About the Project
Xylella fastidiosa, a xylem-limited Gram-negative bacterium, is an important plant pathogen that attacks several plants of economic importance. Once restricted to the Americas, the bacterium, which causes olive quick decline syndrome, was discovered near Lecce, Italy in 2013. Since the initial outbreak, it has invaded large swathes of olives in southern Italy, and is of great concern throughout Mediterranean basin and beyond. Currently, there is no known cure for this deadly disease of olives and the only approaches to control are to destroy the host trees and create buffer zones around them or to manage the insect vector population.
The outbreak in southern Italy is characterised by extensive leaf scorch and dieback of olive trees, which has caused significant economic loss. Once the host plant is inoculated by the vector the bacteria colonise the plant xylem vessels, eventually forming a biofilm, which is believed to be responsible for obstructing passage of water and nutrients to the aerial parts of the plant, particularly when the host plant is subjected to water stress. Therefore, in olives, the appearance of dieback symptoms often depend on the time of the year. However, the mechanisms and timings of these symptoms are poorly understood.
The aim of this studentship is to develop and analyse mathematical models, parameterised by existing datasets, to better understand seasonal X. fastidiosa biofilm growth in olive hosts that lead to dieback. The principle aim of the project is to better predict the timing of dieback and how this interacts with the environment. In particular, the student will:
1) Develop partial differential equation (PDE) models for seasonal xylem flow of water and nutrients via evapotranspiration,
2) Develop PDE models of seasonal biofilm growth and aggregation, including extracellular polymeric substances,
3) Combine the above models to understand the mechanisms of X. fastidiosa-induced dieback in olives in seasonal environments.
The student will analyse the models using a combination of asymptotic mathematical techniques and numerical simulation using the High Performance Computing facility IRIDIS at Southampton. Model predictions will compared to field observations of olive dieback, as well as remotely sensed canopy-level data (hyperspectral and thermal images).
The successful candidate will have a strong background in mathematics, statistics, engineering, theoretical physics or quantitative ecology. In addition, the candidate will have demonstrated substantial knowledge of mathematical or population modelling, and simulation techniques for solving models in a suitable scientific programming language (e.g. Fortran, R, Matlab etc). A demonstrated interest in population ecology, population modelling and/or plant disease biology is desirable but not required.
The SPITFIRE DTP programme (www.spitfire.ac.uk) provides comprehensive personal and professional development training alongside extensive opportunities for students to expand their multi-disciplinary outlook through interactions with a wide network of academic, research and industrial/policy partners. The student will be registered at the University of Southampton and hosted at CEH. Specific training will include:
• PDE theory
• PDE modelling
• Plant water and nutrient transportation modelling
• Biofilm modelling
• Numerical analysis
• Scientific programming
• High performance computing
• Scientific writing.
Furthermore, the student will have the opportunity to engage in national and international conferences, as well as present at X. fastidiosa specific workshops, policy engagement meetings and conferences.
Applicants for must have obtained, or be about to obtain, a 2.1 degree or higher. If you have a 2.2 degree, but have also obtained a masters qualification, you are also eligible. Substantial relevant post-graduate experience may also be sufficient, please contact the supervisors for more information.
To apply please use the SPITFIRE application system: (http://noc.ac.uk/gsnocs/project/modelling-mechanisms-olive-die-back-caused-xylella-fastidiosa-biofilms).
Funding Notes
This project is one of a number of proposed topics that are in competition for funding from the NERC SPITFIRE Doctoral Training Partnership http://www.spitfire.ac.uk/. Commencing in autumn 2018 if successful.
Full studentships (fees and stipend) are only available to UK nationals and other EU nationals that have resided in the UK for three years prior to commencing the studentship. If you are a citizen of an EU member state you will eligible for a fees-only award, and must be able to show at interview that you can support yourself for the duration of the studentship at the RCUK level.
References
[1] White SM, Bullock JM, Hooftman DA, Chapman DS. Modelling the spread and control of Xylella fastidiosa in the early stages of invasion in Apulia, Italy. Biological Invasions. 2017 Feb 21.
[2] Payvandi S, Daly KR, Jones DL, Talboys P, Zygalakis KC, Roose T. A mathematical model of water and nutrient transport in xylem vessels of a wheat plant. Bulletin of mathematical biology. 2014 Mar 1;76(3):566.
[3] Whidden, Mark, et al. "A Two-Dimensional Multiphase Model of Biofilm Formation in Microfluidic Chambers." Bulletin of mathematical biology 77.12 (2015): 2161.