Genetic improvement analysis of nitrogen uptake, utilization, translocation, and distribution in Chinese wheat in Henan Province

Genetic improvement analysis of the nitrogen use efficiency (NUE) of wheat (Tritium aestivum L.) was undertaken to determine the factors guiding NUE in order to develop new wheat cultivars with high yield, high NUE and high quality. To investigate the genetic improvement of wheat NUE and its components, 31 wheat cultivars that had been widely planted in Henan Province since 1941 were grown under high N treatment (HN) and low N treatment (LN). The results indicated that grain yield and NUE have increased significantly with cultivar development since 1941, with an annual genetic gain of 1.03% and 0.74%, respectively, under HN and LN. The significant increase in NUE mainly resulted from a significant increase in N uptake efficiency (NupE) and N utilization efficiency (NutE). NutE was the predominant component contributing to NUE under HN, while NupE was more important than NutE for NUE under LN. The improvement of NutE occurred at the expense of lower grain N content (GNC) as grain yield increased. Breeding was shown to increase N translocation (NTE) by an annual genetic gain of 1.33% and 0.33%, respectively, under HN and LN. N accumulation at the maturity stage was higher in the modern cultivars compared to the pre-modern cultivars, mainly as a result of increased N accumulation during the stem elongation phase. The N translocation capacity of the vegetative tissues increased, and the N translocation efficiency of the sheath and chaff were higher than that of the leaves. Important genetic improvement targets for high NUE include increasing pre-anthesis N assimilation ability and post-anthesis N translocation capacity. Furthermore improvements in wheat breeding should include increasing both N uptake and NHI to improve NUE and reverse the trend of declining GNC.