Rice Breeding Program-04



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Project Leader and Principal UC Investigators

Kent S. McKenzie, Director

Farman Jodari, plant breeder, long grains

Carl W. Johnson, plant breeder, Calrose medium grains

Jeff Oster, rice pathology


The California public rice breeding program has now developed 38 improved varieties since accelerated research began in 1969.  Foundation seed for 16 public varieties and basic seed for two Japanese premium quality varieties were produced on 180 acres in 2004 at the Rice Experiment Station (RES) near Biggs. The  rice breeding program consists of four ongoing research projects developing adapted varieties for specific grain and market types.  The rice pathology project supports these efforts.  Progress in these areas is detailed below.

Breeding nurseries report

Seeding of the 2004 breeding nursery began at RES on May 10.  Stand establishment conditions were generally good and the season was near ideal for rice production, especially in Butte County where reported yields averaged 9,500 pounds/acre.

In 2004, 971 new crosses for rice improvement were made, bringing the total since 1969 to 30,030.  Crosses made in the early spring were grown during the summer at RES, while crosses made during the summer 2004 were planted in the Hawaii winter nursery and/or the station’s greenhouse for grow out and selection in 2005.

The 2004 RES breeding nursery occupied 83 acres.  Water-seeded yield tests included 4,114 small plots and 3,375 large plots.  Small seed-increase plots and cooking samples were grown on three acres and included 65 advanced breeding lines. Thirty-eight experimental lines in more than 3,000 headrows were grown for seed increase, quality evaluations and purification. 

The nursery included about 59,600 water-seeded and 9,500 drill-seeded progeny rows.  Selections were made for approximately 10,000 progeny rows. F2 populations from 2002 and 2003 crosses were grown in precision drill-seeded plots on 14 acres.  An estimated 200,000 panicles were selected from the various F2 populations for further screening and advancement. Twenty-four hundred headrows of M-205, S-102 and four experimental lines were grown for breeder seed production in 2004.

The Hawaii Winter Nursery is an integral element in the rice breeding program.  It allows for the advancement of material and screening for cold tolerance during the winter to hasten varietal development.  The 2003-2004 nursery site was seeded Nov. 8-10, 2003 with 7,080 progeny rows, 500 transplanted F1 rows and 500 rows for the USDA-ARS geneticist at UC Davis.  A new nursery site in Hawaii was identified in September 2004 and 8,820 rows were planted in November.  F1 plants from 2004 crosses were transplanted in the nursery in December.  Growth, fertilization and weed control were good considering this newly cleared land experienced heavy rains. A successful harvest was completed in April 2005 and selections returned to RES for planting this summer.

The 2004 UC Davis cold tolerance nursery contained three acres of precision drill-seeded F2 populations and 7,000 dry-seeded progeny rows.  Blanking in the breeding rows and F2 populations was at a moderate level and allowed selection of panicles for advancement in 2005. A new cold tolerance nursery was established in San Joaquin County with the cooperation of two local growers.  The four-acre, drill-seeded nursery included 10,320 rows and 3.6 acres of F2 populations.

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 2004, entries that performed well were 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 783 entries and check varieties in 2004.  Superior entries were advanced to the 2005 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 of conventional long-grain and specialty types are a major aim of this program, followed by resistance to cold-induced blanking and other traits.

In the conventional long grain area, efforts continue to improve upon the starch characteristics of L-204 to more closely approximate those of Southern long grains.  Improvements in milling quality, cold tolerance and cooking quality are also being sought.  DNA marker technology is being used on a limited basis for identifying genes that confer improved starch characteristics in conventional and Rexmont-type long grains.

During the 2004 season, a total of 109 advanced conventional long-grain selections were tested in statewide and preliminary yield tests.  Overall yields were lower than expected because of extended mild weather conditions during the growing season.  Several experimental lines yielded significantly higher than L-204. Milling yields were high, something attributed to mild temperatures during grain filling.  Two high-yielding entries — 99-Y-469 and 99-Y-041 — were grown in headrow blocks in 2004.   Both experimental lines have yielded consistently higher than L-204.

Newrex is special quality rice with high starch content that cooks dry with minimal solids loss and is thus a superior type for canned soups, parboiling and noodle making.  L-205 has shown superior processing qualities along with excellent agronomic characteristics. Modifications in milling and storage procedures are expected to alleviate reported post-harvest milling yield reductions.  This early maturing semidwarf variety is less susceptible to cold-induced blanking but may lodge with excessive nitrogen fertilization.  Several experimental lines yielded comparably to L-205.

