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To identify trees with potential in a disease resistance breeding programme, it is necessary to screen large numbers of individuals which have been exposed to the disease in question. In 2013, Forest Research set up field trials in 14 locations in south-east England where ash dieback was known to be present in the wider environment. The field trials contained around 155,000 ash trees which had been growing in forest nurseries the UK and Ireland but which could no longer be sold to the open market. Plants raised from fifteen different seed sources were obtained, spanning ten of the UK’s native tree seed zones alongside Irish, French and German ash trees. The health status of trees in the trials was monitored for three (14 trials) or four (6 trials) consecutive years following onset of disease symptoms.
This project ran from February 2013 until March 2019, although some of the experiment sites have been retained and taken forward into the Living Ash Project phase II for longer term monitoring.