Researchers closer to understanding cause of mango disorder

Researchers have found that bacterial infection is the likely cause of resin canal discolouration (RCD) in Australian mangoes, which is estimated to cost the Northern Territory mango industry between $5 million and $10 million per year.

Mangoes have an extensive network of canals just under the skin and in the flesh which store resin, or sap. The normally flesh-coloured canals become brown or black as the mangoes ripen when infected with RCD.

Although affected mangoes are safe to eat, the discolouration makes them less appealing to consumers, and researchers have previously struggled to establish the cause.

Umar Muhammad has been researching RCD in mangoes for his PhD with the ARC Training Centre for Innovative Horticultural Products, based at the Tasmanian Institute of Agriculture (TIA). Muhammad and his fellow researchers artificially induced the RCD bacteria into healthy mangoes, and found zero infection in the controls and 100% infection in the manually infected fruit. Dr Cameron McConchie, Research Leader at the Department of Primary Industry and Resources, said this discovery was the biggest local breakthrough in understanding the cause of RCD.

“We found RCD occurs post-harvest and that avoiding contamination is essential to prevent it,” he explained.

The researchers also found that RCD can spread through contact with the intact skin of infected mangoes, and some mango cultivars are more susceptible to RCD than others.

“At this stage, we can only say that Kensington Pride are susceptible, and it appears that symptoms are more severe in fruit from Darwin than further south,” Dr McConchie said. “We know that some of the new mango varieties we’ve been developing are very resistant to RCD, even when the infection is injected directly into the fruit.”

TIA’s Associate Professor Alistair Gracie, who has overseen Muhammad’s project, said it had been a collaborative, cross-sector success between mango growers, Northern Territory Government scientists and TIA’s food science researchers.

Images courtesy of the University of Tasmania.