5,000 Bt genes join stored grain pest armoury

CSIRO scientists are hot on the trail of an insecticidal protein belonging to the species Bacillus thuringiensis (Bt), which they hope will kill stored grain pests.

To most people, Bt is associated with environmentally safe, sprayable formulations for the control of caterpillar pests.

It is also the source of the insecticidal gene that is the active component of insect-resistant transgenic cotton and other crops.

However, Bt is proving to be much more versatile than just a caterpillar killer. More than 120 different insecticidal proteins have been discovered in Bt so far and, as there is no sign of the rate of discovery slowing, there are probably at least as many more yet to be discovered.

Although many of these proteins are specific for caterpillars, others have been shown to be toxic for some beetle, fly, locust and even nematode pests.

CSIRO scientists decided it might be fruitful to look for new and useful strains of Bt in Australia, banking on our unique biological heritage, according to CSIRO entomologist Ray Akhurst.

The search was underwritten by growers through the GRDC and by the Rural Industries Research and Development Corporation. CSIRO Entomology established a collection of Bt strains containing unknown toxins and evaluated these strains for effect against some significant Australian insect pests, including stored grains beetles.

From over 5,000 strains collected, some 83 new strains of Bt have been identified and tested against pests such as the lesser grain borer, cowpea weevil, corn earworm and cluster caterpillar. Dr Akhurst said these strains are currently being analysed to identify which of the several insecticidal proteins produced by each strain is responsible for killing the pests.

While the exact toxic proteins are still awaiting identification, Dr Akhurst is confident it's just a matter of time before they're used for protecting stored grains without leaving undesirable residues.

Programs 1.8.1, 2.7.1, 2.7.1 Contact: Dr Ray Akhurst 02 6246 4123