Calmati-201, a true Basmati aromatic long grain released in 1999, is a variety well suited for the warmer growing regions in California.  It is susceptible to cold-induced blanking and heavy fertilization should be avoided.  A considerable number of Basmati lines were evaluated in 2004 for agronomic and cooking quality characteristics.  Seven advanced selections with improved cooking qualities were evaluated in statewide tests.  Experimental line 04-Y-153 shows a great deal of promise and was purified in headrow blocks for possible release pending further evaluation in 2005.  Compared to Calmati-201, this line has shown a significantly higher elongation ratio, more slender grain shape and a flakier cooked grain texture.

Increase blocks of 38 Basmati and conventional type selections were also grown for detailed milling quality and cooking quality evaluation. A number of Basmati lines have been advanced in Hawaii and will be yield-tested in 2005.

Efforts continued in 2004 with materials from Southern U.S. and foreign sources to breed Jasmine types through pedigree and mutation breeding.  One promising waxy long-grain experimental, 99-Y-494, performed better than L-204 and L-205 in 2004 yield tests.

Continued improvement of long-grain milling yield is another important long-grain objective.   Advanced breeding lines are being screened for their resistance to grain fissuring.  The RES is also participating in a USDA initiative to apply genomic discoveries, such as molecular markers, to improved milling quality and disease resistance in rice. (More information and updates on this four-year project can be found online at http://www.uark.edu/ua/ricecap/.)  The milling yield potential of 38 advanced long-grain lines in two maturity groups were evaluated in 2004 harvest moisture studies.

Stem Rot (SR) resistance originating in the wild species, Oryza rufipogon has been transferred to a number of high-yielding long grain lines. Twenty-four entries with a range of SR resistance were evaluated in yield tests.  A few top performers showed significant improvement — low SR scores, low blanking, early maturity and high yield potential.  Improvements in milling yield, cold tolerance and early maturity of SR resistant lines to levels of L-204 and L-205 are being pursued through further crossing and backcrossing.

Blast resistance in long grain lines is also being pursued.  Cooperative efforts are continuing with USDA scientists in Texas and at UC Davis for the development of molecular markers to better track genes associated with blast resistance.  A considerable number of early generation blast resistant lines were selected in 2004 and screened in greenhouse tests.  Selections were also made from F2 and F3 lines at the Hawaii winter nursery and at the new San Joaquin cold tolerance nursery.

Premium quality

Premium quality is a broad term used to identify California varieties such as M-401 that have unique cooking characteristics preferred by Japanese, Korean and other ethnicities.  This type of rice is typically glossy after cooking, sticky with a smooth texture and remains soft after cooling.  Aroma and taste are also distinctive features.  Developing high-yielding varieties of this type continues to be a challenge in California.

Calhikari-201 is the first adapted premium quality short grain for California.  Although agronomic performance and yield are superior, cooking quality is below Koshihikari. It has not been well-accepted in the Japanese market.  Breeding efforts are targeting improved resistance to stem rot and cool temperature blanking and improved yields.  Eleven experimental lines were advanced, most of which showed higher yield potential and better lodging resistance than Calhikari-201.  Agronomic data will be combined with quality data to select entries for further testing in 2005.

A parallel breeding effort is seeking to improve premium quality medium grains for the M-401 market.  Yields of advanced breeding lines approached the Calrose medium grain check in statewide tests.  As a group, medium grain milling yields were excellent.  Selection emphasizes larger kernels and M-202 grain and milling yields, as well as improved lodging resistance.

The predominant conventional short grain is S-102, released in 1996 and a consistent high yielder.  Two preliminary breeding lines selected from crosses with S-102 displayed very high yield potential and comparable head rice milling yield.  These lines are being advanced from small plots and progeny rows and will be further evaluated in 2005.  Newer conventional short grain lines have improved SR resistance, something that’s been difficult to achieve in the past.  Furthermore, previous weaknesses such as poor seedling vigor, susceptibility to cold temperature blanking and late maturity are not evident in newer materials.  Additional crossing and screening is bringing blast resistance into the breeding pool of these short grains. DNA marker technology should expedite development of disease resistance in conventional short grains.

Special purpose varieties often have unique or undefined cooking characteristics that make quality evaluation and selection difficult.  Improvement of short-grain waxy types (i.e. mochi, glutinous or sweet rice) is focused on improved agronomic and quality characteristics. A set of waxy lines will be advanced from preliminary yield testing.  Quality evaluations are planned, as well as industry evaluations on the more promising lines.

Amylose (starch) content is an important factor in the eating, cooking and processing quality of rice.  A special project begun in 1999 is utilizing induced mutation technology to assist in the development of a low-amylose variety.  Two such low-amylose experimental lines have undergone laboratory analysis both in California and Japan and were field tested for agronomic performance.  Overall, these lines showed lower yield potential than Calhikari-201, as well as reduced grain weight and panicle size.  Small production fields were grown at RES in 2003 and 2004 for large-scale milling, quality evaluation and test marketing.  Production of seed and paddy rice for test marketing is planned for 2005.  New low-amylose materials are being evaluated in small plots and progeny rows.

