To confirm whether the parameter chosen to identify efficient germplasm is adequate, or otherwise, a sub-set of genotypes from the solution culture screening are evaluated against B-efficiencies derived from the field.

• The level of genotypic variation in tolerance to low boron (B) supply was investigated in solution culture grown, 10 day old (D10) oilseed rape (Brassica napus L.) plants, by using a rapid screening technique whereby root length, root elongation rate and total root dry weight were used to indicate plant response to B.
• Root length proved more reliable in determining genotype responses, and was used to characterise a total of 61 genotypes, of which Huashuang 2, Nangchang rape, Huashuang 1 and Zhongyou 821, and to a lesser extent, Zheyou 2, Dunkeld, Xinza 2, Nangjin 2051, 92-58, 92-13, and Awassa 115 exhibited some form of tolerance to low B supply.
• The genotypic rankings based on this early vegetative response corroborated with field based B-efficiency.
• The results demonstrate the expression of the B-efficiency mechanism in the early vegetative stages of plant growth, and establish the value of root length as a selection criterion for B-efficiency in oilseed rape.