Projects on biocide resistance in pests, weeds and vectors

Understanding adaptive evolution to herbicides in ryegrass

Intense pesticide and herbicide pressures have resulted in the evolution of resistance in multiples pests, insect vectors and weeds. Resistance is both a huge socio-economic issue limiting our capacity to control disease and sustain food production and the most obvious example of adaptive evolution, occuring within a human life-span. Since resistance is due to mutations affecting the genome, it is best investigated using genome sequencing technology. Our lab currently focuses on developing a landscape-scale understanding of herbicide resistance in rigid ryegrass (Lolium rigidum Gaud.), the most nocious weed in Australia and many Mediterranean regions.

Ryegrass infestation along the margins of a wheat paddock in Victoria
Resistance is increasingly found to be endowed by multiple genes, which warrants to renew the set of tools available in weed research to incorporate recent advances in phenomics and genomics. We are aiming to identify all the mutations confering resistance using genome-wide association mapping and use these association to predict levels of resistance in any uncharacterised population of ryegrass based on genomic information
With enough weed populations characterised, we will be able to test the most likely model of resistance emergence, between multiple local mutations and a few resistance hotspots that help mutations diffuse through gene flow.

The multiple evolutionary scales of herbicide resistance evolution

Exploring the potential of gene drives to restore herbicide susceptibility

Herbicide resistance is a growing problem. As resistance spreads, herbicides lose their efficacy and struggle to control weeds. This can reduce crop productivity and can represent a costly loss for farmers. In order to make currently ineffective herbicides useful again, we need to reintroduce susceptibility.

Ryegrass infesting wheat (Photo: Ben Camm)

To reintroduce susceptilibty, we need to be able to change the allele frequencies at the population scale. Simply releasing susceptible weeds will not change the population as the same problem persists, susceptible plants are selected against and resistant plants increase in frequency. By making it so that only susceptible alleles are passed on, it is possible to change the allele frequency at the population scale. This is the core concept of a gene drive.

A gene drive, a genetic element capable of self replication, is able to edit a specific allele and replace it with itself. Through this method, progeny of a gene drive individual will always inherit a copy of the gene drive, as will their progeny. After a number of generations, the gene drive may fixate.

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