THE RICE RESEARCH STATION --USDA--UC RICE BREEDING PROGRAM

NEW VARIETIES--NOW AND SOON TO COME

Highlights

• New varieties M5 and S6 perform well in '75
• Short-stature D7 proposed for release as "Calrose 76"
• Early short-stature medium-grain seed supplies increased
• Late short-stature medium-grain seed supplies increased
• Very early pearl is promising
• New long-grain ready for release
• Short-statured M5 and S6 may evolve from irradiated lines
• Smooth D7, early D7, and early smooth D7 are under test

Marked progress toward new rice varieties for California continued in 1975. These have a higher yield potential, reduced lodging, and other desirable characteristics. Primary responsibility for varietal development rests with the Rice Experiment Station at Biggs. The facility is owned and managed by the rice industry.

Complementing the rice plant-breeding program at the Rice Experiment Station is basic genetic, plant physiology, and disease and insect resistance research conducted by scientists of the USDA and University of California, stationed at Davis. Plans to phase out old varieties as new ones become available are being developed by Directors of the Rice Experiment Station and the California Crop Improvement Association (the official seed certifying agency).

NEW VARIETIES M5 AND S6 PERFORM WELL

þ M5 (early smooth medium) was available in 1975 for the first year of fairly extensive commercial plantings. Grower reports have been exceptionally favorable. Except for being 10-12 days earlier, M5 is essentially identical to CS-M3. In replicated state-wide yield tests since 1972, M5 has yielded 5% less than Earlirose, 7% more than Colusa, and equal to CS-M3.

þ Seed from about 1400 acres of S6 (smooth pearl) has been approved for certification. This should be enough to plant 40,000 acres in 1976. S6 is an excellent replacement for Colusa, averaging 13% higher yield than Colusa in 1975, as in the previous 4 years.

þ EARLY SHORT-STATURE MEDIUM IS INCREASED

Approximately 125 cwt of seed was produced of the smooth large medium-grain experimental 74-Y-52. It is of Earlirose maturity, has short straw that resists lodging, good head rice, and translucent kernels. In state-wide tests it averaged 8 cwt more yield per acre than M5. A possible disadvantage is that small pieces of panicle branches remain attached to some threshed seed. The seed supply will be increased further in preparation for naming and release.

LATE SHORT-STATURE MEDIUM IS INCREASED

About 50 cwt of seed was produced of the late smooth medium-grain experimental 81659, which we also refer to as short-stature CS-M3. It is like CS-M3 but is about a foot shorter, lodges less, and yields more. In test plots at Biggs, it averaged 101.2 cwt per acre. Seed will be increased further for possible naming and release.

þ D7 PROPOSED FOR RELEASE AS "CALROSE 76"

The short-stature Calrose selection D7, produced by the USDA and UC Davis, continued to perform well. If all goes well in 1976 it will be released in 1977 under the name "Calrose 76." Table 1 summarizes four years of data on the agronomic performance and kernel characteristics of D7. Its merits: high yield, short stature, lodging resistance, cold tolerance equivalent to CS-M3 and Calrose, and grain quality equivalent to CS-M3 and Calrose. We conclude that D7 is essentially identical to Calrose except for being 10 inches shorter (14 inches shorter than CS-M3). It has longer awns and is more resistant to lodging. A 24-acre seed increase is planned for 1976. D7 is also being widely used as a short-stature parent with tall varieties to produce even better varieties for future use.

 

Table 1. D7 performance, 1973-1975
	CS-M3	D7
Yield, lb/A (19 tests)	7198	7531
Height, inches (14 tests)	48	34
Lodging, % (15 tests)	45	18
Seedling vigor score (1=poor, 5=good; 13 tests)	4.00	3.96
Awn length, inches, Davis, 1975	0.06 (Calrose)	0.18
Awn length, inches, Butte Co., 1975	0.17	0.56
100-kernel wt., paddy, grams (9 tests)	2.66*	2.64
100-kernel wt., brown, grams (5 tests)	2.16	2.16
100-kernel wt., milled, grams (5 tests)	2.08*	2.07
Head rice , % (5 tests)	68.8	69.1
Amylose, % (5 tests)	18.8	18.4
* Average of CS-M3 x Calrose

þ LONG GRAIN

The long-grain 72/3764 again performed well in state-wide tests. It lodges less than current varieties and has yielded more than CS-M3 in all tests except where stem rot was serious or at the very coldest locations. This long grain is more susceptible to stem rot. It has larger seeds than present southern long-grain varieties. Its physicochemical properties are similar to theirs, and the new California long-grain variety has been judged broadly acceptable to the industry. Our new long-grain has a lower head rice than short- or medium-grain varieties. That apparently would not be a problem if the grain is parboiled. Approximately 300 cwt are available for testing market acceptability. Additional pure seed is available for further seed increase should our industry decide to go ahead with it to capture new markets for California-grown rice.

