Evaluation of Phosphorus Efficiency in Rapeseed (Brassica napus L.) Recombinant Inbred Lines at Seedling Stage

The phosphorus (P) efficiency of 135 recombinant inbred lines (RILs) derived from the cross between a P-efficient cultivar and a P-inefficient cultivar of rapeseed (Brassica napus L.) was evaluated at seedling stage. Young seedlings were cultured in nutrient solution with 5 μmol L−1 P (low P) or 1 mmol L−1 P (normal P) added. Shoot dry weight (SDW), root dry weight (RDW), root/shoot ratio (R/S ratio), average maximum root length (AMRL), shoot P uptake (SPU), total P uptake (TPU), and P use efficiency (PUE) were investigated, and the correlations between these traits and P efficiency among the RILs were analyzed. Compared with the normal-P treatment, the low-P stress seriously restricted plant growth at seedling stage, and significant differences were observed among the RILs with the largest variations in SDW and RDW. The SDW, RDW, R/S, and AMRL showed normal distribution in the RILs with transgressive segregation under low-P treatment. According to the correlation analysis, the relative SDW and RDW could be used as major indexes for evaluating P efficiency in rapeseed, but the absolute values of various traits under low-P treatment should be considered to eliminate genetic effect. On the basis of the indexes of relative SDW and RDW, lines 065, 102, and 070 were screened out as genotypes with extremely high P efficiency and lines 105, 076, and 011 as genotypes with extremely low P efficiency.