Distribution of quality components in different morphological sections of sugar beet (Beta vulgaris L.)

The technical quality of sugar beet is essential for economical sugar manufacturing. In particular, it depends on the chemical composition of the beet. The concentrations of the quality components are influenced by agronomical conditions. Due to progress in breeding and cultivation methods over the past decades, the components and their distribution in different morphological sections may have changed. Therefore, the distribution of sucrose, dry matter, potassium, sodium, alpha-amino N, soluble N, nitrate, betaine, reducing sugars, glucose and raffinose were analysed and the standard molasses loss was calculated for the current agronomical conditions. Cultivation methods (variety, population density, N and K application) were varied in several field trials at two sites in 1997 to obtain heterogeneous beet material. The beets were segregated into four horizontal sections according to morphological criteria (root with root groove, hypocotyl, lower stem with dead petioles, upper stem with living petioles). On average, the sucrose concentration decreased from the root to the lower stem, and especially by one third to the upper stem. The dry matter concentration did not vary markedly between the four sections. In comparison to this, the concentration of potassium, sodium and alpha-amino N increased considerably from the lower to the upper stem. Therefore, the standard molasses loss (K, Na, alpha-amino N), calculated to evaluate the technical quality of sugar beet, increased as well. The concentration of soluble N, reducing sugars and glucose were approximately three times higher in the upper stem than in the root. In contrast to this, the concentration of raffinose, betaine and nitrate did not change markedly. There was a close relationship between soluble N and alpha-amino N in each section. The range of all components within the single sections differed extremely due to the variation in cultivation methods. But for most components the highest variation was found in the upper stem. Taking all components into account, the technical quality of sugar beet deteriorates the more shoot material (lower and upper stem) is included during harvesting and topping. (C) 2002 Elsevier Science BN. All rights reserved.