Varietal Improvement-76



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Project Leader and Principal UC Investigators

Glenn Nader, livestock farm advisor, UC Cooperative Extension Butte/Sutter/Yuba Counties


Traditional rice varieties have outlasted most U.S. crops.

In the pre-market-order era of 1917-67, there were only three basic rice varieties: Colusa, Caloro, and Calrose. The first two are now nearly 60 years old, and Calrose is 30 years old. This points up a very unusual situation: the "old" varieties of most U.S. crops have been replaced by improved varieties more frequently than has been done with rice in California. Calrose was the most widely grown variety in the mid-1960's, and continues to be very popular, while Colusa is being increasingly replaced by S6. Caloro is now almost gone.

The advent of transition varieties: CS-M3 and CS-S4.

During the period 1968-73, the CS-M3 and CS-S4 varieties were released, culminating studies respectively begun in 1946 and 1957. CS-M3, the first smooth-hull variety in California, has proved very popular; it is very similar to Calrose in yield and adaptation. CS-S4, essentially a smooth-hull version of Caloro, was released when the popularity of Caloro was declining. And now it, too, has faded out.


Figure 1. Typical response of new California short-stature varieties (M7, Calrose 76) to nitrogen rates in comparison with a tall, lodging-susceptible variety (CS-M3). (Cooperative Extension Data)

The release of "new" varieties with increased potential.

Virtually all of the work on these "new" varieties was made possible by the California Rice Marketing Order, passed in 1969. Two varieties, S6 and M5, are now well into commercial farm production. S6 is a tall early-maturing pearl with yielding ability 13% greater than Colusa, and M5 is a tall medium grain of intermediate maturity. This period, 1974-77, has also been marked by the release of the first short-stature varieties, Calrose 76, M7 and M9. These rices have greater yielding ability at high fertility levels and are resistant to lodging (see figure 1). To obtain the maximum yield potential from these varieties, water depth also should be managed carefully during the period of stand establishment and early tillering. Table 1 shows the essential characteristics of these three new varieties.

The "new" varieties have a considerable potential for increasing rice farm income. As a general calculation of the dollar potential of new varieties assume the following:

1) new variety "X yields 10% more than the variety it replaces. Most new varieties to be released will yield at least 10% more than the old variety.

2) new variety ' X" is ultimately grown on 100,000 acres annually.

3) current state average yield is 5500 lb/acre for old varieties.

4) rice price is $7.50/cwt.

Then: 10% x 5500 lb/acre = 550 additional lb/acre at 7.50/cwt

        = $41.25 additional value/acre x100,000 (acres)

        = $4,125,000 dollars additional value/year from a single new variety

Table 1. Principal publicly developed rice varieties in California.
Variety Year released Grain type Hull type Plant Ht. Principle improved merit(s)
"Old" Varieties
Colusa 1917 short rough tall  
Caloro 1921 short rough tall  
Calrose 1948 medium rough tall  
"Transition" varieties
CS-M3 1968 medium smooth tall Smooth hull
CS-S4 1971 short smooth tall Smooth hull
"New" varieties
S6 1974 short smooth tall Smooth hull, 13% more yield than Colusa
M5 1975 medium smooth tall Smooth hull, 10 days earlier than CS-M3
Calrose 76 1976 medium rough short Short stature, cold-tolerant, 5% more yield than CS-M3
M7 1977 medium smooth short Smooth hull, short stature, cold-tolerant, and 10-15% more yield than CS-M3
M9 1977 medium smooth short Smooth hull, short stature, 10% more yield than the best current early varieties
Future varieties
Long grain   long ? ? Long grain
Short stature, very early   medium rough or smooth short Short stature, cold-tolerant
Short stature M5   medium smooth short Smooth hull, short stature, cold-tolerant
Short stature M6   short smooth short Smooth hull, short stature, cold-tolerant

Many improved varieties will become available to rice growers in the near future.

The availability to rice growers of a number of improved short-stature short-grain and medium-grain varieties will shape the future. Because of the continual development of new and better varieties for California use, it is expected that the future useful life of most new varieties will generally range from 5 to 10 years, in contrast to the 30-to-60-year life span of the old California varieties. So, to simplify rice production and handling procedures, it will be necessary to discontinue some, if not all, of the older varieties as they become obsolete and as newer varieties gain acceptance.

The goals of our coordinated rice-breeding programs are to improve a number of plant characteristics which in combination will increase yield, improve quality, minimize production costs, reduce the risk of crop loss during years of adverse weather, and develop a long grain for market flexibility. In the years of breeding for a long-grain rice under this Program, one has been developed that is high-yielding under California conditions, but the cooking characteristics are acceptable to only a part of the trade. A long-grain rice that can compete in the domestic marketplace is considered of great importance to the California industry, so the search continues, building upon the promising success achieved so far. Table 1 summarizes the total California varietal picture.

Numerous crosses have been made to incorporate improved grain quality. The cross to develop M7 and the final cross that resulted in M9 were respectively made in 1973 and 1971. Four and six years later, respectively, Foundation seed of these was available. The rapid progress was made possible by a close cooperative program between the Rice Experiment Station, UCD, Cooperative Extension and the USDA, stimulated by funding by this Board. Additionally, private rice plant breeders from many sectors, including several in California and those of the International Rice Research Institute in the Philippines, through their cooperation, have materially helped advance our successful varietal improvement program. Greenhouses and a winter nursery in Hawaii have also been major factors in accelerating the program.

Should the world undergo a cooling trend, such as some scientists now think is under way, the only way to avoid possible catastrophic results to the world's rice industry is the development of cool-season varieties that will mature faster than those now used. Blanking resistance of the best present varieties is barely adequate for the colder portions of the state. A continuing effort will be made to develop, identify, and incorporate greater cold tolerance and blanking resistance. Your rice geneticists have recently identified good blanking-resistant lines but will take up to ten years to develop them into commercially useful varieties.


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