Selection of a non-sugarcane gene for control of canegrubs : SRDC final report BS95S

Abstract

Four types of non-sugarcane genes were investigation for potential toxictiy to canegrubs. They were: toxins from the bacterium Bacillus thuringiensis (Bt); plant proteinase inhibitors; plant lectins; and avidin. Each of these was tested in an artificial diet based on the wheatgerm and casein and developed within the project.A Bt toxin with toxicity to canegrubs was not identified. The Bt isolates tested, which had activity against New Zealand grassgrub, bound to the gut lining of larvae of Antitrogus consanguineus. This binding proved to be not sufficient for toxicity.Snowdrop and wheatgerm lectin were shown to reduce canegrub growth rates and increase mortality of canegrubs when fed to grubs. Avidin, a biotin-binding protein, reduced canegrub growth rates but was not toxic to canegrubs.Gut proteinases from three species of canegrubs were characterised; serine and trypsin proteinases were shown to predominate within an alkaline environment. Proteinase inhibitors with activity against the canegrub gut proteinases were identified; amongst these were those potato, soybean and wheatgerm. Soybean trypsin inhibitor significantly reduced canegrub growth rates and survival.A gene construct containing the potato proteinase inhibitor gene was prepared and sugarcane plants transformed with it. Plant have tested positive for the presence of the gene, but none have produced the proteinase inhibitor. A gene construct containing the snowdrop lectin gene was also prepared, and attempts made transform it into sugarcane plants. No plants containing the gene have yet been regenerated.