The Genotype Identification And Related Indicators Screening Of Nitrogen Use Efficiency In Brassica Rapa Pekinensis

Chinese cabbage is one of important vegetables in China and plays a significant rolein the development of national economy. During production of Chinese cabbage, thefertilizer nitrogen is a key factor on affecting yield and quality. However, nitrogen useefficiency was declined with more nitrogen fertilizers used, resulting in serious economyloss for the farmers and in pollution to ground water, lakes and rivers. Thus it is necessaryto control the amount of nitrogen fertilizers and to improve the efficiency of nitrogen use.Breeding the new variety with high nitrogen use efficiency is one effective way.In this study,9Chinese cabbage elite inbred lines and5promisingcombinations were used as materials to study their nitrogen metabolism indicators,horticulture and nutrition indicators under normal and two low N levels over twoyears. The results are listed as followed:1) The nitrogen use efficiency of14genotypes were divided into5types, high efficiencyunder extra low nitrogen--high efficiency under low nitrogen--high efficiency undernormal nitrogen,high efficiency under extra low nitrogen--low efficiency under lownitrogen--low efficiency under normal nitrogen,medium efficiency under extra lownitrogen--medium efficiency under low nitrogen--medium efficiency under normalnitrogen, low efficiency under extra low nitrogen--low efficiency under low nitrogen--lowefficiency under normal nitrogen, and low efficiency under extra low nitrogen--mediumefficiency in low nitrogen--low efficiency under normal nitrogen.2) Four genotypes were screened by analyzing nitrogen metabolism under the lowestnitrogen level,12Q-343with low nitrogen absorption ratio,12Q-354with high nitrogenabsorption ratio,09-268with low nitrogen use efficiency, and09-267with highlow nitrogen use efficiency.3) We screened16N-metabolism related indicators according to the theory in whichindicators were affected by both genotypes and circumstances. The results indicated4indicators were eliminated including soluble sugar in out head leaf, SAPD value, fresh/dryof leaf (Fw/Rw) and height/width of head. With regression analysis, it showed that nitrogen use efficiency was positively associated with head height and width of Chinesecabbage.