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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Research Unit » Research » Publications at this Location » Publication #320496
Title: Lineage, temperature, and host species have interacting effects on lesion development in Phytophthora ramorum

Author
item EYRE, C - University Of California
item HAYDEN, K - University Of California
item KOZANITAS, M - University Of California
item Grunwald, Niklaus - Nik
item GARBELOTTO, M - University Of California

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/9/2014
Publication Date: 12/5/2014
Citation: Eyre, C.A., Hayden, K.J., Kozanitas, M., Grunwald, N.J., Garbelotto, M. 2014. Lineage, temperature, and host species have interacting effects on lesion development in Phytophthora ramorum. Plant Disease. 98(12):1717-1727.

Interpretive Summary: Phytophthora ramorum is the causal agent of sudden oak death in California and Oregon. There are four recognized clones of the pathogen. The two major clones present in North America are called NA1 and NA2, respectively. With a few exceptions, NA1 is found in natural forest ecosystems and nurseries, and NA2 is generally restricted to nurseries. Isolates from the NA1 and NA2 lineages were used to infect rhododendron, camellia, and California bay laurel to study if the clones differ in the disease they cause. Isolates within both clones were highly variable in their ability to to infect each host. Apparently, the clones vary also in response to temperature and this paper discusses how temperature and host response could affect disease management.

Technical Abstract: There are four recognized clonal lineages of the pathogen Phytophthora ramorum. The two major lineages present in North America are NA1 and NA2. With a few exceptions, NA1 is found in natural forest ecosystems and nurseries, and NA2 is generally restricted to nurseries. Isolates from the NA1 and NA2 lineages were used to infect rhododendron, camellia, and California bay laurel in detached leaf assays to study the effects of lineage, temperature, and host on pathogenicity and host susceptibility. Isolates within both lineages were highly variable in their ability to form lesions on each host. There was also a tendency toward reduced lesion size in successive trials, suggesting degeneration of isolates over time. Temperature had a significant effect on lesion size, with a response that varied depending on the host and isolate. Phenotypic differences between lineages appear to be heavily influenced by the representation of isolates used, host, and temperature. The importance of temperature, host, and lineage are discussed with respect to disease management, as well as future range expansions and migrations of the pathogen.