Pre-harvest silicon spraying: Impact on decay, metabolism, and overall quality of ‘Galaxy’ apples after harvest and cold storage

Abstract

New strategies to reduce apple decay and maintain fruit quality during postharvest with low environmental impact are crucial. Thus, we aimed to assess the effects of pre-harvest foliar silicon (Si) application on decay incidence, metabolism, and overall fruit quality of ‘Galaxy’ apples at harvest and after cold storage. The experiments were performed during four seasons in commercial orchards and stored in cold rooms, and the following treatments were evaluated: 0, 1.12, 2.24, and 3.36 g L−1 of foliar sodium silicate (SS) (2015-16 and 2017-18 seasons), 0, 1.68, and 3.36 g L−1 of foliar SS (2018-19 and 2019-20 seasons), and 0, 1.68, and 3.36 g L−1 of sodium metasilicate (2019-20 season). Upon being harvested, the fruit were kept in cold storage. Foliar Si treatment of ‘Galaxy’ apples did not reduce decay incidence and severity after cold storage, and in some cases, it increased decay incidence. Moreover, Si treatment did not increase physiological disorders such as russeting, bitter pit, flesh breakdown, and mealiness. In some periods, Si treatment enhanced ripening metabolism as supported by higher ethylene biosynthesis, ACC oxidase activity, and reduced flesh firmness. Therefore, foliar Si application does not provide benefits to ‘Galaxy’ apple decay control.