Rice Experiment Station scientists

Kent S. McKenzie, director

Virgilio Andaya, director of plant breeding: plant breeder, Calrose Medium grains

Farman Jodari, plant breeder, Long grains

Stanley Omar Samonte, plant breeder, Premium Quality and Short grains

Jeffery Oster,
plant pathologist

Cynthia Andaya, research scientist, DNA marker laboratory

The rice breeding program consists of five research projects developing California-adapted varieties for specific grain and market types. Virgilio Andaya is responsible for the Calrose medium grain project and is also director of plant breeding. Stanley Omar Samonte oversees short grains and premium quality breeding. Farman Jodari leads the long grain project and also serves as liaison with Southern U.S. breeding programs. Plant pathologist Jeffrey Oster supports efforts to improve disease resistance in all projects. Cynthia Andaya is in charge of the DNA marker laboratory and the grain quality lab. Progress highlights from 2014 are reported below.

Breeding nurseries

Seeding of the 2014 breeding nursery began May 12 and was completed May 30. A total of 1,360 crosses were made for rice improvement, bringing the total to 45,184 since 1969. Crosses made in early spring 2014 were grown during the summer at RES to produce second-generation seed. Crosses made in summer were planted in the Hawaii winter nursery and/or in the RES greenhouse to accelerate the selection process.

The 2014 RES breeding nursery occupied approximately 76 acres. Water-seeded yield tests included 5,054 small plots and 3,038 large plots. The nursery included about 60,600 water-seeded and 19,970 drill-seeded rows and plots. Second-generation populations from 2012 and 2013 crosses were grown in precision drill-seeded plots on seven acres. An estimated 150,000 panicles were selected from various second-generation populations for screening and advancement. Approximately 1,600 headrows of M-202, A-202, Koshihikari, and experimentals 08Y3269 and 09Y2141 were grown for breeder seed production in 2014.

Selection and harvest of the 2013–2014 Hawaii winter nursery was completed and seed returned to RES for planting in May. The 2014–2015 winter nursery included 9,281 progeny rows planted November 3–6, 2014 and 600 first-generation crosses transplanted December 8, 2014. Selection and harvest was set for April 2015, with seed to be returned for processing and planting in the RES breeding nursery.

The San Joaquin cold-tolerance nursery was planted in cooperation with two local growers. This seven-acre, drill-seeded nursery included 6,720 rows and five acres of second-generation populations. Stand establishment and weed control was good. Very little blanking was observed in the rows, but blanking occurred in the second-generation populations.

Statewide yield tests

Statewide yield tests were conducted in grower fields and at RES in 2014 to evaluate promising advanced selections from all three maturity groups—very early, early, or intermediate-to-late. More detail is reported in the Rice 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 536 entries and check varieties. Yield of the top experimental lines compared well with check varieties. Superior entries will be advanced to 2015 statewide yield tests.

Calrose medium grains

Calrose medium grains are the cornerstone of California rice production, accounting for most of the state’s total rice acreage. M-202, M-205, and M-206 are the most dominant early maturing Calrose varieties.

Acreage of M-202, released in 1985, has decreased because of the increased popularity and acceptability of M-206, released in 2003. M-205 is another high-yielding variety, released in 2000, that is best suited to the warmer areas of the Sacramento Valley.

M-104, also released in 2000, is a very early, cold-tolerant variety and was the dominant variety in San Joaquin County. The very early M-105 was released in 2011 as an alternative to M-104. Its number of days to heading and yield performance are in between M-206 and M-104. Though not as early maturing or as cold tolerant as M-104, M-105 is notable for its superior milling yield over M-104, M-205, or M-206. Other medium grains still in commercial production include M-208, M-401, and M-402.

Breeding objectives for Calrose varieties continue to be the development of high and stable grain yield, high milling yield, and excellent grain quality, cold tolerance, and disease resistance. This project also is taking steps to improve grain quality and cooking attributes to match the preferences of international markets.

