Objectives

The varietal improvement program headquartered at the Rice Experiment Station at Biggs has primary responsibility for developing improved varieties. Desired characteristics are high yield, good cooking and milling quality, resistance to lodging, low temperature tolerance, resistance to disease and insect pests, tolerance to herbicides, and good seedling vigor. The breeding program includes short, medium, and long grain types, sweet rice, and a range of maturity types to meet the requirements of the California rice industry.

Aerial view of experimental plots at the Rice Experiment Station.

Progress from rice breeding has resulted in essentially all growers using improved varieties, with emphasis on the early maturing ones. Hazards from unfavorable weather in early spring and late fall have greatly decreased interest in growing varieties requiring over 105 days (intermediate maturity) to reach 50 percent heading. The statewide estimated average yield was 7,040 pounds per acre for 1983. The most recent three-year average is 7,030 pounds per acre.

Variety Release in 1984

The new long-grain variety L-202 is ,being released to growers in 1984, with 550 hundredweight of foundation seed available. This variety is early maturing (approximately 90-92 days to 50 percent heading), semidwarf stature, highly resistant to lodging and has been judged acceptable for both the domestic and export markets by the two major cooperatives.

Reaction of L-202 to stem rot and sheath blight was similar to M9 in tests at Biggs. L-202 gave good milling appraisals in 1982 and again in 1983, averaging 57.4 percent head rice when harvested over a range of moistures. Seedling vigor is weaker than that of California short grain or medium grain varieties. Blanking response is similar to M9 and M-201. Like other long grains, L-202's heading is delayed more by cool temperatures than are the short and medium grain varieties. L-202 is highly responsive to nitrogen fertilizer and has given high yields in statewide tests conducted during the past two years. It is adapted to the warmer 50 to 60 percent of California's rice growing area. Unlike L-201, L-202 is tolerant to Ordram© and Bolero@ herbicides.

Varieties on the Horizon

An early maturing smooth, medium grain experimental variety has continued to perform well since first yield tested at the Rice Experiment Station in 1981. It is considered a candidate to replace M9 in the cooler areas. Head rice yield in 1983 averaged over several harvest moistures was exceptionally high. Plans are to grow 10 acres or more in 1984 for probable release in another year if it continues to give good performance.

Other promising experimental varieties are a long grain with very high grain yield but lower head rice yield, an intermediate-maturity short grain that may be an improvement over S201 in milling yield and grain appearance, and a high yielding very early maturing sweet rice. A small increase of the sweet or mochi rice will be made in 1984 to provide grain for industrial evaluation.

Breeding Procedures

The combinations of characteristics desired in new varieties are achieved by making crosses among selected parents and by radiation to induce mutations. During 1983, over 1,100 new crosses and back crosses were made. The segregating or F2 generation from these crosses will be grown in 1984. Also during 1983, the second generation plants from 1,015 crosses were grown on 28 acres. About 300,000 panicles were selected from individual plants of these populations. From 25,000 to 30,000 third generation lines from crosses, and a like number of higher generation selections will be grown in three-foot or four-foot panicle rows in 1984 for further selection and purification.

Grain Quality

Grain quality is measured by chemical and cooking characteristics, grain translucency, grain size, and head yield. Rice from 2,450 selections that had passed other tests, almost all long grains, was milled and sent to the USDA Laboratory at Beaumont, Texas, for determing the percent amylose and alkali spreading reaction. The information obtained was used as a basis for discarding atypical lines before planting in 1983.

The new long grain variety L-202 has been selected for resistance to the herbicide Bolero.

Actual cooking tests are conducted to further classify long grain experimental lines that pass the quality tests made at Beaumont. In 1983, five or 15 grams each of 3,300 rices were cooked and evaluated for fluffiness. Several of the long grain experimental lines have cooking and other quality attributes that approximate those of quality southern U.S. long grain rice. Finally, a few of the most promising lines were provided to segments of the industry for quality evaluations.

Strong selection pressure was practiced for grain breakage, translucency, grain size and grain shape. About 20 percent of the 300,000 panicles examined during the winter and early; spring are retained for seeding and further selection. Translucency is difficult to combine with large grain size and non-angular shape in short grains.

Head rice yields are difficult to assess accurately because they are influenced by many environmental factors. Efforts will be expanded in 1984 to evaluate the heritability of head rice differences and to determine the range of differences among advanced experimental and currently grown varieties when harvested at comparable moisture levels. In addition, a pilot study will determine the range of variation of head rice of less advanced experimentals.

Progress is being made in combing many desirable characteristics in early-generation populations. The increased emphasis on breeding for disease resistance appears to be successful in transferring an increased level of resistance to stem rot into California-adapted backgrounds. These improvements will become evident in future varietal releases. Future variety releases also are expected to show improved grain quality and increased yield stability throughout the rice growing areas of California.