Oilseed rape (Brassica napus L.) genotypic variation in response to boron deficiency

Boron efficiency of 16 oilseed rape genotypes was tested using both hydroponic and pot-soil growing techniques. From the nutrient solution experiment (0.1 and 10 mu M B), 4 representative contrasting genotypes were selected based on relative root and shoot growth. These were then grown in pots with low-B soil (0.25 mg kg(-1)). From the nutrient solution experiment, 2 genotypes selected as B-inefficient did not show any growth disorders, and the concentration of B in the shoots was above critical. Furthermore, 4 contrasting genotypes were subjected to the stable B-11 isotope-enriched uptake solution for 6 h to verify possible low B-induced active uptake by roots and xylem loading of B. The concentration of B-11 in either root cell sap or xylem exudate was higher than in the external nutrient solution, which indicated the presence of low B-induced active uptake for all tested genotypes, and, to some extent, their efficiency with low B. In conclusion, a combination of different growing techniques under controlled environmental conditions together with different parameters including relative root and shoot weight, shoot B concentration, and B uptake provided reliable B efficiency results in oilseed rape genotypes