Rice  Breeding Program-87

 

 

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Project Leader and Principal UC Investigators

 

 

 Some 918 new crosses and backcrosses were made, and the second (segregating) generation from 1,125 crosses was grown for selection and purification. Additional germplasm sources were introduced and evaluated for disease resistance.

More than 100,000 rows were grown at various locations for selection, purification, generation advance, evaluation for cold tolerance, disease reaction, seed quality, seed increase and seed maintenance.

Several thousand experimental lines were screened in the greenhouse for disease resistance, cold tolerance, and for use as parents of crosses or for generation advance. Some 4,100 small plots for preliminary yield evaluation and 2,276 plots for advanced yield evaluation were grown at the Rice Experiment Station.

Reduced Lodging Brings Benefits

Resistance to lodging, affected by height and straw strength, is a selection criteria at each stage of the breeding program.

Short-stature varieties developed over the years have increased yields and harvesting efficiency. Additional benefits have been less straw produced per acre and less smoke produced from necessary open field burning of that straw.

Selections Combine Early Maturity, High Yields.

Many experimentals of all grain types representing a complete range of heading from two weeks earlier than S-201 to those that are a few days earlier than M-401 are evolving in the breeding program.

Progress is being made in combining higher yield and other desirable characteristics with earlier maturity. Evidence continues to show that rough (pubescent) lines dry down faster after heading than do smooth (glabrous) lines.

Quality Goal Narrows Selections

Seed characteristics such as size, plumpness, shape, translucency, uniformity, and breakage were the basis for making up to 60,000 selections from approximately 350,000 breeding lines. Because of the potential beneficial effect on milling quality, uniform maturity within and among panicles also are selection criteria.

Differences in field yields of advanced experimentals harvested at the correct moisture have had more economic impact than differences in milling yields. Long-grain experimentals generally have a lower optimum harvest moisture (19 to 21 percent) than current short and medium-grain varieties (22 to 25 percent).

Promising Long-Grain Lines Evolve

Screening continues for long-grain lines with improved physiochemical and cooking qualities, tolerance to low temperatures and improved milling quality. Several promising long-grain lines that are one to two weeks earlier than L-202 have been identified.

An experimental long-grain rice that cooks softer than L-202 but retains kernel integrity upon cooking received favorable reviews from an industry taste panel, and efforts will continue to develop a variety with these characteristics.

The new aromatic long-grain variety, A-301, was grown commercially for the first time in 1987.

Sweet Rices Show Potential

Sweet rices are evolving from crosses between the highly cold tolerant Calmochi-101 and non-mochi lines. A sweet rice that is five days later than Calmochi-101 is showing good yields.

 Disease and Weevil Resistance Advance

The transfer of stem rot resistance from the weedy species O. rufipogon produced an experimental long-grain line that yielded only two percent less than L-202. However, it had more blanking and will require further backcrosses.

Stem rot resistance derived from the wild rice O. rufipogon also reduces sclerotia production to two to five percent of what is produced by current varieties.

Transfer of aggregate sheath spot resistance is progressing, but not as quickly as the transfer of stem rot resistance. Selection for improved seed production and other characteristics among lines with improved levels of water weevil tolerance also is progressing.

Yield Drop Emphasizes Cold-Tolerance Needs

Increased yields and yield stability are primary goals of the breeding  program. However, the same conditions that aided cold-tolerance selections in 1987 contributed to an overall statewide average yield drop from 1986.

84-Y-9, an experimental very early, short-stature, cold-tolerant, medium-grain line has excellent milling yields and will be increased on the Rice Experiment Station.

New Varieties Released

Two new varieties, S-101 and M-203, have been released this year.

Foundation seed of S-101 was allocated to seed growers in 1987 on a "certification pending continued good performance" basis. Therefore, both Foundation and Registered seed of S-101 will be available.

S-101 is a short-stature, translucent, smaller seeded short-grain rice. When compared with S-201, it heads seven days earlier and more uniformly, matures 10 to 12 days earlier, yields an average of 450 pounds per acre more, is about three inches shorter, and is more resistant to stem rot. S-101 has excellent resistance to lodging and has given good head rice yields. It is rough (pubescent) and has awns.

