How does colonization of roots by mycorrhizal fungi suppress infection by root parasitic weeds: a role for strigolactones?

Supervisors: Professor Julie Scholes
Co-supervisor Dr Duncan Cameron

Key words: Parasitic plants, mycorrhiza, strigolactones, plant defence, phosphate

Root parasitic plants and arbuscular mycorrhizal (AM) fungi are found in natural and agro-ecosystems. Parasitic plants rob the host plant of nutrients negatively impacting host growth and performance which, in natural plant communities leads to changes in competitive interactions between host and non host species, and in agro-ecosystems to severe losses in yield. In contrast, AM fungi facilitate the uptake of phosphorus and nitrogen by the plant promoting host growth under nutrient limiting conditions and enhancing host resistance to a range of microbial pathogens. The infection process of both parasitic plants and AM fungi is intimately linked to the host because host root exudates contain chemicals known as strigolactones which trigger the germination of parasitic plant seeds and the branching of AM fungal hyphae which increases their ability to colonise host roots. Recent research has shown that colonization of roots by AM fungi suppresses subsequent infection by parasitic plants. The aim of this project is to identify the mechanism(s) underlying this phenomenon. The project will address the following questions (i) Is there a reduction in strigolactone concentration in host root exudates following mycorrhizal colonization thus reducing germination of parasitic weed seeds? (ii) Does mycorrhizal colonization up regulate host defences that are active against parasitic plants? (iii) Does infection of roots by parasitic plants suppress subsequent infection by mycorrhizal fungi? What is the outcome of simultaneous infection of host roots by parasite and symbiont? These questions will be addressed using state of the art confocal microscopy, mass spectrometry based metabolic finger-printing, and gene expression profiling to assess plant defence and nutritional chemistry.

For more information about how to apply, or the application process, please contact Mrs S Carter (s.a.carter@sheffield.ac.uk).

To apply now go to: http://www.sheffield.ac.uk/postgraduate/online