Irradiation-induced lenticel discolouration in ‘B74’ mango fruit is modulated by ripeness

ABSTRACT

As a disinfestation treatment, irradiating unripe ‘B74’ mango can result in severe Irradiation-Induced Lenticel Discolouration (IILD). We tested the hypothesis that ‘B74’ fruit sensitivity to IILD would reduce as fruit ripen such as to mitigate skin damage. In two growing seasons, ‘B74’ fruit were sampled from five commercial farms, held for periods of 2–12 d at 20°C, treated with γ-irradiation at various doses from 0 Gy to 800 Gy, and assessed for external quality up to the ripe stage. Regardless of dose, irradiating ripening fruit at ~70% yellow skin reduced IILD severity on the ripened fruit by 36–47% compared to irradiating unripe green mature fruit at ~10% yellow skin. Irradiation of ripening fruit at 300–800 Gy consequently resulted in 74–100% marketable fruit at ripe compared to 5–59% for irradiation of the green mature fruit. Irradiating ripening fruit also minimised delays in loss of green skin during ripening. ‘B74’ fruit sensitivity to IILD decreases as fruit ripen and so delaying γ-irradiation until the fruit have partially ripened may be a commercially viable option to reduce quality loss due to IILD. However, fruit would need to be marketed quickly to compensate for a shorter post-treatment shelf-life.

KEYWORDS:

• Irradiation
• lenticel discolouration
• mango
• ripeness

Acknowledgments

We thank staff at Steritech and ANSTO for assistance with irradiation treatments, Peter Leach for providing expert advice and information on disinfestation treatment requirements, Bob Mayer and Leanne Taylor for their statistical and technical support, respectively, and mango growers for access to their orchards and packhouses.

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

The data that support the findings of this study are available from the corresponding author, JRM, upon reasonable request.

Additional information

Funding

This research was funded by Horticulture Australia Ltd (projects MG06005 and MG10008) using contributions from Harvest Fresh Fruits and matched funds from the Australian Government. The Department of Agriculture and Fisheries, Queensland and the Australian Institute of Nuclear Science and Engineering (grant ALNGRA13042) also co-funded this research.