State yields stable

California rice acreage and yield remained essentially unchanged during 2002.  An estimated 540,000 acres was grown last year, about 90 percent of it seeded with varieties developed at the Rice Experiment Station (RES) near Biggs.  Statewide yields remained unchanged from the previous year at 8,200 pounds/acre, reflecting continued improvement over previous years.

Seed production and maintenance

The California public rice breeding program has now developed 37 improved varieties since accelerated research began in 1969.  Foundation seed for 15 public varieties and basic seed for two Japanese premium quality varieties were produced on 166 acres at RES in 2002.

Breeding nurseries report

The 2002 rice breeding nursery was expanded into new research lands at RES.  Seedbed preparation went smoothly.  Seeding of the breeding nursery began May 3.  Water seeding and drill seeding went generally well.  Seedling drift and mixing was not as severe as in 2001.  In some parts of the nursery, problems with herbicide injury were reflected in varietal differences.  Limited but high lodging in some parts of the nursery were attributed to higher fertility and possibly deeper cultivation.

In 2002, 783 new crosses were made at RES for rice improvement, bringing the total number of crosses made since 1969 to 27,969.  The 2002 nursery occupied approximately 72 acres.  Water-seeded yield tests included 3,625 small plots and 3,144 large plots.  Small seed-increase plots were grown on four acres and included 77 advanced breeding lines.  Forty experimental lines (2,800 headrows) were grown for seed increase, quality evaluations and purification.  The nursery included about 68,400 water-seeded progeny rows.  Selections were made from about 12,000 of these rows.

Second generation (F₂) populations from 2000 and 2001 crosses were grown in precision drill-seeded plots on 10 acres.  An estimated 200,000 panicles were selected from these for further screening and advancement.  Headrows of M-202, M-205, M-206, S-102, Calmochi-101, Akitakomachi and Koshihikari were grown for breeder seed production in the 2002 foundation seed program.

Selected material is being advanced in the Hawaii Winter Nursery and greenhouse facilities.  The University of Hawaii informed RES in 2001 that it would no longer operate the site.  A new nursery site was identified in September of that year and 7,800 rows were planted, but by January 2002 serious problems began to emerge and the site was eventually abandoned.  A second site was successfully planted with 7,210 rows on Nov. 2-5, 2002.  An additional 460 rows were simultaneously seeded in flats and were transplanted to the field Dec. 3-5.  The Internet is again proving a valuable tool, as RES scientists receive weekly digital photographs from the nursery to help in management decisions.

 The 2002 cold tolerance nursery at UC Davis contained three acres of precision-drill seeded F₂ populations and 10,000 dry-seeded progeny rows.  Seedling and stand establish was good.  Blanking in the breeding rows and F₂ populations was moderate.  Feeding by Canada geese was not a problem, as it had been in recent years.  The comparatively cool temperatures at UC Davis allow for selection of material  with moderate resistance to blanking, a valuable location in the breeding program.

Statewide Yield Tests

Statewide yield tests are conducted in grower fields each year to evaluate promising advanced selections from all three maturity groups.  Conducted at eight locations in 2002, entries that perform well are advanced for further testing.  More detail is reported in the variety trials section of this annual report.

Preliminary yield tests are the initial step of replicated large plot testing for experimental lines.  These tests included 666 entries and check varieties during 2002.  Superior entries were advanced to the 2003 statewide yield tests.

Long Grains

The long-grain breeding project continues its research and breeding efforts to develop superior long-grain varieties on four major quality types — conventional, Newrex, Jasmine and Basmati.  Milling and cooking quality improvements remain a priority, followed by resistance to blanking and other agronomic and disease resistance traits.

In the conventional long grain area, extensive efforts are under way to improve the starch characteristics of L-204, released in 1996, to more closely approximate those of Southern long grains.  Improvements in milling quality, cold tolerance and cooking quality are also being sought.

During 2002, a total of 117 advanced conventional long grains were selected.  Several entries yielded higher than L-204.  Some showed improved milling yields and at least one showed significant improved cooking quality.  Work also progressed on disease resistance, with one stem rot-resistant line showing high yield potential, and other crosses made for blast resistance and other improvements.

 Newrex, a higher amylose content rice preferred for use in canned soup and other processed foods, is typified by L-205, a relatively new variety that began commercial production in 2000.  Statewide yields for this variety averaged 8,860 pounds/acre.  Several experimental lines performed very well.

Calmati-201, a true basmati aromatic long grain, released in 1999 possess cooking qualities approaching those of imported basmatis.  At RES last year, Calmati averaged 9,470 pounds/acre at RES and 7,720 off-station.  It’s a good performer in warmer regions.  Heavy nitrogen fertilization should be avoided.

A considerable number of basmati lines were evaluated for agronomic and cooking characteristics last year.  Three advanced selections were tested statewide.  Two lines were purified in headrow blocks.  Increase blocks of 46 selections were grown out for further evaluation and a number of these are being advanced in the Hawaii Winter Nursery.  Selection emphasis is on slender, flaky cooking kernels with high elongation ratios.

