Dr Mahbub Rahman

Overview

• Open for the University of Adelaide’s role in current and future international collaborations for the areawide management of insect vectors of diseases through sustainable use of insecticidal proteins Bacillus thuringiensis svar. israelensis (Bti) biopesticides.

Inducible tolerance to Bt-toxin: significance, mechanism, and new management strategies.

• Our understanding of the diverse biological pathways leading to insect resistance against Bt-toxins outside mutations in major Bt-receptor genes (type I resistance) is still limited. Further, one of the unintended outcomes of intensive selection pressures has been the emergence of new Bt-resistance mechanisms in pest insects. For example, in addition to genetic resistance based on target site mutations (which produces individuals resistant to high toxin concentrations), we have shown that exposure of insect larvae to low to medium levels of Bt crystal toxins causes the induction of immune and metabolic responses, resulting low level resistance (which we refer to here as inducible tolerance) in insect population that can be transmitted to offspring by epigenetic inheritance mechanisms (caused by gene and protein regulatory mechanisms) (Rahman et al., 2004).

Managing Bt resistance and induced tolerance with effective refuge crops in preparation for Bollgard III. 

• The overall aim of this project is to improve the ability of refuges to counter both the threat of resistance developing via genetic mutation, and the potential threat of crop failure via inducible tolerance. By accessing and countering these threats while concurrently developing better refuge management and benchmarking techniques to improve refuge governance, the ultimate aim is to avoid the cost of losing Bt cotton efficacy.

Mechanisms and management of inducible tolerance to synthetic insecticides and Bt-toxins in Australian populations of diamondback moth Plutella xylostella. 

• Resistance in Australian populations of diamondback moth (DBM) to older insecticide classes was widespread in both canola and Brassica vegetable crops. As a result, the choice of insecticides for the effective control of DBM was increasingly limited to newer synthetic pesticides, such as emamectin benzoate (Proclaim^®), spinosad (Success^®), indoxacarb (Avatar^®), and commercial Bt-formulations.
• To monitor potential resistance evolution and ensure that resistance, if there was any, was being managed efficiently, we investigated diamondback moth field populations collected from QLD, NSW, and SA for resistance to these newer pesticides and Bt formulations.