Dynamics of aerial and terrestrial populations of Phytophthora ramorum in a California watershed under different climatic conditions
| Authors: | Catherine A. Eyre, Melina Kozanitas, Matteo Garbelotto |
| Year: | 2013 |
| Type: | General Technical Report |
| Station: | Pacific Southwest Research Station |
| Source: | In: Frankel, S.J.; Kliejunas, J.T.; Palmieri, K.M.; Alexander, J.M. tech. coords. Proceedings of the sudden oak death fifth science symposium. Gen. Tech. Rep. PSW-GTR-243. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 95-97 |
Abstract
We present a study of the epidemiology of sudden oak death (SOD) in California within a watershed based on temporally and spatially replicated surveys of symptoms, viability of the pathogen from symptomatic leaves, and genetic analyses using polymorphic SSR markers.
Phytophthora ramorum is sensitive to climate; its optimal growth and transmission conditions are in the spring with warm rainy weather, and although it can survive and persist in harsh conditions, its capacity for transmission and dispersal are significantly reduced in drought conditions. Its main method of transmission is via rainsplash. The San Francisco Bay Area experienced a period of drought for several years prior to, and including, 2009, where conditions for P. ramorum were suboptimal and SOD outbreaks were notably fewer. However, 2010 saw a return to wetter conditions. We studied the population dynamics of P. ramorum resident in two different substrates (leaves and soil) during that climatic transition to study the effects on diversity and isolation success. Population genetics have been used to reconstruct the global history and migration of the pathogen to understand its origins and emergence as a significant pathogen in North America and Europe. Our study is one of the first to address the population dynamics of P. ramorum at a local micro-evolutionary scale and to compare the populations in different substrates.