Rice Breeding Report - 2005




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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

Junda Jiang, plant breeder, premium quality and short grains

Jeff Oster, rice pathologist




The California public rice breeding program has now 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. Details of progress from 2005 are summarized below.

Breeding nurseries report

Seeding of the 2005 breeding nursery was delayed until May 20th because of an unusually late, wet spring and was completed by May 27th. A number of agronomic problems and record high temperatures combined to bring plot yields at the Rice Experiment Station (RES) to among the lowest ever. Statewide commercial yields were also down 16 percent from 2004.

In 2005 a total of 1,725 new crosses were made for rice improvement, bringing the total to 31,775 since 1969. Crosses made in early spring were grown during the summer at RES to produce second generation seed. Crosses made in summer 2005 were planted in the Hawaii winter nursery and/or in the greenhouse to accelerate the selection process.

The 2005 RES breeding nursery occupied approximately 83 acres. Water-seeded yield tests included 4,157 small plots and 3,488 large plots. Small seed-increase plots and cooking samples were grown on 2.5 acres and included 36 advanced breeding lines. Forty experimental lines in 3,316 headrows were grown for seed increase, quality evaluations and purification.

The nursery included about 59,600 water-seeded and 12,030 drill-seeded progeny rows. Selections were made for approximately 10,000 progeny rows. Second generation populations from 2003 and 2004 crosses were grown in precision drill-seeded plots on 14 acres. An estimated 200,000 panicles were selected from various second generation populations for further screening and advancement. Approximately 2,400 headrows of M-401, M-402, M-206, M-207, L-205, L-206 and Calmati-202 were grown for breeder seed production in 2006.

A new site for the Hawaii winter nursery was cleared and planted by RES staff with 8,820 rows in November 2004. First generation plants from 2004 crosses were transplanted into the nursery later in December 2004. New paddies were constructed in July 2005 and another 8,400 progeny rows were planted in November 2005. First generation plants from 557 new crosses were transplanted to fields in December. Selection and harvest was scheduled for April 2006, with seed to be planted at RES by late spring.

The 2005 cold tolerance nursery at UC Davis contained three acres of precision-drilled, second generation populations and 8,800 dry-seeded progeny rows. Blanking was reported at moderate levels. Irrigation problems damaged all the long grain and much of the short grain progeny rows. The cold tolerance nursery in San Joaquin County was planted in the fields of two cooperating growers. This four-acre, drill-seeded nursery included 10,320 rows and 3.6 acres of second-generation populations. Blanking levels at this site were medium and provided good 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. Conducted at eight locations in 2005, 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 984 entries and check varieties. Superior entries were advanced to 2006 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.

Blast resistant M-207 was released in 2005. A second blast-resistant line was released as M-208 in 2006. This new variety is described as an early, smooth, high-yielding semidwarf, Calrose quality medium grain with blast resistance. Plant breeder Carl Johnson describes the new variety as an improvement over M-207 because it matures four days later; lodges 9 percent less; has improved whole head rice; and has four percent higher seed weight. M-208 can be commingled with other Calrose types with similar size, shape and weight.

M-208 is adapted to the majority of the M-202 growing areas and will have similar fertilization requirements.

Another promising experimental Calrose medium grain in development is 03-Y-254. Described as a very early, smooth, high-yielding, semidwarf with improved yield and stable whole-grain yield, it will be retested in 2006. Its maturity and seedling vigor are similar to M-104.

Twenty-six Calrose medium grain entries from 2005 yield tests were grown in the Hawaii winter nursery. Maturities range from M-103 to M-205. These entries have greater yield potential than their respective highest-yield maturity checks. Lodging resistance is superior to M-202 and quality is equal to or better than M-202.

Much effort continues to incorporate blast resistance into Calrose medium grains—49 percent of all Calrose crosses and 39 percent of the Hawaii winter nursery rows. These represent 78 pedigrees. New experimental lines have overcome the agronomic deficiencies observed earlier in this breeding effort. Thirteen entries with blast resistance have yielded more than the highest Calrose check. Some of these have been advanced in Hawaii and are being tested in 2006. Another yield test with selected entries from 541 rows is planned for 2006. 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 have been made. Seven lines were to be advanced in 2006. No breeding research was conducted on transgenic herbicide-resistant M-202.

Milling quality tests included 589 entries. Forty-nine of the 145 saved entries had head rice yields similar to the best Calrose medium grain check. The current standard bearers are M-103, M-206 and M-205. Forty-nine of 74 advancing blast entries had head rice yield equal to respective checks.

Milling samples from seed increase fields and advanced experimental plots were harvested twice a week as grain moisture levels decreased from 25 percent to 17 percent. Average head and total milled rice was determined at high, intermediate and low grain-harvest moistures.

Stem rot resistance for Calrose medium grains remains a priority. Part of the 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.

