|Rice Breeding Program-99
Rice Experiment Station Scientists
D. Marlin Brandon, director and agronomist
Carl W. Johnson, plant breeder
Kent S. McKenzie, plant Breeder
Farman Jodari, plant breeder
Jeffery J. Oster, plant pathologist
|The last year of the last
century proved to be the beginning of a major transition at the Rice Experiment
Station. Successful long-grain breeder Shu-Ten Tseng retired after 29 years at
RES. Replacing him is Farman Jodari, who has extensive experience in breeding
long-grain rice in the Southern United States. A new 5,000+ square-foot greenhouse
was completed, giving scientists much-needed space in which to accelerate rice breeding,
plant pathology and weed control work. Sadly, at the beginning of this year,
long-time RES Director D. Marlin Brandon passed away. RES scientist Dr. Kent S.
McKenzie, who has overseen the development of short grain and premium quality rice for 11
years, assumes the mantle of leadership as the new RES director.
Statewide Yields Off Again
California rice acreage continued the expansion of the last several years with 548,000 acres harvested last year. More than 90 percent of this acreage was grown with varieties developed at the Rice Experiment Station. Statewide rice yields in 1999 were off again last year at about 7,300 pounds/acre, up from 6,840 pounds/acre in 1998 but well off the 8,300 pounds/acre in 1997. Prolonged record low summer temperatures resulting in high levels of blanking are to blame for 1999s low productivity.
The breeding nurseries were plagued with a variety of problems last year. Planting was delayed until May 10 because of wet ground. Water seeding and drill seeding went well in nurseries but scientists report problems with seedling drift in the disease nursery. Crawfish again damaged stands in the rice water weevil area. Weed control was good in the drill-seeded nursery but Londax®-resistant arrowhead turned up in the water-seeded nursery. Aerial application of herbicides were prohibited by the state Department of Pesticide Regulation and mechanical sprayers could not be used. Only a portion was sprayed by hand. Some parts of the nursery suffered from low nitrogen fertility, heavy stem rot and cool-temperature sterility.
Plant breeders made 997 new crosses for rice improvement in 1999, bringing the total number of crosses since 1969 to 25,153. The breeding nursery occupied 67 acres, where approximately 75,000 progeny rows were grown for selection, purification and generation advance. The nursery contained 3,916 small plots and 2,613 large plots in various water-seeded yield tests. An estimated 25,000 panicles and 12,000 rows were harvested for selection, advancement, quality evaluations and purification for progeny rows. Thirty-five experimental lines were grown in headrows for seed increase, quality evaluations and purification. Three advanced experimental lines are undergoing breeder seed increase. Headrows of M-402, Calmati-201 and new varieties M-104 and M-205 were grown for breeder seed production.
The Hawaii winter nursery, which accelerates advanced breeding material and allows for cold tolerance screening, contained 5,000 rows planted December 3, 1998. Additional transgenic nurseries were transplanted December 29, 1998, including a direct seeded test sown at the Kauai Branch Station on January 7, 1999; however, it proved unsuitable as a nursery location.
With the discovery of blast at the Hawaii rice research area in 1998, a program was begun to destroy straw residue and spray with the fungicide Quadris® at the nursery. No evidence of blast was reported in 1999. Plans are being made to net a portion of the nursery to prevent future bird damage. All seed selections shipped back to California were inspected to minimize the risk of introducing blast to the RES.
The 1999-2000 Hawaii winter nursery of 5,000 rows was transplanted Dec. 6-9, 1999. An additional nursery of transgenic material was seeded Nov. 30 and transplanted Dec. 21. The nursery was to be harvested in late March or early April and planted in the 2000 RES breeding nursery.
The 3.5 acre cold tolerance nursery at UC Davis was planted with precision-drilled F2 populations and 9,900 dry-seeded progeny rows. Stands and grass control were good. Blanking was moderate but not as severe as it could have been given the weather. Damage was reported to some F2 populations by cold water and an indigenous flock of Canada geese. Panicle selections will be advanced.
Although the San Joaquin cold tolerance nursery is on hold until a new location can be found, researchers planted more than 700 rows of advanced breeding lines of the San Joaquin Statewide Yield Tests site to provide additional cold tolerance information. Two refrigerated greenhouses at the RES are also used in selecting for blanking resistance.
