What's New

Early view Forest Pathology article, 21 January 2013

Identification of Phytophthora species baited and isolated from forest soil and streams in northwestern Yunnan province, China

W.-x. Huai, G. Tian, E. M. Hansen, W.-x. Zhao, E. M. Goheen, N. J. Grünwald and C. Cheng

Forest Pathology DOI: 10.1111/efp.12015

Phytophthora species were surveyed by collecting soil samples and placing bait leaves in selected streams during June–October in the years 2005, 2006 and 2010 at three sites in oak forests in Diqing Tibetan Autonomous Prefecture of NW Yunnan province, China. Seventy-three isolates of Phytophthora spp. were recovered from 135 baited leaf samples and 81 soil samples. Eight Phytophthora species were identified by observation of morphological features and ITS1-5.8S-ITS2 rDNA sequence analysis. The eight taxa included two well-known species P. gonapodyides and P. cryptogea, two recently described species P. gregata and P. plurivora, two named but as yet undescribed taxa, P. taxon PgChlamydo and P. taxon Salixsoil, and two previously unrecognized species, Phytophthora sp.1 and P. sp.2. The most numerous species, P. taxon PgChlamydo, and the second most abundant species, P. taxon Salixsoil, were recovered at all three sites. Phytophthora cryptogea was detected only once at site Nixi. Phytophthora gregata and P. sp.2 were isolated from a stream only at site Bitahai, while the other three species were each found at two sites. Phylogenetic analysis revealed that the isolates belonged to three ITS clades, one species including six isolates in clade 2, six species including 66 isolates in clade 6 and one species in clade 8. There was a relatively rich species and genetic diversity of Phytophthora detected in the investigated regions where the forest biotic and abiotic factors affecting the growth and evolution of Phytophthora populations were diverse.


Aggressive tree disease could cost millions

The Copenhagen Post

Christian Wenande December 29, 2012 - 06:59
Getting an overview on the spread of the Phytophthora in Denmark is not adequate, plant pathologist contends
In Denmark alone the economic damage sustained by the Phytophthora disease, shown here affecting the bark of a beech tree, could exceed hundreds of millions of kroner (Photo: Skov og Landskab)

If you’re on a stroll in the woods in 2013 and see a small net bag in a waterway or lake then do not remove it. Most likely, it’s not trash.

The net bag is part of the University of Copenhagen’s effort to get an overview of the country’s new and very aggressive tree disease, Phytophthora, which has begun wrecking havoc to a number of parks in the country.

Naturstyrelsen, the state nature agency, has granted funds to the pilot project that will take samples from as many as 60 trees throughout Denmark and combine them with visual observations of the trees from which the samples stem.

According to the Environment Ministry, similar efforts are being carried out in other EU and Scandinavian countries.

Phytophthora, which takes its name from the Greek and literally means ‘the plant destroyer’, is of the plant-damaging water-mould genus and has caused tremendous damage to crops and trees worldwide. In Denmark alone the economic damage sustained by the disease could exceed hundreds of millions of kroner.


Biosensors and Bioelectronics new article
Development of a lab-on-a-chip device for diagnosis of plant pathogens
Sandra Julich, Marko Riedel, Mark Kielpinski, Matthias Urban, Robert Kretschmer, Stefan Wagner, Wolfgang Fritzsche, Thomas Henkel, Robert Möller, Sabine Werres
Biosensors and Bioelectronics, Volume 26, Issue 10, 15 June 2011, Pages 4070-4075


A lab-on-a-chip system for rapid nucleic acid-based analysis was developed that can be applied for diagnosis of selected Phytophthora species as a first example for use in plant pathology. All necessary polymerase chain reaction process (PCR) and hybridization steps can be performed consecutively within a single chip consisting of two components, an inflexible and a flexible one, with integrated microchannels and microchambers. Data from the microarray is collected from a simple electrical measurement that is based on elementary silver deposition by enzymatical catalyzation. Temperatures in the PCR and in the hybridization zone are managed by two independent Peltier elements. The chip will be integrated in a compact portable system with a pump and power supply for use on site. The specificity of the lab-on-a-chip system could be demonstrated for the tested five Phytophthora species. The two Pythium species gave signals below the threshold. The results of the electrical detection of the microarray correspond to the values obtained with the control method (optical grey scale analysis).



