Breeding - 85
 

 

 

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Project Leader and Principal Rice Experiment Station Investigators

Howard L. Carnaban, plant breeder

S. T. Tseng, plant breeder

Carl W. Johnson, plant breeder

Jeff J. Oster, plant pathologist

 

Objectives

The general objectives of the rice breeding program at the Rice Experiment Station at Biggs are to develop varieties with a range of maturity for long, medium and short grain types as well as specialty rices for limited markets.

Desired plant characteristics common to all varieties are high yield; resistance to lodging; resistance or tolerance to diseases, insect pests, low temperatures and herbicides; and good grain quality.

Breeding for Early Maturity

The breeding, release and widespread use of earlier maturing varieties has advanced average harvesting time by 10 to 15 days. This has reduced the threat of unfavorable weather during reproduction and harvest. It also has alleviated somewhat the problem of straw disposal, as atmospheric conditions for straw burning are more favorable earlier in the fall.

The problem of obtaining good yields from very early maturing varieties has been addressed. Excellent progress also is being made in improving the grain quality of early and very early maturing rices.

Early maturity continues to be an important thrust of the rice breeding program.

Increased Yields

Figure 1: Average California yields,  1976-1985

Average statewide rice yields have shown spectacular improvements over the last 10 years (Fig. 1). The 7,400 pounds per acre in 1985 is the highest on record.

Rice yields in the other rice growing states (Arkansas, Louisiana, Mississippi, Missouri, and Texas) also rose spectacularly with an increase of nearly 23 percent from 1983 to 1985. Although the 1985 average statewide yields in these five states of just over 5,000 pounds per acre is still well below California's 7,400 pounds, these differences may narrow with the yield increases indicated in the southern states (Fig. 2).

The yield potential for rice still far exceeds present yields, and improvements are expected to continue.

Lodging Resistance

Figure 2: Average yields of rice growing states in 1985

The short stature varieties now grown in California have provided growers with the means of more efficient harvesting with less straw to be burned. Short stature alone does not assure resistance to lodging. The current high

yielding varieties also require stiffer stems. Future varietal releases should have as good as or better lodging resistance than current varieties.

Improved Grain Quality

Grain quality characteristics are measured by chemical analysis, cooking tests, translucency visual qualities and head yield. All promising long grain selections (nearly 2,400 in 1985) are tested for amylose content and gelatinization temperatures of the starch by the USDA Rice Quality Laboratory in Beaumont, Texas. These tests are used to eliminate experimental lines that do not meet acceptable standards.

Unknown factors contribute to differences in cooking characteristics of long grain varieties. Small samples are cooked and evaluated for fluffiness.

Selections also are screened for translucency, grain size, grain shape and breakage. Translucency of short grain types is being improved but, in this process, there is a tendency to shift from the typical round pearl shape to a slightly oblong shape.

Head yields are influenced by environmental and genetic factors. Inherited factors that may influence breakage during shelling and milling are kernel shape, plumpness and chalkiness. Uniformity of heading time and uniformity of kernel maturity within panicles also contribute to improved head rice. More attention is being given to milling quality by rigid selection for all heritable characteristics that improve head rice yields, but it must be recognized that environmental factors such as moisture content at harvest and mechanical factors such as combine adjustments strongly influence head rice yields of all varieties.

Recent research indicates that long grain varieties should be harvested at a lower moisture percentage (19 to 22) than short and medium grain varieties whose optimum harvest moisture is 21 to 26 percent.

Disease Resistance

The rice breeding program continues to emphasize selection for disease resistance. Although absolute resistance to stem rot and aggregate sheath spot has never been found in cultivated rice, there are varietal differences in susceptibility, and progress is being made in selecting for more disease resistance within fairly high yielding lines Progress also is being made in the slow process of transferring disease resistance from wild species of rice to cultivated rice with acceptable agronomic and grain characteristics.

Rice Water Weevil Tolerance

It is not possible to predict when weevil tolerant varieties with acceptable yield and quality will be developed, but the goal is worthwhile and the work is being continued.

New Variety Prospects

The new variety M-202 released to growers in 1985 will be available for commercial production in 1986. M-202 is more resistant to blanking and shatter losses but more susceptible to stem rot and lodging than M-201. Yields are comparable to M-201.

Foundation seed of the new variety Calmochi-101 is adequate for production in 1986. It excels most other varieties for resistance to blanking, has pubescent leaves and hulls and dries faster from heading to harvest than smooth varieties. It is 17 days earlier than Calmochi-202, has larger kernels and has yielded more.

A possible replacement for M-101 has higher yields, higher head rice at the lower moisture contents at harvest, better straw strength and significantly better stem rot resistance. It is, however, about 5 days later than M-101.

An initial seed increase has been made and will be allocated to seed growers for certification pending continued satisfactory performance.

A long grain specialty aromatic or scented rice is being evaluated. It is short statured and of intermediate maturity in warmer areas but has poor seedling vigor. Foundation seed will be produced in 1986. The potential new variety will be named and released if performance continues to be satisfactory. It is expected to occupy a very limited acreage.

Two promising short grain experimentals will be further tested and purified in 1986 and work will continue on other promising breeding lines that may become varieties of the future.

 

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