Statewide Yield Tests
Statewide Yield Tests conducted annually in grower fields help scientists evaluate the performance of advanced experimental lines and commercial varieties. The first large-plot seeding at RES took place May 10-14, the second May 26-27. Water-seeding and conventional management practices were used. Results from these trials are reported in more detail in the "Variety Trials" section of this report.
Preliminary Yield Tests are the initial step of replicated large plot testing of experimental lines. These tests included 488 entries and check varieties. Top experimental lines performed well and will be advanced for further testing in 2000 Statewide Yield Tests.
Farman Jodari took over stewardship of the long-grain breeding program in 1999. Efforts will concentrate on conventional long grains, Newrex types and now both Basmati and Jasmine aromatics.
Although long grains developed at the RES possess superior agronomic characteristics, improved cooking and milling qualities are necessary to be more competitive with Southern U.S. long grains. Significant improvements toward these objectives were made with the introduction of L-204 in 1996. Researchers are fine-tuning screening procedures with new, sophisticated testing procedures.
During 1999 a total of 99 advanced conventional long grain selections were tested in the Statewide and Preliminary Yield Tests. Detailed quality evaluation is under way for four of these entries.
Newrex is a special quality type rice used in parboiling, soup canning and rice noodles. L-205 is a Newrex type developed at RES and released in 1999. Major soup manufacturing companies have expressed considerable interest in it. Grain yields of L-205 in RES yield tests were 10,600 pounds/acre (compared to 10,300 for L-204). This variety is an early maturing semidwarf that showed significantly less blanking last year. It averaged one to two days later and slightly taller than L-204. L-205 could become prone to lodging under excessive nitrogen fertilization.
Four experimental Newrex lines performed well in yield tests last year with yields over 10,000 pounds/acre.
Calmati-201, a true basmati type aromatic long grain, was also released in 1999. This variety possesses extreme cooked kernel elongation and cooking qualities that approach those of imported basmatis. This semidwarf heads about the same time as A-201 and an average five days later than L-204. Calmati-201 grows several inches taller than L-204. It is also susceptible to blanking and is not recommended for cooler regions. Heavy nitrogen fertilization should also be avoided in blanking-prone areas. Average grain yields from 1996 to 1998 were 7,120 pounds/acre, compared to 8,440 for L-204. In 1999, however, yields of Calmati-201 were sharply reduced to 4,840 pounds/acre because of blanking. Nonetheless, this variety is expected to perform well for the basmati market. Yield levels of this variety are inherently lower than other varieties even in their country of origin. A number of other basmati experimental lines with greater kernel elongation were advanced for yield performance in 2000.
Several waxy long grain lines were tested in large plots. Two of these lines significantly outperformed L-204 and are being used as donor parents in cold tolerance and yield improvement efforts.
Work on Jasmine rice also began in 1999. Crosses were made with germplasm lines from Southern U.S. breeding programs and foreign introductions. A Thai Jasmine variety was irradiated to create mutants for breeding. Selections will be made in 2000 for early maturing and short plant mutants.
Newer California long grains are a significant improvement over previous varieties, as was evidenced by head rice yields of 65.8 percent for L-204 and 63.7 percent for L-205. With proper harvest management and favorable weather conditions, these varieties are expected to continue to produce high milling yields. Plant breeders are selecting for a wide window of harvest and other mechanisms of milling yield stability.
Stem rot resistance originating from the wild species Oryza rufipogon has been transferred into a number of long grain lines. Thirty-one entries with a range of resistance were tested in Statewide and Preliminary Yield Tests. Improvements in yield, cold tolerance and early maturity of stem rot resistant lines is being pursued.
Rice blast resistance is another important objective for long grain development. Twenty-eight blast resistant lines all derived from crosses with Southern blast resistant varieties were tested in small plot tests in 1999. Several will be studied for yield performance in 2000. A considerable number of early generation blast resistant lines were selected and are being tested by the RES plant pathologist. Selections also made from 45 second backcrosses.
Premium Quality & Short Grains
Premium quality is a term used to identify California medium grain varieties like M-401 that have unique cooking characteristics preferred by certain ethnic groups. This rice tends to be glossy after cooking, sticky with a smooth texture and soft after cooling with distinctive aromas and tastes. Two important new varieties were released in 1999:
M-402 a late-maturing semidwarf medium grain with higher head rice milling yield than M-401. Mean yields were significantly higher, averaging 8,440 pounds/acre (compared to 7,350 pounds/acre for M-401).