BREEDING NURSERY HIGHLIGHTS

Matthew Calloway was hired to fill a new breeding nursery manager position in 2014. This position was created to increase breeding efficiency and effectiveness of the entire breeding program. Calloway reports to the director of plant breeding, Virgilio Andaya.

Among the check varieties, the highest overall grain yield averaged across the statewide tests was M-205 (9,820 pounds/acre), followed by M-206 (9,670 pounds/acre). The newest very early medium grain, M-105, averaged 8,630 pounds/acre, while M-202 had the lowest at 7,740 pounds/acre. Pooled grain yield of the check varieties in 2014 was 8,960 pounds/acre, compared to 10,270 pounds/acre in 2012 and 10,750 pounds/acre in 2010.

It was a warm year in 2014, causing rice plants to flower earlier than in previous years. The average combined number of days to heading of the check varieties was the shortest in the last five years. Lodging was minimal.

New variety: M-209

The advanced line 08Y3269, which has performed well in statewide testing, was approved for release in 2015 as M-209. It is a semidwarf, smooth, early maturing Calrose rice derived from a cross made in 2004 with M-205. The line was evaluated by milling and marketing organizations for milled rice quality and cooking quality. It was found to possess superior grain quality.

Tested in 38 statewide experiments, it had better overall grain yield (9,680 pounds/acre) than M-202, M-205, and M-206. Best yields were registered at the Rice Experiment Station and in Butte, Colusa, Sutter, and Yolo counties. A trending analysis of yields over locations showed that 08Y3269 may be better suited for the more favorable rice production areas and be less competitive in warmer or cooler environments.

Milled rice grains of 08Y3269 are heavier and slightly longer than M-205 and M-206. Amylose content is close to M-206—both are higher than M-202 and M-205. Protein content is comparable to M-202, M-205, and M-206.

Milling yield is one of the most important criteria considered before releasing a new variety. Percent head rice yield of 08Y3269 when harvested at 18% to 22% moisture was 65%/71% (head/total), compared to 62%/67% for M-202, 65%/70% for M-205, and 66%/70% for M-206. Compared to the checks, head rice yield of 08Y3269 was lower at harvest moistures above 22%.

Cold-induced blanking in 08Y3269 ranged from 2% to 6% in San Joaquin field observations from 2012 to 2014. In greenhouse tests, there was a wider spread: 13% to 20%. Combined tests indicate that 08Y3269 had an average blanking of 12.6%, compared to 11.8% for M-202, 12.1% for M-205, and 10.6% for M-206. These results indicate that 08Y3269 may sustain greater damage if grown in cooler areas.

The new variety had reaction to stem rot comparable to M-205, and better reaction compared to M-202, M-206, and M-208. It has better reaction to aggregate sheath spot compared to M-206 and M-208. However, 08Y3269 has no blast resistance gene. Thus, it showed greater susceptibility to this disease than M-208 and comparable susceptibility with M-202, M-205, and M-206.

BLAST RESISTANCE

Backcrossing efforts continue to bring different blast resistance genes into M-206 and other varieties. DNA markers facilitate the selection of materials for crossing and generation advance. In 2014, 10 lines were entered into preliminary yield tests. Five lines of M-206 were entered into statewide tests. One line, 12Y113, performed better (9,750 pounds/acre) than M-206 and M-208 at the Rice Experiment Station. However, it had lower percent head rice and grains were smaller and lighter. This line is currently being evaluated by milling and marketing organizations. It is under consideration for experimental increase, further purification, and evaluation.

STEM ROT RESISTANCE

Screening of a mapping population for stem rot resistance continues to narrow regions of chromosomal interest. Several stem rot resistant lines were evaluated. One line, 14Y3060, had superior grain yield (10,990 pounds/acre) compared with the highest-yielding check variety, M-205 (10,750 pounds/acre). However, this line did not show the high level of resistance as 87Y550 and had smaller grain size and low head rice yield. It will be used for crossing and further evaluation.

