Assessment of breeding progress in sugar beet by testing old and new varieties under greenhouse and field conditions

• Breeding progress of sugar beet was between 0.6 and 0.9% white sugar yield a−1.
• It is caused by improved biomass partitioning and better technical quality.
• New sugar beet varieties have higher assimilation rates than older ones.
• No change in leaf area index and cambium rings was observed.
• Further yield increase due to breeding progress seems to be possible.

Breeding has led to a continuous increase of the performance of sugar beet varieties and thereby contributes to meet the global needs for food and biomass. This study aimed to analyze the extent of the breeding progress in sugar beet and to determine which parameters and traits were modified by breeding. In 2007 and 2008 sugar beet varieties registered between 1964 and 2003 were cultivated in field trials and in greenhouse experiments to exclude effects from changes in agronomic operations and climatic conditions. Differences in white sugar yield related to the reference variety registered in 1964 were regarded as breeding progress. The results showed an increase in the white sugar yield of 0.6–0.9% a−1 from 1964 to 2003 due to breeding. This was achieved by an improved biomass partitioning (higher root to leaf ratio and higher sugar to marc ratio), better technical quality (decreased concentration of K, Na, and amino N combined as standard molasses loss) and enhanced assimilation (higher chlorophyll content, higher assimilation rates). No changes were observed in leaf development and cambium ring formation. A principle component analysis pointed out that breeding targets have shifted with time from “yield” to “biomass quality”. To continue the breeding progress in future it is essential to integrate multiple resistances and tolerances against biotic and abiotic stress.