Abstract:

Highland barley is a staple grain and feed crops in Xizang region, soil nitrogen deficiency is one of the main factors limiting its production in the region. Exploring the appropriate methodology for evaluating low−nitrogen tolerance in highland barley germplasm was expected to provide materials and theoretical basis for the selection and breeding low−nitrogen tolerate varieties, as well as for the research of the underlying physiological mechanisms of low−nitrogen tolerance. In this study, hydroponics experiment was performed, using 208 highland barley germplasms as test materials, and setting up two treatments of normal nitrogen supply (5mmol·L⁻¹) and low nitrogen stress (0.1mmol·L⁻¹). Agronomic traits and nitrogen utilization traits of different germplasm under the two nitrogen treatments were determined. The affiliation function method was used to calculate the comprehensive value (D value) of low nitrogen tolerance of each highland barley genotypes, and principal component analysis, regression analysis and correlation analysis were subsequently performed to establish the prediction function and index system for evaluating the low nitrogen tolerance ability of highland barley. The results showed that: (1) under low nitrogen treatment, highland barley seedling shoot fresh weight, root fresh weight, shoot dry weight, root dry weight, plant dry weight, nitrogen content and nitrogen accumulation per plant were significantly reduced, while the root−shoot ratio, nitrogen uptake efficiency, nitrogen utilization efficiency were significantly increased. The coefficients of variation for each highland barley trait at different levels of nitrogen supply reached more than 10%, indicating that the selected highland barley germplasm had a rich genetic background, which provided the possibility for screening low−nitrogen−tolerant highland barley varieties. (2) Through principal component analysis, the 10 traits were transformed into three mutually independent composite indicators, whose cumulative contribution rate reached 92.81%. (3) Regression analysis between the low−nitrogen tolerance index and the comprehensive evaluation value (D value) for low−nitrogen tolerance of the traits were performed. The regression analysis led to the establishment of the prediction model for predicting the low−nitrogen tolerance ability of highland barley germplasm. (4) Based on the results of correlation analysis and regression analysis, the following indices for evaluating the low−nitrogen tolerance of different highland barley germplasm were determined, including plant dry weight, root dry weight, root fresh weight, shoot fresh weight, shoot dry weight and nitrogen uptake efficiency.

Key words: Highland barley, Low?N tolerance, Evaluation indices, Prediction model, Regression analysis