Rice Experiment Station, Administration and Plant Breeding Staff |
The California Cooperative Rice Research
Foundation (CCRRF) is committed to the development
and release of excellent highyielding
and high-quality rice varieties. The RES
Breeding Program implements rice variety development
for all market classes of long, medium,
and short grains.
The focus of the RES rice breeding program is to develop improved rice varieties with high-yielding and superior-quality grain types and market classes that are commercially competitive in the world market for the benefit of California rice growers now and in the future. The Rice Experiment Station is now up to full strength with the majority of positions filled. Dr. Harrell’s leadership has brought progress and stability. This year features the release of two new varieties: The long awaited herbicide resistant Medium Grain with the ROXY® technology, released as M-521 and a Premium Quality Short Grain, Calhikari-203
Breeding NurseriesThree breeding nurseries are established to accelerate breeding activities. The breeding nursery locations include: (1) Rice Experiment Station facility in Biggs, CA (77,552 lines), (2) the Hawaii Winter Nursery for generation advance and seed increase in Lihue, HI (8,203 lines), and (3) the San Joaquin Cold-Tolerance Nursery for cold-induced blanking screening (4,165 lines). Each of these nurseries has a unique role in the California breeding program. The RES facility allows for the creation of new varieties and summer seed production and evaluation. The Hawaii facility allows for a winter generation to be produced, giving the breeders two generations per year. The San Joaquin nursery evaluates the cold tolerance of varieties, and is used in conjunction with refrigerated greenhouses at RES.
Medium Grain
M-521 (19Y4000)
Confidence in the productive ability of M-521 is high as it was evaluated in the UCCE State Wide (SW) Yield Tests for four years (2019-2022), for a total of 41 yield experiments. Based on the pooled four-year SW Yield Tests, field performance of M- 521 was similar to M-206 and M-210 in all SW test locations beginning in 2019. It has very good seedling vigor, flowered at 87 days, with a plant height of 96cm, and a lodging potential like M-206 and M-210. Yield performance of M-521 in different zones or UCCE test locations is summarized in the table below. Location specific performance indicated 2-4% yield advantage of M-521 over M- 206 and M-210 in San Joaquin and Biggs. In other locations, M-521 had an average of 2% lower yields than the two Calrose varieties.
Grain Characteristics and Milling Quality of M-521The milled grains of M-521 were marginally lighter, slightly longer, and slightly narrower than the M-206, and M-210 varieties. When cut at 22% moisture and above, M-206 had a head and total of 68/71, while M-210 and M-521 had 67/71. At 18-22% moisture, the milling yield of M-521 was slightly improved to 67/72, similar to M-210. As is typical, when harvested at moistures below 18%, all three entries tended to have reduced head rice as grains became drier.
RVA and Quality Evaluation of M-521The average apparent amylose (20.66%) and protein content (5.96%) of M-521 was similar to M-206 and M-210. All three had low gel type typical of a Calrose-type medium grain. Based on the average of four-year RVA (rapid visco analysis) data, M-521 does not deviate significantly from the profile of M-206 or M-210. Results indicate that M-521 cooking characteristics are similar to M-206 and typical of a Calrose type rice.
Cold-induced Panicle Blanking and Disease Screening TestsCold tolerance screening is performed in San Joaquin and in the refrigerated greenhouse at RES from 2019 to 2022. Averaging the four-year results in San Joaquin shows that M-521 had blanking of 1.3%, compared to 1.5% for M-206 and 1.2% for M-210. Overall, in both San Joaquin and greenhouse testing, M-521 had a cold tolerance level similar to M-206 and M-210. Based on the four-year stem rot resistance screening, M-521 had an average stem rot score of 3.38, which is moderately susceptible to stem rot disease. M-206 and M-210 were both susceptible to stem rot with scores of 3.77 and 3.45 respectively. For blast resistance, screening is limited to the detection of incorporated blast genes using DNA markers detected by the RES Genetics Lab. M-521 and M-210 were both positive for the presence of the Pi-b blast gene, while M-206 was negative for the desired gene. Therefore, if a blast outbreak occurs, M-210 and M-521 are expected to show resistance.
Calhikari-203 (17Y2087) Premium Quality Short Grain Rice17Y2087 is a semidwarf, early maturing, high yielding premium quality short grain rice approved for release in 2023. The new variety will be named Calhikari-203 (CH-203). It has a 11-13% yield advantage over CH-202 and CH-201, averaging 9,050 lb/A yield based on five-year UCCE SW yield tests. CH-203 consistently showed higher lodging resistance of 33% vs. CH-202 at 65% and CH-201 at 61%. CH-203 has high milling quality. Test evaluations indicated the excellent grain appearance, cooking, and taste qualities of CH-203 for the premium quality short grain market. Taken together, the attributes of CH-203 make it suitable for comingling with existing premium quality short grains or a viable alternative to CH-202 or CH-201.