MUTATION BREEDING

Mutation breeding has been used to generate useful traits in populations derived from M-202, M-205, M-206, M-401, and other varieties. Project scientists are looking for mutants that are short, early maturing, with noble traits and tolerance to certain herbicides.

Development of herbicide-resistant rice lines is a special project. A research associate has been hired to screen for herbicide resistance or tolerance in the laboratory, greenhouse, and field conditions.

Long grains

The long grain breeding project focuses on four major rice types—conventional, jasmine, basmati, and aromatics. Milling and cooking-quality improvements of conventional long grains and specialty types remain major priorities, followed by resistance to cold-induced blanking and other agronomic and disease-resistance traits.

CONVENTIONAL LONG GRAINS

In conventional long grains, extensive cooking-quality screening and selection efforts have eliminated the majority of texture softness from California long grain breeding material. Consequently, the primary focus is currently on milling yield and cold tolerance.

L-206 is an early-maturing variety with high yield potential released for commercial production in 2006. It is well-adapted to most rice-growing regions of California, except the coldest areas of Yolo and San Joaquin counties. Milling yield of L-206 is 1% to 2% lower than L-204. Recent studies, however, show that L-206 is significantly more resistant to grain fissuring, indicating more stable milling yield at lower harvest moisture. Primary advantages of L-206 over L-204 are improved cooking quality, higher grain yield, and earlier maturity. Its cooking and starch characteristics are similar to Southern long grains.

Grain yield of L-206 in 2014 statewide yield tests averaged 9,170 pounds/acre. Average yield for M-205 in the same test sites was 9,370 pounds/acre. Average head rice yield of L-206 during the 2006 through 2014 seasons was 62%.

The long grain project is seeking to enhance quality and agronomic traits, including milling, cooking qualities, market acceptance, and grain yield. Entries 12Y020 and 11Y1005 performed well in 2014 statewide tests. Of special importance is the performance of these selections in both 2012 and 2013 at the Yolo test location, where they compared favorably with L-206 and M-206. Cooler conditions at the Yolo site have been challenging for many long grains in the past. Both entries are three days later than L-206 and about five inches taller. Milling yields of these lines averaged 3% higher than L-206. Overall kernel size and weight of 11Y1005 is the same as L-206. Kernels of 12Y020 are slightly larger than L-206. Quality evaluations indicate both entries have typical Southern long grain amylose and gelatinization temperature type. RVA amylographic profile of both lines is moderate—similar to L-206.

SPECIALTY LONG GRAINS

Expanded breeding efforts continued in specialty long grains, including jasmine, basmati, and conventional aromatics such as A-201. Specialty types occupy 50% of the long-grain nursery.

Calmati-202 is a true basmati variety released in 2006. It is an early-maturing, semidwarf, pubescent, aromatic, elongating long grain. Because of its susceptibility to blanking, it is not suited for colder locations. Average yield of Calmati-202 in 2014 early tests was 6,280 pounds/acre, compared to 9,250 pounds/acre for L-206. Grain and cooking quality of Calmati-202 is considerably closer to imported basmati types than Calmati-201. Because of its finer grain shape, the yield of Calmati-202 is 10% lower than Calmati-201. Calmati-202 is susceptible to fissuring. Thus, timely harvest and proper handling is needed to preserve milling and cooking qualities. Recommended harvest moisture is 19 percent.

Two improved experimental basmati lines—12Y1054 and 14Y149—were tested in 2014 statewide yield tests. Cooking quality evaluations of these lines in earlier generations have shown considerable quality advantages over Calmati-202. Line 12Y1054 is a very early maturing, pubescent, true basmati type. Line 14Y149 is an early basmati line with a significantly closer amylographic profile to imported basmati types.