In press: Revista Iberoamericana de Micología

Developing a taxonomic identification system of Phytophthora species based on microsatellites

J. del Castillo-Múnera, M. Cárdenas, A. Pinzón, A. Castañeda, A.J. Bernal, S. Restrepo

Phytophthora spp. is the most important genus of the Oomycete plant pathogens. Nowadays, there are 117 described species in this genus, most of them being primary invaders of plant tissues. The different species are causal agents of diseases in a wide range of crops and plants in natural environments. In order to develop control strategies against Phytophthora spp., it is important to know the biology, ecology and evolutionary processes of these important pathogens.


Hoopa Forestry Fighting to Stop Spread of Sudden Oak Death

Two Rivers Tribune, By Kristan Korns


Hoopa Tribal Forestry and UC Berkeley researchers are working to prevent the spread of an infestation of tree-killing spores which is now less than five miles from the boundary of the Hoopa Valley Reservation.

The spores, known as Phytophthora ramorum or Sudden Oak Death, can infect dozens of plant species and they kill Tan Oak trees. The disease has had devastating effects on forests in California and Oregon.

Darin Jarnaghan, the Hoopa Forestry Department manager, said, “The alarming thing is it’s getting closer. It’s moving eastward towards us.”

The disease is new, and isn’t fully understood yet by researchers and biologists. It wasn’t named until 2000, and was first found in Southern Humboldt in 2002. It has had devastating effects on forests in California and Oregon.

Yana Valachovic, the Director of the Humboldt and Del Norte University of California Cooperative Extension based out of Eureka, said that everyone was taken by surprise when the disease first appeared.

“This is an introduced pathogen to California. It’s not native, and we don’t know where it comes from,” Valachovic said. “The disease was discovered in Southern Humboldt around the Garberville/Redway area, but at the time they didn’t know what to do or how it spread.”





APHIS Revises Federal Order Requiring Notification for Phytophthora ramorum high-risk hosts

SUBJECT: APHIS Revises Federal Order Requiring Notification for Phytophthora ramorum high-risk hosts


Effective immediately, the Animal and Plant Health Inspection Service (APHIS) is amending two Federal Orders, dated January 28, 2011 (DA-2011-04) and February 25, 2011 (DA-2011-10) requiring advance notification for certain shipments of P. ramorum high-risk host nursery stock.


The attached Federal Order, which supersedes all previous Federal Orders on P. ramorum notification, removes notification requirements for nurseries in counties within regulated areas that have never tested positive for P. ramorum or have tested negative for the past three years.




Fungal Biology article online 2 November 2012

Four phenotypically and phylogenetically distinct lineages in Phytophthora lateralis

 Clive M. Brasier, Selma Franceschini, AnnaMaria Vettraino, Everett M. Hansen, Sarah Green, Cecile Robin, Joan F. Webber, Andrea Vannini

Fungal Biology, Available online 2 November 2012


Until recently Phytophthora lateralis was known only as the cause of dieback and mortality of Chamaecyparis lawsoniana in its native range in the Pacific Northwest. Since the 1990s however disease outbreaks have occurred increasingly on ornamental C. lawsoniana in Europe; and in 2007 the pathogen was discovered in soil around old growth C. obtusa in Taiwan, where it may be endemic. When the phenotypes of over 150 isolates of P. lateralis from Taiwan, across the Pacific Northwest (British Columbia to California) and from France, the Netherlands and the UK were compared three growth rate groups were resolved: one slow growing from Taiwan, one fast growing from the Pacific Northwest and Europe and one of intermediate growth from a small area of the UK. Within these growth groups distinct subtypes were identified based on colony patterns and spore metrics and further discriminated in a multivariate analysis. The assumption that the three main growth groups represented phylogenetic units was tested by comparative sequencing of two mitochondrial and three nuclear genes. This assumption was confirmed. In addition two phenotype clusters within the Taiwan growth group were also shown to be phylogenetically distinct. These four phenotypically and genotypically unique populations are informally designated as the Pacific Northwest lineage, the UK lineage, the Taiwan J lineage and the Taiwan K lineage. Their characteristics and distribution are described and their evolution, taxonomic and plant health significance is discussed.


