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Around The Vineyard

“in house” detection of Grapevine leafroll associat- with expertise in bacterial, fungal, and viral taxono-
ed -3 (GLRaV-3). However, many different leafroll my is able to associate the presence of the microor-
viruses can cause leafroll disease and obtaining a ganisms found with disease symptoms (or potential
negative result for GLRaV-3 would have given the disease development).
false impression that the vineyard block or sample
in question was not infected. Need for Accreditation of Laboratories

Next Generation or As mentioned earlier, at the moment, there is no
High Throughput Sequencing accreditation system for laboratories performing
grapevine diagnostic testing. The closer we have
The next generation sequencing (NGS) also known gotten to these efforts is a ring test run by the
as high throughput sequencing (HTS) is a powerful Lodi Wine Grape Commission. A ring test consists
method that allows the laboratory to detect any in providing laboratories with “blind” samples of
organism present in a sample. known infection status to determine if the labora-
tory’s in-house procedures are able to detect the
When NGS or HTS is applied, the complete correct infection status in each sample. In the past,
sequence of the genetic material or microbiome while affiliated to various laboratories I was a par-
present in the tested plant material or soil can be ticipant of such ring tests.
obtained. Generally, during the sample prepara-
tion, the pathogens specific sequences are enriched In the fall of 2018, the Lodi Wine Commission
to increase the sensitivity of the assay (for example ran a ring test to evaluate the different labs that
the lab may just amplify fungal sequences). The offer testing for the diagnostics of grapevine virus-
data obtained is analyzed with sophisticated soft- es. The laboratories received a large number of
ware that is able to list the bacteria, fungi, virus, or homogenized samples that were infected with
other organisms (beneficial or pathogenic) present various grapevine viruses. The results of each lab-
in the sample. The method can provide relative oratory were shared privately with the participant
quantitative data, generally expressed in percent- laboratories. To the best of my knowledge no
ages, of each organism found. The NGS has been accreditation was granted. While it is a great first
widely used in research and has allowed the discov- step to carry out a ring test with the laboratories,
ery and characterization of important viruses such future tests could be improved by providing the
as Grapevine red blotch associated virus. Presently, laboratory with portions of grapevines rather than
this technique is being applied for the commercial a homogenized powder. While it is understanding
testing of plant and soil samples to detect bacterial that homogenized samples may avoid the possibili-
and fungal microorganisms. A plant pathologist ty of uneven distribution of viruses in the grapevine

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