Response Mechanisms of “Hass” Avocado to Sequential 1–methylcyclopropene Applications at Different Maturity Stages during Cold Storage

Abstract

1–Methylcyclopropene (1–MCP) is used for extending the postharvest life of the avocado during storage. Evaluated the effect of 1–MCP application at different times after harvest, i.e., 0, 7, 14, and 21 d at 5 °C, to identify the threshold of the ethylene inhibition response in “Hass” avocado. Our results showed that fruits from two maturity stages at harvest: low dry matter (20–23%) and high dry matter (27%). Changes in ethylene production rates and transcript accumulation of genes involved in ethylene metabolism were measured at harvest and during storage. 1–MCP treated fruit up to 14 d of storage showed similar values of firmness and skin color as fruit treated at harvest time. In contrast, when the application was performed after 21 d, the fruit showed ripening attributes similar to those of the untreated ones. To further understand the molecular mechanisms responsible for the lack of response to 1–MCP at 21 d of storage, transcriptomic analysis was performed. Gene ontology analyses based on the DEG analysis showed enrichment of transcripts involved in the ‘response to ethylene’ for both maturity stages. All genes evaluated showed similar expression profiles induced by cold storage time, with a peak at 21 d of storage and an increased softening of the fruit and peel color. This was a two-year field study, and results were consistent across the two experimental years. Our results should help growers and markets in selecting the optimal timing of 1–MCP application in “Hass” avocados and should contribute to a deeper understanding of the molecular mechanisms of the avocado ripening process.

Effects of Delaying the Storage of ‘Hass’ Avocados under a Controlled Atmosphere on Skin Color, Bioactive Compounds and Antioxidant Capacity

“…After 30 days of storage at 5 °C, twice as much ethylene was found in the RA-stored fruits than in the fruits stored under a CA ( Figure 1 A). The increase in ethylene production in fruits stored under RA conditions could be due to an advanced ripening process, which was consistent with the findings of our previous study [ 9 , 24 ], and occurred because RA technology cannot delay the ripening process; however, CA can delay the onset of climacteric ethylene production [ 18 ]. Other cultivars stored under RA or CA, such as ‘Edranol’ and ‘Fuerte’, exhibited similar patterns of ethylene production [ 9 ].…”

“…After 30 days of cold storage, the parameter value decreased (near 200 N). Similar effects were reported by Olivares et al [ 9 , 18 ] and Alamar et al [ 19 ], in which RA-stored fruit softened rapidly for 35 days at 5 °C (3–4 days to reach the RTE stage). Furthermore, Burdon et al [ 20 ], reported that CA-stored fruit ripened more slowly than RA-stored fruit.…”

“…Burdon et al [ 20 ] found that when the fruit was subjected to a longer delay time to storage in a CA (15 days), better color development occurred during this stage. In a previous study characterizing the ethylene response in Hass avocados, we demonstrated that after 20 days of storage, a greater number of enzymes and genes related to metabolic processes, including cell wall biogenesis, intracellular signal transduction, phenylpropanoid metabolic processes and the response to ethylene, were activated [ 18 ]. Additionally, cold storage induced the expression levels of all genes involved in ethylene synthesis and perception, which were much greater after 21 days at 5 °C, concomitant with higher levels of ethylene and increased softening of the fruit [ 18 ].…”

“…These technologies extend quality and shelf life by reducing the respiration rate and ethylene production [ 16 , 17 ]. Low-temperature storage in combination with a controlled atmosphere (CA) is the main technology used to extend the storage life of avocados [ 18 ]. CA storage applies decreased oxygen levels (between 2.5 and 5 kPa) and increased carbon dioxide levels (5–7.5 kPa CO 2 ) in containers [ 19 ].…”