Agronomy Fact Sheet Series 2007-3

Authors

F. Jodari, plant breeder, Rice Experiment Station, Biggs, CA

C.W. Johnson, plant breeder, Rice Experiment Station, Biggs, CA

J.J. Oster, plant pathologist, Rice Experiment Station, Biggs, CA

K.S. McKenzie, plant breeder and director, Rice Experiment Station, Biggs, CA

J.E. Hill, Extension Agronomist, Dept. of Agronomy and Range Science, UC Davis

W.M. Canevari, C.A. Greer, R.G. Mutters,  are Farm Advisors, UC Cooperative Extension, San Joaquin, Butte Colusa/Yolo /Glenn and Sacramento/ Sutter/Yuba counties respectively

R.L. Wennig, staff research associate, Dept.of Plant Sciences, UC Davis

Introduction

L-206 is a conventional long-grain quality rice variety released for commercial production in California in 2006. Cooked grain texture of L-206 is harder than L-204 as indicated by its amylographic profile and therefore compares favorably with Southern US produced long-grains. Milling yield of L-206 is 1-2 percent lower that L-204. The primary advantages of L-206 over L-204 are improved cooking quality, higher grain yield, and earlier maturity.

Description

Agronomic characteristics of L-206 have been compared with L-205 and M-202 in the following table. L-206 is a photoperiod insensitive, very early to early maturing, semi-dwarf, long-grain variety. Its seedling vigor is similar to L-205 and slightly lower than M-202. Days to 50% heading is an average of 4 days earlier than both L-205 and M-202. L-206 is 6 cm shorter than l-205 and 11 cm shorter than M-202. Lodging potential is not significantly higher than L-20-5; however, due to earlier maturity plants may lean due to excessive dryness after harvest maturity. Susceptibility to cold induced blanking (greenhouse blanking score), and susceptibility to stem rot and aggregate sheath spot pathogens of L-206 is not significantly different from L-205 and M-202. Seed size is slightly smaller than l-204, slightly larger than l-205, and slightly larger than most Southern US varieties.

Performance

Grain yield of L-206 averaged aver 6 years (2000-2005)was 10170 Ib/acre at RES, similar to L-205 and significantly higher than M-202. The average yield .of L-206 at Sutter-east, the cooler test location, was 8930 Ib/acre which was not significantly different from L-205 or M-202. Yields of L-206 at the colder locations .of Yolo and San Joaquin and the warmest location at Glenn were not competitive with M~202, (data not shown). Grain yields of L-206 tested in additional locations of Colusa, Yuba, Butte, and Sutter-west sites. during 2005 and 2006 were not significantly different from L-205 or M-202. Milling yield average of L-206 from the 2001 - 2005 tests at RES was 62 percent compared to 63 percent for L-205.

Table 1. Summary of Agronomic Characteristics for
L-206, L-205, and M-202
averaged over Sutter-East and RES locations during 2000-2005

1 -Seedling vigor visual score where 1-poor and 5=excellent
    2 -Stem rot score where 0=no damage and 10=plant killed
    3 -Number of top leaves killed by aggregate sheath spot
    * - Significantly different from L-206 (0.05 probability level)

Area of Adaptation

L-206 should be adapted to all but the coolest rice growing areas of Yolo and San Joaquin counties and the warmest areas of Glenn County. Greenhouse tests indicate that L-206 is slightly more resistant to cold induced blanking than L-204. In the warmest areas of California's rice production region, very early varieties such as L-206 may not reach their maximum yield potential because of excessive earliness and inability to take advantage of a longer growing season.

Management Guidelines

The following guidelines are based on research, observation and experience acquired in the development and testing of  L-206. Suggested cultural practices are intended to assist in the production of optimum yields and quality of L-206.

• Uniform water depth, fertility, seed distribution and weed control are important because they affect uniformity of heading, harvest moisture and in turn grain and head rice milling yield.
• Fertilizer rates and management should be similar to those used for medium-grain varieties. Due to a shorter plant height, L-206 may tolerate slightly higher rates of nitrogen than taller varieties.
  However, excessive nitrogen use should be avoided since it is more likely to delay maturity in cooler areas, increase disease, and reduce grain quality.
• Preferred seeding dates are May 1 to 15. Later seeding dates increase the risk of cool temperature induced blanking. L-206 should be seeded at the rate of 130 to 150 lbs/acre. Early season water depth should be maintained uniformly at about 2 to 4 inches to promote optimum tillering and stand establishment.
• L-206 is less resistant than medium grains to cold induced blanking. Water depth should be increased to 8 inches before panicle initiation (50 to 55 days after planting) until heading to protect panicles from exposure to low temperature during cool nights. L-206 has not performed as well as medium grain varieties in cooler San Joaquin and Yolo County sites and may not be suitable for these areas.
• Draining L-206 too early will reduce grain and milling yields. Grain ripening period is about 40 to 45 days after 50% heading. L206 fields shouldˇ be drained in reference to this ripening period to avoid soil moisture deficiency before the optimum harvest time.
  Maximum milling yield is obtained when grain moisture at harvest is 17% and the soil is still relatively moist. Harvest moistures as low as 15% may also yield maximum head rice in certain years. However, the risk of rapid decline in milling yield will increase if adverse weather condition such as heavy dew or rain occurs. Caution should be taken to prevent grain moisture from dropping too low before harvest, but harvest should not begin until grain moisture falls below 19%. L-206 will dry down significantly faster than medium grains. It will also thrash easier than medium and short grains, so the harvester cylinder speed should be reduced to promote maximum head rice yield.