M-203 is an early mutant (same maturity as M-202) from the premium quality, medium-grain variety, M-401. Eight-hundred and seventy cwt. of Foundation seed were produced in 1987.

M-203 is satisfactory for the premium quality, medium-grain market. It yields an average of 14 percent less than M-202 and lodges similarly to M9. It is not a replacement for M-202 or M-201. However, its earlier maturity makes it an attractive alternative to M-401 in years when bad weather lingers into late spring.

Nitrogen Needs Explored

Nitrogen trials showed that S-101 has moderate nitrogen needs similar to those of S-201, M-201 and M-202. L-202 requires slightly more nitrogen than the lodging resistant short- and medium-grain varieties. M-203 had significant lodging at moderate rates of nitrogen and required 25 to 50 pounds less nitrogen per acre than other varieties for optimum yield. Excessively high nitrogen rates significantly delayed grain maturity and yields.

 

Carnahan Notes Breeding Progress

When Howard L.. Carnahan came to work as director of the plant breeding program at the California Cooperative Rice Research Foundation in 1969, state rice crops yielded an average 5,250 pounds to the acre. As he retires in 1988, that average has jumped impressively to 7,500 pounds.

While technological advances in the mechanization of the industry and improvements in cultural practices have played a role in those increased yields, a t least 80 percent of the credit is due to improved varieties, Carnahan says. It is an achievement of which he is obviously proud.

Carnahan acknowledges being one of those "fortunate" individuals who knew early in life what he wanted to do. While a youth he read the classic work of 19th Century botanist and pioneering geneticist Gregor Mendel. Carnahan was smitten by the plant breeder's bug and has since enjoyed along and distinguished career as a research scientist in a variety of public institutions and private industry.

Howard L. Carnahan steps down this year as director of plant breeding at the Biggs research facility after a long, productive career of service to the California rice industry.

While the overall mission of the plant breeding program remains unchanged (i.e. to create new varieties), the specific objectives Carnahan's research team has pursued have changed over the years and will probably continue to evolve to meet the demands of a dynamic industry.

"We dropped the objective of pursuing rice with a higher protein content," he points out, "because we found that as the protein content increased, the yields decreased. Since they get paid by yield, that wasn't going to help the economy of the California grower.

Some objectives have proved elusive, such as the search for a hybrid rice seed. Since hybrid rice would show more vigor and therefore produce more than traditional self-pollinated varieties, the goal of obtaining a commercially viable hybrid cultivar has been tempting. But inherent production limitations have proved a formidable stumbling block. "We haven't ruled it out entirely," Carnahan says. "We concluded more basic research is needed. "

Probably the single most important varietal improvement during Carnahan's leadership was the creation of L-202, the tremendously successful long-grain variety released in 1984. "Two of the biggest obstacles we had to overcome were cold-temperature tolerance and cooking quality," he said. L-202 yields up to 98 percent of top shortand medium-grain yields and has been well received in domestic markets.

Another accomplishment during the Carnahan era is the industry shift from late maturing to early maturing varieties. In 1969, 75 percent of the acreage was planted to Calrose, a medium grain, and Caloro, a short grain. They required 115 to 120 days to flower. Now 95 percent of the acreage takes 90 to 95 days to flower, giving growers more latitude in planting seed and enabling them to harvest in better weather.

Over the course of Carnahan's 19 years a t Biggs, CCRRF has released 21 varieties. But the researcher notes there are another seven or eight crosses in long, medium, short and specialty grains made within the last few years that should be ready for distribution soon.

The facility itself has undergone notable changes during Carnahan's tenure. There are now three plant breeders instead of two. Acreage has nearly tripled in size to 370 acres. Greenhouse space has doubled. There are 12 seed bins where once there were four. And a new seed house makes the time-consuming selection task much easier.

Carnahan is optimistic about the future of the facility. He believes further refinements can be made in existing varieties, such as shorter plant height, improved seed vigor, stronger straw, cold-temperature tolerance, higher yields, and better marketing and milling quality.

"Plant breeding is a continuous thing," Carnahan says. "You may reach plateaus, but you continue to move up."

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