Preliminary results on the effect of 1-naphthaleneacetic acid on restoring ‘Rocha’ pear ripening treated with 1-MCP

Loss of ripening capacity is still a major problem associated with the use of 1-methylcyclopropene (1-MCP), despite its benefit in preserving climacteric fruit under long-term cold storage, specially, in controlled atmosphere. Several strategies have been tested to overcome this problem, namely the use of phytohormones (e.g., ethylene). In this study, ‘Rocha’ pear treated with 1-MCP was after storage exposed to a synthetic phytohormone, the auxin 1-naphthaleneacetic acid (1-NAA) at 2 mM, for 2 h. Before treatment, as well as 3, 6 and 24 h after treatment, the primary impact of 1-NAA on the expression of genes encoding ethylene receptor (PcETR2) and ethylene biosynthesis enzyme (PcACS4) was determined. The restoration of ripening capacity was assessed across shelf-life by measuring ethylene production and 1-aminocyclopropane-1-carboxyl acid oxidase (ACO) activity. Herein, the expression of PcACS4 significantly increased in pears treated with 1-NAA compared to pear treated only with 1-MCP. Additionally, the expression of PcETR2 was enhanced, revealing the potential of the 1-NAA treatment in inducing the production of new ethylene receptors. Time course physicochemical analysis revealed that fruit ripening was promoted by 1-NAA treatment, as judged by the higher ethylene production (ca. 50%) and ACO activity (ca. 15%) compared to treated only with 1-MCP. The application of the auxin indicated its potential in reactivating the ripening of ‘Rocha’ pear under the effect of 1-MCP.