Calhikari-201 an early maturing semidwarf short grain descendant of Koshihikari with better seedling vigor, resistance to lodging and higher yield potential than other Japanese varieties. Cool temperature blanking and susceptibility to stem rot are challenges.
S-102, released in 1996, is the predominant California short grain and the top-yielding entry in statewide tests during the last two years. No new entries yielded significantly more than S-102. Grain characteristics and milling performance of several other entries are now under examination.
Development of special purpose rice is currently focused on improvements of agronomic and quality characteristics to Calmochi-101. Entry 96-Y-196 is a glabrous waxy line that has produced higher than Calmochi-101 since 1996, although head rice yield and seedling vigor have been lower. Breeding for large-seeded types similar to the "Italian types" continues with several entries performing well in Statewide Yield Tests in 1999.
Short and premium-quality medium grain lines, including several derived from crosses between M-401 and the Louisiana medium grain variety Lafitte, were screened successfully for blast resistance. These materials were rapidly advanced to statewide tests. Cool temperature blanking is a problem with these lines. Breeding for stem rot resistance combined with good agronomic characteristics is proving difficult in short grain and premium quality medium grains. Efforts are under way to improve seedling vigor in these lines. Work is also continuing with the germplasm line PI 506230 to transfer tolerance to rice water weevil.
Calrose Medium Grains
Calrose medium-grain breeding objectives include high stable yield potential, resistance to lodging and disease, improved seedling vigor, better milling yields and resistance to cold temperature blanking. An increased effort to incorporate blast and stem rot resistance is also being made, including crosses and backcrosses with newly acquired germplasm sources. Evaluation of transgenic M-202 continues.
Two new medium grains will be released to growers as new varieties this spring. M-205, experimentally known as 94-Y-615, is an early maturing, high-yielding semidwarf that has been in statewide tests since 1995. Compared to M-202, it heads three days later, is slightly shorter and lodges significantly less. It has an 11 percent yield advantage, an improved stem rot score and a slightly improved whole and total milling yield. Kernel characteristics are similar to other early maturing Calrose types. The new variety is susceptible to blast and has slightly lower seedling vigor. Cooking characteristics are similar to M-202 and M-204. It will be best suited for warmer production areas.
The second new medium grain is M-104, a very early, high yielding Calrose type known experimentally as 95-Y-214. Compared to M-103 it heads about the same time, has improved seedling vigor, better lodging resistance and an 8 percent yield advantage over all locations. It also is susceptible to blast. Compared to M-202 it heads eight days earlier and shows higher head rice yields. Its kernel characteristics are similar to M-202 and has similar cooking characteristics to both M-103 and M-202. It will be best suited for the coolest production areas (San Joaquin). In warmer areas it could also be used for late plantings or in duck ponds.
A number of other promising medium grains with harvest moisture lower than M-202 are under evaluation in statewide tests. At the Hawaii winter nursery, 23 Calrose medium-grain entries with greater yield potential, superior lodging resistance and/or improved grain quality are also being evaluated. One of the stem rot entries, 99-Y-393, yielded 8.6 percent higher than just-released M-205.
A great deal of emphasis is being placed on blast resistance in Calrose medium grains. Thirty-eight percent of 370 Calrose medium-grain crosses were made for blast resistance and more than 2,000 selections were advanced from Hawaii for blast resistance. A special modified yield test will be conducted in 2000 from 565 blast-resistant rows grown in 1999. Plant breeders say it will take four to five backcrosses to obtain lines with blast resistance and respectably high yields. Cooperative projects with USDA are also developing DNA fingerprinting techniques to assist in selection for blast resistance genes.
Transgenic M-202 lines with resistance to different broad spectrum herbicides were again evaluated under field conditions at RES. This included yield testing, headrows and a drill-seeded nursery. However, confidentiality agreements in the research contracts restrict an in-depth discussion of results.
A major concern in these materials is the potential for defects resulting from transgenic techniques used to insert the herbicide resistance gene. Other crops have shown a yield drag of at least 5 percent and initial indications from RES show that the transgenic M-202 under study is not equal to "regular" M-202. Herbicide-resistant M-202 should be viewed as a potential tool for weed control in particular situations. Issues ranging from seed production to consumer acceptance must also be addressed.
