Exploiting pathogenomics and resistance for control of Fusarium wilt of lettuce

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Fusarium wilt disease of lettuce, caused by the soilborne fungus Fusarium oxysporum f.sp. lactucae (FOL), results in severe economic losses in protected and field-grown crops globally. The pathogen is part of the F. oxysporum species 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. Recently, race 4 (FOL4) emerged in Europe and has caused extensive losses in the UK and Ireland. 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 lettuce resistance to FOL4 in the lettuce types widely grown under protection and hence development of resistant cultivars is highly desirable.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. oxysporum and Trichoderma spp. to reduce FOL may also be explored.