Rice Breeding Program - 2006

 

 

 

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Project Leader and Principal  Investigators

Kent S. McKenzie, Director

Farman Jodari, plant breeder, long grains

Carl W. Johnson, plant breeder, Calrose medium grains

Jeff Oster, rice pathologist

 

 

The California public rice-breeding program has developed 42 improved rice varieties since accelerated research began in 1969.  The rice-breeding program consists of four ongoing research projects developing adapted varieties for specific grain and market types. The rice pathology project supports each of these efforts.  Progress in these areas from 2006 is reported below.

Breeding nurseries report

Seeding of the 2006 breeding nursery was delayed for the second consecutive year until May 22nd because of wet soil conditions and was completed by May 27th. Record high temperatures at flowering caused sterility in some nursery materials.

In 2006 a total of 1,780 new crosses were made for rice improvement, bringing the total to 33,555 since 1969. Crosses made in early spring were grown during the summer at RES to produce second generation seed.  Crosses made in summer 2006 were planted in the Hawaii winter nursery and/or in the greenhouse to accelerate the selection process.

The 2006 RES breeding nursery occupied approximately 80 acres.  Water-seeded yield tests included 4,112 small plots and 3,292 large plots.  Small seed-increase plots and cooking samples were grown on 2.5 acres and included 36 advanced breeding lines.  Forty-two experimental lines in 3,368 headrows were grown for seed increase, quality evaluations and purification.

The nursery included 50,500 water-seeded and 10,451 drill-seeded progeny rows.  Selections were made for approximately 10,000 progeny rows. Second generation populations from 2004 and 2005 crosses were grown in precision drill-seeded plots on 10 acres.  An estimated 200,000 panicles were selected from various second generation populations for further screening and advancement. Approximately 3,000 headrows of S-102, M-202, M-204, M-208, Calhikari-201, Calamylow-201, Akitakomachi, and Koshihikari were grown for breeder seed production.

The 2005-2006 Hawaii winter nursery included 8,400 progeny rows and a first generation nursery of 557 crosses. The 2006-2007 winter nursery of 8,460 rows was planted November 4th and 5th.  First generation plants from 570 crosses were transplanted to the nursery between December 6th and 8th. Selection and harvest was completed in April 2007, with seed to be planted at RES by late spring.

The 2006 cold tolerance nursery at UC Davis contained three acres of precision-drilled, second generation populations and 9,000 dry-seeded progeny rows.  Blanking was reported at moderate levels. The cold tolerance nursery in San Joaquin County was planted in the fields of two cooperating growers.  This four-acre, drill-seeded nursery included 14,420 rows and 3.6 acres of second-generation populations. Blanking levels at this site were very high, providing opportunities for selecting resistant material.

Statewide yield tests

Statewide yield tests are conducted in grower fields each year to evaluate promising advanced selections from all three maturity groups – very early, early or intermediate-to-late.  They were conducted at seven locations in 2006. (The San Joaquin location was not available). Entries that performed well 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 784 entries and check varieties.  Superior entries advanced to 2007 statewide yield tests.

Calrose medium grains

Calrose medium grain breeding focuses on high-yield potential, resistance to lodging and disease, seedling vigor, improved milling yields and resistance to cold temperature blanking.

A second blast-resistant Calrose medium grain was released in 2006.  M-208 is an early, smooth, high-yielding semidwarf and is characterized as an improvement over M-207.  M-208 averaged one day and six days later than M-202 and M-206, respectively. Lodging and seedling vigor is similar to M-202. Kernels are slightly larger in size and weight than other recent Calrose medium grains. Small improvements are also reported in taste and texture. M-208 is adapted to the majority of the
M-202 growing areas.

The experimental line 03-Y-254 mentioned in last year’s report will not be tested further because of high-temperature blanking. Another promising experimental Carlose in the second year of testing is 04-Y-227. It has improved yield and higher stable head rice.

Thirty Calrose medium grain entries from 2006 yield tests were grown in the Hawaii winter nursery.  Maturities range from M-104 to M-205.  These entries have greater yield potential than their respective highest-yielding checks.  Their lodging resistance is superior to M-202 and whole grain milling is 2 to 3 points higher.

Much effort continues to incorporate blast resistance into Calrose medium grains – 28 percent (117 of 417) of all Calrose crosses and 38 percent of 1,081 Hawaii winter nursery rows. These represent 169 pedigrees. New experimental lines have overcome the agronomic deficiencies observed earlier in this breeding effort.  There are now 71 entries with blast resistance yielding more than the average of all Calrose checks. Ten have been advanced in Hawaii and are to be tested in 2007. Another yield test with selected entries from 852 rows is planned for 2007. More Calrose medium grains with blast resistance should be in some stage of seed increase within the next five years.

