In planta detection used to define the distribution of the European lineages of Phytophthora ramorum on larch (Larix) in the UK

Abstract

Two genetically distinct evolutionary lineages of the oomycete pathogen Phytophthora ramorum are responsible for the major epidemic on larch (Larix spp.) in the UK: EU1 (historically widespread) and the recently identified EU2 (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 EU2. 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 EU2 is restricted to Northern Ireland and a small area of southwest Scotland where it is the dominant lineage. There was no evidence of EU2 spread into England and Wales where only EU1 was found. However, EU2 was more widely distributed in southern and eastern parts of Scotland than previously reported. Furthermore, EU1 and EU2 were detected <10 km apart in larch plantations. This study provides the first reports of natural EU2 infection on European larch (Larix decidua), hybrid larch (Larix × eurolepis), beech (Fagus sylvatica), noble fir (Abies procera) and western hemlock (Tsuga heterophylla).

Diversity and detections of Phytophthora species from trade and non‐trade environments in Ireland

“…At the European level, more than 16 Phytophthora taxa (including informally named taxa) have been detected on Rhododendron species and hybrids in ornamental plantings and plant nurseries (Jung et al, 2016). In this study P. ramorum was recorded on 30 hosts, all of which have been shown to be susceptible (Fera, 2010;Kliejunas, 2010;King et al, 2015). Phytophthora ramorum has been detected every year by the PHL since its first detection in trade (first detection 2002;EPPO 2003) and non-trade (first detection 2003; Brennan et al, 2010) locations.…”

“…Phytophthora ramorum has been detected every year by the PHL since its first detection in trade (first detection 2002;EPPO 2003) and non-trade (first detection 2003; Brennan et al, 2010) locations. In this study P. ramorum was recorded on 30 hosts, all of which have been shown to be susceptible (Fera, 2010;Kliejunas, 2010;King et al, 2015). Phytophthora kernoviae has also been found each year (except 2010) since its first detection in Ireland in 2008 (EPPO, 2010).…”

Spotting the pests of tomorrow—Sampling designs for detection of species associations with woody plants

“…The Sudden larch death epidemic caused by the oomycete Phytophthora ramorum in the UK and Ireland is an example of a genotype of a pest causing unexpectedly high damage on a new host. Until 2009 P. ramorum was known in Europe mainly as a pest of horticultural and amenity plants and trees, but then it was found causing extensive damage to Japanese larch ( Larix kaempferi ) in plantations, which was related to lineage and genotype diversity changes in 2009–2014 (Harris, Mullett, & Webber, ; King, Harris, & Webber, ).…”

Buying better biosecurity: Plant‐buying behaviour and the implications for an accreditation scheme in the horticultural sector

“…Such introductions can have devastating effects for the host species, though these impacts may extend to additional species and habitats as host ranges expand (Dart & Chastagner, ; Denman, Kirk, Brasier, & Webber, ; Frankel, ; Frankel & Palmieri, ; Freer‐Smith & Webber, ; Hansen, Parke, & Sutton, ; Harwood, Xu, Pautasso, Jeger, & Shaw, ; King, Harris, & Webber, ; Tooley & Kyde, ; Tooley, Kyde, & Englander, ). Not only do pest and disease introductions risk ecological damage, economic losses can occur through reductions in horticultural and timber stock, decreases in property values due to dead and dying trees, and the allocation of resources for monitoring, tracking and containment efforts (Frankel & Palmieri, ; King et al, ). The mass felling of the important commercial timber species Japanese Larch ( Larix kaempferi ) in Scotland and Wales owing to P. ramorum serves as one such example (Frankel & Palmieri, ).…”