Breeding for bold grain types, similar to the Italian varieties like Arborio, continues with a few large-seeded experimental lines.  Agronomic performance thus far has been superior to Arborio but marketing organizations have shown only limited interest.

One of the additional project objectives is to transfer rice water weevil tolerance to California varieties. Cooperative research with new technologies to study grain quality components is also part of this project.  This includes evaluation of single kernel grain moisture impact on milling yield.  Additionally, RES has been evaluating a Foss Cervitec™ 1625 Grain Inspector.  This automated high-speed grain image inspection system evaluates head rice, damaged kernels, fissuring and kernel dimensions. It holds great potential for evaluating breeding material for quality traits.

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 that began in 1996 have resulted in the expected release of M-207 in spring 2005.  To reduce the risk of genetic vulnerability and to tap into new potential sources of blast resistance, progeny from high-yielding Chinese introductions were grown out in five distinct populations at the Hawaii Winter Nursery.

M-206 was released to growers for registered seed production in 2003.  About 30,000 acres of this new variety were grown in 2004.  Some of the comments recorded by medium grain plant breeder Carl Johnson about M-206 include:

  • Field yields equal to or superior than M-202

  • Whole grain, head rice improvement of 1-2 points over M-202

  • More synchronous heading than M-202

  • Panicles more visible than other Calrose medium grains

  • A well-adapted companion variety to spread harvest

  • Response to blast similar to M-202 but not as susceptible as M-104 and M-205

  • Field dry-down rate slows and remains at 20%-24% moisture for three to five days

The advanced experimental line 00-Y-805 was proposed for varietal release in 2005 as M-207.  This new variety is a very early to early maturing, smooth, high yielding, semidwarf Calrose medium grain with resistance to the blast race in California.  Compared to M-202 it matures four days earlier, lodges 10 percent more, dries down faster, yields about the same and has 1-2 points less total and whole grain milled rice.  It has similar size, shape, weight and starch characteristics as other Calrose medium grains.  Milling and marketing organizations have judged it very similar to M-206 and M-202 in cooking and taste evaluations.

M-207 is adapted to all growing areas but is seen primarily as an alternative for fields in Glenn and Colusa counties with recurring blast damage.  Better alternatives exist for other areas.  Care should be taken to avoid over-fertilization to reduce lodging and disease pressure.  Harvesting should be done at 18-25 percent moisture to improve head rice potential.  Test data indicates the new variety dries down faster than M-206 or M-202.

Other promising medium grain experimental entries are being examined.  Harvest moisture values are a key factor, as well as lodging resistance, seedling vigor and milling yield.  Increased emphasis has been placed on blast resistance.  Fifteen blast-resistant entries were evaluated. The line 02-Y-816 is a blast resistant, early, smooth, high yield semidwarf with resistance to lodging and milling yields comparable to M-202.  It has tested well in statewide tests and has an area of adaptation similar to M-202.

Twenty-six Calrose medium grain entries from 2004 yield tests were grown in the Hawaii winter nursery for purification, seed increase and additional agronomic evaluation.  With maturities ranging from M-103 to M-205, these entries have greater yield potential, superior lodging resistance and quality equal to or better than M-202.  Half of these have blast resistance, half don’t.

Sources of blast resistance from RES, southern U.S. and foreign germplasm were crossed with California lines. Ninety-seven of 400 Calrose crosses were blast related and 33 percent of 885 rows grown in the Hawaii nursery were blast related.  These represent 94 pedigrees.

A special test for blast resistant entries was conducted at RES.  Breeding efforts have overcome a 30 percent yield drag, higher blanking levels and lower milling yields and have produced improved experimental lines with blast resistance.  Thirteen entries yielded more than the highest check, M-206, and will be advanced for further testing in Hawaii.

Another yield test with 1,297 rows is planned for 2005.  The performance of these entries suggests that more Calrose medium grains with blast resistance will be in some stage of seed increase in the next five years.

Several crosses made onto herbicide resistant Clearfield rice were advanced. Lines were screened for cold tolerance. RES conducted no breeding research on transgenic herbicide resistant M-202 in 2004.

Selection for grain quality factors continues to be an integral part of the medium grain breeding effort.  Good head rice yield is among the most important criteria for advancing a breeding line.  There were 441 entries in preliminary yield tests for factors contributing to improved milling yield.  Thirty-eight of the 183 saved entries had head rice similar to the best checks such as M-103, M-206 and M-205.  Forty-one of 76 advancing blast entries had head rice equal to or three points higher than M-202.

