Successful development and implementation of a practical proactive resistance management plan for Bt cotton in Australia.

This article describes the design and > 20 years of effective implementation of a proactive resistance-management plan for transgenic Bacillus thuringiensis (Bt) cotton that targets Helicoverpa armigera (Hübner) and Helicoverpa punctigera (Wallengren) in Australia, considering pest biology and ecology, insights from resistance-evolution modelling, and the importance of the human component to effective implementation. This is placed in the context of processes associated with adaptive resource management. Bt cotton has provided Australian cotton growers with technology to manage Helicoverpa species that previously challenged the industry's viability, while at the same time resulting in no detectable changes in the resistance allele frequency in field populations of either Helicoverpa species in eastern Australia. This is the most long-lived and successful global example of a proactive resistance management plan for an insect pest. Six key learnings important to the successful development and implementation of a proactive transgenic-crop resistance management plan are: the programme has to have a strong science base; there has to be broad stakeholder support at all levels; there has to be a strong implementation programme; the plan needs to be supported by auditing and enforced remediation of deviations from the mandated resistance management plan; A programme of rigorous and on-going resistance allele monitoring; an attitude of continuous improvement for all aspects of the resistance management plan. The lessons learnt from the deployment of Bt cotton in Australia are relevant globally and provide important guidelines for the deployment of transgenic crops for insect control wherever they are grown. © 2021 Society of Chemical Industry.

Potential impact of differential production of the Cry2Ab and Cry1Ac proteins in transgenic cotton in response to cold stress.

Transgenic Bollgard II cotton, Gossypium hirsutum L., expresses Cry1Ac and Cry2Ab proteins that provide control of lepidopteran larvae, including Helicoverpa and Heliothis species (Lepidoptera: Noctuidae) worldwide. Experiments conducted at Katherine, Northern Territory, Australia evaluated the impact of night minimum temperatures on Cry1Ac and Cry2Ab protein levels in Bollgard II cotton. In both 2003 and 2004, potted plants were either grown outside continuously or protected from cold in a glasshouse each night. In 2003, bulked samples of leaves were taken after two periods of low minimum temperature and used to determine a cold-stress threshold and critical period. In 2004, replicated samples were taken on 10 dates spanning five periods of low minimum temperature, allowing analysis of seasonal variation in Cry protein levels. The protein level was markedly higher for Cry2Ab than for Cry1Ac. Cry1Ac protein level peaked midseason and was not adversely affected by minimum temperatures down to 2.6 degrees C. The Cry2Ab protein level remained approximately constant but was reduced by low minimum temperatures (threshold, approximately 14 degrees C) for up to 6 d after each chill. The rate of Cry2Ab protein loss was 1.15 and 1.01% per chilling day-degree below threshold in 2003 and 2004, respectively. Impact would seem to be negligible on both the overall efficacy against lepidopteran larvae in-crop and on the current pyramided genes/high-dose/refuge Bt resistance-management strategies because the cold-stress effect is transient, a high level of Cry2Ab protein is still expressed, and there is no impact of chilling on Cry1Ac protein level.

Identification of the sex pheromone of Holotrichia reynaudi.

The male attractant pheromone of the scarab beetle Holotrichia reynaudi, an agricultural pest native to southern India, was extracted from abdominal glands of females with hexane and analyzed by gas chromatography-mass spectrometry. Field testing of the candidate chemicals, indole, phenol, and anisole, both alone and as binary mixtures, led us to conclude that anisole was the major component of the sex pheromone. Neither male nor female beetles were attracted to indole or phenol on their own. Similarly, when indole and anisole were combined, the attractiveness of the solution did not increase over that obtained with anisole alone. However, combination of phenol and anisole did alter the attractiveness of anisole, with fewer male beetles attracted to the binary mixture than to anisole on its own. The behavior of female beetles was not altered by any of the chemicals tested. Anisole is also the sex pheromone of H. consanguinea, making this the first known example of two melolonthine scarabs sharing the same pheromone.