Several crosses with herbicide-resistant Clearfield® rice were made. No breeding research was conducted on transgenic herbicide-resistant M-202.

Milling quality tests included 441 entries.  Fifty-two of the 151 saved entries had head rice yields similar to the best Calrose check.  The current standard bearers are M-103, M-206 and M-205.  Also, milling samples from seed increase fields and advanced experimental plots were evaluated at grain moistures ranging from 17 percent to
25 percent to determine average head and total milled rice.

Stem rot resistance for Calrose medium grains remains a priority. Part of this effort is tapping sources of resistance from the short-grain and long-grain projects. Poor seedling vigor, high floret blanking and low yield performance are, unfortunately, associated with sources of resistance.

In 2005 a germplasm discovery was made that could allow rice to be grown in 8-inch or deeper water and thus holds potential as another weed control tool. Yields were within 300 pounds/acre of a similar check variety and it had good head rice yield. Further research on this material is planned in 2007 in conjunction with the UC weed control project.

Progress has been made on improving straw strength with experimental lines having lodging resistance better than M-204.  Resistance to low temperature blanking continues to be screened in the RES refrigerated
greenhouses.

Long grains

The long grain breeding project focuses on four major rice types – conventional, Newrex, Jasmine and Basmati.  The cooking quality of conventional long grains is determined by their starch characteristics and while the quality of California long grains has improved, research is continuing to improve softness.

A new conventional long grain, L-206, was released for commercial production in 2006. Its primary advantages are improved cooking quality, higher grain yield and earlier maturity. Milling yield is slightly lower than L-204.

L-206 is a very early to early-maturing semidwarf. Average heading date is four days earlier and plant height is slightly shorter than L-205 and M-202. Lodging potential is similar to L-205, but it may lean with excessive dryness at harvest. Susceptibility to cold-induced blanking and to rice diseases is similar to L-205 and M-202.  Cooked grain texture is less sticky than L-204.

L-206 is suited to all but the coldest rice growing areas and the warmest locations in Glenn County. Its grain yield averaged 8,930 pounds/acre in cooler areas of Sutter County and 10,170 pounds/acre at the Rice Experiment Station. The five-year head rice yield averaged nearly 63 percent, comparable to L-205.

Other promising conventional long grains are being evaluated. A total of 92 conventional long grains advanced to statewide and preliminary yield tests in 2006.

Newrex is a special, high-starch long grain that cooks dry with minimal solids loss, making it a superior choice for canned soup, parboiling and noodle making. L-205 is a Newrex type with excellent agronomic characteristics and processing qualities.  Efforts are under way to reduce fissuring in milling and storage. Several experimental lines performed well in statewide trials, with grain yields averaging between 8,850 pounds/acre and 10,090 pounds/acre. L-205 averaged 8,560 pounds/acre. Several entries showed superior head rice yield.

Specialty long grains evaluated in 2006 included a considerable number of Basmati lines. Twenty-one selections with improved cooking qualities advanced to statewide and preliminary yield tests. Efforts also continued to improve Jasmine types through pedigree and mutation breeding. Twenty-six advanced Jasmine selections were tested in 2006.  A limited number of high-yielding waxy long-grain lines – useful in cold tolerance and yield improvement efforts – were also advanced.

Calmati-202 is a true Basmati aromatic long grain released in 2006.  It is an early maturing semidwarf with good seedling vigor. It is not adapted to cold locations. It has shown lower yield than check varieties but significant improvement in grain and cooking quality. It is expected to compete well with imported Basmati rice.

Both Calmati-201 and Calmati-202 are susceptible to fissuring at low harvest moistures, thus timely harvest and proper handling is needed to preserve milling and cooking qualities. Recommended harvest moisture is 18 percent.

Milling quality is another focus of long-grain improvement. Grain characteristics are being selected that will lend milling yield stability to long-grain lines under adverse weather conditions to allow a greater period of harvest.  Efforts to enhance milling quality include screening advanced lines for resistance to grain fissuring. In 2006 nearly 200 advanced lines – from long and short-grain projects – and 120 selections from the medium-grain project were examined. Milling yield potential of 32 advanced long-grain lines in the Statewide Yield Tests were also evaluated.

RES is also participating in a cooperative project with USDA – “RiceCAP” – to apply genomic discoveries to improved milling quality and disease resistance in rice.  Arkansas, California, Louisiana and Texas are pooling knowledge gained from molecular research to target milling yield and sheath blight resistance. RES is contributing results of fissuring studies from three milling populations and a long-grain milling quality population for developing molecular markers associated with milling quality.

Stem rot resistance from the wild species Oryza rufipogon has been transferred to a number of high-yielding long grain lines. Twenty-two entries with a range of stem rot resistance were tested in 2006 yield tests. A few entries continue to show significant improvement – low stem rot scores, low blanking, early maturity and high yield potential. Long-grain breeding efforts are also focused on incorporating blast resistance.

