Since 1960, with the continuous growth of the global population, human demand for crops has also been increasing. In order to achieve high crop yield, people have increased the application rate of chemical fertilizer (especially nitrogen fertilizer). The production of nitrogen fertilizer requires a large amount of fossil energy fuels, resulting in excessive consumption of non-renewable resources and increasing the production cost of crops, while the utilization rate of nitrogen fertilizer by crops is generally very low, with only 30% and 40%. Unused nitrogen fertilizer has become a new source of pollution into nature. In this context, the study of crop tolerance to low nitrogen has a strong practical significance in solving food supply, saving non-renewable resources, protecting the ecological environment and so on.

Previous studies have shown that polyploid plants tend to have stronger ability to resist adverse environment than diploid plants. Wheat is one of the three major food crops in the world, and it is also a common allopolyploid (the existing wheat is mainly tetraploid or hexaploid). In this experiment, two newly synthesized allotetraploid wheat AT1 and AT2 and their respective diploid parents and natural tetraploid IW131 (BBAA, TriticumTurgidum, BBAA) were used as experimental materials to evaluate whether the newly synthesized allotetraploid wheat had stronger tolerance to low nitrogen than its diploid parents by growth and physiological indexes under low nitrogen conditions. To analyze whether the parental preference of newly synthesized allotetraploid wheat changed under normal and low nitrogen conditions, and to compare two newly synthesized allotetraploid wheat with a natural tetraploid wheat IW131 (BBAA) to explore whether the low nitrogen tolerance of tetraploid wheat changed during the evolution process after the tetraploid event. Finally, the expression of genes related to nitrogen transport in wheat was analyzed to analyze the genetic basis of parental preference in newly synthesized allotetraploid wheat under low nitrogen conditions.

It was found that AT1 and AT2 of newly synthesized allotetraploid wheat did not have stronger tolerance to low nitrogen than their diploid parents; AT1 was more inclined to the parent (AA), under normal conditions and low nitrogen stress, different from AT1, the parental preference of AT2 changed after low nitrogen stress, and AT2 preferred the parent (SS), under normal conditions, while AT2 preferred the parent AA under low nitrogen stress. Compared with AT1 and AT2, natural tetraploid wheat has more advantages in low nitrogen tolerance, but like newly synthesized allotetraploid wheat, its low nitrogen tolerance is also lower than that of diploid parents, indicating that wheat does not gain a lower nitrogen tolerance than its parents after allotetraploidy, but it has been improved in the process of evolution. The differential expression of genes related to nitrogen transport determines the parental preference of newly synthesized allotetraploid wheat to some extent.