|Rice Breeding Program-89
Rice Experiment Station Scientists
D. Marlin Brandon,director and agronomist
Carl W. Johnson, plant breeder
Kent S. McKenzie, plant breeder
Shu-Ten Tseng, plant breeder
Jeffrey J. Oster, plant pathology
In their ongoing efforts to improve California rice
varieties, plant breeders with the Rice Experiment Station made just
over 1,000 crosses and grew 77,000 progeny rows. This work takes place at
nurseries in San Joaquin County, UC Davis, Biggs and Hawaii. Greenhouse
facilities at the RES are used during the winter to make crosses and to
screen germplasm for desirable traits. This section of
the report highlights breeders accomplishments. Results of statewide yield
tests are reported under the section on variety development.
Varieties up and coming
The experimental rice cultivar 85-Y-502 was developed at the RES and will be released this year as S-301—a smooth, sparsely awned, short grain of intermediate maturity that compares favorably with other short grains and should fare well in that market.
Expect to hear more about 88-Y-774, a high-yielding, very early long-grain experimental line that has performed well in statewide yield tests. It matures earlier than the dominant California long grain, L-202, and has similar grain quality characteristics. Performance and quality evaluation will continue as Foundation seed is increased in 1990.
Considerable effort is being made to incorporate new, genetically diverse material into the breeding program. A broader germplasm base will reduce the risk of genetic vulnerability that exists in current California varieties.
Historically, RES breeders have used varieties from other U.S. breeding programs, germplasm exchanges and rice collections to incorporate improvements into California varieties. More recently the breeders have successfully utilized induced mutation to facilitate genetic improvements. Also, a plant introduction permit issued to the Rice Experiment Station in 1988 should hasten the introduction of foreign germplasm into the breeding program.
The major thrust of long grain breeding is to develop new varieties with the traditional cooking characteristics of Southern long grains that produce well in California's cooler, drier climate. It has been a difficult task, but researchers note the following developments:
The focus of work on medium grain varieties is to improve agronomic performance and grain quality of the traditional Calrose-type rice. The majority of research is on early and very early varieties. Specific objectives include higher yield potential, cold tolerance, seedling vigor, higher milling yield and resistance to lodging, disease and insects.
Renewed emphasis is being placed on improving grain milling yields, appearance, and cooking quality of the premium quality M-401 and Kokuho Rose type medium grains. While cultural practices, harvest conditions, grain moisture and other factors affect grain quality, these limitations may eventually be overcome by exploiting genetic influence.
In a cooperative effort with USDA ARS researchers at Beltsville, Md., the breeders last year began evaluation of high-lysine rice lines derived from biotechnology research. Observed shortcomings of these lines include lodging, stem rot, blanking, low yield and other agronomic deficiencies. The researchers hope to eliminate some of these undesirable characteristics through backcrossing.
Short grain research is concentrating on correcting some of the deficiencies found in current varieties, including yield potential, lodging resistance, cold tolerance, grain quality, pubescence and awning.
A new breeding effort is being directed toward developing premium quality short-grain rice that may be preferred by potential Japanese consumers. While there is evidence that Japanese markets will accept M-401-type rices, it appears premium quality short grains would be preferred. More effective evaluation methods have begun and germplasm is being evaluated.
Work on specialty rices includes an effort to identify and improve the quality and agronomic characteristics of Calmochi-101.
Cooperative research with a USDA geneticist is being done to confirm the allelopathic (ability to retard weed growth) characteristics of several lines. Target weeds include ducksalad and sedge.
Breeders made 24 new crosses to transfer stem rot resistance from a wild species, Oryza rufipogon, to California varieties. Preliminary tests show some of the offspring yield well and those are being used in additional crosses. One long grain in particular, 87 Y 550, has shown acceptable yield potential and is being used extensively as a donor parent.
Greenhouse and field studies show stem rot virulence can vary. Breeders observed different disease levels on lines derived from O. rufipogon. Stem rot-resistant lines have also shown a propensity to resist aggregate sheath spot (AS). Progress is being made to transfer AS resistance into all grain types.
Good seedling vigor can improve stand establishment, decrease competition from weeds, reduce impact of seedling diseases, and permit deeper water for weed suppression.
Current California varieties have very good seedling vigor, but foreign germplasm has been identified that has even better seedling vigor. Unfortunately, most of this foreign germplasm has many undesirable traits. Researchers are monitoring the situation to ensure that future California varieties will maintain desirable characteristics.
Screening in growth chambers for seedling vigor and resistance to water mold will continue.
A critical part of the breeding program is selection of rice grains that display desirable translucency, kernel size and shape, and resistance to breakage. Cooking quality evaluations were performed on 3,450 long grain selections and more than 300 medium grain lines.
Milling quality is particularly difficult to improve. Advanced breeding lines and released varieties were harvested at decreasing grain moisture content to determine milling performance. Milling yield evaluations showed that optimal harvest moisture is a function of individual varieties and, therefore, is partially controlled by genetics. Consequently, renewed efforts to improve milling yield will seek to optimize the biological component.
The uncertain status of Furadan® (carbofuran) has accelerated research on lines with tolerance to the Rice Water Weevil. Those lines with the most promise unfortunately suffer from low yield potential. Considerable agronomic improvement is needed while maintaining weevil tolerance.