Disturbance of energy metabolism under high-CO2 storage contributes to the development of blackheart in potato (Solanum tuberosum L.) tubers

Blackheart (BH) is a physiological disorder of potato ( Solanum tuberosum L.) tubers characterized by internal discoloration that can develop under high-CO 2 storage conditions. However, the precise mechanisms of BH development under elevated CO 2 remain unclear. This study aimed to elucidate the metabolic factors underlying the development of BH in potato tubers. Metabolite profiling associated with browning reactions and energy metabolism was conducted in potato tubers stored under air or 5, 10, and 20% CO 2 at 4 °C for 1, 2, and 3 months, followed by transfer to ambient air. BH symptoms developed only in tubers stored under 20% CO 2 for 2 and 3 months after the transfer, initially appearing in the pith and subsequently expanding toward the perimedullary tissue. Upon re-exposure to ambient air, respiration rate markedly increased, accompanied by accumulation of fermentation-related metabolites such as ethanol and acetaldehyde. Additionally, succinate accumulated while malate levels declined, suggesting a bottleneck in oxidative phosphorylation that likely promoted the formation of reactive oxygen species. The resulting oxidative stress may have reacted with accumulated chlorogenic acid and peroxidase, leading to enzymatic browning. Furthermore, the ethylene response factor VII gene APETALA2.12-like2 and fermentation-related genes encoding alcohol dehydrogenase and lactate dehydrogenase were upregulated under 20% CO 2 , suggesting their involvement in CO 2 -induced stress responses. These findings indicate that BH development in potato tubers results from CO 2 -induced disturbance of energy metabolism, including fermentation and oxidative phosphorylation, providing insights into the metabolic and physiological basis of this postharvest disorder. • Pith-specific blackheart is associated with distinct CO 2 stress responses. • Enhanced fermentation contributes to blackheart development in potato tubers. • TCA cycle–OXPHOS bottleneck is linked to H 2 O 2 accumulation under CO 2 stress. • H₂O₂–phenolics–peroxidase interactions result in browning in potato tubers. • ERF-VII gene StRAP2.12-like2 is involved in CO 2 stress response.