Combining field observations and genetic data to reconstruct the invasion of Phytophthora ramorum in California

Abstract

Although it has been convincingly shown that forest populations of the pathogen Phytophthora ramorum have undergone a significant bottleneck and reproduce exclusively asexually (Ivors et al. 2004, 2006; Mascheretti et al. 2008), objective results showing that nurseries were the original source of the introduction remain elusive (Mascheretti et al. 2008). A previous attempt to define routes of pathogen movement resulted in a largely unresolved network (Mascheretti et al. 2009), showing at best that populations from Santa Cruz and Marin Counties were important sources within California. Previous attempts at reconstructing the entire history of the sudden oak death (SOD) epidemic in California were limited by: 1) incomplete sampling; 2) the inability to include singleton samples; and 3) over-collapsing of non-spatially contiguous, yet genetically similar, samples into large meta-samples that confounded the coalescent analyses. Here, we employ a complete sampling coverage of 832 isolates of P. ramorum (the causative agent of SOD) from 60 California forests, genotyped at nine microsatellite loci.

Parent Publication

• Proceedings of the sudden oak death fifth science symposium

Citation

Croucher, Peter J.P.; Mascheretti, Silvia; Garbelotto, Matteo. 2013. Combining field observations and genetic data to reconstruct the invasion of Phytophthora ramorum in California. 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: 69-73.