Influence of genotype and environment on the composition of harmful nitrogen in sugarbeet

The total soluble nitrogen in sugarbeet impairs sugar recovery during processing and is therefore called harmful nitrogen. It consists of amino N, betaine, nitrate and the non-identified residual N. For quality assessment in Germany only amino N is determined as a representative of all soluble nitrogen compounds. The aim of the project was to study the effect of genotype and environment on the components of harmful nitrogen and their relationship. For the study sugarbeet brei samples from variety trials with 52 genotypes at 22 sites in 2000 and 2001 were analyzed.

For total soluble N, amino N and betaine the effect of environment was higher than the effect of genotype. Furthermore, interactions between environment and genotype became evident. The data show a good correlation between the concentration of total soluble N and amino N, although the slope was not identical for all genotypes. The proportion of amino N on total soluble N increased with increasing amino N concentration, irrespective of whether the amino N concentration was increased due to the influence of genotype or environment. The proportion of betaine decreased with increasing proportion of amino N, since betaine showed not as much response to environmental factors as amino N. This clearly demonstrated that the composition of total soluble N varied and thus it cannot be judged as constant, neither among different genotypes nor for one genotype in different environments.