Integrated control of Sclerotinia disease in celery and lettuce

By Tracey Moreton (Waitrose CTP PhD student)

My Journey

Starts in the beautiful region of Murcia, Spain. Here I visited celery and lettuce farms in Los Alcazares and Aguilas where I set off to collect samples of the plants infected with Sclerotinia. Over a two-day period, I visited commercial and organic farms collecting the appropriate samples, from where they would be transported back to England for preparation of experimental work.

New Partnerships

Phase I of the project would not be possible if it were not for the support and help from all the staff and farmers in Spain at G’s. In particular Pedro who was a mound of very useful information and was as enthusiastic as myself and to James and Mendez for being my chauffeurs.

The Science

There are several factors that perpetuate Sclerotinia incidence on crops, such as climate and the extensive host range of the pathogen. In addition, the disease not only presents itself at cultivation but in storage as well.

The project topic that I will be investigating is Sclerotinia sclerotiorum Which is a soilborne fungal pathogen that causes stem and crown rots in a wide range of crop plants resulting in extensive economic losses worldwide. The fungus can survive for several years in the soil as sclerotia, which when close to the soil surface germinate carpogenically to produce mushroom-like apothecia. Subsequent release of air-borne ascospores then initiate the infection process. Control of S. sclerotiorum focuses on the prevention of ascospore infection with the use of fungicides, but generally there are no attempts to eradicate sclerotia. This project aims to explore practices that reduce sclerotial survival in order to improve Sclerotinia control in celery and lettuce in Spain.

The Plan

The main objectives are to:

1. Collect sclerotiorum isolates from UK and Spanish lettuce and celery crops and characterise using molecular genetics to identify any differences in population structure.
2. Determine the temperatures required to kill sclerotiorum sclerotia or prevent carpogenic germination for UK and Spanish isolates to evaluate the feasibility of solarisation.
3. Investigate other means of killing sclerotia such as bio-solarisation, bio-fumigation and anaerobic disinfestation.

Keywords: Sclerotinia sclerotiorum, stem rot, crown rot, apothecia, bio-solarisation, bio-fumigation, anaerobic disinfestation.

The first trip was a success and the Spanish samples are now being cultivated to grow sclerotia.

 

Spanish samples placed in a constant 20^oC room

 

A. B. C. D. 

 

A. Celery placed on damp paper and left to develop sclerotia. The appearance of mycelium (white fluffy structures) will eventually produce the sclerotia.

B. Small dark circular characteristics of sclerotia appear.

C. Lettuce sample with sclerotia.

D. First harvest of Spanish sclerotia from lettuce and celery samples