þ VERY EARLY PEARL IS PROMISING

A very early-maturing pearl, 74-Y-10, has somewhat oblong translucent seeds, lodges much less than currently available early varieties, has high head rice, and heads 8 to 9 days earlier than Earlirose. In 2 years of tests it has averaged 69 cwt per acre, compared with 54 cwt for Maxwell and 77 for Earlirose. 74-Y-10 yielded more than Earlirose at Biggs under high fertility, and lodged much less.

This experimental, the best we have in the very-early-maturity group, should perform well if such earliness should be needed.

IRRADIATION OF VARIETIES

X-2 generations (second generation after irradiation) were grown by Rice Station breeders of populations of several varieties, including M5 and S6. Shorter plants selected from each population are hoped to produce short-stature counterparts of these varieties.

þ DEVELOPMENT OF SMOOTH D7, EARLY D7, AND EARLY SMOOTH D7 AT UCD

Several smooth D7 (SD7) lines yield-tested in 1975 gave promising results. These lines were developed from 1972 crosses of CS-M3 x D7, followed by selection for short-stature smooth-hull recombinants. In general these lines perform like D7 but have the advantage of smooth hulls.

An early D7 (ED7) line was selected in 1974. In 1975 this line was 15 days earlier than D7 at Davis, and also had short stature. Yield-tests of this short-stature line are planned in 1976 in areas suited for Earlirose.

Crosses have been made to develop early smooth D7 (ESD7) lines. Some 15 ESD7 lines are under winter increase. These short-stature lines, 8-15 days earlier than D7 or CS-M3, will be yield-tested in 1976.

REPORT ON THE RICE BREEDING OBJECTIVES

The above summarizes the long strides toward earlier-maturing non-lodging short-statured rice varieties. Now, read about companion plant breeding progress.

BREEDING FOR EARLY MATURITY

The overall breeding aim is adapted varieties representing a range in maturity from about 10 days earlier than Colusa to a few days earlier than Calrose or CS-M3. Such earlier varieties would provide more latitude for preparing adequate seedbeds, permit an earlier harvest, facilitate residue disposal, and in some cases fit into a double-cropping system. Under test in 1975 were many very early pearl and medium-grain lines heading up to 10 days earlier than Colusa.

INCREASED YIELD

In 1975, in cooperation with the Extension Service, plant breeders tested 369 experimental rices and check varieties in combine-size plots in 2 or more tests as follows:

Maturity Group	# of Entries	# of Tests
Very Early	30	3
Very Early (Preliminary)	59	2
Early	31	6
Early (Preliminary)	108	2
Late	26	5
Late (Preliminary)	114	2

This program is a key part of the variety improvement program, permitting tests of all promising lines under a wide range of environmental conditions before the best performers are released for commercial use. In brief, the 1975 yield trials revealed:

1. Among the very early lines, only four averaged higher yields than Earli. rose (the best yielded 740 pounds more per acre).
2. þ Among the early lines, seven outyielded Earlirose, one by 710 pounds per acre. Twenty-three outyielded Colusa, one by 1670 pounds per acre.
3. þ Twenty-five late-maturing varieties and experimentals were compared in Butte, Glenn, Sutter, Fresno, and Kern counties. Average yields ranged from 66 cwt per acre to 91.9 (74.7 cwt for the CS-M3 check variety). The promising long-grain experimental, 72/3764, averaged 79.5 cwt. The short-stature D7, tentatively named "Calrose 76", averaged 80.6 cwt. Ten experimentals averaged higher yields than D7, but heading of several of these was delayed 7 to 8 days at the coldest test site (Sutter).

SHORT STATURE AND LODGING RESISTANCE

Plant breeders continue to select for short plant height and for resistance to lodging at all levels of testing -- rows, small plots, and in combine-size plots. Most of the high-yielding short statures that come through the water satisfactorily will average about 36 inches tall under high fertility conditions (about a foot shorter than present varieties under such conditions). These short-stature types do not lodge during the grain filling period, the time when yields are particularly depressed by lodging. They sometimes undergo partial lodging as harvest time approaches, though not as much as do tall varieties.

SEEDLING VIGOR

We now have many experimental short-stature lines that closely approach the seedling vigor of our current tall varieties. That is not to say that the new high-yielding short-stature types express their full yield potential in deep water. Since short-stature materials seem to express their reduced plant height at an early date (before maximum tillering), water deeper than 6 inches early in the growing season would probably reduce stand density.