Selection for grain quality factors is focusing on improved head rice and total milled yields. Advanced experimental lines in the second year of statewide tests and/or breeder seed increase were evaluated for the factors that comprise these characteristics. Samples were milled at low, intermediate and high harvest moisture. Laboratory milling tests showed that 24 of 83 experimental entries had head rice one to three points better than the best Calrose check variety.
The greatest challenge in improving stem rot resistance for Calrose medium grains has been improving seedling vigor. New sources of resistance are continually being tapped, including breeding lines from 94-Y-561, a long grain, and new backcrosses to Oryza rufipogon. The majority of experimental entries in statewide yield tests have lower SR scores than the average of Calrose checks. Efforts to transfer high levels of seedling vigor have declined because of higher priority research on blast resistance and transgenic M-202.
Progress has also been reported in the development of experimental lines with greater straw strength, a component of lodging resistance. In other objectives, greenhouse screening for cold-temperature tolerance continues; efforts are under way to find a suitable location for a new cold nursery in San Joaquin; and a cooperative research effort with USDA, UC Davis and UC Riverside scientists is studying salt tolerance in rice.
Breeding for disease resistance is a cooperative effort between the plant breeders and plant pathologist. As breeding materials are cycled through the disease nursery, intense selection pressure aims to identify lines with desirable agronomic traits. Most of this effort is geared toward stem rot, but blast resistance is now also an important objective.
Forty-eight new crosses were made to transfer stem rot resistance derived from O. rufipogon to adapted California varieties. The pathologist also made 120 first and second backcrosses to transfer resistance from wild rice that has even greater resistance and at least one wild species has blast resistance, as well. There were 10,000 rows grown in the 1999 stem rot nursery, only a fraction of which show resistance greater than M-201. Work is also continuing to identify the location of stem rot resistance genes and to obtain useful DNA markers.
A nitrogen by variety trial showed that stem rot severity is very nitrogen responsive and increases with increasing nitrogen levels. Sheath spot is less nitrogen responsive. M-202 and the new variety Calhikari-201 showed the most disease increase. Calmati-201 and M-402 showed very little change.
Severity of rice blast was low in 1999 but the disease was found in Butte County for the first time, enlarging the infestation area that also includes Colusa, Glenn and Sutter counties. None of the statewide tests were significantly affected by blast. The plant pathologist made 291 crosses and backcrosses with blast resistant sources in 1999. About 4,500 lines were screened at the new RES greenhouse. The Hawaii winter nursery was again to be treated with the fungicide Quadris® to prevent a reoccurrence of blast.
A cooperative project with researchers at UC Davis and in the Southern U.S. has begun to develop molecular markers that would allow the detection of multiple resistance genes. California is currently faced with only one race of the disease, but multiple sources of blast resistance would serve as a kind of insurance policy against future infestations from other races. Screening for blast is being done in the off season in the new 5,000 square-foot greenhouse built at RES with funds provided by the Rice Research Board and the CCRRF/Rice Research Trust.
Seedling vigor work was done with Italica livorno and M-16, varieties from Italy and Hungary, respectively. Three new crosses were made in 1999 to transfer seedling vigor from these varieties. Good seedling vigor may, among other benefits, help reduce the adverse affects of some seedling disease. Incubator tests were also used to screen 50,000 seedlings involved in backcrosses from Italica livorno and M-16. Approximately 1,500 seedlings were selected and transplanted to further screen for short stature and stem rot resistance. Advanced generation selection from backcross populations that derived their high seedling vigor from M-16 have been recovered and appear to have high vigor, short stature, improved grain quality and yield potential, and better stem rot resistance than M-16. Several new Russian varieties with promising levels of seedling vigor have been identified and will be further evaluated as potential donors.
Bakanae disease, caused by a fungus, was found for the first time in Butte and Colusa counties last year. Typically, symptomatic plants are scattered throughout affected fields. Incidence is low and no major impacts on yield are expected. The disease usually does not greatly affect yield elsewhere in the world.
Symptoms appear in tillering stages, giving plants greatly elongated, rolled, yellow leaf blades. Most plants die before maturity. The fungus has been isolated from plants having blanked, gray-colored panicles and characteristic light pink or orange powdery growth on their stems near the waterline.
The origin of this disease is unknown, but draining fields during early stand establishment and/or incorporation of rice straw could have contributed to its development. Monitoring will continue to assess the economic impact of Bakanae Disease.