THE OLD method of producing seeds of sugarbeets was to grow vegetative plants one season, store them over winter in pits or field trenches, and reset them in the field the second year to let them seed.

Because it took so much work, the production of the seed cost more in this country than in Europe, and for many years the American beet sugar industry relied on the European sources of seed.

Research workers of the New Mexico Agricultural Experiment Station and the Department of Agriculture demonstrated in the 1920's that excellent yields of seed could be had in the southern part of New Mexico if the sugarbeet were grown on the seasonal schedule of a winter annual—a plant from fall-sown seed that blooms and fruits the following spring.

The new method—the winter-annual method—was developed by J. C. Overpeck and his coworkers. It greatly reduced labor requirements and permitted complete mechanization of the field operations. It met the need for homegrown seed of disease-resistant varieties.

Seed was grown by the winter-annual method on 62 acres in 1932. More than 12 million pounds of sugarbeet seeds were produced on about 7 thousand acres in 1937.

The winter-annual method proved to be successful also in the Virgin River Valley of southern Utah, the Salt River Valley of Arizona, the Willamette River Valley of Oregon, and southern California.

We produced enough seeds for our needs and for export to Europe during the Second World War. More than 10 million pounds were shipped overseas in 1947, but the seed became a small item of foreign trade as soon as the European countries could reconstruct their own seed establishments.

THE SUGARBEET and other cultivated varieties of Beta vulgaris produce two to five or more flowers in dense clusters. The flowers cohere at the base and grow together during maturation to form glomerate fruits, which usually comprise as many seeds as there were flowers in the cluster. The dry, hard fruits are the "seed" of commerce and often are referred to as glomerules, seedballs, or multi-germ seed.

The first fruits formed on the spikes of the flowering sugarbeet are the largest. The size of fruit and the number of seeds per fruit get smaller toward the end of the branches. The fruits formed on the tips usually are single seeded.

Investigators have found sugarbeet plants that have a single flower in each axis of the entire inflorescence.

These plants produce single-seeded fruits, or monogerm seed. This characteristic is inheritable, and monogerm varieties of sugarbeets have now been developed.

The sugarbeet is a biennial plant and normally requires two seasons for the growth of seed plants.

When the sugarbeet is grown for sugar, only the vegetative phase of growth—a rosette of leaves and the fleshy taproot that yields the sugar—is desired.

The reproductive phase of growth, with the production of seedstalk and flowering branches, can be induced in vegetative plants by cool temperatures. This temperature effect is called thermal induction.

Length of day, or photoperiod, also influences the growth and development of the sugarbeet, and the effect of temperature and light as an impulse to reproductive development is referred to as photothermal induction.

The temperatures that favor reproductive development in sugarbeets are fairly well established. Temperatures above 70° F. favor only vegetative growth. With proper nutrition and protection from hazards, the sugar-beet can be grown vegetatively for several years. Temperatures near freezing greatly reduce metabolic activity and have low inductive effect. The most effective range of temperatures for thermal induction is 45° to 55°.

Most commercial varieties of sugar-beets require 90 to 110 days of exposure to inductive temperatures for reproductive development. In a district suited to the production of sugar-beet seed by the winter-annual method, therefore, the winters must be mild to permit survival of the plants, but the period of cool temperatures must be long enough to supply the photo-thermal induction required for reproductive growth the following spring.

If the sugarbeet is grown for sugar in a region where the photothermal effect is just on the threshold of inducing reproductive development, some of the plants will shoot seedstalks. A few may produce seeds. These precocious plants are bolters.

Bolters reduce yield and quality and increase the amount of trash to be handled in the field and at the factory. Varieties that resist bolting have been developed for use in northern regions and in southern districts where spring weather supplies high dosages of photothermal induction.

Breeding work to develop sugarbeet varieties usually is conducted in the region where the varieties will be used for sugar production. The level of bolting resistance established in the basic strains is maintained through seed produced in a manner that forces all parental plants into reproductive development. The district chosen for commercial seed production by the winter-annual method must supply the photothermal requirements bred into the variety.

Bolting-resistant varieties are grown chiefly in the Willamette Valley and in other regions that have relatively long, mild winters. Commercial seed of varieties of ordinary bolting resistance can be produced farther south.

As long as the breeder knows the photothermal requirement of the elite—foundation—seed and chooses the proper district for commercial seed production, no great change in the level of bolting resistance should result from one generation of increase by the winter-annual method.

Photothermal requirements for reproductive growth can be established rather precisely in varieties through breeding. It is important to maintain this varietal characteristic in the commercial seed supplied to the grower.

THE BOLTING resistance of a variety has definite bearing on regional adaptation for production of sugar and on the district in which seed can be grown by the winter-annual method.

