Time-Resolved Transcriptomics Provides Insights into Cultivar-Dependent Sucrose Loss During Ambient Storage of Sweet Corn

Postharvest sucrose depletion severely limits the organoleptic quality and commercial value of sweet corn during ambient storage. To characterize the temporal transcriptional responses associated with cultivar-dependent sugar loss, ears of two supersweet corn hybrids, ‘Shenketian 811’ (SKT) and ‘Overland’ (AFL), were stored under monitored ambient conditions (24–26 °C) for 7 days. Kernel sugars, total soluble solids, whole-ear respiration rates, and transcriptomic profiles were assessed at five time points. Sucrose concentration declined from 77.9 to 30.9 μg mg−1 fresh weight in SKT and from 80.3 to 20.3 μg mg−1 fresh weight in AFL. Weighted gene co-expression network analysis (WGCNA), followed by within-cultivar module–trait analysis, identified one module positively and one negatively associated with sucrose concentration in both cultivars. Subsequent gene-level correlation analysis of the 1071 genes in these modules identified 571 non-redundant sucrose-associated genes, which were enriched in carbon metabolism, glycolysis/gluconeogenesis, the citrate cycle, and starch and sucrose metabolism. Pairwise differential-expression analysis further identified 194 genes showing recurrent storage-responsive or cultivar-dependent expression, of which five genes involved in sucrose cleavage or sucrose–starch interconversion were prioritized. Notably, the cell-wall invertase gene ZmINVCW1 exhibited a sustained AFL-biased expression pattern, which was validated by RT-qPCR, while total cell wall invertase activity was also significantly higher in AFL at multiple sampling points. This time-resolved analysis characterizes recurrent transcriptional responses associated with cultivar-dependent sucrose loss and provides a focused framework for further functional studies of postharvest sucrose retention.