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In planta detection used to define the distribution of the European lineages of Phytophthora ramorum on larch ( Larix ) in the UK
Author(s) -
King K. M.,
Harris A. R.,
Webber J. F.
Publication year - 2015
Publication title -
plant pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.928
H-Index - 85
eISSN - 1365-3059
pISSN - 0032-0862
DOI - 10.1111/ppa.12345
Subject(s) - phytophthora ramorum , larch , biology , oomycete , lineage (genetic) , european union , botany , beech , fagus sylvatica , ecology , phytophthora , pathogen , genetics , gene , business , economic policy
Two genetically distinct evolutionary lineages of the oomycete pathogen Phytophthora ramorum are responsible for the major epidemic on larch ( Larix spp.) in the UK : EU 1 (historically widespread) and the recently identified EU 2 (reported only from Northern Ireland and a small area in southwest Scotland). Methods for lineage discrimination have required pure cultures of P. ramorum but, as the pathogen is challenging to isolate from infected larch tissue, only limited data have been available on the distribution of EU 2. In this study a protocol was developed to determine the lineage of P. ramorum in infected larch tissue without the need for isolation. The protocol was applied to 134 UK samples collected during 2013–14. In addition, lineage testing was applied to over 300 P. ramorum isolates cultured from a wide range of hosts between 2002 and 2012. Combined data confirmed that EU 2 is restricted to Northern Ireland and a small area of southwest Scotland where it is the dominant lineage. There was no evidence of EU 2 spread into England and Wales where only EU 1 was found. However, EU 2 was more widely distributed in southern and eastern parts of Scotland than previously reported. Furthermore, EU 1 and EU 2 were detected <10 km apart in larch plantations. This study provides the first reports of natural EU 2 infection on European larch ( Larix decidua ), hybrid larch ( Larix × eurolepis ), beech ( Fagus sylvatica ), noble fir ( Abies procera ) and western hemlock ( Tsuga heterophylla ).