Possible Mechanisms Underlying the Postharvest Increased Abscission of Seeded Table Grape After Seedless-Inducing Treatment

The seedless treatment of seeded table grapes can have a negative impact on the table grape industry due to the occurrence of berry abscission during storage. This study aimed to investigate grape berry abscission by utilizing two distinct cultivars of table grapes, specifically ‘Ziqiu’ and ‘Shine Muscat’. The results revealed that seedless treatment grapes had a higher percentage of berry abscission during post-harvest storage than seeded ones. This may be attributed to the interaction between auxin and ethylene. In the early stage of storage, the higher level of auxin in the abscission zone of seeded grapes compared to seedless grapes may be associated with the continued high expression of auxin synthesis genes (VvYUC2 and VvYUC4) and transport gene (VvPIN4) in seeded grape seeds, as well as auxin transport gene (VvAUX1) in the abscission zone. The higher auxin content in the abscission zone enhances the expression of ethylene receptor genes (VvETR1, VvETR2, and VvEIN4), thereby reducing the sensitivity of the abscission zone to ethylene and decreasing the berry abscission percentage. Consequently, enzymes such as polygalacturonase (PG), pectinesterase (PE), and beta-galactosidase (β-GAL) are quickly activated, leading to pectin degradation and the initiation of the abscission process. Increased ethylene sensitivity in the abscission zone also leads to a reduction in superoxide dismutase (SOD) and catalase (CAT) activities, causing reactive oxygen species (ROS) to accumulate, and malondialdehyde (MDA) content to rise. Which results in cell membrane damage, and an acceleration of the grape berry abscission process. This study sheds light on the mechanisms behind grape berry abscission in response to seedless treatment and provides valuable insights for the table grape industry to improve the storage and transportation of seedless grapes.