Potential regulator of ethylene and ABA in aroma recovery of kiwifruit after transferring from cold storage

Cold storage (CS) combined with preservative treatment is widely employed to effectively extend the storage duration of kiwifruit. Nevertheless, the olfactory quality of cold-stored kiwifruit tends to deteriorate during the post-ripening phase. In this study, abscisic acid (ABA) or ethylene (ET) was supplementary administered to cold-stored kiwifruit (CS combined with a preservative 1-MCP treatment) prior to transferring from CS, with the aim of examining the impact of ABA and ET on aroma restitution during the post-ripening period (designated as MCP+ABA and MCP+ET, respectively). The results revealed that the firmness of the MCP+ABA and MCP+ET treatments remained higher than that of the control (CK, without 1-MCP treatment) throughout the post-ripening phase, both of which moreover promoted the accumulation of soluble solids and titratable acids in kiwifruit comparing to 1-MCP group. The ethylene production and respiration rate of the fruit treated with MCP+ET and MCP+ABA fell within the intermediate range between the 1-MCP and CK groups. Compared to the 1-MCP group, both MCP+ABA and MCP+ET treatments significantly improved the accumulation of volatile components, particularly aldehydes and ketones during the early stage, and esters during the later stage of post-ripening. The activity analysis of pivotal enzymes involved in aroma biosynthesis revealed that ABA stimulated an increase in alcohol dehydrogenase (ADH) activity, while ET had a notable inducing effect on alcohol acyltransferase (AAT) and hydroperoxide lyase (HPL) activities. Furthermore, transcriptomic sequencing analysis revealed differential induction of gene expression in the pathways associated with aroma biosynthesis by ABA and ET, wherein they significantly upregulated distinct genes. Additionally, principal component analysis provided a more intuitive depiction that ABA and ET appeared to enhance the restoration of aroma in cold-stored kiwifruit by activating diverse metabolic pathways or key genes. In a comprehensive assessment, the present study postulates that both ABA and ET exert restorative effects on the aroma of cold-stored kiwifruit, thus offering theoretical support for aroma restitution technology in cold-stored fruit.