Efforts also continue to breed jasmine types through pedigree and mutation breeding.  A waxy long grain with excellent milling and agronomic characteristics was tested and is intended for use as a donor parent in cold tolerance and yield improvement efforts.

Milling yield potential of 40 of the most advanced long-grain lines from the statewide yield tests was analyzed last year.  Milling yield improvements, particularly of Rexmont types, is a major objective.  Researchers hope to develop a broader harvest window without loss of milling quality.

Stem rot resistance originating from Oryza rufipogon has been transferred to a number of high yielding long grains.  Twenty-seven entries were tested last year.  Improvements in yield, cold tolerance and early maturity of these lines is being sought through further crossing and backcrossing.

Breeding efforts are also progressing to develop blast resistance in California long grains.  A cross between L-204 and a Southern variety is showing promise.  Cooperative efforts with USDA scientists in Texas and at UC Davis are developing genetic markers.  A considerable number of early generation blast-resistant lines were selected in 2002 and are being screened in greenhouse tests at RES.  Other selections were made from populations at the Hawaii Winter Nursery and the UC Davis cold tolerance nursery.

Premium Quality

Premium quality is a term used to identify California medium grains like M-401 that have unique cooking characteristics preferred by certain ethnic groups.  These varieties tend to be glossy after cooking, sticky with a smooth texture, and remain soft after cooling.  They are similar to Japanese short grains like Koshihikari.

In 1999 Calhikari-201 and M-402 were released.  Commercial demand for premium quality short grains remained low in California.  Consequently, acreage of Calhikari dropped to about 250 acres.  M-402 increased modestly to about 6,600 acres.  The smaller kernel size of M-402 remains an issue. 

Calhikari-201 was developed through complex crossing and selection to capture the cooking characteristics of premium Japanese varieties and the agronomic strengths of California short grains.  It is the first such release of an adapted premium quality short grain.  Calhikari-201 continues to yield well, although not as well as M-202, and is susceptible to stem rot and cool temperature-induced blanking.  Further breeding improvements will focus on these weaknesses.  Twelve experimental lines were advanced to improve Calhikari-201 last year and five of these warranted further agronomic and cooking evaluation.

S-102, released in 1996, is the predominant California short grain.  Research is focusing on improvements in yield potential, disease resistance (including blast) and grain and milling characteristics for this very early variety.

Special purpose rice has unique characteristics that sometimes make it difficult to characterize.  Improvements of short-grain waxy types (i.e. mochi, glutinous or sweet rice) is focusing on agronomic and quality characteristics.  Several entries performed better than Calmlochi-101 in statewide tests, some showing a significant yield advantage.

Breeding for bold grain types similar to the Italian varieties like Arborio continue.  Quality evaluations and interest from marketing organizations is described as limited.

Amylose content, an important component of starch, is a major quality component.  Induced mutation has been used to develop low amylose Japanese varieties that are probably not well-adapted to California.  A special project begun in 1999 involving Calhikari-201 has produced material now being advanced through the winter nursery and the RES nursery.  Two of these mutants were included in statewide yield tests last year.  Lower yields of these lines were anticipated because of kernel size smaller than Calhikari-201.  Breeding efforts and evaluations of commercial interest will continue.

Development of blast-resistant varieties remains another high-priority objective.  Agronomic performance of four lines in preliminary yield tests is encouraging, with yields higher than check variety S-102 being reported.  They will be further tested in 2003.  Breeding for stem rot-resistance remains another important objective.  In 2002, three short grain lines with stem rot resistance were evaluated in statewide tests.

Tolerance to Rice Water Weevil is another important objective for this grain class.  Two medium-grain entries (plus the parent donor line PI 506230) were tested in 2002 and  will be further evaluated in 2003.  Approximately 400 selections were made from rows in the RWW nursery in 2003.

Calrose Medium Grains

Calrose medium grain breeding continues to focus on high yield potential, resistance to lodging and disease, seedling vigor, improved milling yields and resistance to cold temperature blanking.  Efforts to incorporate blast resistance began in 1996.

In 2002 growers planted substantial acreage of recent releases M-104 (41,862 acres) and M-205 (88,497 acres).  These are now established varieties.  M-104 is recommended for cooler regions; M-205 is recommended for warmer areas only.

Experimental line 98-Y-242 has been named and released as M-206.  Foundation seed will be available for the 2003 growing season.  This is a very early to early semidwarf, glabrous, Calrose quality medium grain under evaluation in statewide trials since 1999.  Compared to M-202, it is four days earlier, has improved lodging resistance, higher blanking resistance and improved head rice.  It is characterized as more stable in less than optimal field conditions and has more synchronous heading.  It is not resistant to rice blast.  Milling yields are reported higher than M-104 and M-202.  Quality evaluations are similar and therefore good for commingling with other Calrose medium grains.  It will be another alternative to M-202 and M-205 in warm and cool production areas.  In cold areas it can be an alternative to M-202 or M-104.

