Unveiling on-tree fruit softening: a new physiological disorder in sweet persimmon (Diospyros kaki Thunb.) triggered by pre-harvest high temperature stress

초록

The present study investigated the causes and physiological characteristics of on-tree fruit softening (OTFS) in sweet persimmon, a newly identified physiological disorder likely triggered by abnormal preharvest high-temperature stress due to climate change. OTFS consistently initiated at the stylar end of the fruit and progressed as ethylene production increased. Additionally, high-temperature stress increased reactive oxygen species (ROS) accumulation, leading to elevated hydrogen peroxide, ion leakage, and acetaldehyde, while decreasing total antioxidant scavenging capacity. To investigate the potential role of acetaldehyde in OTFS, persimmons were treated with exogenous acetaldehyde via vacuum infiltration. Although acetaldehyde levels in the intact fruit were elevated, no softening occurred, suggesting it may be a consequence rather than a primary cause of softening. Consistent with this observation, qRT-PCR analysis revealed that the expression levels of DkACS1, DkACS2, and DkACO2, key genes involved in ethylene biosynthesis, were markedly upregulated at the stylar end on the first day of heat stress. In summary, high-temperature stress induced OTFS in sweet persimmon, with symptoms initiating at the stylar end and accompanied by increased oxidative stress and upregulation of ethylene biosynthesis-related genes.

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