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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.


Youtube video of Phytophthora plurivora zoospores attracted to Beech root exudates

New Phytopathology article accepted for publication
Mr. Jaime Aguayo, Dr. Gerard C. Adams, Dr. Fabien Halkett, Dr. Mursel Catal, Mr. Claude Husson, Zoltán Á. Nagy, Dr. Everett Hansen, Dr. Benoit Marçais, and Dr. Pascal Frey
Pytopathology 0 0:ja
Alder decline caused by Phytophthora alni has been one of the most important diseases of natural ecosystems in Europe during the last 20 years. The emergence of Phytophthora alni subsp. alni (Paa)—the pathogen responsible for the epidemic—is linked to an interspecific hybridization event between two parental species: Phytophthora alni subsp. multiformis (Pam) and Phytophthora alni subsp. uniformis (Pau). One of the parental species, Pau, has been isolated in several European countries and recently in North America. The objective of this work was to assess the level of genetic diversity, the population genetic structure, and the putative reproduction mode and mating system of Pau. Five new polymorphic microsatellite markers were used to contrast both geographical populations. The study comprised 71 isolates of Pau collected from 8 European countries and 10 locations in North America. Our results revealed strong differences between continental populations (Fst=0.88; Rst=0.74), with no evidence for gene flow. European isolates showed extremely low genetic diversity compared to the North American collection. Selfing appears to be the predominant mating system in both continental collections. The results suggest that the European Pau population is most likely alien and derives from the introduction of a few individuals, while the North American population probably is an indigenous population.

Eukaryotic Cell early release article

Wood Focus Magazine, 22 Sep 2012

Tackling larch enemies - genetic analysis of Phytophthora ramorum.

British forestry scientists have identified a new lineage of a deadly tree pathogen that could devastate Japanese larch populations in the UK and oak species in the USA.

The Phytophthora ramorum (P. ramorum) pathogen causes ramorum disease, which is responsible for diseases in more than 120 plant species around the world. Genetic analysis has confirmed the fourth genetically distinct lineage of the pathogen – one that separated from the pathogen’s other strains thousands of years ago.

The California Oak Mortality Task Force in the USA and the UK Forestry Commission are looking to arrest the disease’s progress. Spokesperson for the US organisation, Katharine Palmieri, explains, ‘Each lineage is distant enough from the other that, if reintroduced to one another, unintended consequences could occur, such as mating successfully with each other and creating a hybrid that could be more virulent.’


Thousands of trees felled in disease outbreak

Get Surrey By Jennifer Maxfield  September 11, 2012

THOUSANDS of trees in Surrey have been felled after a highly destructive disease was found in the south east for the first time.

Ramorum disease, caused by the fungus-like pathogen phytophthora ramorum, has infected woodland near Dorking and it could easily spread to other areas.

Around 7,000 trees in the county have been felled so far while 1,000 have been removed in West Sussex. The Forestry Commission became concerned that trees were showing symptoms during a helicopter survey of the region in June and ground-based checks confirmed their fears

The disease has been responsible for the premature felling of more than three million larch trees in the UK since it was first found in the West Country in 2009.

Most cases have occurred in the wetter, western parts of Britain as well as Ireland and the Isle of Man.

This month’s confirmation that the disease has reached the south east is the first time it has affected the region's larches.

Alison Field, south-east England director for the Forestry Commission, described it as "bitterly disappointing" news.

Evidence of the disease. Pic: Forestry Commission Picture Library/Isobel Cameron


Fatal juniper fungus spreads to new sites

Sep 10, 2012 The Teesdale Mercury

A DISEASE that is threatening to wipe out Teesdale’s juniper bushes has spread to other areas of the UK. 
The fungus-like phytophthora austrocedrae was first found in juniper trees on Natural England’s Moor House estate in the upper dale last year.

The disease infects the plant through the root system causing the foliage to decline and eventually die.

Now, after investigations by the Food and Environment Research Agency (FERA), the disease has been found at nine new sites.

A spokesperson for Natural England said: “Since we reported the phytophthora outbreak in Moor House and upper Teesdale National Nature Reserve in March, there has been confirmation of a small, isolated infected area on the other side of the River Tees. All other tests over the remaining juniper area were negative and the extent of the restricted area has been reduced following public consultation.”

 As well as the further outbreak in the North East, phytophthora has been found in several sites in Cumbria and at one private garden in Devon. The levels of infected juniper found at the sites range from five per cent to 100 per cent.

Steps to contain the disease have been in place in upper Teesdale since the outbreak was identified.