Cotton Engineered with Mpp51Aa2 Affects Predator Bug Lifespan and Reproduction

Jenn Hoskins
7th April, 2024

Cotton Engineered with Mpp51Aa2 Affects Predator Bug Lifespan and Reproduction

Image Source: Natural Science News, 2024

Key Findings

  • A new GE cotton variety, MON 88702, effectively controls pests like Lygus spp. and thrips, reducing the need for chemical insecticides
  • MON 88702 cotton's Bt protein is over 200 times more effective against Lygus spp. than the original version, significantly decreasing pest populations
  • While the Bt protein can negatively affect the lifespan and reproduction of beneficial pirate bugs (Orius spp.), varied diets and lower Bt concentrations in the field limit this risk
Cotton is a vital crop worldwide, but its production is often threatened by pests like plant bugs (Lygus spp.) and thrips (Thrips spp.), which can cause significant economic losses. Traditional transgenic cotton varieties, which have been modified to resist certain pests, do not deter these particular insects, leading farmers to rely on chemical insecticides. However, overuse of these chemicals has resulted in pest resistance, making it increasingly difficult to manage these pests effectively[2]. In response to this challenge, a new genetically engineered (GE) cotton variety, known as MON 88702, has been developed. This cotton produces a protein called Mpp51Aa2, initially referred to as mCry51Aa2, derived from the bacterium Bacillus thuringiensis (Bt). This protein is toxic to certain insects when ingested, including the troublesome Lygus spp. and thrips[1]. Agroscope, the research institution behind this study, has shown that this new cotton variety can effectively control these pests, potentially reducing or even eliminating the need for chemical insecticides. Previous studies have demonstrated that MON 88702 cotton can significantly reduce the number of Lygus nymphs and thrips, resulting in a higher cotton yield when compared to non-transgenic cotton varieties[2]. The Cry51Aa2 protein, which has been optimized in MON 88702 to improve its insecticidal activity, has proven to be over 200 times more effective against Lygus spp. than the original version, leading to a substantial decrease in Lygus populations in field trials[3]. However, an important consideration in the development of pest-resistant crops is the potential impact on non-target organisms, such as beneficial predators that naturally control pest populations. One such predator is the Orius spp., known as pirate bugs, which contribute to the biological control of various agricultural pests. Previous research indicated that high concentrations of the Bt protein could adversely affect these beneficial insects[4]. The latest study by Agroscope has further investigated these effects under more realistic feeding conditions. Laboratory studies revealed that when Orius majusculus, a species of pirate bug, was fed exclusively on frozen spider mites reared on Bt cotton, their lifespan and ability to reproduce were negatively impacted. However, when their diet included a mix of Bt protein-containing spider mites and Bt-free moth eggs, the negative effects on lifespan were mitigated, although their reproductive capacity was still affected. Interestingly, when the predators were fed living caterpillars of the Spodoptera littoralis moth, which had also fed on Bt cotton and thus contained the Bt protein, there were no observable negative effects on the longevity or fecundity of the Orius majusculus. This suggests that the impact of the Bt protein on non-target beneficial insects may depend on the type of prey they consume and the concentration of the protein within that prey. The study concludes that in field conditions, where a variety of prey is available and the concentration of the Bt protein ingested by the predators is likely to be lower than in controlled laboratory settings, the risk to beneficial Orius spp. populations is limited. This finding is crucial as it supports the notion that MON 88702 cotton could be integrated into pest management programs without significantly harming the populations of natural pest control agents. In summary, the genetically engineered cotton variety MON 88702 shows promise as a tool for managing pests that have become resistant to current insecticides. It effectively targets specific pests while having a limited impact on beneficial predatory insects, offering a more sustainable approach to cotton pest management. This development is a step forward in agricultural biotechnology, potentially reducing the environmental footprint of cotton production by decreasing the reliance on chemical insecticides.

BiotechEcologyAgriculture

References

Main Study

1) Prey-mediated effects of Mpp51Aa2-producing cotton on longevity and reproduction of Orius majusculus

Published 5th April, 2024

https://doi.org/10.1007/s11248-024-00378-w

Related Studies

2) First transgenic trait for control of plant bugs and thrips in cotton.

https://doi.org/10.1002/ps.5234

3) A transgenic approach for controlling Lygus in cotton.

https://doi.org/10.1038/ncomms12213

4) Prey-mediated effects of mCry51Aa2-producing cotton on the predatory nontarget bug Orius majusculus (Reuter).

https://doi.org/10.1111/1744-7917.13143


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