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

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.”

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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

http://dx.doi.org/10.1016/j.funbio.2012.10.002

ABSTRACT

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.

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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.

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