Objectives This study aimed to screen potato cultivars with high yield and nitrogen use efficiency (NUE) in the Yinshan region of Inner Mongolia.

Methods Fifteen potato cultivars from the Yinshan region were selected using to carry out a pot experiment and a field experiment. Each cultivar was subjected low and normal nitrogen amount in the pot experiment, and denoted as LN and NN treatment, respectively. The yield, biomass, and N content were investigated at harvest, growth indexes Principal component analysis (PCA) was applied for preliminary assessment. Three N levels (0, 150, and 300 kg/hm²) were setup as treatments in the field experiment, and total of 21 plant growing and nitrogen uptake indices were measured at different growing stages of potatoes for calculation of nitrogen use efficiency indices. Then, the comprehensive nitrogen efficiency values (CEV) were derived using the entropy weight fuzzy membership function method, and a tuber yield-nitrogen efficiency index (TYNEI) was calculated based the tuber yield and CEV of a cultivar.

Results The 21 assayed traits exhibited significant differences among the 15 cultivars and between the two nitrogen supplying levels (P<0.01), and the coefficient of variations (CV) under LN treatments were higher than under NN treatments for all the indices. The highest CV gapes between LN and NN treatments was on the root nitrogen uptake-related parameters, with the highest CVs among cultivars was 40%. N uptake efficiency (NUpE) was significantly positively correlated with plant height, stem diameter, dry matter yield, and N uptake yield, all of which had high loadings in PC1. Based on the tuber yield and N efficiency index (TYNEI) derived from a two-year field trials, the 15 potato cultivars were classified into three types: high-yield and high-N-efficiency, medium-yield and medium-N-efficiency, and low-yield and low-N-efficiency. The cultivar Xisen 6, Houqihong, and Jizhangshu 12 belong to the double high type, Favorita, Lucinda, Kexin 23, and Neishu 7 belong to double medium type. The field experiments showed consistent results with the results from pot experiments.

Conclusions Under both the low and normal nitrogen conditions, all 21 indicators of the tested potato germplasms with varying N efficiencies exhibited significant genotypic differences. Compared to low-yield and low nitrogen use efficiency types, high-yield and high-nitrogen use -efficiency cultivars primarily demonstrated high tuber yields, as well as stronger nitrogen uptake and utilization capacities. After screening using the entropy-weighted fuzzy membership function method, biological nitrogen fertilizer efficiency, the contribution rate of nitrogen fertilizer to yield, agronomic use efficiency, partial factor productivity of nitrogen fertilizer, and the apparent nitrogen use efficiency were identified as evaluation indicators for nitrogen efficiency in potato germplasms. Based on cluster analysis using a tuber yield-nitrogen efficiency index, the 15 potato germlasms were classified into three types, among which Xisen 6, Houqihong, and Jizhangshu 12 were identified as high-yielding and nitrogen-efficient varieties.