History, current state and perspectives of sugar beet quality breeding – Part 2

Quality breeding aims to improve the technical quality of sugar beets and thereby the cost-effectiveness of sugar production without prejudice to other performance characteristics, such as yield and resistances. Its history goes back to the 19th century, but since the mid-1930s it focuses systematically on certain characteristics which determine quality. Its successes are demonstrated by the secular sugar beet statistics, the annual assessments of the German Federal Varieties Agency, comparative variety trials (regional and super-regional variety assessments), in practical sugar beet farming, in the modern breeding material of sugar beet breeders, and, last but not least, in the sugar factories. Advances in serial beet analysis have contributed decisively to increase successful selection and to produce better varieties.

Introductorily, the theoretical and methodological bases (quality assessment and quality analysis) for systematic sugar beet quality breeding and its historical development are presented. Particular attention is paid to the breeding work done in the United States from the beginning of the 1950s to improve the juice quality of sugar beets (clear juice purity) through reduction of the alkali (potassium and sodium) and soluble nitrogen (various amino acids, glutamine, a-amino-N, etc.) contents. This work produced the greatest progress in elucidating the scientific foundations (trait correlations, hereditability, etc.) since the start of quality breeding.

The current state of sugar beet quality breeding in Germany is presented and discussed by reference to the secular development of sugar content and sugar yield (since 1850), Federal Varieties Agency trials (assessment of new varieties since 1972), and personally owned breeding material (experimental hybrids of European origin from 1979 and 1997). The decline in alkali and amino-N contents to be observed in this material since 1972 results, aside from other factors, from the breeding objectives and efforts to improve the technical quality of sugar beet varieties. This development is evidently directly connected with a continuous decline of the alkalinity reserves in beets, which could jeopardize part of the successes in quality breeding achieved so far (reduction of the standard molasses loss) if the factories do not introduce countermeasures (greater reduction of the soluble N fraction relative to the alkali content) in order to avoid having to add alkalinity agents (soda or natron brine).

Because of their practical importance for quality breeding, special attention is devoted to the selection criteria and strategies now applied in or available to sugar beet breeding. This includes consideration of novel ideas regarding sugar beet quality assessment (nonsugar concept).

Looking ahead, various genetic engineering approaches are presented, which might contribute to the solution of existing problems relating to the technical quality of sugar beets (reduction of sucrose losses during storage, nitrogen accumulation, etc.).

Part 1: 2000-591-602.pdf