Twenty new very early experimental lines (heading in less than 90 days at Biggs) were compared with M-101, M9, Earlirose, and S-201. Eleven of the 12 highest yielding lines were short-grain types. Many of these were two to seven days earlier than S-201, which was the leader in average yields. Two medium-grain types averaged 600 pounds per acre more than M9 and 1,100 pounds more than M-101. One is as early as M-101.

The rice panicle is formed at ground level about 30 days before heading. Top: First signs of developing panicle. (250x) Bottom: Rice panicle about five days later. (100x)

Nineteen early lines (heading in 90 to 99 days at Biggs) were compared with standard varieties S-201, L-201, M9, Calmochi-202 and the tall variety S6. Twenty of the 23 short-statured lines in this test produced yields superior to M9, indicating that further yield increases are still possible. In these trials, S-201 and L-201 ranked third and eighth, respectively.

Twenty-four late varieties and experimental lines were tested in four locations. All of these reached 50 percent heading at Biggs in more than 105 days. M-401, the new variety released in 1981, showed an average yield of 9,780 pounds per acre. Fifteen of the experimental lines were better than M7.

A trial was conducted in the Sutter Basin to determine the potential of a number of very early varieties for double cropping after wheat. From a June 11 planting date, the average yield of all 24 lines was 7,880 pounds per acre, with some cultivars yielding 8,300 pounds per acre. Several other experiments were conducted cooperatively with farm advisors and other project leaders, including studies on nitrogen and zinc fertilization practices, relative grain versus straw production, calcium peroxide seed coating, and a cooperative effort on sample collecting and field monitoring with Chevron's experimental Bolero program.

Table 1. Characteristics of Publicly Developed Rice Varieties-1983

Grain	Height*	Maturity	Seed widely available	Comments
Short
S6	Tall	Early	1977	Replaced Colusa, wide adaptation but only moderate resistance to blanking. Has irregular maturity. Replaced by S-201. Foundation seed no longer available.
S-201	Short	Early	1981	Very high yield potential, replaced S6; more resistance to blanking than S6; maturity like S6.
Medium Grain
M-101	Short	Very Early	1981	Earliest variety; excellent seedling vigor; good resistance to blanking best suited for special conditions such as cold areas and/or late planting dates; head rice can be low, so harvest as near to 25% moisture as possible to enhance head yield. May not yield as well as other varieties at normal planting dates.
M9	Short	Early	1979	Very high yield potential in warmer areas; not adapted to colder areas or to very early seeding because of poor seedling vigor; mixed maturity of seeds on panicles. Somewhat difficult to thresh cleanly - special harvest adjustment may be necessary. May be more susceptible to sheath blight.
M-201	Short	Early	1984	Same maturity but with improved yield potential compared to M9; 2-3 inches shorter than M9 with greater resistance to lodging. Intended as a replacement for M9.
M-301	Short	Intermediate	1981	High yield potential, replaced M5; good seedling vigor and resistance to blanking, can be seeded 10 days later than optimum date for late varieties, or earlier to spread harvest season; straw strength not as good as M7. Foundation seed no longer available.
M-302	Short	Intermediate	1983	Replaced M-301; has better straw strength; more translucent grains; is about 2 days later; has good seedling vigor and resistance to blanking. Can be seeded 7 or 8 days later than late varieties to spread harvest season.
M7	Short	Late	1979	High yield potential; good seedling vigor and resistance to blanking; very good straw strength.
Calrose 76	Short	Late	1979	High yield potential; good seedling vigor and resistance to blanking; rough hulls and leaves; long awns in warmer areas.
M-401	Short	Late	1983	Intended as a premium quality rice and not as a replacement for M7. Has high yield potential; 3 days earlier than M7 but lodges more and is more sensitive to blanking. Sensitive to early draining and over fertilization.
Long Grain
L-201**	Inter- mediate	Early	1981	Very high yield potential in warmer areas; not adapted to colder areas; injury by Ordram® has been observed at rates greater than 3 a.i. lbs/acre; threshes readily at low cylinder speeds. Harvest at moisture content as near to 25% as possible to enhance head yield; matures in 7 to 10 fewer days after heading than do short- or medium-grain varieties.
Sweet
Calmochi -202**	Short	Early	1983	A sweet rice replacing Calmochi-201. Similar to S-201 in growth characteristics but 2 days later. Has smaller seeds. Yield much greater and lodges less than Calmochi-201, but yields not as high as S-201.
* The varieties with short height have replaced rapidly the tall varieties. Proper management of the short-stature varieties to obtain high yield includes: (1) managing water depth and other factors to obtain a dense stand; (2) good weed control; (3) nitrogen fertilization of 20 to 40 units higher than has been used for tall varieties; and (4) draining as late as possible before harvest.
** L-201 and Calmochi varieties should not be grown unless arrangements have been made first with a marketing agency.
PREPARED BY THE CALIFORNIA COOPERATIVE RICE RESEARCH FOUNDATION AND THE UNIVERSITY OF CALIFORNIA COOPERATIVE EXTENSION