Identifying factors that contribute to mango resin canal discolouration (MG12018)

What was it all about?

Resin canal discolouration is a quality defect that reduces the market value of ripe mango fruit. When market reports of the defect increased over a period of two years, this project was undertaken in 2013 to start identifying possible factors that contribute to the discolouration.

A pre-season survey of mango growers, packers and wholesalers highlighted that rain around harvest, early fruit harvest maturity, and/or over use of chemicals were among the most commonly perceived factors that could be associated with this defect.

Research was carried out on Kensington Pride fruit produced around Darwin during the 2013 mango season. The research team monitored fruit from orchard to market, conducted specific trials on suspected contributing factors, and completed detailed scientific evaluation of affected fruit.

Findings suggest that…

• Occurrence of resin canal discolouration varies considerably between different orchards and for different harvest dates
• It increases in severity as fruit develop from firm ripe to overripe
• It can be found in green fruit on the tree or at grading but only when the fruit or stems have severe physical injury or pathogen infection
• Incidence is higher in fruit that are exposed to commercial handling procedures than those ripened directly off the tree
• It can be present in the flesh even without skin symptoms 

• Incidence was higher in early-season fruit than those picked later 

• Incidence was higher in fruit harvested soon after a rain event
• Symptoms may be associated with bacterial infection. 


The observations suggest that resin canal discolouration is likely to occur when field conditions result in the production of ‘sensitive’ fruit that, in turn, express the defect when exposed to the common harvest and postharvest stresses.

Further research was required to confirm the causes of resin canal discolouration and to develop reliable prevention measures.