We queried the identification of turnips in our sample of 2019. Apparently it is difficult to be precise among taxa. Here is the official explanation from CEH:
Within the current scheme we identify the pollen within honey by sequencing a small part of a single plant-specific gene which has the most comprehensive database for plants. It is perfect our purpose, environmental monitoring of change (we follow the sequence rather than the identification given), it is not intended for the certification of honey. We can only give the closest match to the region we have sequenced; sometimes this is to the plant species level, other times it is only the plant family. Brambles rarely match to a higher taxanomic level than genus (Rubus) as they evolve so rapidly. Identification to species in the genus Brassica must also be regarded with caution. They are so highly cultivated that an identification of B. rapa (turnip) could very easily be B. napus (OSR). Therefore, if you get a high abundance of any brassica species it is most likely to be that flowering in highest numbers surrounding your hive.
The result is of course just from pollen within the nectar rather than an analysis of the the nectar. It can also be influenced by the date you sample. For example our results hardly show any lime as the bees had left that and moved on the bramble and clover on the frames sampled. It is interesting to read but treat with caution.