Advanced experimental lines in the second year of statewide testing or breeder seed increase were also evaluated for head and total milled rice.  The environmental effects on head rice yield vary every year.  Ninety-nine percent of milling rows for statewide and preliminary tests headed in a 10 day period.  Fields dried down evenly because of the excellent 2004 growing season.

Efforts to improve stem rot resistance above levels comparable to M-201 continue.  Sources of resistance are being tapped from both long-grain and short-grain projects.  Unfortunately, good sources of stem rot resistance are also associated with poor seedling vigor, high floret blanking and low yield performance.

Efforts to transfer higher levels of seedling vigor have decreased because of greater emphasis on blast resistance.  Progress is reported on improving straw strength relative to M-204.  Research on resistance to low-temperature blanking continues at cold tolerance nurseries and in RES greenhouses.  Five backcross populations involving Chinese introductions are being advanced to improve diversity in the genetic pool for Calrose medium grains.

Rice pathology

Breeding for disease resistance is a cooperative effort between plant breeders and the RES plant pathologist.  About 2,000 rows a year in statewide and preliminary yield tests are screened for stem rot and sheath spot resistance.  In the RES greenhouse about 450 entries a year are screened for sheath spot resistance, 400 entries for Bakanae disease and 5,000-10,000 entries for major gene resistance to blast.  An additional 6,000 rows of early generation material derived from crosses with resistant parents are also cycled through the disease nursery.

In 2004 there were about 8,000 rows in the stem rot nursery.  Several current varieties and resistant lines were evaluated for yield in an inoculated nursery.  Efforts to quantify yield loss with specific stem rot scores in current varieties and resistant lines continued.  Resistant line 01-Y-502 showed a significant yield advantage over L-205 in three years of this work. Several short grain lines out yielded S-102 but not significantly.  About 5,200 field transplants and an equal number of greenhouse plants were screened for stem rot and sheath spot resistance in a cooperative effort with the USDA geneticists at UC Davis.

Crosses have also been made to transfer bordered sheath spot resistance from the wild species Oryza rufipogon.  This is also a source for resistance to sheath blight.  A greenhouse screening program has been set up to test statewide entries for sheath spot resistance, especially important for medium grains that do not yet possess this resistance. Molecular markers will be sought for resistance derived from O. rufipogon in cooperation with the USDA lab at UC Davis.

Rice blast was much less severe than in previous years.  About 5,600 lines were screened in the greenhouse in 2004 for blast resistance.  Since only one known race of the fungus has been identified in California and others are known to exist elsewhere in the world, researchers have adopted a breeding strategy to incorporate a number of different genes with multiple sources of resistance.  A cooperative project with the USDA lab at UC Davis is developing molecular markers for blast resistance.  Markers would allow detection of multiple resistance genes in the same variety or breeding line without actually screening against the races necessary to differentiate these genes. A series of experiments was designed to improve the accuracy of screening techniques.

In 2004 a new method of detecting Bakanae fungus was developed that uses larger seed lots and is more sensitive.  Three seed treatment trials were conducted in 2004 in Butte, Sutter and Colusa counties.  All treatments included a 24-hour soak and a 48-hour drain or a 24-hour drain at a constant temperature of 73 F. One of the important findings from this work is that the fungus can persist in treated seed.  At a bleach concentration of 1 percent, significant Bakanae developed.  This is not the case with bleach concentrations of 2-3 percent. Seed rinsing is not necessary with these bleach concentrations, thus the Clorox label will be amended to include 2.5 percent Clorox Ultra® with no rinse.

Varietal differences in susceptibility to Bakanae were analyzed for a second year.  Results from each year correlate very well.  In addition, three varieties with different levels of the Bakanae fungus were tested at three locations for effects on yield.  The correlation between yield and Bakanae is high for M-205 and M-202 but not M-206.  Thus M-206 may be considered tolerant to Bakanae.  Further testing with a wider range of seed infestation is needed.

For the first time, all statewide entries were screened against the Bakanae fungus in the greenhouse.  Results show a range of disease severity but are inconsistent from trial to trial.  Further work on screening technique is needed.

Another set of experiments examined the relationship between soak and drain time in low and highly infested seed lots.  The incidence of Bakanae increased with longer soak times and was more pronounced in highly infested seed lots. Submergence immediately after sowing and planting dry seed both greatly reduced Bakanae incidence. Higher temperatures during soaking and draining also reduced Bakanae incidence.  Thus, Bakanae levels probably vary from field to field because of varying soak and drain times, varietal differences, and differences in water management. Straw decomposition through flooding or rotation is encouraged as another means of reducing over-wintering Bakanae inoculum and subsequent disease development.

The building blocks for any breeding program are varieties with traits desirable in commercial production.  In 2004, two entries passed through quarantine.


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