The best crops for rapid reproduction could protect the mango and macadamia industries

Dr. Stephanie Kerr of QUT. Image credit: QUT.

Dr Stephanie Kerr from Queensland University of Technology (QUT) has received funding for two research projects on the rapid breeding of new mango and macadamia varieties that protect against pests, diseases and climate change.

Kerr – a tree genomics expert from the QUT Center for Agriculture and Bioeconomy and the School of Biology and Environmental Sciences – received $22,000 from Hort Innovation to study genetic techniques to accelerate flowering of mango and macadamia trees. She also received the $22,000 award from the Minister of Agriculture and Northern Australia to test the results of rapid macadamia farming.

Mangoes and macadamias account for half the value of the Australian horticultural industry but, unlike other cash crops such as rice and wheat, have not undergone extensive molecular breeding programs to produce elite cultivars, Kerr said.

“These high-value crops are susceptible to pests, diseases and the effects of climate change, especially as both species are driven to flower by cooler temperatures,” she said. “Mango breeders have told me that they already have lower flowering and crop yield during warmer winters.

“Industry responses to horticultural challenges are made more difficult by the time required to select adaptive cultivars. Macadamia trees have a long reproductive cycle. Trees cannot be induced to flower during the juvenile period, which can range from 6 to 10 years.

One potential solution is to shorten the juvenile period of plants. Through his research, Kerr will test new transformation technologies that influence gene expression for flowering to help accelerate the development of elite mango and macadamia cultivars.

The first technique will use nanoparticles to introduce molecules that turn off the expression of genes that prevent the plant from flowering. The second technique will use micro-dermal needling or “micro-wounding” with bacteria to deliver molecules that activate gene expression for earlier flowering.

“These techniques have been used successfully in other tree crops to reduce the juvenile period from 7 to 20 years to weeks or months,” Kerr said. “In the apple tree, for example, the techniques have been used successfully to select trees resistant to fire blight thanks to an overexpression of the FRUITFULL gene which reduced the juvenile period from more than 12 years to only a few weeks.

The new plants will not be genetically modified because influencing gene expression using these techniques did not require changes to the genetic code.

After his initial project to determine if the techniques work on mango and macadamia plants, Kerr will test them in a project to accelerate the reproduction of macadamia trees.

“There are currently no genetic manipulation techniques available that work with macadamia, and those from older publications on mango races have not been used in subsequent research,” Kerr said. “Meeting new horticultural challenges will always be a problem for macadamia, which has only been grown commercially for about 50 years.

“So most macadamia varieties are very close to wild progenitors, which means they still carry many undesirable traits. The mango has been cultivated for hundreds to thousands of years. Many more strains have been developed, but there are still many undesirable traits in many of them.

The goal of developing new tools to test gene function and produce elite cultivars would help the mango and macadamia industries respond more quickly to challenges such as pathogens and climate change.

“I want to help keep Australia at the top of these crop markets,” Kerr said.

Kerr was one of 12 recognized young scientists in the Science and Innovation Awards 2022 – a competitive grant scheme which funds innovative research projects to benefit Australian rural industries.

The awards are coordinated by the Australian Bureau of Agricultural and Resource Economics and Science (ABARES), the research arm of the Department of Agriculture, Water and Environment.