If seed of a bolting-resistant variety is produced in a district where winter conditions do not force all plants of the population into flowering and seeding, there will be a natural selection toward a lower level of inductive requirement.

We can illustrate the remarkable manner in which different levels of photothermal requirement determine regional adaptation of varieties of sugarbeet and the choice of seed for planting by referring to the Imperial Valley of California and the Salt River Valley of Arizona.

The Salt River Valley has the largest acreage of sugarbeets for seed in the United States. This district, centering around Phoenix, in 1948 produced more than 11 million pounds of seed, with a germination of 93 percent, on about 3 thousand acres. With a lower demand for seed in later years, the production has leveled off at about 5 million pounds annually. All the seed is produced by the winter-annual method.

The Imperial Valley, which is approximately 250 miles west, 40 miles south (1/2° latitude), and 1,200 feet lower in elevation than Phoenix, produces more than 100 thousand tons of sugar annually from roots grown on approximately 40 thousand acres. The acreage is grown as a winter crop.

The sugarbeet is fall sown in both the Salt River Valley and the Imperial Valley. A considerable acreage is planted concurrently in September.

The products harvested from the sugarbeet in the two valleys are strikingly different, however.

The production of sugar in the Imperial Valley and seed in the Salt River Valley depends wholly on a level of bolting resistance that has been established and maintained in the varieties. Because of bolting, the seed produced in Arizona would be undesirable in the Imperial Valley. Conversely, varieties adapted to that region could not be grown by the winter-annual method in Arizona.

THE DEVELOPMENT of the sugarbeet, largely during the second half of the 19th century, attracted wide attention, because it was a sugar plant that could be grown in temperate climates. The desire for self-sufficiency in sugar led to the introduction of the sugarbeet in our pioneer West, where land for crops was plentiful but where sugar was scarce and expensive. Seed of the sugarbeet was imported from Europe along with machinery and technical knowledge as well.

European varieties suffered great losses in the irrigated districts west of the Rocky Mountains because of curly top, a virus disease. In districts east of the Rockies, leaf spot and root rot caused heavy losses in yield and reduced quality.

It became evident during the 1920's that European varieties were susceptible to American diseases of the sugar-beet and that disease-resistant varieties were essential to a continuation of a competitive industry in this country.

The first American variety with distinctive characteristics to reach commercial status was US 1, a curly top resistant variety that was introduced in 1933. The urgent demand for seed of US 1 was a major incentive to the establishment of the seed enterprise.

Other varieties were developed soon by the Department of Agriculture, State agricultural experiment stations, and plant breeders employed by beet sugar companies.

Disease-resistant varieties were available for our major sugarbeet districts as early as 1940. Seed of American varieties have been used almost exclusively in this country since then. The dependence of the American producer and processor on homegrown seed of disease-resistant varieties made the seed enterprise an integral part of our beet sugar industry.

HOMEGROWN SEED of adapted varieties has contributed greatly to high yields of roots.

The acreable yield of sugarbeet roots averaged about 10 to 11 tons during the decades European seed was used in this country.

Beginning with the introduction of homegrown seed of American varieties, the yield of roots has increased steadily. The national average since 1952 has been no less than 16 tons. The crop of 1959 averaged 18.8 tons an acre.

This achievement cannot be attributed entirely to homegrown seed of improved varieties. Homegrown seed of resistant varieties has lessened the disease hazards of the past and brought a stability of crop performance that encourages the grower to apply improved field practices.

The crop averaged approximately 800 thousand acres annually for several decades before the Second World War. The recommended rate of drilling was 15 to 20 pounds to the acre, but the 20-pound rate was more general. Our annual seed requirement for many years therefore was 16 million pounds.

The acreage in sugarbeets has increased since 1950 to the limits permitted by production quotas established under the Sugar Act. The allotment for 1960 was 1 million acres. Despite the increase in acreage, however, the seed requirement has declined because of the practice of using a lower planting rate to obtain a seedling stand more readily thinned by machine.

Machine harvesting of sugarbeet roots became a general practice during the war, but dense, clumpy stands of seedlings obtained with multigerm seed prevented mechanization of thinning and weeding. The pressing need for a reduction of labor requirements focused research on the seed.

The first accomplishment in the research was the development of a method of milling seedballs to produce small segments and possibly single-seeded units. If the product from milling, known as segmented seed, was planted at a low rate, a sparse stand was obtained that facilitated thinning.

SEGMENTED SEED was an accomplishment in the direction of reducing labor requirements, but there were several objections to the milling operations: Approximately one-half of the seed was wasted as fragments and chaff. A significant percentage of the embryos were injured. Seedlings did not emerge normally from damaged embryos. Milling did not reduce fully all seed-balls to single-seeded segments.