Quality evaluations are underway to determine aging effects on elongation and texture of cooked grains of basmati types. This includes two advanced selections, 11Y158 and 10Y1199, that were previously tested. Primary advantages of these lines over Calmati-202 include higher cooked kernel elongation, more slender grain shape, and a cooked grain texture closer to imported basmati. Average grain yields in 2014 were 6,280 pounds/acre for Calmati-202, 6,040 pounds/acre for 12Y1054, and 5,680 pounds/acre for 14Y149.

Efforts continued in 2014 on jasmine types through pedigree and mutation breeding. Crosses and backcrosses were made with jasmine material from Southern U.S. breeding programs and foreign introductions. Photoperiod sensitivity of the original Thai jasmine variety Kao-Dak-Mali has been a significant breeding barrier. Pedigree and mutation breeding efforts are generating breeding lines with diverse and unique quality combinations.

In 2014, nine jasmine types were tested in statewide yield tests and 37 were in preliminary yield tests. Breeding objectives for jasmine types include low amylose, strong aroma, high degree of whiteness, and smooth cooked-grain texture. Entries 11Y106 and 12Y133 have shown good jasmine quality attributes and acceptable agronomic characteristics. Foundation seed increase of 11Y106 is planned for 2015. Efforts also continued in conventional aromatics. Two types entered statewide tests.

A-202

A-202 is a new early maturing conventional aromatic variety that was released in January 2014. It is intended as a replacement for A-301.

Compared to A-301, A-202 is nine days earlier, four inches taller, and has significantly higher seedling vigor. Grain yields in 2012 and 2013 statewide tests were 1,800 pounds/acre higher than A-301. In 2014 it was tested in all locations of the statewide tests. Average yield over all locations was 9,120 pounds/acre for A-202 and 9,270 pounds/acre for L-206. Because of a planting error, yields of A-202 and A-301 could not be compared.

Three-year average head rice yield for A-202 is 61%. Susceptibility of A-202 to stem rot and aggregate sheath spot is similar to A-201 and A-301. A-202 is susceptible to cold-induced blanking (as is A-301) and is therefore not recommended for cooler locations. Areas of adaptation include Butte, Colusa, Yuba, Glenn, and Sutter counties. Milled kernels of this new variety are slightly bolder than A-301. Amylose content, gelatinization temperature type, and starch profile is similar to A-301 and L-206. Subjective evaluations of cooked grain texture indicate that A-202 is slightly softer than L-206.

MILLING QUALITY

Continued improvement in milling yield and stability remains an important objective in the long grain program. Grain characteristics are being evaluated that will lend milling yield stability under adverse weather, and thus allow for a wider window of harvest.

In 2014, all specialty long grains in the preliminary and advanced yield tests were evaluated in special plots for milling yield evaluation. Advanced lines were evaluated at six to eight harvest moistures. Preliminary entries were tested at two harvest moistures. The goal for long grain is to maintain a minimum 64% head rice yield in advanced breeding lines.

DISEASE RESISTANCE

Stem rot resistance from the wild species Oryza rufipogon continues to be incorporated into an increasing number of high yielding, long grain lines. Despite a close linkage between the stem rot resistance trait with increased chalkiness and cold susceptibility, selections are being obtained that have broken this linkage and have a combined low stem rot score, low blanking, and high milling yield.

In 2014, one entry was tested in statewide tests and 18 were tested in the preliminary tests. Entry 13Y1037 is a stem rot resistant line that compared favorably with L-206 in grain and milling yield.

Short grains and premium quality

The short grain and premium quality project includes conventional short grains, premium quality short grains, premium quality medium grains, waxy short grains, low amylose short grains, and bold grains such as Arborio. Breeding goals emphasize improving grain quality, milling yields, and tolerance to cold temperature, lodging resistance, as well as very early to early uniform maturity, and resistance to diseases.

PREMIUM QUALITY SHORT GRAINS

Calhikari-202 (CH-202), released as a new premium quality short grain variety in 2012, continues to show its advantages over Koshihikari and CH-201 in yield, quality, taste, and agronomic traits.

