Tomato Necrotic Streak Virus
» Tomato necrotic streak virus was first discovered on tomatoes growing in Florida in 2013.
» Infection by this virus results in the development of necrotic streaks along the veins of tomato leaves.
» The virus can be transmitted at a low level via seed, but under field conditions, it is believed to be transmitted by infected pollen, likely in association with insect vectors.
Many different viruses infect tomato, and the resulting diseases can
cause significant economic losses. Most viral diseases of tomato
cause mosaic or yellowing symptoms of the leaves, discoloration of
the fruit, stunting of plants, and/or distortions of growth. In 2013, a
previously unknown virus was detected on tomato plants growing
in the Palm Beach and Miami-Dade County areas of Florida. The
virus was given the name Tomato necrotic streak virus, and the
disease it causes is called tomato necrotic streak.1
TOMATO NECROTIC STREAK VIRUS (TOMNSV)
Tomato necrotic streak virus (TomNSV) was discovered when
tomato plants in southeastern Florida showing virus-like symptoms
were tested for the presence of known tomato viruses. All of these
tests were negative, indicating that the observed symptoms were
caused by a previously unidentified pathogen.2 Further
investigation revealed the presence of a previously unknown
species of Ilarvirus.
TomNSV was detected again on tomato plants from the same or
nearby fields in southeastern Florida in 2014 and 2015. After the
cause of the disease was identified, other crop and weed species in
the same fields and surrounding areas were tested for the
presence of the virus, but no other plant species were found to be
infected by TomNSV in these areas.1
SYMPTOMS AND HOST RANGE
Symptoms of TomNSV infection of tomato are somewhat similar to
symptoms caused by Tomato chlorotic spot virus (TCSV) and
Groundnut ringspot virus (GRSV). Infected leaves develop necrotic
or brown streaks along the veins (Figure 1). Flowers that are on the
plant at the time of infection usually abort, and any flowers that
form after the plant has been infected produce small fruit that
show no other symptoms. Fruit that are developing on the plant at
the time of infection can develop zippering symptoms (Figure 2).1
With the use of inoculation tests, TomNSV was shown to be able to
infect tomatoes and tobacco, both belonging to the plant family
Solanaceae, but other members of this family, including peppers
and jimsonweed, were not susceptible to TomNSV. So far, the only
other plant found to be a host of this virus is lambsquarters
(Chenopodium album), a member of the plant family Chenopodiaceae.
TRANSMISSION OF TOMNSV
Studies have shown that TomNSV can be transmitted from virus
infected to healthy tomato plants in infected sap, a process known
as mechanical transmission. The virus also can be transmitted
when part of a TomNSV infected tomato plant is grafted onto a
healthy plant.1 The TomNSV pathogen also can be transmitted in
infected tomato seed, but initial studies have found that the rate of
seed transmission is fairly low (only 0.33%). However, even this low
level of seed transmission could be enough to initiate an epidemic
in a field of tomatoes. In the study, plants grown from infected seed
were stunted and had severely distorted leaves (Figure 3). The
initial flowers produced on these plants aborted, but later
developing flowers produced small fruit.
The related Tobacco streak virus is also seed transmitted.6
Studies with TSV have shown a seed transmission rate of about
10% when either the male or female plant parents were infected
with the virus. Seeds coming from a female plant infected with TSV
had a lower rate of germination than did non-infected seed or seed
that was infected from the male parent (through infected pollen).
Seed transmission has also been observed with PMoV.7
The primary mode of transmission of TomNSV to plants in the field
has yet to be determined. However, based on the mode of
transmission of related viruses, it is likely that TomNSV is
transmitted through a combination of virus-infected pollen and
feeding by insects, such as thrips. Studies on the transmission of
the Tobacco streak virus have shown that infection occurs when
thrips feed on healthy plants in the presence of TSV-infected
pollen.8 No infection occurred when TSV infected pollen was placed
on healthy plants in the absence of thrips feeding. Also, no
infection occurred when thrips fed on healthy plants in the
absence of virus-infected pollen, even if the thrips were allowed to
feed on TSV infected plants before feeding on the healthy plants.
Researchers speculate that the wounds created by the feeding
thrips allow the infected pollen to come into contact with internal
plant cells, and the virus can move from the pollen into these cells
where infection occurs.
A similar mode of transmission is suspected for the related
Parietaria mottle virus. In this case, infection by PMoV occurs when
insects, including species of thrips, aphids, and whiteflies, feed on
plants in the presence of PMoV infected pollen.7 It is likely that
future studies will show that the transmission of Tomato necrotic
streak virus results from a combination of insect feeding and the
presence of TomNV infected pollen.
Tomato necrotic streak virus was discovered just a few years ago, in
2013. There is a lot about this pathogen and the disease it causes
that is still unknown, including the sources of virus inoculum and
reservoir hosts, the modes of transmission and spread, differences
in susceptibility of tomato varieties, and effective methods of
control. It is also not clear if this virus will be a minor pathogen on
tomato or if it has the potential to cause significant epidemics and
economic losses. With time and additional research, that
information will become known.
1 Badillo-Vargas, I., Baker, C., Turechek, W., Frantz, G., Mellinger, H., Funderburk, J., and Adkins, S. 2016. Genomic and biological characterization of Tomato necrotic streak virus, a novel Subgroup 2 Ilarvirus infecting tomato in Florida. Plant Disease 2016 100:6, 1046-
2 Adkins, S., Baker, C., Badillo-Vargas, I., Frantz, G., Mellinger, H., Roe, N., and Funderburk, J. 2015. Necrotic streak disease of tomato in Florida caused by a new ilarvirus species related to Tulare apple mosaic virus. New Disease Reports 31:16.
3 Zitter, T. 2014. Minor virus diseases. In Compendium of Tomato Diseases and Pests; Second Edition, Jones, B., Zitter, T., Momol, T., and Miller, S. The American
Phytopathological Society, St. Paul.
4 Caciagli, P., Boccardo, G., and Lovisolo, O. 1989. Parietaria mottle virus, a possible new Ilarvirus from Parietaria officinalis (Urticaceae). Plant Pathology 38:577-584.
5 Batuman, O., Miyao, G., Kuo, Y. W., Chen, L. F., Davis, R. M., and Gilbertson, R. L. 2009. An outbreak of a necrosis disease of tomato in California in 2008 was caused by a new Ilarvirus species related to Parietaria mottle virus. Plant Disease 93:546-547.
6 Sdoodee, R. and Teakle, D. 1988. Seed and pollen transmission of tobacco streak virus in tomato (Lycopersicon-esculentum cv grosse lisse). Australian Journal of Agricultural Research 39:469-474.
7 Aramburu, J., Galipienso, L., Aparicio, F., Soler, S., and Lopez, C. 2010. mode of
transmission of Parietaria mottle virus. Journal of Plant Pathology 92:679-684.
8 Sdoodee, R. and Teakle, D. 1987. Transmission of tobacco streak virus by Thrips tabach a new method of plant virus transmission. Plant Pathology 36:377-380.
For additional agronomic information, please contact your local seed representative. Developed in collaboration with Technology Development & Agronomy by Monsanto.
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