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Control of Fusarium in Lettuce

Integrated control of Fusarium wilt of lettuce in relation to pathogen and microbial community dynamics

Funded by the BBSRC CTP for Sustainable Agricultural Innovation and G's Fresh

PhD project being carried out by Emily Turner and supervised by Prof. John Clarkson

Fusarium oxysporum is responsible for wilt disease of many species of commercial crops worldwide, it is a soilborne, ascomycete, filamentous fungus that colonises and penetrates the root systems of host plants. Fusarium wilt disease of lettuce, caused by Fusarium oxysporum f.sp. lactucae (FOL), is a major constraint to production of protected and field-grown crops globally.

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 races; FOL1 is the most widespread (particularly in southern Europe and the USA) whilst FOL2 and 3 are confined to Asia. More recently FOL4 has emerged which has particularly affected protected lettuce in Northern Europe including the UK.

These areas are experiencing increased prevalence of Fusarium wilt with higher temperatures favouring increased disease development and losses of 50-80% are common, this threat will be further exacerbated by climate change. Lettuce breeding companies are beginning to address these challenges by identifying sources of resistance to both FOL1 and FOL4 but other approaches for control and management of FOL as well as an understanding of its biology and dynamics are urgently required to enable a swift response to new outbreaks in a changing climate.

The main aim of my PhD is to develop sustainable integrated disease management approaches for both FOL1 and FOL4 in lettuce with a focus on field production in Spain.

The project will involve identification and characterisation of FOL isolates from Spain, evaluation of solarisation, biological control and the use of disease resistant / tolerant lettuce varieties for control as well as development and implementation of different approaches to microbial community analyses with a focus on monitoring of FOL and beneficial microbes. The project is a collaboration between Gs Growers, the University of Warwick and NIAB Cambridge.

Lettuce plants in pots infected with fusarium on a shelf in a control environment unit