Evaluation Of Low Nitrogen Tolerance For Maize Inbred Lines Selected Shaan A And Shaan B Groups

Expanding the amount of nitrogen fertilizer can increase the maize yield.The excessive application of nitrogen fertilizer in production not only caused a waste of nitrogen fertilizer,but also resulted in serious pollution to the environment,it also adverse to the sustainable development of agriculture.Maize is one of the most important grains,to ensure the production of maize can prevent food security risks and ensure food self-sufficiency.Therefore,researching the low nitrogen tolerance and the characteristics in the low nitrogen condition of maize,is of great significance to improve the maize resistance,increase production and reduce the dependence of fertilizer.In this study,six maize inbred lines?KA105,KA064,91227,KB106,KB024,KB207?were selected from Shaan A and Shaan B groups,and 4 inbred lines?Zheng 58,Chang 7-2,PH6WC and PH4CV?as controls,were experimented in 2018 and 2019,which were treated in two nitrogen treatments(0 kg·ha^-1,180 kg·ha^-1)in Yangling and Wugong.Related agronomic and physiological traits were investigated,such as plant height,SPAD value,the leaf area,photosynthetic,nitrogen metabolism-related enzyme activity,genes expression and nitrogen contents of leaf,stem,and grain.Also,10 maize inbred lines were planted in the laboratory,the nitrogen-related gene expression and physiological traits at high and low nitrogen treatments were analyzed.The conclusions are as follows:1. Through analysis of yield,KA105,KB024,KB207,and PH6WC were evaluated as low-nitrogen-tolerant maize inbred lines;The harmonic mean,the stress tolerance index,geometric mean productivity and mean productivity were identified as low-nitrogen tolerance screening indexes;The ear height,SPAD value at jointing stage and silking stage are identified as the second screening indicators;2. The filed experiment results showed the higher nitrogen accumulation after silking is important to nitrogen content in grains.And low-nitrogen-tolerant inbred lines maintained a high net photosynthetic rate and water use efficiency during the growth,these genotypes also maintain high nitrogen metabolism enzyme activity during jointing and silking stages so that guarantee higher nitrogen absorption and assimilation;Low-nitrogen-tolerant materials can increase nitrogen-related gene expression under stress condition to increase resistance.3. The plant height,the root length,chlorophyll content,and gas exchange of maize inbred lines were changed in low nitrogen condition at seedling stage.Compared with normal inbred lines,low-nitrogen-tolerant inbred lines maintained higher chlorophyll content and water use efficiency for more active photosynthesis.4. KA105,KB024,KB207,and PH6WC have high nitrogen transport,absorption and assimilation after silking,these inbred lines showed a positive response to low nitrogen stress at the carbon and nitrogen metabolism,enzyme system,and gene expression.