Attack of the drones to fight tree rot in Scotland

Scotland on Sunday by Julia Horton, 28 October 2012

The drones will carry cameras that can transmit close-ups of leaf damage

DRONES more commonly ­associated with the war on ­terror are to patrol the skies over Scotland in a bid to eradicate diseases that threaten to wipe out swathes of forest.

The unmanned planes are smaller than conventional drones and armed with high resolution cameras to capture images that will help woodland managers spot telltale signs of fatal fungal infections in trees.

A trial carried out by the Forestry Commission Scotland at Carradale on the Kintyre peninsula used drones to map the spread of Phytophthora ramorum, a fungus which has recently spread from rhododendrons to larch – forcing estates to fell thousands of trees in a bid to contain the outbreak. The aerial devices also took to the skies over the west coast to assess storm damage in some of the most inaccessible parts of the country.

Now a study carried out for the Forestry Commission suggests that every forestry manager in Scotland should have access to a small-scale drone to improve all aspects of woodland management.

“Only the wide application and routine use of this technology directly by forest managers will enable the technology to deliver its potential benefits, cost effectively,” said Ian Thomas, a chartered forester who helped compile the study. “This means every forestry manager having the technology in the boot of their car, and knowing how to use it.”


Plant Disease Nov 2012 article

Infectivity and Inoculum Production of Phytophthora ramorum on Roots of Eastern United States Oak Species.

Widmer TL, Shishkoff N, Dodge SC

Little is known about colonization of roots of trees by Phytophthora ramorum. We examined zoospore concentration and exposure time needed to infect six Quercus (oak) species and the inoculum produced from their roots. Sprouted acorns, exposed to zoospores (3,000/ml) for different times and transplanted to potting soil, were susceptible to infection within 1 h of exposure but root weights were not impacted after 4 weeks (P = 0.952). Roots of Quercus prinus seedlings, inoculated with sporangia, had 0.6 to 3.2% colonization of the total root mass after 5 months. Neither root lesions nor obvious root sloughing were observed. Inoculum threshold levels were tested by exposing radicles to varying zoospore concentrations for 24 h. Results showed that radicle infection occurred even at 1 zoospore/ml. To test inoculum production, roots were inoculated with sporangia and transplanted into pots. Periodically, samples of runoff were collected and plated on selective medium. Afterward, root segments were plated to calculate percent colonization. After 16 and 35 days, root colonization and inoculum production from oak was lower than that of Viburnum tinus, a positive control. This study shows that P. ramorum is able to infect sprouted oak acorns and produce secondary inoculum, which may be important epidemiologically.


Plant Disease Nov 2012 article

Variation Among Phytophthora cinnamomi Isolates from Oak Forest Soils in the Eastern United States.

Eggers JE, Balci Y, MacDonald WL

Phytophthora cinnamomi isolates from geographically diverse oak forest soils in the Mid-Atlantic regions were studied to determine the extent of genotypic, phenotypic, and pathogenic variation. Four microsatellite loci were targeted for genetic analysis. Phenotypic characteristics measured included sexual and asexual spore dimensions and colony growth rate and morphology. Red oak (Quercus rubra) logs were inoculated with selected isolates to determine relative pathogenicity. Microsatellite analysis showed that the genetic variability of P. cinnamomi isolates was low, with two predominant microsatellite fingerprint groups (MFG). Isolates in MFG1 (48% of the total isolates examined) were characterized by DNA fragment lengths of 120 and 122 bp at locus d39, 169 and 170 bp at locus e16, and 254 and 255 bp at locus g13. MFG2 isolates were characterized by marker sizes of 122 and 124 bp at locus d39, 161 and 163 bp at locus e16, and 247 and 248 bp at locus g13. Asexual and sexual spore dimensions varied greatly among isolates but were similar to previously published descriptions. Phenotypic differences were most pronounced when data were grouped by MFG; the most significant were colony morphology and growth rate. Neither characteristic was a reliable predictor of isolate genotype. Differences in growth rates of MFGs were observed, with MFG1 being less tolerant at higher incubation temperatures. No variation in pathogenicity was observed on red oak logs. The low level of phenotypic and genotypic variation of P. cinnamomi suggest that other factors such as climate might play a more important role in its northern distribution and the diseases it causes.