Evaluation of low nitrogen resistance of

Nitrogen (N) plays a crucial role in forage yield. However, excessive application of N fertilizers in agricultural production not only increases the production cost but also leads to serious environmental problems. Therefore, mining low-N tolerant oat germplasm is important for the sustainable development of grass and pasture. Relevant physiological indices of five oat germplasm were measured and analyzed in the seedling leaves under low-nitrogen culture conditions, aiming to identify important physiological indices suitable for screening low-nitrogen-tolerant oat and to rank the low-nitrogen-tolerance ability of each oat variety. The results showed that the physiological indexes of oats under low-nitrogen conditions were significantly different from those under normal culture conditions, and the total root length, total nitrogen, photosynthesis index, and NR enzyme activity of leaves in the five oat germplasm showed a decreasing trend, while the proline, MDA, SOD, POD, and GS enzyme activities showed an increasing trend, but the magnitude of changes in the physiological indexes varied among different varieties. By analyzing the physiological indexes, the photosynthetic index and antioxidant enzyme activities were found to be important in assessing the ability of oats to tolerate low nitrogen and therefore can be used as important indexes for screening oats for low nitrogen tolerance. The results of the comprehensive analysis showed that the order of low-N tolerance of each variety was as follows: Qingyongjiu 035> Jiayan No.2> Qingyin No.2> ZNY255> ZNY256, and the results of the present study provide a reference for the further large-scale screening of low-N-tolerant oat resources and the selection of varieties.