Contents lists available at ScienceDirect Scientia Horticulturae journal homepage: www.elsevier.com/locate/scihorti Fumigation and dip treatments with 1H-cyclopropabenzene and 1H- cyclopropa[b]naphthalene suppress ethylene production and maintain fruit quality of cold-stored ‘Cripps Pink’ apple Vijay Yadav Tokala a,b, *, Zora Singh a,c , Poe Nandar Kyaw a,d a School of Molecular and Life Sciences, Curtin University, Perth 6845, WA, Australia b Amity Institute of Horticulture Studies and Research, Amity University, Uttar Pradesh, Noida 201313, India c Centre for Crop and Food Innovation, Western Australian State Agricultural Biotechnology Centre, College of Science, Health, Engineering & Education, Murdoch University, Perth WA, 6150, Australia d Department of Horticulture, Yezin Agricultural University, Yezin 15013, Myanmar ARTICLE INFO Keywords: Ethylene Ethylene antagonists 1H-cyclopropabenzene 1H-cyclopropa[b]naphthalene 1-Methylcyclopropene Fruit dip Fumigation ABSTRACT The effects of dip and fumigation treatments with two novel ethylene antagonists namely 1H-cyclopropabenzene (BC) and 1H-cyclopropa[b]naphthalene (NC) as well as 1-methylcyclopropene (1-MCP), in reducing the ethylene production and respiration rates and maintaining fruit quality of cold-stored ‘Cripps Pink’ apple were in- vestigated. The apple fruit were fumigated with 1 μM BC, 1 μM NC, or 18 μM 1-MCP for 18 h. For dip treatment the fruits were dipped in 20 L aqueous solution containing 5 % ethanol only, 2 μM BC in 5 % ethanol or 2μM NC in 5 % ethanol for 5 min (at 20 ± 2 °C). The untreated fruit were considered as control. Following 100 d and 150 d of cold storage, in sequence the fumigation treatment with 1-MCP, the fumigation and dip treatments with BC and NC were effective in retarding the ethylene production, reducing physiological loss of weight (PLW) as well as in maintaining higher firmness, total phenol levels and titratable acidity in the fruit, when compared to control and ethanol treatments. The BC and NC fumigation treatments performed better than respective dip treatments in retarding ethylene production and maintaining the quality of ‘Cripps Pink’ apple fruit. 1. Introduction Apple is an important pome fruit, grown globally and are highly relished for their sweet taste, crispy texture and characteristic aroma. Apple fruit is a rich source of bioactive compounds as well as dietary fibres and is free from cholesterol, sodium and fats, which makes it healthiest choice for sustained energy (Skog and Chu, 2003). Based on the pattern of respiration rates and ethylene production during the ri- pening process, the apple fruit is categorized as a climacteric fruit (Biale and Young, 1981; Watkins, 2003). In climacteric fruits, the fruit ri- pening process involves a spike in respiration and ethylene production known as a ‘climacteric peak’. The postharvest physiological and qua- litative changes associated with fruit ripening process are directly or indirectly promoted by the phytohormone ethylene (Anwar et al., 2018). Apple fruit is sensitive to external ethylene exposure and in turn produce large amounts of ethylene during the ripening process (Burg and Burg, 1962). Hence, proper storage conditions and efficient in- hibition of ethylene action are essential to slow down the postharvest ripening processes and ultimately extend the storage life as well as maintain optimum fruit quality during storage (Gross et al., 2016). Different approaches have been investigated to antagonize the ethylene action in the fruit and vegetables. 1-Methylcyclopropene (1- MCP) has been proved to be most effective in antagonizing ethylene action and retarding the endogenous ethylene production in the fruit. 1- MCP counteracts the ethylene action in the fruit at the cellular level by irreversibly blocking the ethylene receptor sites and by inhibiting the expression of ethylene-responsive genes (Sisler, 2006). The commercial application of 1-MCP has been widely adopted by apple production industries around the world and it has been reported to reduce rates of respiration and ethylene production as well as delay fruit softening. However, the effectiveness of 1-MCP in inhibiting the action of ethylene varied among different cultivars, storage temperatures, concentrations and treatment duration (Watkins, 2006). The 1-MCP application also caused some negative effects such as reduced sensory properties in ‘Anna’ and ‘McIntosh’ apples (Pre-Aymard et al., 2005; Watkins, 2008), aggravated physiological disorders in ‘Empire’ apple (Saba and https://doi.org/10.1016/j.scienta.2020.109597 Received 31 May 2020; Received in revised form 2 July 2020; Accepted 8 July 2020 Abbreviations: BC_1H, cyclopropabenzene; NC_1H, cyclopropa[b]naphthalene; 1-MCP_1, methylcyclopropene ⁎ Corresponding author at: School of Molecular and Life Sciences, Curtin University, Perth 6845, WA, Australia. E-mail address: vijayyadav.t@postharvest.org (V.Y. Tokala). Scientia Horticulturae 272 (2020) 109597 Available online 15 July 2020 0304-4238/ © 2020 Elsevier B.V. All rights reserved. T