Non-oak native plants are main hosts for sudden oak death pathogen in California

Abstract

The finding of Phytophthora ramorum -the pathogen that causes sudden oak death in four California native trees -on rhododendron in Europe led us to hypothesize that its host range in California's natural forests was much greater than previously suspected. In addition to the affected oak species, we have now identified an additional 13 species from 10 plant families that act as hosts for P. ramorum in California. Our data indicates that nearly all of the state's main tree species in mixedevergreen and redwood-tanoak forests -including the coniferous timber species coast redwood and Douglas fir -may be hosts for P. ramorum. The broad host range of P. ramorum, the variability of symptoms among different hosts and the ability of the pathogen to disperse by air suggests that it may have the potential to cause long-term, landscape-level changes in California forests.

Pathogenicity and sporulation of Phytophthora pinifolia on Pinus radiata in Chile

“…are amongst the most serious and invasive plant pathogens on both agricultural and forestry crops (Fry and Goodwin 1997;Rizzo et al 2002). In terms of forestry, the recent emergence of species such as Phytophthora ramorum and P. austrocedrae (Rizzo et al 2002;Greslebin et al 2007) has reinforced the fact that these pathogens are a serious threat to forestry worldwide, both in natural ecosystems and plantations Garbelotto et al 2003;Greslebin and Hansen 2010). The appearance of a needle blight of Pinus spp.…”

Sudden Oak Death: Interactions of the Exotic Oomycete Phytophthora ramorum with Naïve North American Hosts

“…and tanoaks (Notholithocarpus densiflorus) and shown to be the causal agent of the observed outbreaks. Discovery and research milestones of this decade included (i) the determination that P. ramorum was also the causal agent of a leaf and branch dieback of ornamental plants, later named ramorum blight, which affected rhododendrons and viburnums in German and Belgian commercial plant nurseries (123,124), (ii) the discovery that ramorum blight was also present in U.S. and European nurseries outside Belgium and Germany (29,37,114), (iii) the determination that P. ramorum was mostly an aerially dispersed oomycete (25,28,86) and in fact the first forest Phytophthora ever to have been described with such a transmission mode in the temperate zone (several others were to be discovered in the years to follow), (iv) the discovery that infectious airborne sporangia were not produced in significant numbers on the bole lesions responsible for oak and tanoak mortality but rather were extremely abundant on foliar lesions of a newly discovered host, California bay laurel (Umbellularia californica) (25,28), and on the leaves and twigs of tanoaks (26,27), (v) the progressive discovery that over 100 species could be infected by the pathogen, including both U.S. native and ornamental species (29,43,114), (vi) the determination that the source of the California infestation could be traced back to infected ornamental plants (22,81,101) and that the pathogen itself was comprised of four genetically distinct lineages, each with a fixed mating allele (52,66,67,117,125), (vii) evidence that the pathogen could be retrieved from soil and water in both forests (25,41) and nurseries (107), (viii) the understanding, based on the sequencing of the entire genome (115), that while sexual reproduction in P. ramorum currently appears to be absent and not fully functional (5,10,…”

Proceedings of the fourth meeting of the International Union of Forest Research Organizations (IUFRO) Working Party S07.02.09: Phytophthoras in forests and natural ecosystems

“…This data has lead to a number of comparative genomics papers looking at P. ramorum and P. sojae. More importantly from a sudden oak death perspective, the genome sequence has allowed for the development of microsatellite markers for use in P. ramorum population genetic studies (Ivors andothers 2006, Prospero andothers 2007 …”