A ProMED-mail post
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International Society for Infectious Diseases
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Date: Tue 29 Jun 2021
Source: DownToEarth [abridged, edited]
https://www.downtoearth.org.in/news/agriculture/how-maharashtra-s-tomato-belt-can-tackle-its-viral-menace-77696

A plethora of viruses as well as insect vectors and pests pose an emerging threat to the tomato belt; it is a wake-up call to stakeholders to adopt good agricultural practices. Currently, the tomato virus is wreaking havoc in districts of Maharashtra. Tomatoes have turned into yellow, spongy, plastic-textured fruits.

Last year [2020; ProMED post http://promedmail.org/post/20200528.7388319], farmers complained of early ripening and substantial yield loss. Samples from Satara and Ahmednagar [districts] were found to be infected with _Cucumber mosaic virus_ (CMV), _Groundnut bud necrosis virus_ (GBNV), and _Tomato  chlorosis virus_. Samples from Pune [contained] CMV, GBNV, _Tomato mosaic virus_, _Pepper mottle virus_, and _Potato virus Y_ [PVY]. This year [2021], viruses detected were CMV, GBNC, _Capsicum chlorosis virus_, _Potato Virus X_, PVY, and [additional members of] the potyvirus group. _Tomato brown rugose fruit virus_ [also] poses a serious threat in India. As of now, we are not sure of its presence.

"One factor for the extensive spread [of the viruses] could be a change in climate and cultivation time," the Indian Institute of Horticultural Research said. Increasing international trade in seeds and fruits has enhanced the risks manifold. International trade and travel have compounded the problem [with] sap-sucking insects [that] spread many crop viruses, with new strains emerging. Seeds from reputed sources must be procured. Multiple virus invasions make [it] more difficult to get resistant/tolerant stock.

[Byline: GK Mahapatro, K Chandrashekar, Rahul Ghadge]

--
Communicated by:
ProMED
promed@promedmail.org

[The viruses identified above and their main routes of transmission are:
_Cucumber mosaic virus_ (CMV; _Cucumovirus_) -- more than 60 species of aphids;
_Groundnut bud necrosis virus_ (GBNV; _Tospovirus_) -- thrips;
_Tomato leaf curl New Delhi virus_ (ToLCNDV; _Begomovirus_) -- whiteflies;
_Tobacco vein distorting virus_ (TVDV; _Polerovirus_) -- aphids;
_Tomato chlorosis virus_ (ToCV; _Crinivirus_) -- whiteflies;
_Tomato mosaic virus_ (ToMV; _Tobamovirus_) -- seed, mechanical means;
_Potato virus Y_ (PVY; type member of genus _Potyvirus_) -- aphids;
_Pepper mottle virus_ (PepMV; _Potyvirus_) & members of the potyvirus group -- like PVY;
_Capsicum chlorosis virus_ (CaCV; _Orthotospovirus_) -- thrips;
_Potato Virus X_ (PVX; type member of _Potexvirus_) -- mechanical means;
_Tomato brown rugose fruit virus_ (ToBRFV; _Tobamovirus_) -- seed, pollinator insects.

For more information on the viruses see links below and previous ProMED posts in the archives.

It is not clear whether multiple viruses were found in single samples or specific fields, or whether different viruses were present in different plants. In the scenario described, however, co-infections in at least some of the plants appear likely. Multiple viral or viroid infections are common in field plants with the potential for synergism (symbiotic enhancement of disease). If additional infections occur over a number of crop cycles, the virus population will gradually build up, both in number of co-infecting (possibly synergistic) virus species and in amounts of infectious units per virus species. This invariably leads to severely reduced plant vigour and a dramatic drop in yield.

It is thought that combinations of various pathogens may have contributed to the general decline of citrus health in the region due to accumulation of parasitic pathogens in old orchards over time (see ProMED-mail post http://promedmail.org/post/20170109.4750640). A similar situation may have developed for tomato planting stock. Regular monitoring of virus populations, as may have commenced in Maharashtra, is an important first step for developing management programmes for farmers.

Tomato seeds are traded widely and are known to pose a risk for spreading viruses and other pathogens (for example, ProMED-mail post http://promedmail.org/post/20140122.2222560). Use of certified clean seeds or tomato transplants is crucial and certification programmes for the crop would be needed to address the problems above.

