A Department of Primary Industries researcher has made a world-first discovery on the location of genes that enable Australia's main summer cereal crop not only to resist insect attack but also to leave the insects dead in their tracks.
Entomologist with the DPI's Agency for Food and Fibre Sciences, Adam Hardy, said that the research, supported by the Grains Research and Development Corporation, had identified the genetic markers in one type of Indian grain sorghum that gave the plant the capacity to kill midge larvae.
The world-first discovery meant that new and improved sorghum varieties could be developed.
Mr Hardy said: "Sorghum is Queensland's dominant summer grain crop, worth about $135 million a year, depending on seasonal conditions, and is used as a cattle feed domestically and in the export market.
"Over the last four years, we have been screening international sorghum lines that contain some extra resistance to sorghum midge, a tiny insect pest that in the past has caused significant economic loss in the form of damaged seed heads."
"After growing selected sorghum varieties in the glasshouse, we conducted molecular marker work in collaboration with the CSIRO and, as a result, have identified the location of genes causing this unique resistance.
"While we have sorghum varieties with good levels of resistance to midge, they have only one resistance mechanism, meaning midge could overcome the resistance in the same way as the flu can overcome antibiotics.
"The new varieties, however, will have two unrelated types of resistance, greatly reducing the ability of the midge to overcome the resistance."
Mr Hardy said that the resistance trait also gave the plant the capacity to kill the pest.
"At this stage we are not sure what causes the midge larvae to die," he said, "but we do know that the plant can kill over 60 per cent of larvae just after flowering, before they affect setting of seed.
"This further reduces the need to spray to control midge, something Australian sorghum growers have rarely had to do since DPI sourced midge-resistant hybrids about 10 years ago.
"The discovery of the genetic markers means that sorghum breeders will be able to run DNA tests of plant material to quickly identify which of their developmental varieties possess the trait.
"DNA testing will allow easy identification of experimental varieties that possess the desirable traits from among the multitude of lines that are tested each year.
"DNA testing not only allows positive identification of the correct plants to keep developing but also makes previously impossible field selection of this resistance possible."
Mr Hardy said that Australian sorghum growers would not have to wait long to start using the "killer sorghum".
"One commercial seed company has a variety expected to be released this year with this new resistance present," he said. "However, it is expected that it will be a few years before other seed companies develop such varieties."