þ RESISTANCE TO BLANKING

Breeders continue to eliminate breeding lines that. show excessive blanking. That has been a continuing problem in crosses derived from tropical germplasm. The short-stature line D7 has provided an invaluable new genetic source for short-stature crosses. This year was cooler than normal and the breeders discarded many lines that reacted with delayed maturity and/or blanking. Even so, many lines that perform satisfactorily at Biggs are delayed excessively in heading and also blank severely at the coldest sites, such as at Davis. The growing of several hundred lines each year at the Davis facility has been helpful in this screening. Also helpful in screening fairly advanced lines for resistance to blanking has been the new greenhouse facility at the Rice Experiment Station for controlled cool night temperatures.

INCREASED PROTEIN CONTENT

Protein is of key importance in human nutrition. For this reason, research emphasis is being directed toward determining ways of increasing the protein quality and content of California rice. From the Biggs early-maturing rice variety trial grown in 1974 at 130 lb of nitrogen and 180 lb per acre preplant, brown rice seed of 13 entries at each nitrogen level was analyzed for protein. The higher nitrogen rate resulted in more protein in the rice -- 7.8% vs. 7.2%. Varieties differed in protein from 6.6% to 8.4°/a (S6 averaged 7.1%). In 1975 tests the two standard California check varieties averaged more than 1% less protein than the 82 experimental lines selected for higher protein.

GRAIN QUALITY

Chemical and Cooking Characteristics:

Percent amylose and alkali reaction (chemical measures of rice quality) were determined on 3155 lines in early 1975 by the USDA laboratory in Beaumont, Texas. Those results were a basis for discarding lines lacking the combination of amylose and alkali reactions representative for rices of short, medium, and long grain. Varieties that reach the seed-increase stage are evaluated also by experts for taste and cooking behavior.

Translucency and Seed Size:

The plant breeders apply strong selection pressure for kernel translucency, seemingly extremely difficult to get in a large round pearl rice. Selecting pearls for translucency almost invariably gives somewhat small seed and/or a slightly oblong shape. With potential pearl, medium, and long-grain varieties, however, progress toward improved seed appearance is generally good.

Head Yield:

Potential new varieties at the stage of preliminary seed increase are harvested at several moisture levels and dried by accepted commercial procedures, and the percent head rice is determined. Only those with acceptable head rice are considered for further seed increase.

STEM ROT RESISTANCE

Besides the work at the special stem rot screening nursery, breeders routinely select for tolerance to stem rot in all breeding nurseries. The UC Davis Department of Plant Pathology assists in this screening.

ADDITIONAL CHARACTERISTICS;

Aside from the primary characteristics, plant breeders select also for absence of awns or for small awns, good tillering ability, erect stiff darkgreen leaves, and good panicle exsertion. They continue to select both smooth- and rough-seeded kinds. They select for tolerance to currently used herbicides and resistance to shattering but avoid lines that are hard to thresh.

Limited efforts continue toward developing a good sweet rice variety for California. In addition, a few scented rices have been used as parents in the long-grain breeding program. A scented rice might result as a by-product of this program.

UC entomologists, in cooperation with the plant breeders, have identified a promising source of tolerance to the rice water weevil. Seven crosses have been made between this source (WC 1403) and promising short-stature lines. Second-generation seed will be available for screening in 1976.

INTRODUCTION OF FOREIGN GERMPLASM

Since 1969 over 10,000 rice cultivars have been introduced from foreign countries and grown under strict U. S. quarantine regulations by USDA and UC scientists at the University of California Imperial Valley Field Station near E1 Centro. The program is partially funded by the Rice Research Board.

In 1975 rice lines from five general groups containing 565 varieties were introduced, seed-treated, planted, grown, inspected, harvested, threshed, packaged, and distributed. The material introduced was: 35 saline-resistant lines, 23 lines from Brazil, 451 lines in the IRRI cold-water nursery, 36 lines from mainland China, and 17 lines grown in 1974 which produced no seed.

This phase of the rice research program will likely be suspended in 1976, at least temporarily, since most of the required germplasm has been introduced.

EXTRA DIVIDENDS FROM IMPERIAL VALLEY RICE RESEARCH

Work on control of rice water weeds by fish was conducted in cooperation with an irrigation district fish biologist working on control of weeds in irrigation ditches in the Imperial Valley. In this research, young fish of the species Tilapia mossambica were introduced after the rice had emerged from the water. Weeds were controlled that germinated after fish population build-up was sufficient (usually within 2 weeks). Algae and water weeds growing in or on the water were also controlled almost completely. Since these fish die when water temperatures drop below 60°F, annual stocking would be required if they were permitted for biological weed control in Central Valley rice fields and irrigation systems.