By Robert M. Harveson Extension Plant Pathologist PREC, Scottsbluff
Posted February 22nd, 2015 by Star Herald
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.