For people, grossed out by brown spots in apples and the like: researchers at the Tasmanian Institute of Agriculture have found a way to make some cosmetically “ugly” fruit more palatable.
Mangoes have an extensive network of canals underneath their skin and in the flesh that contain resin or sap. When the fruit is infected with Resin Canal Disorder (RCD), these canals turn an unsightly shade of brown or black. While the affected mangoes are safe to eat, the discolouration causes many of us to chuck the fruit in the bin.
TIA PhD Candidate Umar Muhammad is part of a collaborative, multi-state research project within the ARC Training Centre for Innovative Horticultural Products. Emerging research into RCD has been difficult. While it’s estimated that it causes up to a 30 per cent loss in the Australian mango industry, there was no consensus of whether RCD occurs prior to or after harvest. It was difficult to find RCD samples in orchards.
So Mr Muhammad took a new approach to the problem: he learned how to spread the disease better. He developed a method that allowed researchers access to unprecedented levels of RCD-infected fruit – inoculating healthy fruit, then injecting RCD into select groups via needle. Then, 100 per cent of the injected mangoes developed RCD and zero control mangoes developed the disorder.
Northern Territory Research Leader Dr Cameron McConchie, of the Department of Primary Industry and Resources, said this discovery was a major breakthrough in preventing RCD: “We discovered that RCD occurs post-harvest and that avoiding contamination is essential to prevent it. We did not fully understand the cause until after Mr Muhammad artificially induced the RCD bacteria into healthy mangoes.”
The research team found that RCD can spread merely through contact with the intact skin of infected mangoes. They also found that some mango cultivars, like Kensington Pride, are more susceptible to RCD than others.
There is still research to be done, but it appears adjustments to systems like post-harvest handling or more complex changes like developing RCD-resistant varieties may help farmers get more value from their fruit.