13C and 15N partitioning among shoots, roots, and soil in Brassica napus genotypes varying in seed oil content potential

Abstract

Four genotypes of Brassica napus (cultivars Topas, Sentry and Polo, and the experimental line 04C204) varying in seed oil content (SOC) potential (from 42.2% to 50.0% seed DW) were used to study C and N partitioning among shoots, roots and soil, as well as nitrogen use efficiency (NUE). Topas, with lowest SOC potential, had higher biomass accumulation in shoots and roots and higher NUE than 04C204 with the highest SOC potential. Although the absolute amounts of biomass and N accumulated in Topas were greater than in 04C204, the percentage of 13C partitioned to shoots was lower, and the percentage of 15N partitioned to roots was higher. These results imply that SOC may be more associated with the proportions of C and N partitioned between shoots and roots, than with absolute amounts accumulated in these organs. This study also indicates that while Topas fixed the most CO2, it also had the greatest nitrogen fertilizer demand, while 04C204, with the highest SOC potential, had the greatest proportion of whole plant C retained within shoots of all the genotypes. These results suggest that a breeding strategy to optimize B. napus as a biodiesel feedstock may well be selection for maximum SOC at a minimal investment in vegetative biomass (and hence a lower N fertilizer requirement).