Evaluation of promising medium grain entries focused on, among other traits, moisture at harvest.  For instance, 14 blast resistant entries were evaluated, the most promising of which will be retested in 2003.  One in particular, 00-Y-805, is on a “fast track” for further testing.

There are 27 Calrose medium grains from 2002 that were being grown for purification, seed increase and agronomic evaluation at the Hawaii Winter Nursery.  These entries have greater yield potential than respective checks and lodging resistance superior to M-202.

Sources of blast resistance from RES, the Southern U.S. and foreign sources, including high-yielding Chinese varieties, were crossed with California-adapted varieties.  Fifty-two of 380 of these crosses were blast related.  Thirty-four percent of 808 rows — representing 102 pedigrees — of Calrose medium grain in the Hawaii nursery were blast-related.  A special test of blast resistant entries was conducted at RES.  Breeding efforts have overcome the 30 percent yield drag, higher blanking levels and lower milling yields and have produced improved experimental lines with blast resistance.  Another yield test with 518 rows is planned for 2003.  Eleven of these entries have sufficient merit to be advanced in Hawaii for further testing in 2003.

Selection for grain quality factors, particularly milling yields, continues to be an integral part of the RES breeding effort.  There were 345 entries in 2002 preliminary yield tests for factors that contribute to improved milling yield, 15 of which had head rice yield better than the best check.  Advanced experimental lines in the second year of statewide testing or breeder seed increase were also evaluated for head and total milled rice.

Increased effort in breeding for stem rot resistance continues.  Agronomic limitations such as poor seedling vigor and low yield are a challenge.  Selections will continue to focus on stem rot score and the ability of all tillers to stay green 55 days after heading.

Efforts to transfer high levels of seedling vigor are decreasing because of the greater importance placed on blast resistance.  Other work continues on improved straw strength, low temperature blanking and seeding rates.  The search for a suitable cold nursery in San Joaquin County also continues.

Rice Pathology

Breeding for disease resistance is a cooperative effort between plant breeders and the plant pathologist.  About 2,000 rows a year are cycled through the disease nursery to advance lines resistant to stem rot, sheath spot and blast.  Efforts are also under way on Bakanae, a relatively new disease.

Seventy-eight new crosses were made in the RES breeding projects to transfer disease resistance derived from Oryza rufipogon to adapted California varieties.  There were about 6,500 rows in the 2002 stem rot nursery, less than a fraction of a percent of which showed higher levels of resistance than M-201.  Ninety-two F₃ long grain rows were rated for disease resistance as another step in evaluating stem rot molecular markers.  Eighty-six rows derived from crosses with wild species were evaluated for disease resistance.  The pathologist also continued the second year of a test to correlate yield loss to stem rot score among resistant lines.  Resistant line 01-Y-502 out-yielded S-102, while 00-Y-578 yielded more than S-102 in another long-term project measuring yield data over a range of disease severities.  A large molecular marker project at UC Davis has been completed, but a new USDA geneticist there has shown an interest in using newer markers and technology.

Crosses have been made to transfer bordered sheath spot resistance from O. rufipogon, sources of which also confer resistance to sheath blight.  Efforts are now under way to combine this trait with stem rot resistance.  A greenhouse testing program will be set up to test advanced breeding materials for sheath spot resistance.  Sheath spot is more prevalent than stem rot and can cause significant damage when conditions are favorable.

Blast severity was much lower in 2002 than in previous years.  None of the statewide yield tests were significantly affected by blast, so entries could not be evaluated.  Nonetheless, about 4,700 lines were screened in the greenhouse during 2002.  A cooperative project with USDA to develop molecular markers for blast resistance genes is continuing.

Bakanae is the newest California rice disease and has spread throughout most of California’s rice-growing areas.  Incidence was usually less than a few percent, but there were reports of 30 percent seedling loss.  Origin of the disease is unknown, but it was likely introduced on illegally imported seed.  In 2002 five observation plots were established in Butte and Yuba counties.  The project looked at many aspects of the epidemiology of the disease, such as seedling loss and blanking.  One of the more important findings from this research is that the disease has the potential to increase rapidly if the seed-borne inoculum is not eliminated.  Laboratory, greenhouse and field tests indicate that a seed treatment of five to 10 percent bleach solution will greatly reduce disease incidence and was the most effective treatment available.  Although some subsequent plant growth reduction can be anticipated, rice plants can be expected to recover through the growing season.  Replacing the bleach solution with fresh water after two hours gave control without any noticeable impact on seedling growth.  Bleach disinfestations may provide relatively cheap and available seed treatment.  A label was being sought for Clorox in 2003.  New materials are also being examined in laboratory and greenhouse testing.