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United States Department of Agriculture

Agricultural Research Service

Research Project: EXOTIC, EMERGING, RE-EMERGING, AND INVASIVE PLANT DISEASES OF HORTICULTURAL CROPS

Location: Horticultural Crops Research

Title: Phenotypic differences among three clonal lineages of Phytophthora ramorum

Authors
item Elliot, M - CANADIAN FOREST SERVICE
item Sumampong, G - CANADIAN FOREST SERVICE
item Varga, A - SIDNEY LABORATORY CDFA
item Shamoun, S - CANADIAN FOREST SERVICE
item James, D - SIDNEY LABORATORY CDFA
item Masri, S - SIDNEY LABORATORY CDFA
item Grunwald, Niklaus

Submitted to: Forest Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 1, 2009
Publication Date: February 1, 2011
Citation: Elliot, M., Sumampong, G., Varga, A., Shamoun, S.F., James, D., Masri, S., Grunwald, N.J. 2011. Phenotypic differences among three clonal lineages of Phytophthora ramorum. Forest Pathology. 41:7-14.

Interpretive Summary: There are three major clones or genetic variants of the sudden oak death pathogen Phytophthora ramorum present in North America and Europe named NA1, NA2, and EU1. These three clones were evaluated for phenotype including (i) aggressiveness on detached Rhododendron leaves and (ii) growth rate at minimum, optimum, and maximum temperatures. Individuals from the NA2 and EU1 lineages were the most aggressive and isolates from the NA1 group were the least aggressive. The NA1 clone of P. ramorum was the most variable in aggressiveness and growth rate. This work has implications for understanding emergence of each clone.

Technical Abstract: There are three major clonal lineages of Phytophthora ramorum present in North America and Europe named NA1, NA2, and EU1. Twenty-three isolates representing all three lineages were evaluated for phenotype including (i) aggressiveness on detached Rhododendron leaves and (ii) growth rate at minimum, optimum, and maximum temperatures. Closely related species P. foliorum and P. hibernalis were included in phenotypic tests since these species are encountered in nursery surveys for P. ramorum. Isolates from the NA2 and EU1 lineages were the most aggressive and isolates from the NA1 group were the least aggressive. The NA1 lineage of P. ramorum was the most variable in aggressiveness and growth rate. The variability in the NA1 lineage was due to the presence of non-wild type (nwt) isolates. There was no significant difference in growth rate among NA1 wild type (wt), NA2, and EU1 lineages at any temperature tested. The difference between wt and nwt P. ramorum isolates is discussed.

Last Modified: 8/29/2014
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