In statewide yield tests from 2010 through 2014, CH-202 had higher grain yield that CH-201 in 33 out of 53 test environments. The five-year average was 8,555 pounds/acre, 4.7% higher than CH-201. CH-202 had 66% higher yield than Koshihikari in 2014. Except for similar seedling vigor ratings, CH-202 outperforms Koshihikari in heading (19 days earlier), lodging (13% less), head rice percentage (1% higher at 67%), and Satake Taste Analyzer rating (71 for CH-202 compared to 69 for Koshihikari). CH-202 also had lower protein concentration, which is associated with better taste.

Three premium quality short grain lines were evaluated in 2014 statewide tests. Two of them, 11Y2230 and 12Y2178, had higher yields than CH-202 by 8% and 9%, respectively. But these lines required seven and 10 days longer to heading. They are to undergo grain quality and taste tests.

PREMIUM QUALITY MEDIUM GRAINS

The top premium quality medium grain line is 11Y2183. It produced higher grain yields than M-402 in statewide tests in both the early maturing and the intermediate-to-late maturing groups by 11% and 14%, respectively. It also showed lower seedling vigor than M-401 and M-402, earlier heading than M-402 (nine days), shorter height, less lodging, and less blanking than M-401. Head rice is similar in length to M-401 and similar in width to M-402, and is less chalky than both M-402 and M-401. It was grown in the experimental seed increase nursery in 2014 and will be maintained in that nursery in 2015.

In 2014 there were eight premium quality medium grain lines evaluated in statewide tests. A noteworthy line is 12Y2175, which had higher grain yields and earlier heading than both 11Y2183 and M-402. It was entered into the early maturing preliminary group.

CONVENTIONAL SHORT GRAINS

Five conventional short grain lines were evaluated in 2014 statewide yield tests, with 09Y2179 and 10Y2043 evaluated in both the very early and the early maturing groups. Average grain yield of 10Y2043 was 9,970 pounds/acre, which was 22% higher than S-102 and 11% higher than 09Y2179. Both 10Y2043 and 09Y2179 had similar maximum yields of about 10,950 pounds/acre in statewide tests at the Rice Experiment Station in 2014 and 2011, respectively. Although 09Y2179 was high yielding, it headed 14 days later than S-102—unlike 10Y2043, which headed two days later than S-102. Because of this late heading, 09Y2179 will be dropped from statewide tests in 2015. Line 10Y2043, however, will be evaluated in statewide tests and will continue to undergo purification in headrows and experimental seed increase.

WAXY SHORT GRAINS

Line 09Y2141, which has been evaluated since 2010, was grown in the foundation seed increase field in 2014. It has been approved for varietal release as Calmochi-203 in 2015.

The line is a high-yielding semidwarf, early maturing, glabrous, waxy short grain line. In comparison to CM-101, released in 1985, 09Y2141 had significantly higher grain yield in all 38 statewide yield tests from 2010 to 2014. Maximum yield attained by 09Y2141 was 12,020 pounds/acre at the Colusa site. It is adapted to the same locations as CM-101. Averaged across test environments, yield was 9,650 pounds/acre for 09Y2141 and 7,590 pounds/acre for CM-101—a 27% yield advantage. Compared to CM-101, this line showed similar seedling vigor, was slightly taller, reached heading one day later, and had similar lodging.

Estimated days from heading to maturity were longer with glabrous 09Y2141 (57 days) than pubescent CM-101 (46 days). The 09Y2141 line matured in 136 days (early maturing) compared to 125 days for the very early CM-101. For this reason, 09Y2141 will be classified as an early maturing variety.

The erect flag leaves of 09Y2141 and their location above the panicles improves light interception for photosynthesis.

Average panicle blanking observed at the San Joaquin cold tolerance nursery was 9.3% for 09Y2141, compared to 6.7% for CM-101. CM-101 is the standard for panicle blanking resistance to low temperature and is usually observed to have low blanking percentages among short grain varieties in cold environments.