Progress is reported in improving straw strength with experimental lines having lodging resistance better than M-204. Resistance to low temperature blanking continues to be screened in refrigerated greenhouses.

Research plans for 2006 include:

  • A strip trial to evaluate yield performance and milling quality for the experimental line 03-Y-254 relative to M-104 and M-206
  • Continued “fast track” development of Calrose medium grains with blast resistance and higher yield potential
  • Introduction of new sources of stem rot and sheath spot resistance from other projects
  • Small and large plot yield tests on Chinese introduction backcrosses

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.

Calhikari-201, a semidwarf, early-maturing premium quality short grain, was developed by RES plant breeders. It is the first California release of this kind and has seen mixed results. Although it yields better than the Japanese variety Koshihikari (from which it was derived), its cooking quality has not been well accepted in the Japanese market. Efforts are under way to improve on cooking quality, as well as its agronomic characteristics.

Fourteen advanced, premium-quality, short-grain breeding lines were included in 2005 statewide yield tests. Thirty-seven lines were in preliminary tests. Sixteen experimental lines were identified for earlier maturity, smooth hull, better lodging or blanking resistance, different parentage, kernel size, better cooking quality or yield potential than Calhikari-201.

Another breeding effort is seeking improvement for the M-401 market. Eleven advanced, premium-quality medium grains were included in statewide yield tests. Forty-seven were included in preliminary yield tests. These entries showed excellent seedling vigor but were susceptible to blanking, lodging and uneven flowering. Nineteen of these experimental lines were selected for early maturity, blanking resistance or better yield potential than the check variety M-401 and will be tested further in 2006.

Among conventional short grains, S-102 is the predominant variety in commercial production. Released in 1996, it has yielded well in statewide tests. Its shortcomings include pubescent leaves and hulls and susceptibility to stem rot. In 2005, three advanced short grains moved into statewide testing, as did 10 preliminary lines. Four of these entries were selected for their smooth hulls. They will be used as parents for new crosses.

Breeding efforts for conventional short grains have focused on improved disease resistance. Two advanced and five preliminary stem rot-resistant breeding lines were identified as having excellent yield potential and resistance to lodging. Because of other shortcomings, however, they will probably prove most useful as donors with stem-rot resistance. Several early-maturing and high-yielding blast resistant lines have been recovered from short grain and premium quality medium grain crosses. DNA marker technology is now in use at RES to accelerate development of improved disease-resistant varieties.

Special purpose varieties often have unique or undefined cooking characteristics that make quality evaluation and selection difficult. Improvement of the sweet rice or waxy, Calmochi-101, is focused on agronomic and quality characteristics. Two experimental lines were tested in statewide yield tests and eight in preliminary yield tests. One entry showed a significant yield advantage over Calmochi-101 but was four days later and susceptible to blanking. Two other very early entries showed significant agronomic advantages, with larger kernels, blanking resistance and better stem rot resistance and will be advanced to statewide yield testing.

A new variety with improved starch characteristics (low amylose) developed through induced mutation has been approved as “Calamylow-201” for a small specialty market in development. Eight new low amylose entries were included in preliminary yield tests in 2005.

Breeding for bold grain types similar to the Italian varieties like Arborio are also continuing.

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. Conventional California long grains are agronomically sound—excellent plant type, lodging resistance, grain yield and seedling vigor. Improvements in milling quality and cold tolerance are being pursued.

DNA marker technology is being integrated into plant breeding efforts at RES with help from rice geneticists at UC Davis. During the 2005 season, a total of 102 advanced conventional long-grain selections were tested in statewide and preliminary yield tests. Overall yields were lower than expected because of delayed planting. However, several long-grain entries yielded significantly higher than L-204, including

03-Y-496, 99-Y-529 and 04-Y-706. Stem-rot resistant experimental lines 01-Y-502 and 03-Y-496 also showed high yield potential.

Conventional long-grain experimental line 99-Y-469 was approved for release as L-206, a very early to early maturing semidwarf. Average heading date is five days earlier and plant height is slightly shorter than L-205 and M-202. Lodging potential is similar to L-205 but may lean with excessive dryness after harvest maturity is reached. 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. Grain yield also compares favorably. It is suited to all but the coldest rice-growing areas and the warmest locations in Glenn County. The five-year head rice yield averaged nearly 63 percent, comparable to L-205. About 15,000 pounds of foundation seed was grown in 2005.

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 8,610 pounds/acre and 9,470 pounds/acre. L-205 averaged 8,560 pounds/acre. Several entries showed superior head rice yield.

Calmati-201 is a true Basmati aromatic long grain possessing cooking quality and kernel characteristics approaching those of imports. This variety is susceptible to cold-induced blanking and is thus not recommended for cooler regions. Thirty-eight selections with improved cooking qualities were tested in statewide and preliminary tests in 2005. A number of these Basmati lines with slender grain and softer texture were advanced to the Hawaii winter nursery and were to be tested for yield performance in 2006.