Maps
India (with states):
http://www.mapsofindia.com/maps/india/india-political-map.htm and
http://healthmap.org/promed/p/310
Maharashtra districts:
https://i.pinimg.com/originals/56/97/e7/5697e77276b192e96d0dee6ef8b3fdb0.jpg

Pictures
Symptoms of some tomato viruses via:
http://www.ipmimages.org/browse/AreaSubs.cfm?area=63 and
https://ars.els-cdn.com/content/image/1-s2.0-B9780123943149000026-f02-01-9780123943149.jpg

Links
Additional news story:
https://www.hortidaily.com/article/9332066/in-tomato-virus-and-covid-lockdown-slash-farmer-incomes-in-maharashtra/
Information on some of the viruses above via:
https://www.sciencedirect.com/science/article/pii/B9780123943149000026,
https://extension.okstate.edu/fact-sheets/common-diseases-of-tomatoes-part-ii-diseases-caused-by-bacteria-viruses-and-nematodes.html#virus-diseases,
http://plantclinic.cornell.edu/factsheets/tomatoviruses.pdf,
https://www.rhs.org.uk/advice/profile?pid=250 and
http://vegetablemdonline.ppath.cornell.edu/factsheets/Viruses_Tomato.htm
International spread of tobamoviruses by seeds (review):
https://www.researchgate.net/publication/321639141_Seed_Transmission_of_Tobamoviruses_Aspects_of_Global_Disease_Distribution
Virus taxonomy via:
https://talk.ictvonline.org/taxonomy/
Information on plant virus vectors via:
http://www.cals.ncsu.edu/course/ent425/text18/plantvectors.html
- Mod.DHA]

[See Also:
Pepino mosaic virus, tomato - New Zealand
http://promedmail.org/post/20210701.8487470
Tomato brown rugose fruit virus - Turkey: (AL)
http://promedmail.org/post/20210524.8377530
2020
----
Tomato leaf curl New Delhi virus, zucchini - France: 1st rep (LP, PR)
http://promedmail.org/post/20201029.7898960
Tomato chlorosis virus: 1st reports, new hosts
http://promedmail.org/post/20200607.7428940
Undiagnosed disease, tomato - India (02): (MH) multiple viruses
http://promedmail.org/post/20200528.7388319
Tomato spotted wilt virus, potato - Australia: epidemiology
http://promedmail.org/post/20200427.7274096
Potato virus Y - USA: population shift (ME)
http://promedmail.org/post/20200223.7017826
2019
----
Tomato leaf curl New Delhi virus, cucurbits - Portugal: 1st rep
(FA,AC) http://promedmail.org/post/20190906.6658287
Tomato brown rugose fruit virus - China: 1st rep (SD)
http://promedmail.org/post/20190903.6654138
Potato diseases - Russia: survey
http://promedmail.org/post/20190606.6506616
2018
----
Undiagnosed leaf curl virus, tomato seed - Egypt
http://promedmail.org/post/20181012.6086559
Cucumber mosaic & tomato spotted wilt viruses, capsicum - Europe:
(Balkan region) http://promedmail.org/post/20180914.6028544
Tomato chlorosis virus - Netherlands
http://promedmail.org/post/20180719.5914214
Leaf curl viruses, tomato & cucurbits - Italy: (SC)
http://promedmail.org/post/20180319.5697141
2017
----
Tomato leaf curl New Delhi virus, zucchini - Morocco: 1st rep (SS)
http://promedmail.org/post/20171206.5487792
Tomato leaf curl New Delhi virus, zucchini - Spain: (AN)
http://promedmail.org/post/20171114.5442041
2016
----
Tomato leaf curl virus, eggplant - India: (TN)
http://promedmail.org/post/20160415.4160915
2015
----
Vegetable viruses - Spain: (AN) alert
http://promedmail.org/post/20151204.3839034
Tomato mosaic virus - Israel: (Negev)
http://promedmail.org/post/20151015.3717154
2013
----
Yellow leaf curl & blights, tomato - Pakistan: (SD)
http://promedmail.org/post/20130206.1531086
2010
----
Tospovirus complex, tomato - Brazil
http://promedmail.org/post/20100719.2419
and additional items on tomato viruses in the archives]

Website: http://www.isid.org

Published: July 6, 2021