Agdia Commercializes Rapid Molecular Assay for Detection of GLRaV-3 (Grapevine leafroll-associated virus 3)

Grape leaves with grapevine leafroll symptoms

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Agdia, Inc. (Elkhart, IN) is pleased to announce the commercialization of a rapid, user-friendly, RNA-based assay, on their AmplifyRP® XRT platform, for the detection and identification of Grapevine leafroll-associated virus 3 (GLRaV-3).

Grapevine leafroll disease (GLD) is considered one of the most destructive and thus, economically important diseases affecting wine, juice and table grapes, Vitis vinifera, worldwide.  The pathology of GLD is complex, and several viruses in the Closteroviridae family have been linked to symptomology.  Nevertheless, the type member of the Ampelovirus genus, Grapevine leafroll-associated virus 3 (GLRaV-3), is considered the primary causal agent.  It is believed that GLRaV-3 originated somewhere in the Old World and is now widely distributed throughout production regions of Africa, Asia, Europe, North America, South America and Oceania. 

Symptoms of GLD vary greatly depending on environment and host variety, typically presenting in early to mid-summer.  Red varieties, such as Cabernet Franc, will express infections as interveinal reddening, while primary and secondary veins remain green.  This is in contrast to varieties like Chardonnay that exhibit interveinal chlorosis, lacking irregular red pigmentation;  therefore, symptoms commonly go unnoticed on white varieties.  Moreover, these symptoms are easily mistaken for nutrient imbalances, such as potassium or phosphorus deficiency.  By harvest, many red and white varieties exhibit leafroll symptoms; nevertheless, like pigmentation, leafroll incidence and severity is variable.  In addition to foliar symptoms, GLD can reduce fruit yield by as much as 40% and reduce berry quality by causing reduced sugar content, poor pigmentation and a lack of ripening.  Finally, GLD has been correlated with a high incidence of grafting failure.

Grapevine leafroll-associated virus 3 is vectored locally in a semi-persistent manner by multiple species of phloem-feeding mealybugs (Order Hemiptera), including Pseudococcus maritimus, Pseudococcus viburni and Pseudococcus longispinus.  Mealybugs move from plant to plant via ambulation and wind-facilitated aerial dispersal.  Moreover, these insects can be moved within vineyards on clothing and equipment.  Several species of soft scale insects are known to transmit GLRaV-3.  Nevertheless, this vector-virus-host relationship is not well characterized and not believed to be epidemiologically important. 

Mechanical transmission via infected harvesting and pruning equipment has not been proven in the field.  Long-distance dispersal is via the exchange of infected propagative material, such as scion wood and rootstock as GLRaV-3 is graft transmitted.  It is important to understand that propagative materials can remain asymptomatic indefinitely, perpetuating the spread of this virus to newly established vineyards.  This makes diagnostic testing of propagative materials a paramount step in managing GLRaV-3.

Agdia’s new AmplifyRP® XRT assay for detection of GLRaV-3 is based on recombinase polymerase amplification (RPA).  This technology promotes the rapid amplification and detection of nucleic acid targets, DNA or RNA, while maintaining a single operating temperature of 39o – 42C.  The AmplifyRP® XRT products achieve target sensitivity and specificity comparable to PCR, while having clear advantages over the lab-based technology.  AmplifyRP® XRT products do not require a nucleic acid purification step; crude sample extracts are prepared using a simple extraction buffer and tested directly.  This makes the testing process simple and saves the end-user valuable time.  Moreover, this facilitates the implementation of this technology at remote locations with limited resources.  When paired with Agdia’s AmpliFire® isothermal fluorometer, the XRT system is a rapid, user-friendly tool that can be implemented in the field or the lab by personnel with limited experience in molecular diagnostics.

Agdia states their new assay was tested against an extensive collection of GLRaV-3 isolates included in groups I, II, III, V, VI, VII, IX and X  providing 100% accuracy for detection of true positives.  Moreover, no cross-reactivity was observed with a comprehensive panel of grape pathogens, including Arabis mosaic virus, Grapevine fanleaf virus, Grapevine fleck virus, Grapevine leafroll-associated virus 1, 2, 4, 5, 6, 7, 9 and 10, Grapevine red blotch virus, Little cherry virus 2, Pineapple mealybug wilt-associated virus 1, 2 and 3, Plum bark necrosis stem pitting-associated virus, Tomato ringspot virus, Tobacco ringspot virus and Xylella fastidiosa.  Sensitivity for this assay is comparable to that observed with the published qPCR to which it was compared.  This product includes an endogenous control and was developed to test leaf, petiole and stem tissue.  For more information on Agdia’s complete line of AmplifyRP® assays, please visit Agdia’s website http://www.agdia.com/amplifyrp-and-amplifire-summary

About Agdia

A leading provider of diagnostic solutions for agriculture, Agdia, Inc. has been serving plant breeders, propagators, growers, universities, regulatory organizations and private testing laboratories since 1981. The company offers a comprehensive portfolio of validated, easy-to-use diagnostics for identifying plant pathogens, plant hormones, and transgenic traits.  Moreover, Agdia operates an ISO accredited, in-house, testing services laboratory.  Agdia’s quality management system is ISO 9001:2015 certified and their Testing Services Laboratory is ISO 17025:2017 accredited.  Visit the company’s website at www.agdia.com, e-mail info@agdia.com, phone 1-574-264-2615 (toll-free 800-622-4342) or fax 1-574-264-2153.

AmplifyRP® and AmpliFire® are registered trademarks of Agdia, Inc.

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