Basmati experimental line 04-Y-153 was released in early 2006 as Calmati-202, an early maturing semidwarf. Seedling vigor is similar to L-205 and M-202. Maturity is six days later than L-205 and four days later than M-202. Plant height is about the same as L-205 but slightly shorter than M-202. Susceptibility to cold-induced blanking is significantly higher than

L-205 and therefore it is not adapted to cold locations. It also showed significantly lower yield potential than L-205 and M-202, averaging about 6,740 pounds/acre. Milled rice kernels of 04-Y-153 are longer and more slender than Calmati-201 yet slightly shorter than imported Basmati. The overall appearance of Basmati is important to consumers of this rice type. The coherence of cooked grains, as well as the grain shape and texture of this new variety make it a “distinguishable improvement” over Calmati-201. Both varieties are susceptible to fissuring at low moisture, so growers are advised to harvest at no less than 17 percent moisture.

Work continues on milling yield improvements. Grain characteristics are being selected for that will lend milling yield stability to long-grain lines under adverse weather conditions to allow a wider harvest window. The milling yield potential of 32 advanced long-grain lines was evaluated in 2005. Crossing and backcrossing continues with materials from the South and from foreign sources to breed Jasmine types through pedigree and mutation breeding. A waxy long-grain line,

99-Y-494, showed impressive yield potential in statewide tests in 2005. Waxy lines are used as donor parents in cold tolerance and yield improvement efforts.

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 has contributed the results of fissuring studies from three milling populations and a long-grain milling quality population. Further information on this four-year project is available online at http://www.uark.edu/ua/ricecap/.

Stem rot resistance from the wild species Oryza rufipogon has been transferred to a number of high-yielding long grain lines. Thirty-seven entries with a range of stem rot resistance were tested in 2005 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.

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.

Screening for stem rot resistance usually begins with third generation crosses. In 2005 there were about 7,500 rows in the stem rot nursery, 3,400 of them drill seeded. This resulted in less seed drift and a more uniform stand that enabled the use of greater nitrogen fertilization without lodging. Increased nitrogen results in greater disease severity and thus better screening opportunities. Promising long grain and short-grain resistant lines are emerging but progress has been slow with medium grains. Two long-grain and two medium-grain lines with resistance derived from O. rufipogon and two lines with resistance derived from Oryza nivara have been backcrossed with M-206 in an effort to address this problem. 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 370 crosses in 2005 for this purpose.

In addition, 161 lines resulting from a cross of M-202 with O. officinalis were made at the International Rice Research Institute (IRRI) in the Philippines. This species has even higher levels of stem rot resistance than O. rufipogon but has a different genetic structure than cultivated rice. An additional 18 crosses between M-206 and O. officinalis were planned for 2006. About 3,600 field transplants and an equal number of greenhouse plants were screened at RES for stem rot resistance with the help of the USDA geneticist and staff from UC Davis.

A screening program for experimental entries with sheath spot resistance not derived from wild species like O. rufipogon is also in place. This is especially important for medium grains, which currently do not have O. rufipogon-derived resistance. The test revealed large differences in susceptibility to sheath spot, a disease that is actually more widespread than stem rot and can cause significant damage to rice. Additionally, 29 backcrosses were made in a new effort to transfer sheath blight resistance to M-206 and L-205.

Rice blast has been in California for 10 years now and has spread significantly since it was first discovered in Glenn and Colusa counties. However, the severity of the disease has been low the last seven years. 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. The Pi-z gene is the source of this resistance and is present in nearly all materials advancing through the medium grain program. About 7,300 lines were screened for blast resistance in the greenhouse during 2005. New breeding lines from the Philippines are being backcrossed into M-206 to incorporate broader blast resistance into this variety. A cooperative project with the USDA lab at Davis is also investigating multiple blast resistance genes.

Bakanae disease, another relative newcomer to California, has been found in Butte, Colusa, Yuba and Sutter counties. It is a seed-borne fungus that probably slipped into the state on rice that did not pass through quarantine. A great deal of attention has been given this disease to understand its prevalence, its life history and best methods of control. Since it is spread by infected seed, investigations have focused on soaking treatments with bleach. Results of this testing suggest best treatments are a 2.5 percent bleach solution without a rinse or a 5 percent bleach solution for two hours followed by replacement with water. The 5 percent treatment is a little more effective and a little less harmful to seedling growth.

A study comparing varietal susceptibility to Bakanae also continued with mixed results. In general, however M-205 showed more susceptibility than either M-202 or M-206 (least susceptible). Another useful finding from this work is that a density of one Bakanae-infected seedling per square foot at six-to-eight weeks after planting would likely result in a five percent yield loss.

Also in 2005, 37 entries passed through quarantine. Another 161 entries from crosses made at IRRI between M-202 and O. officinalis (stem rot resistance) are expected to be harvested and passed through quarantine in 2006.


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