Screening phosphorus-efficient genotypes of rapeseed (Brassica napus)at seedling stage by TOPSIS

Based on preliminary screening on the field, eight rapeseed varieties with different phosphorus efficiencies were adopted in the study. Under phosphate (Pi) deficient and sufficient solution culture conditions, eight indices (root length, shoot fresh weight, root fresh weight, single plant dry weight, root to shoot ratio, phosphorus content, shoot APase activity and root APase activity) that are significantly related to phosphorus efficiency in rapeseed seedling were analyzed. The indices were then ranked using TOPSIS method to precisely screen out real phosphorus-efficient rapeseed genotype. The results show that under Pi deficient and sufficient conditions, rapeseed variety, W17 ranks first and W39 ranks last under TOPSIS ranking, which tallies with filed observation. The rankings for W23 under Pi deficient conditions, and W11 and W31 under Pi sufficient conditions also agree with filed observations. But the ranks for W31 and W290 under Pi deficient conditions and the other 4 varieties under Pi sufficient conditions have an order of difference. More significantly, the ranks for W11, W27 and W288 under Pi deficient conditions exhibit 2 ~ 4 orders of difference with filed observations. It then implies that TOPSIS accurately screens out phosphorus-efficient rapeseed genotype W17 and phosphorus-inefficient rapeseed genotype W39. For the other varieties, TOPSIS ranking has a certain degree of coherence with field observations. This indicates that TOPSIS can improve material screening veracity and is especially suitable for screening extreme varieties.