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Agdia Expands ImmunoStrip Catalog with Release of Lettuce Mosaic Virus Test

Agdia announces the release of a new ImmunoStrip product for the detection of lettuce mosaic virus and an improvement to its existing ELISA product.

Lettuce mosaic virus (LMV, Potyvirus) is considered one of the most important pathogens of lettuce worldwide due to its potential for total crop loss. This virus was first described in 1921, infecting field grown lettuce in Florida. Since then, LMV has spread to every lettuce-growing region of the world on every continent except Antarctica. All types of lettuce are susceptible to LMV infection, as are several agronomically important crop hosts, including chickpea, common pea, endive, safflower, and spinach. Additionally, LMV is known to infect several cultivated ornamental species and common weeds found near lettuce fields worldwide. In addition to the widespread incidence and potential for high virulence in lettuce cultures, the LMV-lettuce pathosystem is considered an important model for the study of host-virus interactions.

Figure 1. Symptoms of LMV infection on lettuce. Image courtesy of Agdia EMEA

Symptoms of LMV infection vary depending on the host species, environmental conditions, the LMV isolate causing the infection, and the stage of growth the host was in at the time of infection . In addition, the variety of lettuce and the corresponding presence of resistance genes contribute greatly to the severity of symptoms. Typical symptoms on lettuce include chlorosis, failure to form heads, leaf distortion, mosaic, necrosis and clearing of veins (Figure 1.). Severe necrosis and plant death are commonly seen in susceptible varieties, while tolerant and resistant varieties may show low titer infections with no symptoms or no detectable virus infection, respectively. Current resistance to LMV is conferred by the recessive mo11 and mo12 genes, and both have remained relatively durable since their introduction. Nevertheless, these genes are absent in many lettuce varieties, and LMV isolates capable of breaking resistance when present have been documented for several decades.

Lettuce mosaic virus belongs to the genus Potyvirus and is transmitted locally by several species of aphids (Hemiptera) in a non-persistent and non-circulating manner. The infection is not limited to a specific plant tissue. Like other viruses thus transmitted, the transmission efficiency of LMV is ephemeral in the aphid vector but nevertheless effective. Aphid vectors acquire LMV within seconds using plant tissue stylet probes. Virions are localized for transmission in the stylet of the aphid via what is known as the “auxiliary strategy”. In this scenario, a protein on the viral capsid (CP, capsid protein) binds to a non-structural secondary protein known as HC-Pro (helper component proteinase), which forms a reversible bridge with an insect protein located on the cuticular mucosa. of the stylus. The HC-Pro molecule is encoded by the virus and must be acquired before or at the same time as the virus to be effective. This strategy differs from other non-persistent viruses, such as cucumber mosaic virus and alfalfa mosaic virus, whose capsid proteins bind directly to the stylet protein.

Figure 2: Agdia’s new ImmunoStrip LMV

Following acquisition of the virus, aphids must migrate from infected plants and feed on healthy plants within hours for horizontal transmission of LMV to occur. It is well documented that plant viruses interact with hosts and vectors at the molecular level, manipulating both to facilitate the most efficient acquisition and transmission of virus. This is true for potyviruses; however, the unique host-virus-vector interactions are context-specific. In general, infected hosts produce modified chemical compounds to increase vector immigration and shorten feeding times on infected plants. In addition, viruliferous aphids experienced improved fitness and an increased number of winged adults within the population. In combination, this manipulation of the disease cycle by the causative agent facilitates the most efficient spread of non-persistent viruses.

Lettuce mosaic virus is spread over long distances via the movement of infected seeds and plants, to a lesser extent. Up to 10% of commercial seed produced by infected mother plants will be infected, with virions detectable in the developing pericarp, endosperm and cotyledons.

Figure 3: Interpretation of ImmunoStrip results

Field grown lettuce is usually sown directly into prepared seedbeds using seed pellets in specialized planters. Infected seeds germinate and serve as the primary inoculum for probing aphids. In areas with high aphid populations, relatively low plant infection rates can facilitate catastrophic outbreaks within and between neighboring fields. Additionally, the persistence of LMV in weedy hosts in the absence of cultivated hosts makes LMV management a multi-faceted exercise, including planting certified virus-free seeds and seedlings, using varieties resistance, fallow periods, vector management and removal of alternative hosts.

Agdia states that its new ImmunoStrip for the detection of LMV was tested against a diverse panel of LMV isolates from multiple geographic regions, including a resistance-breaking isolate. The band detected all true positives. Agdia reports that no cross-reactivity was observed for several potential cross-reactants, including beet western yellows virus, bean wilt virus 1 and 2, cauliflower mosaic virus , cucumber mosaic virus, Impatiens necrotic spot virus, tomato bushy stunt virus, tomato spotted wilt virus and turnip mosaic virus. A slight cross reaction has been observed with Bidens mottle virus. This product was developed for use with leaf and seed matrices and will include separate applicable protocols.

Agdia’s ImmunoStrip platform offers end users unparalleled utility; samples can be tested in the field or in the lab by people with no prior diagnostic experience, and results are viewed in 30 minutes. In addition, this product includes everything needed to perform a test and does not require any special equipment.

The test protocol is simple and includes; 1) Collection and extraction of samples in Agdia buffer bags, 2) Exposure of the ImmunoStrip to sample extract, and 3) Allowing results to develop. Test results are visualized as a single control line or a control and test line for negative or positive results, respectively (Figure 3.). The introduction of Agdia’s LMV ImmunoStrip expands its catalog to 49 plant pathogens on this platform. Along with the new ImmunoStrip, Agdia is simultaneously releasing an improved version of its LMV ELISA test with greater analytical sensitivity than the original version. Additionally, the new ELISA will detect a Greek isolate of LMV missed by several other commercially available LMV ELISA tests.

For more information:
Agdia inc.
52642 County Road 1
Elkhart, IN 46514
phone 1-574-264-2615
fax 1-574-264-2153
[email protected]