Effect of pre-harvest nitrogen on hormone profiles and dormancy break in potato tubers

Abstract

​​This study tested whether pre-harvest nitrogen (N) supply alters the timing of dormancy release and the profiles of abscisic acid (ABA) and cytokinins (CKs) in apical buds of potato tubers. A field experiment was conducted with two cultivars, Brooke and VR808, receiving standard (100% N) and reduced (30% N) doses. After harvest, tubers were stored and assessed weekly for dormancy followed by collection of apical buds for hormone profiling and subsequent analysis using Liquid Chromatography–Tandem Mass Spectrometry (LC-MS/MS). Multiple PGRs were targeted; of these, only ABA and DZR were quantifiable and profiled across stages and treatments. Reduced nitrogen delayed dormancy break in both cultivars by around one week. Across the various dormancy stages, ABA in the apical buds remained stable and unaffected by nitrogen, indicating that a decline in ABA cannot always be associated with dormancy break. DZR showed cultivarand nitrogen-dependent patterns, with shifts evident in Brooke but not in VR808, suggesting that cytokinin (CK) mobilisation could be genotype-conditioned. Overall, the findings suggest that N could modulate dormancy via altered ABA sensitivity rather than ABA decline, while DZR-linked cytokinin dynamics appear genotype-conditioned; this study also confirms the feasibility of nitrogen optimisation as an effective, environmentally friendly tool to extend dormancy, aid storage scheduling, and reduce fertiliser use.​