Both 09Y2141 and CM-101 showed similar, intermediate reactions to stem rot, aggregate sheath spot, and blast.

In terms of grain quality, 09Y2141 had higher head rice percentage at 65%, larger grain size dimensions, and lower viscosity when cooked. Head rice samples from 09Y2141 and CM-101 have no amylose, classifying them both as waxy rice, and alkali spreading values of 6, classifying them in the low-temperature gel type.

External evaluations on cooking quality indicate that 09Y2141 is softer than CM-101 and may be useful for soft mochi and traditional Japanese confectionery.

LOW AMYLOSE SHORT GRAINS

In 2014, there were no low amylose short grain entries in statewide tests. However, four entries performed well in preliminary yield tests. Lines 14Y2110 and 10Y2119 yielded 10,230 pounds/acre and 9,260 pounds/acre, respectively, compared to 6,710 pounds/acre for check variety Calamylow-201 (CA-201).

In the intermediate maturing group, glabrous lines 14Y2175 and 14Y2174 yielded 10,760 pounds/acre and 10,120 pounds/acre, respectively, compared to 7,110 pounds/acre for pubescent CA-201.

ARBORIO OR BOLD GRAINS

Arborio or bold grain rice types are grown on very limited acreage in California. RES has not released a variety of this type, although it released 87Y235 as a germplasm source in 1994.

Three lines evaluated in the 2014 preliminary yield tests showed yield advantages of about 15% over 87Y235. Grain quality analyses will be conducted and considered alongside yield and agronomic performance data to determine whether they advance in statewide yield testing.

Rice pathology

Breeding for disease resistance is a cooperative effort between plant breeders and the RES plant pathologist. About 3,013 rows were screened in statewide and preliminary yield tests for stem rot resistance in 2014. Since 2005, the immediate backcross program has screened entries for blast, stem rot, and aggregate sheath spot. Advancing generations from crosses have been screened for both stem rot and aggregate sheath spot resistance (408 rows, with additional greenhouse aggregate sheath spot screening). In addition, about 2,724 rows derived from breeder crosses have been cycled through the disease nursery to verify disease resistant lines.

STEM ROT

Screening for stem rot resistance included evaluations on about 6,130 rows. Of these, 2,814 rows were drill seeded, resulting in less seed drift and the establishment of more uniform stands.

In addition, 1,054 rows of a mapping population for identification of stem rot resistance genes from Oryza rufipogon were evaluated in the field at RES.

AGGREGATE SHEATH SPOT

The backcross program aims to transfer aggregate sheath spot resistance genes into M-206 and L-206. Populations from various backcrosses are being advanced in the greenhouse and in the field nursery. Some lines show resistance equivalent to that found in wild species. These materials have been put in cold storage for future reference.

Sheath spot screening was expanded into preliminary trial entries.

BLAST

Blast was lower in severity and incidence the last three years than in some prior years since it was first found in California in 1996. A few affected fields continue to be found, mostly on the west side of the valley. M-104 appears to be more susceptible than other varieties, followed by M-205.

Seedlings of all statewide entries were screened against a mixture of the IG1 and IB1 blast races in the greenhouse. This test should confirm the presence or absence of blast resistance genes and provide information on the relative susceptibility of lines without major genes.

The backcross program also seeks to introduce resistance genes into M-206. Only genes with a wide spectrum of blast resistance in worldwide tests have been chosen. Seven backcrosses have been made and screened for blast resistance. Four of these lines have been entered in the early statewide trial the last three years. They yielded more than M-208 and even as much as M-206.

Blast infection has been found in some M-208 fields every year since 2009. DNA testing confirmed that a new race of the fungus has been found. This new race is significantly different pathologically from IG1. Lines with different blast resistance genes from the M-206 backcross program were screened against M-208 isolates. Again, lines with the Piz and sometimes the Pik genes were susceptible. However, lines with other genes were resistant.