Segmenting has been replaced by another milling operation. The seed-balls, after screening to a desired size, are passed between two horizontal steel disks, one of which rotates. The mechanical action of the disks rubs the corky tissue from the seedballs and reduces them to a fairly uniform shape and size.

This type of milling, known as decorticating, processing, or rubbing, is preferred generally to the more severe method of segmenting, because less seed is wasted and the embryos suffer almost no injury.

Commercially processed seed consisting of 30 to 40 percent single-seeded units is widely used at a recommended planting rate of 4 to 6 pounds to the acre. Stands of seedlings can be obtained with processed seed (if properly drilled) that greatly reduce the labor requirements of thinning and weeding.

Segmenting and processing of seed-balls were desperate efforts to produce by machine a seed type that was not obtainable as a natural growth of the sugarbeet plant. Although harvesting of sugarbeets had been fully mechanized, it was still necessary, despite reduced labor requirements with segmented and processed seed, to transport many extra workmen into sugar-beet districts each spring to perform the jobs of weeding and thinning. The discovery of a plant which produced monogerm seed therefore was a major advance.

MONOGERM SEED has further fashioned the plant to meet the producer's agronomic and economic problems.

Its advantages were recognized 50 years ago, and plants producing single-seeded fruits were diligently sought by investigators. But inheritable monogermness in the sugarbeet was not available in this country until its discovery in 1948 by V. F. Savitsky, a collaborator of the Department of Agriculture, employed by the Beet Sugar Development Foundation.

Reports from the Soviet Union have indicated that the monogerm character was under investigation in that country more than a decade earlier.

Monogerm seed was available for trial plantings in some districts as early as 1956, but not until 1958 was the new seed used on extensive acreage.

Monogerm varieties have not been developed for all districts, and the acreage cannot be determined accurately. The seed produced one year, however, may be taken as an indication of the varieties that will be planted for sugar production the following year. Monogerm seed amounted to 11.4 percent of the seed crop in 1957, 24.8 percent in 1958, and 25.4 percent in 1959. Fall plantings in 1959 indicated a marked increase in production of monogerm seed for 1960.

Commercial monogerm seed was largely hybrid by 1960—that is, single-cross, three-way cross, or double-cross.

Practicable methods of producing hybrid seed evolved from the fundamental research by F. V. Owen, a geneticist of the Department of Agriculture, on male sterility in the sugarbeet.

His findings concerning the cytoplasmic and genetic factors that condition sterility of pollen have supplied tools for the production of commercial hybrid seed of both monogerm and multigerm sugarbeets.

Pollen-fertile lines (the so-called type "O") that do not restore pollen production in the offspring when crossed with pollen-sterile lines carrying cytoplasmic factors for sterility are basic parental material for the production of hybrid seed. Backcrossing the type "O" parent to the male-sterile offspring in recurring generations produces a male-sterile equivalent of the line.

Male-sterile equivalents of type "O" lines may be hybridized with complementary pollinators to produce a vigorous F1 (first generation following a cross) for use as single-cross commercial seed. However, male-sterile F1's, which are obtained if the pollinator is type "O," are being used also as the chief seed bearer in the production of broad-base hybrids.

Male-sterile F1's are widely used in the production of three-way commercial hybrids, including US H2 and other hybrids developed by J. S. McFarlane, a geneticist of the Department of Agriculture.

In usual practice, the seed of the male-sterile F1, is mixed with the seed of the pollinator to give a blend consisting of about 10 percent of the pollen parent in the planting stock and presumably about the same ratio of pollen-fertile plants in the seed field.

The commercial crop contains a low percentage of seed that is not hybrid. At greater cost, however, a completely hybrid crop can be obtained if the pollinator is planted in separate rows and removed from the field before harvesting the hybrid seed produced on the male-sterile parent.

The multigerm pollinators were employed in the production of commercial seed of monogerm hybrids before 1960. Seeds of parental sorts, usually a monogerm male-sterile F1 and a multi-germ pollinator, were blended to give the desired ratio of pollen-fertile plants in the seed field.

The large multigerm seedballs were removed by screening. Then the commercial seed was processed to give the desired size and quality. The seed planted by the sugar producer contained a low percentage of fruits that were not monogerm, but the lack of complete purity with respect to this trait was not considered objectionable.

The use of multigerm lines as pollinators in the production of commercial monogerm hybrids made possible further utilization of the disease-resistant multigerm breeding material that has been developed in long research.

Furthermore, utilization of the established multigerm sorts as pollinators made available commercial mono-germ seed of productive hybrids in a much shorter period of breeding than would have been possible with the requirement that both parents be newly developed monogerm sorts.

