Importance of canopy closure and dry matter partitioning for yield formation of sugar beet varieties

Abstract

Phenotyping of sugar beet canopy for yield estimate requires a close relationship between canopy characteristics and final sugar yield. The objective of the study was to identify the importance of early canopy closure and of dry matter partitioning for high sugar yields, or more general, to study whether sugar beet yield is limited more by the source or by the sink capacity. Randomized field trials were conducted with two varieties (sugar type, yield type) in three sowing dates and four harvest dates at two sites in three years (2012–2014). Results showed very stable variety characteristics for all parameters and a linear increase of sugar yield with thermal time from September to November. Although variety 2 had reached canopy closure 100 GDD later and had a lower LAI and leaf yield than variety 1 throughout the growing season, it reached a higher sugar yield. That could be attributed to a higher RUE and a higher fraction of dry matter partitioned to sugar storage, while total dry matter did not differ distinctly. In the storage root, more cambial rings were formed, indicating a higher sink strength. Hence, sugar yield is more determined by dry matter partitioning (sink) than by canopy formation (source), making phenotyping difficult.