Premium quality & short grains

Premium quality is a term used to identify California medium grains like M-401. Preferred by Asian consumers, as well as other ethnicities, this rice is glossy after cooking, sticky with a smooth texture and remains soft after cooling. Aroma and taste are also important characteristics.

Evaluation and selection efforts on this project have increased after several years of staff changes that limited progress. In addition, an expanded effort in the premium quality short and medium-grain crossing program involved a large number of three-way or backcrosses to premium varieties to enhance cooking quality.

Calhikari-201, a semidwarf, early-maturing premium quality short grain yields better than the Japanese variety Koshihikari, from which it was derived. However, it has not been well accepted in the Japanese market.  Efforts are under way to improve cooking quality, as well as agronomic performance.

 Sixteen advanced premium quality, short-grain breeding lines were included in 2006 statewide yield tests. Forty lines were in preliminary tests.

Another breeding effort is seeking improvement for the M-401 market.  Ten advanced, premium-quality medium grains were included in statewide yield tests.  Fifty-one were included in preliminary yield tests.  Selection emphasis on premium-quality medium grains is toward larger kernels with M-202-like grain and milling yields and M-401 cooking quality.

Conventional short-grain breeding activities are directed toward improvements in S-102. A replacement for the waxy variety Calmochi-101 is also part of this breeding effort. A small number of bold grain types, similar to the Italian Arborio variety are being tested.

Calamylow-201, a new variety with improved starch characteristics (low amylose) for a small specialty market, was released for commercial production in 2006. This type of rice is used for chilled or frozen rice products in Japan. It is not recommended for cooler rice growing areas. Crossing and selection is continuing to develop improved low-amylose materials.

Rice Pathology

Breeding for disease resistance is a cooperative effort between plant breeders and the RES plant pathologist.  About 2,500 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. 

"New breeding lines from the Philippines are being backcrossed into M-206 to incorporate broader blast resistance into this variety."

A rapid backcross program involves screening about 2,800 seedlings for blast, and 24,000 seedlings each for stem rot and sheath spot resistance. An additional 6,000 rows of early generation material derived from crosses with resistant parents are also cycled through the disease nursery.

Screening for stem rot resistance usually begins with third generation crosses. In 2006 there were about 6,000 rows in the stem rot nursery, 3,510 of them drill seeded. Drill seeding creates a more uniform stand and better opportunities to screen for lodging.

Promising long-grain and short-grain resistant lines are emerging, but progress has been slow with medium grains. Several current varieties and stem rot resistant lines were evaluated for yield in an inoculated disease nursery. Over three years, the long grain line 03-Y-496 has yielded more than L-205 by nearly 17 percent. It has performed well in off-station trials as well.

Two long grain and two medium grain lines with resistance from O. rufipogon and two lines with resistance derived from Oryza nivara have been backcrossed with M-206. A large breeding population is necessary in work with O. rufipogon because sources of stem-rot resistance within this species come from more than one gene.  The pathologist made 218 crosses for this purpose in 2006. The mode of inheritance of resistance from
O. nivara will be determined in 2007.

In addition, 161 lines resulting from a cross of M-202 with O. officinalis made at the International Rice Research Institute (IRRI) in the Philippines were examined. This species has even higher levels of stem rot resistance than O. rufipogon but has a different genetic structure than cultivated rice. No stem rot resistance was found in these lines. Additional crosses with O. officinalis are continuing.

A screening program for experimental entries with sheath spot resistance not derived from wild species like O. rufipogon continues. This is especially important for medium grains, which do not have O. rufipogon-derived resistance.  This testing revealed large differences in susceptibility to sheath spot. A total of 270 backcrosses were made in a bolstered effort to transfer sheath blight resistance from Teqing, Jasmine 85, and MCR10277 to M-206 and L-205.

Rice blast severity has been low in most years since it was first discovered in 1996. Most affected fields are on the west side of the valley. M-104 appears to be more susceptible than other varieties, followed by M-205. The first blast-resistant variety, M-207, was released in 2005. About 7,500 lines were screened for blast resistance in the greenhouse during 2006.

New breeding lines from the Philippines are being backcrossed into M-206 to incorporate broader blast resistance into this variety. Only genes with a wide spectrum of blast resistance were chosen. In 2006, 314 crosses were made. This effort should be complete within two years. “Pyramided” genes should greatly slow or eliminate the breakdown of major gene resistance. A cooperative project with the USDA lab at UC Davis is also investigating multiple blast resistance genes.

Screening for Bakanae resistance continues in the RES greenhouse. Seed treatment research has been concluded. Backup chemicals have been identified should bleach no longer be available.

Also in 2006, 161 entries from crosses made at IRRI between M-202 and O. officinalis passed through quarantine.

 

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