Rice
Breeding Program-87
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Project Leader and Principal UC Investigators
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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 BenefitsResistance 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 SelectionsSeed 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 EvolveScreening 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 PotentialSweet 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 AdvanceThe 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 NeedsIncreased 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 ReleasedTwo 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 ExploredNitrogen 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.
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