Expression of Genes Associated with Nitrogen Uptake and Metabolism in Potato (Solanum tuberosum L.) under Nitrogen Fertilization and Bacterial Inoculation

Abstract

Potato (Solanum tuberosum L.) is one of the most important crops worldwide due to its nutritional value and adaptability to diverse agricultural and environmental conditions. Nitrogen use efficiency (NUE) is an essential determinant of potato productivity and nitrogen management. This study assessed the expression of genes involved in nitrogen uptake and assimilation in two potato cultivars, Arizona and Riviera, under different nitrogen fertilization protocols and bacterial inoculation treatments. A field experiment was performed during spring 2025 using three nitrogen concentrations (62.5, 125.0, and 187.5 kg N ha-1) combined with four bacterial inoculants: no inoculation, Azotobacter chroococcum, Azospirillum brasilense, and their combination. Expression of nitrogen-related genes was assessed using conventional PCR and RT-qPCR, with EF1α used as the reference gene, and relative expression was estimated using the 2-ΔΔCT method. Conventional PCR confirmed amplification of the expected products for NRT, NR, and EF1α in both cultivars. In contrast, amplification of AMT and GDH was not detected in Arizona, and these genes were excluded from subsequent RT-qPCR analysis. NRT and NR expression showed significant responses at the moderate nitrogen rate of 125 kg N ha-1 combined with bacterial inoculants. NRT expression reached 9.94-fold in Rivera and 8.05-fold in Arizona, while NR expression reached 6.74-fold in Rivera and 5.08-fold in Arizona. Conversely, the highest nitrogen rate generally resulted in reduced expression pr nearly control expression of both genes. These results demonstrated that moderate nitrogen fertilization with bacterial inoculation can enhance the expression of the essential enzyme involved in nitrogen uptake and assimilation. On the other hand, excessive nitrogen use may suppress this response. It has also been shown that combining biofertilizers with optimized nitrogen fertilization is an effective protocol to enhance NUE in potato.