The Difference In Ionome Between High-yield And Low-yield Rapeseed Cultivars And Response Of Their Ionome To Phosphorus Deficiency

As a main oil crop in China,rapeseed(Brassica napus L.)is one of the important source of edible vegetable oil.Higher plants require at least 14 essential mineral elements for growth and development,deficiency of each of which can reduce plant growth and yields.Plant ionome is defined as the mineral element composition of plant.In this study,four high-yield and four low-yield cultivars were identified by the screening of 403 rapeseed genotypes in field experiments.For the four high-yield and four low-yield cultivars grown at an optimal(OP)and low phosphorus supply(LP),continuous flow analyzer and inductively coupled plasma emission spectrometry(ICP-OES)were employed to determine the concentrations of N and P,K,Ca,Mg,S,Fe,Mn,Cu,Zn,B,Mo,Ni,Si,Al and Co in the shoot and root at the seedling stage and seed,silique,straw and root at the maturity stage,respectively.We analyzed the difference in the concentration,content distribution and composition of mineral elements in high-yield and low-yield cultivars at OP and LP,and the correlations between seed yield and these traits were also studied.The results are as follows.(1)Two years of field trial indicated that the seed yields of 403 rapeseed cultivars showed a normal distribution at OP.Based on these results,four extreme high-yield cultivars and four extreme low-yield cultivars were identified.The total root length,total root surface area,fine root length and coarse root length of high-yield cultivars were significantly larger than those of low-yield cultivars at the seedling stage.The seed yield per plant,thousandseed weight,plant height,first branch number,pod number per plant,seed number per pod,harvest index and phosphorus utilization efficiency of high-yield cultivars are significantly larger than those of low-yield cultivars at the maturity stage.(2)There were significant differences in the concentrations of mineral elements in various organs between high-yield cultivars and low-yield cultivars at maturity stage.There were no significant differences in the concentrations of all mineral nutrients in the shoot or root between high-yield and low-yield cultivars at seedling stage irrespective of P treatments.The shoot and root P concentrations,and the root N and B concentrations were reduced and increased in high-yield and low-yield cultivars by P deficiency at seedling stage,respectively.At the maturity stage,high-yield cultivars had lower concentrations of P,K,S and Fe in the seed,N,P,Mn,Cu and Zn in the pericarp,N,P,Fe,Mn,Zn and Al in the straw and P,K,S and Mn in the root than the low-yield cultivars at OP.The P content in the straw decreased,but the concentrations of Zn increased in the high-yield and lowyield cultivars at LP.(3)There were significant differences in the distributions of mineral elements in different organs between high-yield and low-yield cultivars.Compared with low-yield cultivars,high-yield cultivars distributed more N and P from the straw and root to the seed at OP,which promoted the development of seeds and achieved higher seed yield,and distributed more K and S from the straw to the pericarp at OP,which improved photosynthetic carbon metabolism and the transport of photosynthates,and finally produced higher yields.P,B and Si could react with hydroxyl compounds to form lipid compounds.As they had similar physiological and biochemical properties,P deficiency decreased the distributions of B and Si in the seed of high-yield and low-yield cultivars.In addition,there was a significant difference in the composition of seed mineral elements between high-yield and low-yield cultivars.The high-yield cultivars had higher ratios of Ca/P,Mg/P,Mn/P and B/P and lower ratios of S/P in the seed than low-yield cultivars at OP and LP.