CH-203 Yield and Agronomic PerformanceCompared to CH-202 and CH-201, CH-203 had a similar seedling vigor, it flowered at 89 days which is two days later than CH-202, one day later than CH-201. CH-203 is considered semidwarf like the older Calhikari varieties at 90 cm plant height. It also has excellent straw strength as shown by the low lodging potential.
In summary, CH-203 had a superior grain yield over CH-202 or CH-201 in all SW test locations. It is adapted in all rice growing counties of California that makes it a viable alternative rice variety for commercial rice production.
RVA and Quality Evaluation for CH-203All three Calhikari lines had apparent amylose content of 20% and low gel type grain, indicating similar softness when cooked. Low protein content is desirable because low protein content is correlated to high taste scores. Two-year protein analysis indicated that CH-203 had lower protein content than CH-202 or CH-201. Overall, the CH-203 cooking profile was similar to CH-202 and CH-201. The amylographic profile also show that CH-203 more closely overlaps the cooking curve of Koshihikari. Internal and external blind evaluations for grain appearance, cooking and taste qualities by mills, rice handlers, marketing organizations, and some Japanese evaluators indicated the close similarity of CH-203 to Koshihikari and CH-202.
Short Grain Breeding
Promising SPQIn 2022, two high yielding, SPQ entries were identified (21Y2031 and 22Y2119) as potential candidates for SW yield tests in 2023. For grain yield, 21Y2031 showed a 17% yield advantage over CH-202 and CH-201. When 21Y2031 is harvested between 18-22% moisture, the milling yield averages 66/73% head and total. Analysis for chalkiness revealed more chalky kernels (3.2%) for 21Y2031 than CH-202 (1.0%) and CH-201 (2.4%). Compared to CH-202, it also had a higher taste score due to its lower protein content. Line 22Y2119 is another SPQ that had good grain yield and quality performance. It had a 16% yield advantage over CH-202 and CH-201. Its grains were slightly more chalky (1.5%) than CH- 202 (1.0%), but less than CH-201 (2.4%). Lines 21Y2031 and 22Y2119 well be considered for SW yield test in 2023.
Promising Regular Short Grains (S)Across the seven SW locations in 2022, 20Y2001 outyielded both S-102 and S-202. It averaged a yield advantage of 8% over S-202 and 28% over S-102. Compared to S-202 and S-102, line 20Y2001 was more adapted to different SW locations. Grain yield results show that it was the highest yielding line at six out of seven UCCE SW locations. Milling yield of 20Y2001 was high compared to S-202 and had a similar percentage head rice to S- 102 when harvested at 18-22% moisture. It is later flowering, shorter than its sister varieties, and lodges more (46% vs 37-40%). Chalky grain percentages fall between S-202 and S-102. Disease screening data from 2021 at RES revealed high stem rot resistance with a disease rating score of 1.8 for the line. Some future lines to keep an eye on would be 20Y2008 and 20Y2072. Both lines outyielded the standard check varieties at RES.
Promising Sweet Short Grains (SWX)A waxy short grain line included in the SW yield test has been designated 20Y2124. Results show that 20Y2124 had an average yield advantage of 5% for CM-203, and 25% over CM-101. Although the average yield advantage was only 5% greater than CM-203, it had wider adaptation than either of the older varieties. Cold-induced panicle blanking results from the San Joaquin cold tolerance nursery, show 20Y2124 is cold-tolerant like CM- 203 and CM-101.
Genomic SelectionThe Rice Experiment Station breeding program has successfully bred new and improved varieties for California growers using pedigree breeding method. The station also employs marker-assisted selection (MAS) for blast resistance, grain quality traits, and herbicide resistance. The whole variety development process takes about 10-12 years or longer, from the time the cross was made until variety release. While the pedigree method is proven effective, it is time-consuming, labor-intensive, and costly. New breeding tools, such as genomic selection (GS), is emerging and may ensure complex traits are selected with improved accuracy and precision. GS, in principle, is another form of MAS. GS uses all markers spread across the genome to predict the performance of lines with genotypes only (organism’s genetic information) without phenotypes (observable physical traits). Thus, selections can be made earlier that reduce the number of candidates to be examined in the field. The goal of the project is to integrate GS, as a complementary breeding tool to MAS, into the RES breeding program. This efficiency gain has three major steps: • A population, that represents the genetic diversity of the RES breeding program, was assembled and field tested since 2020. • A suitable marker set, that is cost effective and can discriminate the RES germplasm, will be developed for routine use genotyping GS materials (training set and predictive set). • Assess the prediction accuracy of the GS prediction model for selecting complex traits.
