Predicting fungicide resistance evolution: combining theoretical and
experimental approaches

Closing date January 5, start date October 2025. 
Further details and link to application form at https://www.ctp-sai.org/

We are recruiting a PhD student supervised by Dr Nichola Hawkins (Niab),
Prof Nik Cunniffe (University of Cambridge), Dr Phil Madgwick and Dr
Ariane Le Gros (Syngenta). The student will be based in Cambridge UK, as
part of the Collaborative Training Programme in Sustainable Agricultural
Innovation. Please note that the CTP funding covers tuition fees at the
"home student" level only (in addition to stipend and research training
funding), therefore applicants liable for the overseas student rate
of tuition fees will need to be able to cover the difference by other
means. This is a 4-year studentship including an industry placement.

The predictability of evolution by natural selection is one of the
big questions in evolutionary biology. It also has enormous practical
importance in crop protection. Plant pathogens have proved highly
adaptable to crop protection methods, including fungicides, leading to the
rapid evolution of fungicide resistance. If the evolution of resistance
and the characteristics of resistant strains can be predicted in advance,
more effective resistance management strategies can be developed to use
fungicides more sustainably.

The fungal pathogen Zymoseptoria tritici causes Septoria leaf blotch,
a major yield-limiting disease in wheat, and it has evolved resistance
against multiple classes of fungicides. For some fungicides, a small
number of major mutations have led to high levels of resistance, and
resistance management is well understood. However, for the commonly-
and currently-used azole and SDHI fungicides, the situation is more
complex, with multiple different mutations leading to gradual shifts
in sensitivity and affecting different fungicides within the affected
class to different degrees. For the azole fungicide target site, CYP51,
single isolates of Z. tritici can have up to ten mutations. Epistatic
interactions between different mutations affect the overall phenotype
of mutants, both in terms of resistance to different azole fungicides,
and with fitness costs or compensatory effects on enzyme function. This
can produce a rugged fitness landscape, making evolutionary outcomes more
contingent upon selection history. Z. tritici can be readily cultured and
fungicide resistant mutants can be generated under lab conditions, making
it a useful model system for experimental studies of resistance evolution.

This project will combine theoretical and experimental approaches
to investigate the evolution of fungicide resistance, working with
the fungal pathogen Zymoseptoria tritici. Supported by a supervisory
team comprising mathematical modellers and an experimental biologist,
the student will develop mathematical models to generate theoretical
predictions of resistance evolution, which they will test using
experimental evolution and competition assays. The student will generate
near-isogenic transformants with combinatorial sets of CYP51 mutations,
to quantify the effects of mutations and their epistatic interactions on
fungicide resistance and other fitness parameters. The student will then
use these fitness parameters in population genetic and epidemiological
models to discover viable evolutionary trajectories through the rugged
fitness landscape as shaped by selection and stochasticity. Potential
resistance management strategies can be compared in terms of how they
manipulate the fitness landscape to delay resistance evolution. To test
these predictions, competition assays will be run under the different
selective conditions of alternative resistance management strategies,
and DNA tests such as qPCR will be developed to quantify the mutations
after selection.

The student will be able to address fundamental questions in evolutionary
biology, while also contributing towards finding solutions to a practical
problem in plant protection. In testing management strategies such as
mixtures or alternations of fungicides or different dose rates, their
findings will have direct impact on resistance management guidelines
for Z. tritici, as well as having broader application to resistance
evolution in other pathogens and pests.

The student will have the opportunity to develop skills in
experimental biology and mathematical modelling. Lab skills will include
microbiological culturing and phenotyping; cloning and transformation;
mutagenesis and experimental evolution; and molecular diagnostics
to detect and quantify resistant genotypes. Modelling skills will
include mapping a complex biological system to a parsimonious model; and
methods for simulating and fitting stochastic population dynamic/genetics
models. This project would suit a student with a background in molecular,
evolutionary or computational biology who is enthusiastic to expand
their skill set across the full range of these areas.

Further details:
https://www.ctp-sai.org/projects-for-2024-1/predicting-fungicide-resistance-evolution%3A-combining-theoretical-and-experimental-approaches-
Application form: https://www.niab.com/niab_job_apply/239

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