Botany of the sugar beet
As the sugar beet is a biennial plant, vegetative growth during the first year is required for bulking sucrose in the roots for the following year’s reproductive growth. Sugar beets tend to behave as a perennial if flowering is not induced, thus for seed production, the induction of flowering is required. Flowering is stimulated after a period of cool temperatures and long nights, known as vernalization. In practice, the roots harvested from selection plots are placed in a 4 degrees Centigrade cooler for 12 to 16 weeks to induce vernalization. Flowering commences within five weeks after removing the plants from vernalization.
In most commercial U.S. seed production today, fields are seeded in late summer, and plants vernalize in the field during winter in locations with little risk of freezing. Flowering, seed set and seed harvests are completed by August of the next year. In the greenhouse, this procedure can be accelerated and seed can be acquired for testing the year following field selection of mother roots.
Monogerm sugar beet seed
Today’s cultivated sugar beets are derived from wild species of Beta and these plants possess a natural characteristic where two or more flowers occur as fused clusters to produce multigerm seedballs. When these seedballs were planted, two or more seedlings emerged, generally quite close and often intertwined together, resulting in huge labor costs due to the need for extensive thinning of emerging seedlings.
The finding of plants that produced single germ seeds was an enormous benefit to the sugar beet industry. Modern agriculture has now become dependent upon single-seeded cultivars and precision planting. This trait is known as monogermity.
Discovering monogerm plants in the former Soviet Union
Searching for a source of plants that produced only single-germ seed was begun more than 100 years ago. Due to difficulties in detecting monogerm plants, this search was not accomplished until the 1930s when internationally recognized sugar beet breeder and geneticist Viacheslav F. Savitsky and a colleague, M. G. Bordonos, detected a monogerm plant at the Sugar Beet Institute at Kiev (this is now the capital and largest city in the Ukraine).
This particular feature of sugar beets (monogermity) is normally associated with a mutation in plants that have late-season bolting ability, and thus are ordinarily eliminated by natural selection. Therefore it was necessary to look at enormous numbers of plants to find those few plants possessing this trait. In fact, Savitsky and Bordonos had to examine an estimated 22 million plants in order to find approximately 100 seed plants with a mixture of both multigerm and monogerm seedballs.
By 1934, they had identified plants that produced a high percentage (90 percent) of seedballs that were monogerm. The ability to produce this type of seed was found to be quantitative (controlled by several genes) in this case. He then tried to transfer this trait into commercial seeds to produce the early monogerm varieties that were eventually developed for use in the USSR and eastern Europe, but this work was interrupted by the second World War.
Immigration to the United States
In 1947, Savitsky and his wife, Helen, (an excellent microscopist and cytologist) escaped the Soviet Union and came to the United States. They were both employed initially by the Beet Sugar Development Foundation and later by the USDA. Savitsky was stationed at the Sugar Beet Laboratory in Salt Lake City, Utah, and his first task was to find possible sources of monogermity for the sugar industry in the United States.
Discovery of monogermity in North America
Savitsky conducted an intensive survey looking for monogerm plants in 1948. He found five monogerm plants among 300,000 others in a four-acre seed field north of Salem, Oregon. He was able to detect these plants due to his previous experiences in Russia. Two of the plants, designated as SLC 101 and SLC 107 were true monogerms. Seed from SLC 101 was distributed to breeders in the United States, Canada and Europe. That one plant then served as the seed source for incorporating this trait into new monogerm varieties, and still continues for all varieties produced in the United States today.
This discovery in Oregon occurred with “Michigan Hybrid -18,” a variety derived from the Cercospora leaf spot-resistant Polish variety “Buszczynsky.” This Polish variety in turn, had originally been created from CLS-resistant wild beets from Italy. It was hypothesized that the multiple cycles of inbreeding used in Italy from the wild material that was required to identify the CLS resistance was the possible reason for the rare recessive monogerm trait to be expressed and noticed in ‘Michigan Hybrid-18.’
Savitsky later found that this condition was controlled by a single recessive gene, unlike the multi-genic trait discovered from the Russian seed sources. However, this seed source proved to be a weak, self-fertile inbred that lacked disease resistance. Therefore this gene had to be introgressed (transferred) into other beet germplasm before being utilized in commercially acceptable cultivars.
Impact on sugar beet production
As a result of Savitsky’s stellar work, this trait has been available to growers in the United States since 1957 and western Europe since the mid-1960s. It was probably the biggest advancement in sugar beet production until the development of the Round-up Ready sugar beet cultivars in the second decade of the 21st century. In fact, this advancement has proven to be so influential and important that the American Association of Sugar Beet Technologists has created an award known as “The Savitsky Memorial Award” in honor of his contribution to the industry. This award is very prestigious and is given only at the discretion of the ASSBT Board of Directors to individuals who have had a significant impact on the national and international beet sugar community.