Page 39 - Grapevine NovDec 2020
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Around The Vineyard
A close up view of a vine infected with Grapevine leafroll associated virus -3 and
Grapevine red blotch virus.
Viral Diseases in the Fall:
Grapevine Leafroll and Red Blotch
By: Judit Monis, Ph.D.
A virus infection become more pronounced by a number (GLRaV-1 to -4). Because it has not
s the fall season progresses, symptoms of
been possible – to date – to complete Koch’s postu-
in the vineyards. Arguably, leafroll and red lates with GLRaVs, the word “associated” is added
blotch are the most notorious and important viral to the virus name. Koch’s postulates have not been
diseases that manifest in the fall season. Often, it completed with most of the viruses that cause
is difficult to distinguish leafroll from red blotch dis- disease in grapevines. The postulates state that a
ease symptoms in the vineyard. This is especially pathogen must be isolated in pure form from a dis-
true on red-fruited grapevine varieties. In this arti- eased plant, later the pathogen (virus in this case)
cle I will summarize and update information on the is introduced to a healthy plant, and the newly
biology, symptoms, and transmission of the viruses infected plant must show the same symptoms as
responsible for these important diseases. the original infected one. Clearly Koch’s postulates
are important because they could prove the cause
The Viruses responsible for and effect of a pathogen causing disease.
Leafroll and Red blotch Diseases
As I will describe below, researchers can tweak
There are four different virus species associated the definition of Koch’s postulates to prove that a
with grapevine leafroll disease. The viruses belong virus causes a specific disease and drop the word
to one taxonomic family (Closteroviridae) and are “associated” from the virus name. Within the
named Grapevine leafroll associated virus followed Closteroviridae family, species of GLRaV are clas-
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