Long GrainsL-208 is the newest conventional long grain and was released in 2020. Agronomic characteristics, adaptation, milling, and cooking qualities of L-208 are similar to L-207. Based on 2022 SW experiments, L-208 and L-207 had higher yield at locations outside of RES. The new variety, L-208, had approximately a 4.0% yield advantage over L-207 in 2022. It performed better and had higher yield in five out of seven SW experiments.
Promising Long Grain LinesThree LG lines showed promise for future release: 19Y1018, 20Y1029, 20Y1008. The advanced line 19Y1018 is a regular LG in the SW trials for a second time. It was planted in seven locations and out yielded L-208 and L-207 by 1.7% and 5.7%. Line 19Y1018 had less panicle blanking compared to Calaroma-201 in San Joaquin. Based on milling yield trends, the line showed stable head rice performance and can be harvested from 18-26% moisture content.
Genetics LabThe main purpose of the RES Genetics Lab continues to be to provide the breeders with genetic marker information for the selection of potential and advanced lines as well as maintaining the purity of our released varieties. Throughout the year breeders submit leaf samples from F1, head rows, and ROXY® trait lines. Off-types that appear in RES or area producer’s fields are also genetically identified through marker analysis. Results from this year are: • 2,497 parental and F1 plants were analyzed to determine true crossing. • Head row purity was verified in over 3,700 samples which included short, medium, long, and specialty lines. • The presence of the oxyfluorfen herbicide tolerant trait (ROXY®) was determined for about 765 plants whose response to the herbicide was atypical. • With the eventual release of a ROXY® rice variety, an efficient and repeatable assay to identify the presence of the trait was developed. Overall, nearly 7,500 samples were processed, resulting in over 36,000 data points.
CRISPR technologyCRISPR technology has been used successfully in the lab to verify the oxyfuorfen resistant phenotype as well as to explore the targeting of other useful traits. An organism generated by CRISPR technology is considered a genetically edited organism and not a genetically modified organism. The difference is important in both consumer acceptance and government regulation. Genetically edited organisms do not have foreign DNA in their genome. A change in their phenotype is a result of a targeted change in their own DNA. This change could happen naturally and therefore is managed and regulated the same as conventionally bred organisms. The change in phenotype of genetically modified organisms is the result of the addition of DNA from another organism. This change could not happen naturally, so these organisms are managed and regulated in a stricter manner. CRISPR technology is being developed and tested in the RES Genetics lab. No varieties are being released at this time. When CRISPR rice varieties are introduced in the future, it is hoped that RES will be able to enter the market in a timely manner.
Lab ImprovementsIn December 2020 CCRRF authorized the purchase of new analytical equipment for the RES Genetics lab. This will allow for the transition from SSR (simple sequence repeats) marker-based analysis to a SNP (single nucleotide polymorphisms) marker approach. The two techniques are similar in many ways which will result in a smooth transition. The difference is in the speed in which SNP maker results can be collected and analyzed. The running and identification of polymorphic alleles using SSR’s averages 3.5 hours with the equipment available in the lab. Whit the purchase and use of the plate reader and SNP markers the average time to identify polymorphic alleles will be less than 30 seconds. |
Performance of CH-203 in the cooler areas of
Sutter, Yuba, Yolo, and San Joaquin, showed it to
be cold tolerant as indicated by yields exceeding
10,000 lb/A in Yolo and San Joaquin. In Sutter and
South Yolo, CH-203 had a 5-8% yield advantage
over CH-202 & CH-201. In the low yielding site of
Yuba, CH-203 had a 16% yield advantage.
A total of 360 lines, consisting of advanced breeding
lines and released cultivars of all grain types, were selected
to be phenotyped for grain yield and agronomic
traits. These same lines were genotyped to form a training
population. Broad-sense heritability estimates,
based on the phenotype, ranged from 0.64 for seedling
vigor to 0.88 for days to 50% heading. This indicates
good predictability for the agronomic traits. Grain yield
data will be gathered in 2023. In addition to field evaluation,
the population will be genotyped with genomewide,
single nucleotide polymorphism (SNP) markers to
assess the potential of GS in the RES breeding program.