The components of M-208 were also tested individually. They are still resistant to the IG1 strain of the blast fungus but not the IB1 strain. It is too early to judge whether resistance has been overcome in M-208 since infection occurred in about one in 5,000 to one in 10,000 plants. The new race may be able to attack scattered M-208 plants, but it is unknown whether it will severely damage M-208 in the future.

A project by the DNA marker lab to screen for blast has been successful. Resistance genes have been pyramided into three lines and are being advanced for agronomic evaluation. These genes were chosen for their broad spectrum and complementary resistance to blast races. The presence of several resistance genes in a variety should prevent rapid loss of resistance when exposed to natural blast fungus populations.

More than 500 blast single-spore IB1 isolates were taken from M-208, as well as typical IG1 isolates, and screened against monogenic and near-isogenic lines. (Monogenic lines have only one blast resistance gene, while near-isogenic lines have one gene per line.) This screening also evaluated and ranked all gene sources for resistance to IG1 and IB1 isolates.

COMBINING RESISTANCE

The first attempt at combining resistance to blast, stem rot, and aggregate sheath spot is in progress.

This effort involves a cross of a four-gene blast pyramid line with a stem rot resistant line. It has undergone rapid generation advance with greenhouse disease screening for blast and stem rot in 2014.

A fifth generation line will be screened against stem rot in the field in 2015. A portion of the seed will be used in aggregate sheath spot screening in the greenhouse. Scientists hope to identify agronomically acceptable lines with resistance to all three diseases in this way.

DNA marker laboratory

The DNA marker laboratory supports the different breeding programs and special projects. In 2014, the lab was involved in marker-assisted selection for different grain types, DNA fingerprinting various rice materials, pyramiding of blast resistance genes, genetic mapping of stem rot resistance genes, herbicide resistance screening, and mutagenesis. However, the bulk of the work in the DNA lab last year was in three areas: marker-assisted selection for different grain types, fingerprinting materials, and mapping stem rot resistance.

MARKER-ASSISTED SELECTION

Marker assisted selection for both blast resistance and grain quality is now a routine part of work in the DNA marker laboratory. In 2014, 5,400 breeding lines from the medium- and short-grain projects were screened for blast resistance. A total of 4,770 plants were screened for blast resistance in the medium grain project. Similarly, a total of 630 plants were evaluated from the short grain project. About 1,800 long-grain breeding lines were evaluated using five DNA markers for grain quality.

DNA FINGERPRINTING

Another important function of the DNA lab is to assist in variety identity and purity assessment—DNA fingerprinting. A database begun in 2010 now has 220 markers that have been run against 50 rice varieties. The lab has developed a panel of 11 markers that can distinguish California medium grains from each other. A similar panel is in development for short- and long-grain varieties.

In 2014, researchers conducted fingerprinting of various breeding materials for the medium grain project. About 1,030 lines, consisting of 08Y3269 and M-202 head row samples, M-401 mutant lines, and medium-grain quality lines, were assessed with different markers.

Twelve markers were used to evaluate the advanced medium grain line, 08Y3269 (approved for release as M-209).

In the long grain project, about 135 entries—experimentals and mutants—were fingerprinted.

Variety identification also was conducted on commercial rice to answer seed contamination questions.

MAPPING STEM ROT RESISTANCE

An advanced backcross line from 87Y550/M206*2 has been used to map stem rot resistance from Oryza rufipogon. Microsatellite markers continue to be added to the genetic map begun in 2010 and field tested to verify stem rot resistance across seasons and locations. Several genes control stem rot resistance. DNA segments called quantitative trait loci associated with resistance have been identified.

In 2014, a trial at the Rice Experiment Station evaluated 340 lines from a fine mapping population. Tissues were harvested and DNA extractions performed for use in ongoing genotyping work using 29 markers. Another replicated stem rot evaluation may be conducted in 2015.