Exploiting pathogenomics and resistance for control of Fusarium wilt of lettuce

Summary/Findings:

Fusarium wilt disease of lettuce, caused by the soilborne fungus Fusarium oxysporum f. sp. lactucae (FOL), can result in severe economic losses for growers in both protected and field-grown crops globally. Disease resistant lettuce cultivars have been bred to reduce losses due to FOL but in response, the pathogen has evolved new races to overcome these sources of resistance. Four races of FOL are currently identified, with race 1 (FOL1) being the most widespread (particularly in southern Europe and the USA) whilst race 2 and 3 are confined to Asia. More recently, race 4 (FOL4) has emerged in Europe and has caused significant losses in the UK since it was first identified in 2017 with further sites confirmed as infected in 2018. So far, FOL4 has been confined to protected lettuce crops and anecdotal evidence suggests it may be more aggressive than FOL1, especially at low temperatures. Significantly, there is no resistance to FOL4 in the current Little Gem and Butterhead lettuce types grown under protection and hence development of resistant cultivars is highly desirable. Although sources of resistance to FOL4 have been reported in some lettuce types, this has yet to be confirmed and also introgressed into appropriate elite cultivars.

The main aim of this project is to characterise new sources of Fusarium oxysporum f. sp. lactucae (FOL) 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 and characterise virulence genes and study interactions between the pathogen and susceptible/resistant lettuce lines.

Objective 1: Characterise FOL isolates from different European locations

Objective 2: Identify pathogenicity genes expressed during infection and confirm their roles in virulence

Objective 3: Investigate a new lettuce mapping population and identify potential markers for FOL resistance