yielding as standard varieties, but it is a useful donor parent in breeding for cold tolerance.

The work also revealed an unexpected bonus for cold tolerance for short-stature varieties. Thus, in the same 1976 tests, the short-stature variety M7 showed 24.1 percent sterility compared with 40.6 percent for its tall parent, CS-M3. Young panicles of the short-stature varieties are nearer the water level during the cold sensitive state (10 to 15 days before heading). Water remains warmer than air at night; thus, panicles of the short-stature varieties, being nearer the water, are better protected from the nightly low air temperatures.

Wild Species

An exciting basic research area is the transfer of stem rot tolerance from wild species of rice. Screening of thousands of entries of the cultivated species of rice, Oryza sativa, has not revealed any lines more tolerant than Colusa. Since Colusa itself is susceptible to stem rot, more tolerance is desirable. UCD scientists are tackling this problem by screening 15 related wild species of rice. At least one wild species, Oryza rufipogon, has more stem rot tolerance than Colusa and this tolerance appears to be transmitted in crosses with cultivated rice. This work is still in the preliminary stages, so the effort to transmit increased tolerance to materials suitable for California production will continue in 1980.

 

Rice growers turned out in record numbers for the 1979 Rice Field Day at the industry's Rice Experiment Station, Biggs. Rice Research Board member Francis DuBois is on the rostrum explaining the naming system for new California rice varieties. (Photo courtesy Terry Burnham of the Sacramento Bee.)

 

 

Home.gif (3162 bytes)Next.gif (3180 bytes)Back.gif (3162 bytes)