Recovery of ripening capacity in 'Rocha' pears treated with 1-MCP through the application of 1-NAA: Physiological and molecular analysis insights

Abstract

Storing 'Rocha' pear treated with 1-methylcyclopropene (1-MCP) in controlled atmosphere is a common commercial strategy to extend pear storage time and prevent postharvest disorders. However, this strategy represents a challenge to the fruit industry because 1-MCP treatment obstructs the normal fruit ripening, potentially affecting the quality to consumers. To explore possible mechanisms to reactivate ripening, 'Rocha' pears treated with 1-MCP were exposed to 2 and 4 mM 1-naphthaleneacetic acid (1-NAA) and stored at 20 ± 2 °C for 15 days. Typical ripening indicators, such as firmness, skin color, ethylene and aroma volatiles production, sugar content, and the genetic expression of ethylene-related enzymes (ACS and ACO) and receptors (PcETR1, PcETR2, and PcETR5) were determined over the 15 days of storage. A PCA analysis incorporating both physiological and biochemical data showed that 1-NAA promoted the recovery of ripening capacity in 1-MCP treated pears. Treating pears with 1-NAA led to increased activity of genes like PcACS1, PcACS4, and PcETR2, which are involved in ethylene signalling and production. This resulted in higher levels of ethylene and compounds associated with ripening, as well as softer texture, more yellow color, and higher sucrose content. The boost in ethylene-related gene activity likely heightened ethylene sensitivity and production in the treated pears. Consequently, these fruits showed accelerated softening, color change, and aroma development. This suggests that 1-NAA treatment can reverse the ripening inhibition caused by 1-MCP, possibly by enhancing ethylene sensitivity and production. This mechanism could enable consistent ripening of 'Rocha' pears after they are taken out of cold storage, and it may have similar effects on other fruits.