The fact that the commercial mono-germ hybrid obtained by the method outlined would produce multigerm seed and many male-sterile plants if grown to the fruiting stage is of no concern to the sugar producer, since he obtains a new supply of hybrid seed for each crop of roots.

The ultimate goal has been the employment of only monogerm parents in the production of hybrid seed, but multigerm pollinators will continue in use until there is a great wealth of disease-resistant monogerm lines that display a high level of ability to combine.

THE SEED must be of high quality if the full laborsaving advantages are to be realized from the use of monogerm varieties.

In the determination of quality, a multigerm seed was counted as having germinated if it produced a single sprout. Thus a high germination percentage could be obtained with a seed sample in which the actual seed set was low in relation to the number of flowers incorporated in the glomerate fruits.

THE LOW germination percentage of some monogerm lines was a matter of much concern, but the percentage values were higher than formerly obtained with multigerm seed when the basis of evaluation was the number of sprouts in relation to the number of flowers.

Fortunately, the germination of commercial monogerm seed has greatly improved through selection. By proper cleaning and processing, a commercial product of high quality and germination has been made available to growers.

Monogerm seed makes possible single-plant hills along the row. If the drilling rates are right, stands of seedlings can be obtained that are readily thinned by machine or rapidly singled with a long-handled hoe. Monogerm seed should make possible a saving of 50 percent in labor requirements for weeding and thinning.

Some agronomists—the more optimistic ones—have directed their experimental programs with monogerm varieties toward seeding rates that will give an emergence stand approximating the final stand left to grow for root production.

Weed control in the seedling stage is accomplished by selective herbicides and harrowing; in later stages of growth, by timely cultivation. Hand labor usually is not required for this method of production, because harvesting has been fully mechanized.

Actually, a small, commercial acreage of sugarbeets is being grown with complete mechanization of all field operations. Thus the visionary goal of two decades ago appears to be attainable through the use of monogerm seed and the application of improved field practices.

Field practices for seed production by the winter-annual method have been fairly well standardized. The seed is planted in August and September. The row width is usually 20 or 24 inches. The planting rate is 15 to 17 pounds per acre. The seedling stands are not thinned.

Varietal purity is maintained in the commercial varieties of sugarbeets by the separation of seed fields. If the varieties are similar in certain major characteristics, such as disease resistance, the separation of seed fields need not be greater than one-half mile. For stock seed and elites, especially the sorts that involve male sterility, seed fields should be separated by at least 2 or 3 miles, depending on terrain and climatic conditions.

Curly top, a virus disease, is a major hazard to seed production in the Southwest if susceptible varieties are grown. Virus yellows occurs in all major seed-producing districts and is a threat to production and quality. The combined attack of curly top and virus yellows is extremely damaging. The control of these diseases depends on the control of the insect carriers.

The seed is harvested by machine. In some districts, the harvesters are equipped with front cutting bars, which operate both horizontally and vertically. They cut a wide swath through the tall, bushy plants and draw the mass into a windrow. The windrow, when dry, is picked up by traveling thresher, which separates and sacks the seed and returns the large stems and leaves to the field.

Seed is produced by the seedgrower under contract with a sugar company or a seed company that acts as an agent for sugar companies. The sugar company placing an order for seed production furnishes the elite seed or foundation stock. The seedgrower is paid on the basis of clean seed of acceptable quality.

Processing and grading of seed to give a uniform product of a desired quality are performed by the sugar companies after the seed has been moved from the centers of production.

The seed is usually treated with a fungicide, and sometimes with an insecticide, before packaging for sale to growers.

MARKETING of sugarbeet seed in this country is almost exclusively through sugar companies.

A stipulation in the contract between the sugar producer and the processor requires that the seed planted must be obtained from the sugar company buying the roots. A small amount of sugarbeet seed is used to grow a root crop for cattle feed, and seed for this and other purposes can be obtained also from firms handling seeds of field and garden crops.

New strains and varieties of sugar-beets developed by the Department of Agriculture are released through the Beet Sugar Development Foundation under a memorandum of understanding that covers procedures whereby breeder seed and parental lines of hybrids are increased and enter into commercial seed production for the use of growers.

Varieties and strains arising from the breeding programs of individual sugar companies are recognized as their exclusive property.

The production of sugarbeet seed in this country in 1950-1960 was about 10 million pounds annually. It was grown on slightly more than 3,500 acres. The crop value to the grower was approximately 400 dollars an acre. The farm value of the sugarbeet seed crop was about 1.5 million dollars.

Sugarbeets are grown as a source of sugar in 22 States. Returns to growers amount to more than 200 million dollars annually.

Alfred Stefferud

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