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Exploiting pathogenomics and resistance for control of Fusarium wilt of lettuce

Principal supervisor: Dr John Clarkson, School of Life Sciencs

Industry partner: Agriculture and Horticulture Development Board (AHDB)

Project Title: Exploiting pathogenomics and resistance for control of Fusarium wilt of lettuce

University of registration: University of Warwick

Project outline:

Background:

Fusarium wilt disease of lettuce is caused by the soilborne fungus Fusarium oxysporumf.sp. lactucae(FOL), and results in severe economic losses in protected and field-grown crops globally. The pathogen is part of the F. oxysporumspecies complex which comprises multiple host-adapted pathogenic formae speciales(f.spp.) as well as non-pathogenic isolates. FOL is therefore a highly adapted, host specific pathogen. Disease resistant lettuce cultivars have been bred to reduce losses due to FOL but new pathogen races have evolved to overcome this resistance. Currently, there are four FOL with race 1 (FOL1) the most widespread (particularly in southern Europe and the USA) whilst race 2 and 3 are confined to Asia. Race 4 (FOL4) has only emerged very recently in Europe and has caused extensive losses in the UK and Ireland since initial outbreaks in Lancashire and County Dublin with further sites affected in 2018. So far, FOL4 is confined to protected lettuce but anecdotal evidence suggests it may be more aggressive than FOL1, especially at low temperatures; hence there is a significant risk to outdoor production. Significantly, there is no resistance to FOL4 in Little Gem and Butterhead lettuce types widely grown under protection and hence development of resistant cultivars is highly desirable. This PhD is therefore an exciting opportunity to work on a plant pathogen that is new to the UK and which is causing serious concern for the industry.

Aims and objectives:

The main aim of this project is to identify and characterise new sources of FOL4 resistance in lettuce and identify areas of the genome or specific genes associated with this trait. Further work will compare the genetics and biology of FOL1 and FOL4 to identify virulence gene complements and/or mutations related to lettuce cultivar specificity. In addition, biological aspects of the infection process will be examined including the ability of FOL1 and FOL4 to colonise and infect different lettuce cultivars. The potential of non-pathogenic F. oxysporumand Trichodermaspp. to reduce FOL may also be explored.

This PhD is therefore a unique opportunity for a student to develop skills across the disciplines of plant pathology, pathogenomics and plant genetics. The PhD is supported by the industry through AHDB and links have already been established with major lettuce breeding companies. The student will therefore also have the chance to engage with different parts of the horticultural industry during their studies.

Contact: Dr John Clarkson, University of Warwick