Reducing mango industry losses from resin canal discolouration (MG14004)

What was it all about?

Resin canal discolouration (RCD) leads to economic loss, and increased detection of the defect particularly among early-season fruit produced in the NT warranted investigation. This project sought to gain insight into growers’ experience with, and diagnosis of RCD in Kensington Pride fruit produced in the Northern Territory.

In 2013, the research team surveyed 26 growers and packers with 21 reporting problems with RCD. Nine growers considered it an economic issue for their business, while four growers and two packers estimated RCD accounted for 10 to 30 per cent lost production as well as five to 25 per cent lost at packout. The survey highlighted considerable variation in production and post-harvest practices across businesses.

The team developed a standard procedure for accurately diagnosing and quantifying RCD. The use of a standardised protocol, where fruit is evaluated for internal symptoms of RCD at eating ripe, should enable industry personnel to accurately and consistently diagnose and rate the severity of this defect.

Fruit was monitored from tree to market to identify production and post-harvest practices that caused RCD, which was significantly higher in commercially transported and ripened fruit than in fruit ripened with no commercial handling.

The final phase of the project studied the involvement of bacteria in RCD development. Pantoea agglomerans and an Enterobacter species were consistently recovered from Australian mangoes with RCD symptoms but not from fruit with no sign of RCD. Additionally, Pantoea agglomerans was found in mango wash at several orchards and pack sheds.

Kensington Pride mangoes exposed to solutions containing bacteria tended to develop more RCD than fruit processed in bacteria-free solutions. Foliar applications of copper hydroxide and postharvest hot water treatment of inoculated fruit reduced the level of RCD.

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Read a recap of the research in the article Resin canal discolouration – what the research is telling us, produced for the levy-funded Mango Matters publication.