*2.1. Plant Materials and Preharvest Chitosan Treatment*

The study was carried out from 4 October 2019 to 3 February 2020, on kiwifruit (*A. deliciosa* 'Garmrok'). Kiwifruit was harvested from an orchard in Namhae Sub-Station, National Institute of Horticultural and Herbal Science, Rural Development Administration, Korea. 'Garmrok' kiwifruit vines were cultivated on a pergola trellis system and general kiwifruit cultivation recommendations were implemented.

The experiment comprised three treatments that included control (0), 100, and 500 mg·L−<sup>1</sup> chitosan. Untreated fruits served as the control treatment. Chitosan (from shrimp shells; ≥75% deacetylation; Sigma-Aldrich, Seoul, Korea) at a concentration of 20 g·L−<sup>1</sup> was dissolved in distilled water consisting of 0.1 mol·L−<sup>1</sup> acetic acids by stirring to make a stock solution. The resultant stock solution was further diluted with distilled water to make working solutions at 100 and 500 mg·L−<sup>1</sup> concentrations. Tween 80 (0.1%) was added to improve wettability. The chitosan concentrations used in the study were chosen based on our previous studies [8,25]. Each treatment comprised three biological replicates (trees) in a randomized complete block design in which a single tree corresponds to the experimental unit. Kiwifruit on vines was fully dipped in a cup of chitosan solution until the fruit were completely wet. The chitosan was applied at four times: 4 October 2019 (146 days after full bloom (DAFB)), 12 October 2019 (154 DAFB), 19 October 2019 (161 DAFB), and 28 October 2019 (170 DAFB). The fruit from each treatment were harvested on 2 November 2019 (175 DAFB).

Kiwifruit were culled out for uniformity of size and lacking defects. The selected fruit were packed in corrugated cardboard boxes (10 kg capacity) laid with a perforated polyethylene film liner. All experiments were performed in triplicate. Fruit were stored for 90 days at 0 ◦C with relative humidity (RH) of 90–95%. The fruit physicochemical attributes and relative gene expressions were evaluated at 30-day intervals.
