Thidiazuron delays postharvest kiwifruit softening with temporal shifts in ethylene, starch and cell-wall programmes

Rapid softening limits the postharvest life of kiwifruit, but how thidiazuron (TDZ) affects the accompanying transcriptional changes remains unclear. We integrated six physiological traits with 36 RNA-seq libraries to characterize responses to 600 mg L − 1 TDZ. Treatment effects were evaluated at matched times from 4 to 20 days after harvest (DAH). At 20 DAH, treated fruit retained a firmness of 27.72 N, compared with 3.78 N in controls. Titratable acidity, starch, pectin and hemicellulose were also retained. Transcriptional differences were detectable at 4–8 DAH and became more pronounced at 12–20 DAH. Treatment-by-time analysis identified 15,607 interaction-responsive genes in six temporal clusters, while co-expression analysis prioritized three modules and twelve candidates spanning ethylene signalling and biosynthesis, starch and sugar metabolism, and cell-wall precursor metabolism and remodelling. Several candidates increased between TDZ 20 and 40 DAH, whereas others changed little or decreased. An independent transcriptome of ethylene and 1-methylcyclopropene responses provided convergent support for AcACS3 , AcTPPF , AcPG18 , AcPL18 and AcEXPA8 . These findings support a temporal-displacement model linking delayed softening to coordinated changes in ethylene, carbohydrate and cell-wall programmes. The twelve candidates provide a focused basis for investigating the regulation of this delay.